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Čopar S, Kos Ž. Many-defect solutions in planar nematics: interactions, spiral textures and boundary conditions. SOFT MATTER 2024. [PMID: 39150404 DOI: 10.1039/d4sm00586d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
From incompressible flows to electrostatics, harmonic functions can provide solutions to many two-dimensional problems and, similarly, the director field of a planar nematic can be determined using complex analysis. We derive a closed-form solution for a quasi-steady state director field induced by an arbitrarily large set of point defects and circular inclusions with or without fixed rotational degrees of freedom, and compute the forces and torques acting on each defect or inclusion. We show that a complete solution must include two types of singularities, generating a defect winding number and its spiral texture, which have a direct effect on defect equilibrium textures and their dynamics. The solution accounts for discrete degeneracy of topologically distinct free energy minima which can be obtained by defect braiding. The derived formalism can be readily applied to equilibrium and slowly evolving nematic textures for active or passive fluids with multiple defects present within the orientational order.
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Affiliation(s)
- Simon Čopar
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
| | - Žiga Kos
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
- Department of Condensed Matter Physics, Jožef Stefan Institute, Ljubljana, Slovenia
- International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, Higashi-Hiroshima, Japan
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2
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Lemma B, Lemma LM, Ems-McClung SC, Walczak CE, Dogic Z, Needleman DJ. Structure and dynamics of motor-driven microtubule bundles. SOFT MATTER 2024; 20:5715-5723. [PMID: 38872426 PMCID: PMC11268426 DOI: 10.1039/d3sm01336g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 06/03/2024] [Indexed: 06/15/2024]
Abstract
Connecting the large-scale emergent behaviors of active cytoskeletal materials to the microscopic properties of their constituents is a challenge due to a lack of data on the multiscale dynamics and structure of such systems. We approach this problem by studying the impact of depletion attraction on bundles of microtubules and kinesin-14 molecular motors. For all depletant concentrations, kinesin-14 bundles generate comparable extensile dynamics. However, this invariable mesoscopic behavior masks the transition in the microscopic motion of microtubules. Specifically, with increasing attraction, we observe a transition from bi-directional sliding with extension to pure extension with no sliding. Small-angle X-ray scattering shows that the transition in microtubule dynamics is concurrent with a structural rearrangement of microtubules from an open hexagonal to a compressed rectangular lattice. These results demonstrate that bundles of microtubules and molecular motors can display the same mesoscopic extensile behaviors despite having different internal structures and microscopic dynamics. They provide essential information for developing multiscale models of active matter.
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Affiliation(s)
- Bezia Lemma
- Physics Department, Harvard University, Cambridge, MA 02138, USA
- Physics Department, Brandeis University, Waltham, MA 02453, USA.
- Physics Department, University of California, Santa Barbara, CA 93106, USA
| | - Linnea M Lemma
- Physics Department, Brandeis University, Waltham, MA 02453, USA.
- Physics Department, University of California, Santa Barbara, CA 93106, USA
| | | | - Claire E Walczak
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN 47405, USA
| | - Zvonimir Dogic
- Physics Department, Brandeis University, Waltham, MA 02453, USA.
- Physics Department, University of California, Santa Barbara, CA 93106, USA
- Biomolecular Science & Engineering Department, University of California, Santa Barbara, CA 93106, USA
| | - Daniel J Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Molecular & Cellular Biology Department, Harvard University, Cambridge, MA 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
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3
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Caporusso CB, Cugliandolo LF, Digregorio P, Gonnella G, Suma A. Phase separation kinetics and cluster dynamics in two-dimensional active dumbbell systems. SOFT MATTER 2024; 20:4208-4225. [PMID: 38741521 DOI: 10.1039/d4sm00200h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Molecular dynamics simulations were employed to investigate the phase separation process of a two-dimensional active Brownian dumbbell model. We evaluated the time dependence of the typical size of the dense component using the scaling properties of the structure factor, along with the averaged number of clusters and their radii of gyration. The growth observed is faster than in active disk models, and this effect is further enhanced under stronger activity. Next, we focused on studying the hexatic order of the clusters. The length associated with the orientational order increases algebraically with time and faster than for spherical active Brownian particles. Under weak active forces, most clusters exhibit a uniform internal orientational order. However, under strong forces, large clusters consist of domains with different orientational orders. We demonstrated that the latter configurations are not stable, and given sufficient time to evolve, they eventually achieve homogeneous configurations as well. No gas bubbles are formed within the clusters, even when there are patches of different hexatic order. Finally, attention was directed towards the geometry and motion of the clusters themselves. By employing a tracking algorithm, we showed that clusters smaller than the typical size at the observation time exhibit regular shapes, while larger ones display fractal characteristics. In between collisions or break-ups, the clusters behave as solid bodies. Their centers of mass undergo circular motion, with radii increasing with the cluster size. The angular velocity of the center of mass equals that of the constituents with respect to their center of mass. These observations were rationalised with a simple mechanical model.
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Affiliation(s)
- C B Caporusso
- Dipartimento Interateneo di Fisica, Università degli Studi di Bari, via Amendola 173, Bari, I-70126, Italy
- INFN, Sezione di Bari, via Amendola 173, Bari, I-70126, Italy
| | - L F Cugliandolo
- CNRS, Laboratoire de Physique Théorique et Hautes Energies, LPTHE, Sorbonne Université, F-75005 Paris, France
- Institut Universitaire de France, 1 rue Descartes, 75231 Paris Cedex 05, France
| | - P Digregorio
- Departement de Fisica de la Materia Condensada, Facultat de Fisica, Universitat de Barcelona, Martí i Franquès 1, E08028 Barcelona, Spain.
- UBICS University of Barcelona Institute of Complex Systems, Martí i Franquès 1, E08028 Barcelona, Spain
| | - G Gonnella
- Dipartimento Interateneo di Fisica, Università degli Studi di Bari, via Amendola 173, Bari, I-70126, Italy
- INFN, Sezione di Bari, via Amendola 173, Bari, I-70126, Italy
| | - A Suma
- Dipartimento Interateneo di Fisica, Università degli Studi di Bari, via Amendola 173, Bari, I-70126, Italy
- INFN, Sezione di Bari, via Amendola 173, Bari, I-70126, Italy
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4
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Barakat JM, Modica KJ, Lu L, Anujarerat S, Choi KH, Takatori SC. Surface Topography Induces and Orients Nematic Swarms of Active Filaments: Considerations for Lab-On-A-Chip Devices. ACS APPLIED NANO MATERIALS 2024; 7:12142-12152. [PMID: 38808306 PMCID: PMC11129142 DOI: 10.1021/acsanm.4c02020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 05/30/2024]
Abstract
Surface-bound molecular motors can drive the collective motion of cytoskeletal filaments in the form of nematic bands and polar flocks in reconstituted gliding assays. Although these "swarming transitions" are an emergent property of active filament collisions, they can be controlled and guided by tuning the surface chemistry or topography of the substrate. To date, the impact of surface topography on collective motion in active nematics is only partially understood, with most experimental studies focusing on the escape of a single filament from etched channels. Since the late 1990s, significant progress has been made to utilize the nonequilibrium properties of active filaments and create a range of functional nanodevices relevant to biosensing and parallel computation; however, the complexity of these swarming transitions presents a challenge when attempting to increase filament surface concentrations. In this work, we etch shallow, linear trenches into glass substrates to induce the formation of swarming nematic bands and investigate the mechanisms by which surface topography regulates the two-dimensional (2D) collective motion of driven filamentous actin (F-actin). We demonstrate that nematic swarms only appear at intermediate trench spacings and vanish if the trenches are made too narrow, wide, or tortuous. To rationalize these results, we simulate the F-actin as self-propelled, semiflexible chains subject to a soft, spatially modulated potential that encodes the energetic cost of bending a filament along the edge of a trench. In our model, we hypothesize that an individual filament experiences a penalty when its projected end-to-end distance is smaller than the trench spacing ("bending and turning"). However, chains that span the channel width glide above the trenches in a force- and torque-free manner ("crowd-surfing"). Our simulations demonstrate that collections of filaments form nematic bands only at intermediate trench spacings, consistent with our experimental findings.
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Affiliation(s)
| | | | - Le Lu
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Stephanie Anujarerat
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Kyu Hwan Choi
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Sho C. Takatori
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
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5
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Paramanick S, Pal A, Soni H, Kumar N. Programming tunable active dynamics in a self-propelled robot. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:34. [PMID: 38782771 DOI: 10.1140/epje/s10189-024-00430-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/28/2024] [Indexed: 05/25/2024]
Abstract
We present a scheme for producing tunable active dynamics in a self-propelled robotic device. The robot moves using the differential drive mechanism where two wheels can vary their instantaneous velocities independently. These velocities are calculated by equating robot's equations of motion in two dimensions with well-established active particle models and encoded into the robot's microcontroller. We demonstrate that the robot can depict active Brownian, run and tumble, and Brownian dynamics with a wide range of parameters. The resulting motion analyzed using particle tracking shows excellent agreement with the theoretically predicted trajectories. Later, we show that its motion can be switched between different dynamics using light intensity as an external parameter. Intriguingly, we demonstrate that the robot can efficiently navigate through many obstacles by performing stochastic reorientations driven by the gradient in light intensity towards a desired location, namely the target. This work opens an avenue for designing tunable active systems with the potential of revealing the physics of active matter and its application for bio- and nature-inspired robotics.
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Affiliation(s)
- Somnath Paramanick
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Arnab Pal
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai, 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400094, India
| | - Harsh Soni
- School of Physical Sciences, Indian Institute of Technology Mandi, Mandi, 175001, India
| | - Nitin Kumar
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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Redford SA, Colen J, Shivers JL, Zemsky S, Molaei M, Floyd C, Ruijgrok PV, Vitelli V, Bryant Z, Dinner AR, Gardel ML. Motor crosslinking augments elasticity in active nematics. SOFT MATTER 2024; 20:2480-2490. [PMID: 38385209 PMCID: PMC10933839 DOI: 10.1039/d3sm01176c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 01/12/2024] [Indexed: 02/23/2024]
Abstract
In active materials, uncoordinated internal stresses lead to emergent long-range flows. An understanding of how the behavior of active materials depends on mesoscopic (hydrodynamic) parameters is developing, but there remains a gap in knowledge concerning how hydrodynamic parameters depend on the properties of microscopic elements. In this work, we combine experiments and multiscale modeling to relate the structure and dynamics of active nematics composed of biopolymer filaments and molecular motors to their microscopic properties, in particular motor processivity, speed, and valency. We show that crosslinking of filaments by both motors and passive crosslinkers not only augments the contributions to nematic elasticity from excluded volume effects but dominates them. By altering motor kinetics we show that a competition between motor speed and crosslinking results in a nonmonotonic dependence of nematic flow on motor speed. By modulating passive filament crosslinking we show that energy transfer into nematic flow is in large part dictated by crosslinking. Thus motor proteins both generate activity and contribute to nematic elasticity. Our results provide new insights for rationally engineering active materials.
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Affiliation(s)
- Steven A Redford
- The Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
| | - Jonathan Colen
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jordan L Shivers
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Sasha Zemsky
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Program in Biophysics, Stanford University, Stanford, CA 94305, USA
| | - Mehdi Molaei
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
| | - Carlos Floyd
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Paul V Ruijgrok
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Vincenzo Vitelli
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
| | - Zev Bryant
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Aaron R Dinner
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
- Department of Physics, University of Chicago, Chicago, IL 60637, USA
- James Franck Institute, University of Chicago, Chicago, IL 60637, USA
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
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7
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张 德, 张 豪, 李 博. [The Dynamic Model of the Active-Inactive Cell Interface]. SICHUAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF SICHUAN UNIVERSITY. MEDICAL SCIENCE EDITION 2024; 55:39-46. [PMID: 38322532 PMCID: PMC10839493 DOI: 10.12182/20240160508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Indexed: 02/08/2024]
Abstract
Objective To explore the morphodynamics of the active-inactive cell monolayer interfaces by using the active liquid crystal model. Methods A continuum mechanical model was established based on the active liquid crystal theory and the active-inactive cell monolayer interfaces were established by setting the activity difference of cell monolayers. The theoretical equations were solved numerically by the finite difference and the lattice Boltzmann method. Results The active-inactive cell interfaces displayed three typical morphologies, namely, flat interface, wavy interface, and finger-like interface. On the flat interfaces, the cells were oriented perpendicular to the interface, the -1/2 topological defects were clustered in the interfaces, and the interfaces were negatively charged. On the wavy interfaces, cells showed no obvious preference for orientation at the interfaces and the interfaces were neutrally charged. On the finger-like interfaces, cells were tangentially oriented at the interfaces, the +1/2 topological defects were collected at the interfaces, driving the growth of the finger-like structures, and the interfaces were positively charged. Conclusion The orientation of the cell alignment at the interface can significantly affect the morphologies of the active-inactive cell monolayer interfaces, which is closely associated with the dynamics of topological defects at the interfaces.
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Affiliation(s)
- 德清 张
- 清华大学工程力学系 生物力学与医学工程研究所 (北京 100084)Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - 豪舜 张
- 清华大学工程力学系 生物力学与医学工程研究所 (北京 100084)Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - 博 李
- 清华大学工程力学系 生物力学与医学工程研究所 (北京 100084)Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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8
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Wang W, Ren H, Zhang R. Symmetry Breaking of Self-Propelled Topological Defects in Thin-Film Active Chiral Nematics. PHYSICAL REVIEW LETTERS 2024; 132:038301. [PMID: 38307071 DOI: 10.1103/physrevlett.132.038301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 10/09/2023] [Accepted: 11/28/2023] [Indexed: 02/04/2024]
Abstract
Active nematics represent a range of dense active matter systems which can engender spontaneous flows and self-propelled topological defects. Two-dimensional (2D) active nematic theory and simulation have been successful in explaining many quasi-2D experiments in which self-propelled +1/2 defects are observed to move along their symmetry axis. However, many active liquid crystals are essentially chiral nematic, but their twist mode becomes irrelevant under the 2D assumption. Here, we use theory and simulation to examine a three-dimensional active chiral nematic confined to a thin film, thus forming a quasi-2D system. We predict that the self-propelled +1/2 disclination in a curved thin film can break its mirror symmetry by moving circularly. Our prediction is confirmed by hydrodynamic simulations of thin spherical-shell and thin cylindrical-shell systems. In the spherical-shell confinement, the four emerged +1/2 disclinations exhibit rich dynamics as a function of activity and chirality. As such, we have proposed a new symmetry-breaking scenario in which self-propelled defects in quasi-2D active nematics can acquire an active angular velocity, greatly enriching their dynamics for finer control and emerging applications.
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Affiliation(s)
- Weiqiang Wang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
| | - Haijie Ren
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
| | - Rui Zhang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
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Najma B, Wei WS, Baskaran A, Foster PJ, Duclos G. Microscopic interactions control a structural transition in active mixtures of microtubules and molecular motors. Proc Natl Acad Sci U S A 2024; 121:e2300174121. [PMID: 38175870 PMCID: PMC10786313 DOI: 10.1073/pnas.2300174121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 10/07/2023] [Indexed: 01/06/2024] Open
Abstract
Microtubules and molecular motors are essential components of the cellular cytoskeleton, driving fundamental processes in vivo, including chromosome segregation and cargo transport. When reconstituted in vitro, these cytoskeletal proteins serve as energy-consuming building blocks to study the self-organization of active matter. Cytoskeletal active gels display rich emergent dynamics, including extensile flows, locally contractile asters, and bulk contraction. However, it is unclear how the protein-protein interaction kinetics set their contractile or extensile nature. Here, we explore the origin of the transition from extensile bundles to contractile asters in a minimal reconstituted system composed of stabilized microtubules, depletant, adenosine 5'-triphosphate (ATP), and clusters of kinesin-1 motors. We show that the microtubule-binding and unbinding kinetics of highly processive motor clusters set their ability to end-accumulate, which can drive polarity sorting of the microtubules and aster formation. We further demonstrate that the microscopic time scale of end-accumulation sets the emergent time scale of aster formation. Finally, we show that biochemical regulation is insufficient to fully explain the transition as generic aligning interactions through depletion, cross-linking, or excluded volume interactions can drive bundle formation despite end-accumulating motors. The extensile-to-contractile transition is well captured by a simple self-assembly model where nematic and polar aligning interactions compete to form either bundles or asters. Starting from a five-dimensional organization phase space, we identify a single control parameter given by the ratio of the different component concentrations that dictates the material-scale organization. Overall, this work shows that the interplay of biochemical and mechanical tuning at the microscopic level controls the robust self-organization of active cytoskeletal materials.
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Affiliation(s)
- Bibi Najma
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Wei-Shao Wei
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Aparna Baskaran
- Department of Physics, Brandeis University, Waltham, MA02453
| | - Peter J. Foster
- Department of Physics, Brandeis University, Waltham, MA02453
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Zhang Q, Wang W, Zhou S, Zhang R, Bischofberger I. Flow-induced periodic chiral structures in an achiral nematic liquid crystal. Nat Commun 2024; 15:7. [PMID: 38191525 PMCID: PMC10774319 DOI: 10.1038/s41467-023-43978-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 11/26/2023] [Indexed: 01/10/2024] Open
Abstract
Supramolecular chirality typically originates from either chiral molecular building blocks or external chiral stimuli. Generating chirality in achiral systems in the absence of a chiral input, however, is non-trivial and necessitates spontaneous mirror symmetry breaking. Achiral nematic lyotropic chromonic liquid crystals have been reported to break mirror symmetry under strong surface or geometric constraints. Here we describe a previously unrecognised mechanism for creating chiral structures by subjecting the material to a pressure-driven flow in a microfluidic cell. The chirality arises from a periodic double-twist configuration of the liquid crystal and manifests as a striking stripe pattern. We show that the mirror symmetry breaking is triggered at regions of flow-induced biaxial-splay configurations of the director field, which are unstable to small perturbations and evolve into lower energy structures. The simplicity of this unique pathway to mirror symmetry breaking can shed light on the requirements for forming macroscopic chiral structures.
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Affiliation(s)
- Qing Zhang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - Weiqiang Wang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China
| | - Shuang Zhou
- Department of Physics, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Rui Zhang
- Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China.
| | - Irmgard Bischofberger
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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Bonn L, Ardaševa A, Doostmohammadi A. Elasticity tunes mechanical stress localization around active topological defects. SOFT MATTER 2023; 20:115-123. [PMID: 38050783 DOI: 10.1039/d3sm01113e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2023]
Abstract
Mechanical stresses are increasingly found to be associated with various biological functionalities. At the same time, topological defects are being identified across a diverse range of biological systems and are points of localized mechanical stress. It is therefore important to ask how mechanical stress localization around topological defects is controlled. Here, we use continuum simulations of nonequilibrium, fluctuating and active nematics to explore the patterns of stress localization, as well as their extent and intensity around topological defects. We find that by increasing the orientational elasticity of the material, the isotropic stress pattern around topological defects is changed substantially, from a stress dipole characterized by symmetric compression-tension regions around the core of the defect, to a localized stress monopole at the defect position. Moreover, we show that elastic anisotropy alters the extent and intensity of the stresses, and can result in the dominance of tension or compression around defects. Finally, including both nonequilibrium fluctuations and active stress generation, we find that the elastic constant tunes the relative effect of each, leading to the flipping of tension and compression regions around topological defects. This flipping of the tension-compression regions only by changing the elastic constant presents an interesting, simple, way of switching the dynamic behavior in active matter by changing a passive material property. We expect these findings to motivate further exploration tuning stresses in active biological materials by varying material properties of the constituent units.
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Affiliation(s)
- Lasse Bonn
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen, Denmark.
| | - Aleksandra Ardaševa
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen, Denmark.
| | - Amin Doostmohammadi
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen, Denmark.
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12
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Martínez-Prat B, Arteaga O, Sagués F, Ignés-Mullol J. Multimodal fluorescence microscope with fast adaptive polarimetry. HARDWAREX 2023; 16:e00480. [PMID: 37817881 PMCID: PMC10560837 DOI: 10.1016/j.ohx.2023.e00480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 08/02/2023] [Accepted: 09/18/2023] [Indexed: 10/12/2023]
Abstract
Polarized light microscopy is a widely used technique to observe specimens that are optically anisotropic, or birefringent. It has a broad applicability in the study of minerals, soft materials such as polymers, complex fluids or liquid crystals, and organic tissues in biology and medicine. Most of these observations are qualitative in nature, as it is not obvious to quantify the spatial distribution of optical anisotropy of specimens. Moreover, existing commercial implementations for quantitative polarimetry are costly and slow in nature, precluding real time observation of dynamical processes. Here, we present a custom-made implementation of an optical microscope for quantitative polarimetry at the cost of a standard scientific polarizing microscope. The instrument allows to extract the local optical axis and birefringence of transparent materials with a frequency of several Hz. The instrument is built using off-the-shelf optomechanical components, which optimizes cost, availability, and modularity. An example of the latter is the fact that we combine the polarimetry measurements with simultaneous fluorescence microscopy, which results in a powerful multimodal instrument with broad potential applications.
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Affiliation(s)
- Berta Martínez-Prat
- Universitat de Barcelona and Institute of Nanoscience and Nanotechnology (IN2UB), Martíi Franquès 1, 08028, Barcelona, Spain
| | - Oriol Arteaga
- Universitat de Barcelona and Institute of Nanoscience and Nanotechnology (IN2UB), Martíi Franquès 1, 08028, Barcelona, Spain
| | - Francesc Sagués
- Universitat de Barcelona and Institute of Nanoscience and Nanotechnology (IN2UB), Martíi Franquès 1, 08028, Barcelona, Spain
| | - Jordi Ignés-Mullol
- Universitat de Barcelona and Institute of Nanoscience and Nanotechnology (IN2UB), Martíi Franquès 1, 08028, Barcelona, Spain
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13
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Wang Z, Servio P, Rey AD. Geometry-structure models for liquid crystal interfaces, drops and membranes: wrinkling, shape selection and dissipative shape evolution. SOFT MATTER 2023. [PMID: 38031449 DOI: 10.1039/d3sm01164j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
We review our recent contributions to anisotropic soft matter models for liquid crystal interfaces, drops and membranes, emphasizing validations with experimental and biological data, and with related theory and simulation literature. The presentation aims to illustrate and characterize the rich output and future opportunities of using a methodology based on the liquid crystal-membrane shape equation applied to static and dynamic pattern formation phenomena. The geometry of static and kinetic shapes is usually described with dimensional curvatures that co-mingle shape and curvedness. In this review, we systematically show how the application of a novel decoupled shape-curvedness framework to practical and ubiquitous soft matter phenomena, such as the shape of drops and tactoids and bending of evolving membranes, leads to deeper quantitative insights than when using traditional dimensional mean and Gaussian curvatures. The review focuses only on (1) statics of wrinkling and shape selection in liquid crystal interfaces and membranes; (2) kinetics and dissipative dynamics of shape evolution in membranes; and (3) computational methods for shape selection and shape evolution; due to various limitations other important topics are excluded. Finally, the outlook follows a similar structure. The main results include: (1) single and multiple wavelength corrugations in liquid crystal interfaces appear naturally in the presence of surface splay and bend orientation distortions with scaling laws governed by ratios of anchoring-to-isotropic tension energy; adding membrane elasticity to liquid crystal anchoring generates multiple scales wrinkling as in tulips; drops of liquid crystals encapsulates in membranes can adopt, according to the ratios of anchoring/tension/bending, families of shapes as multilobal, tactoidal, and serrated as observed in biological cells. (2) Mapping the liquid crystal director to a membrane unit normal. The dissipative shape evolution model with irreversible thermodynamics for flows dominated by bending rates, yields new insights. The model explains the kinetic stability of cylinders, while spheres and saddles are attractors. The model also adds to the evolving understanding of outer hair cells in the inner ear. (3) Computational soft matter geometry includes solving shape equations, trajectories on energy and orientation landscapes, and shape-curvedness evolutions on entropy production landscape with efficient numerical methods and adaptive approaches.
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Affiliation(s)
- Ziheng Wang
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, Québec, H3A 2B2, Canada.
| | - Phillip Servio
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, Québec, H3A 2B2, Canada.
| | - Alejandro D Rey
- Department of Chemical Engineering, McGill University, 3610 University Street, Montréal, Québec, H3A 2B2, Canada.
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14
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Atzin N, Mozaffari A, Tang X, Das S, Abbott NL, de Pablo JJ. Minimal Model of Solitons in Nematic Liquid Crystals. PHYSICAL REVIEW LETTERS 2023; 131:188101. [PMID: 37977640 DOI: 10.1103/physrevlett.131.188101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 06/20/2023] [Accepted: 09/11/2023] [Indexed: 11/19/2023]
Abstract
Solitons in liquid crystals have generated considerable interest. Several hypotheses of varying complexity have been advanced to explain how they arise, but consensus has not emerged yet about the underlying forces responsible for their formation or their structure. In this work, we present a minimal model for solitons in achiral nematic liquid crystals, which reveals the key requirements needed to generate them in the absence of added charges. These include a surface inhomogeneity, consisting of an adsorbed particle capable of producing a twist, flexoelectricity, dielectric contrast, and an applied ac electric field that can couple to the director's orientation. Our proposed model is based on a tensorial representation of a confined liquid crystal, and it predicts the formation of "butterfly" structures, quadrupolar in character, in regions of a slit channel where the director is twisted by the surface imperfection. As the applied electric field is increased, solitons (or "bullets") become detached from the wings of the butterfly, and then propagate rapidly throughout the system. The main observations that emerge from the model, including the formation and structure of butterflies, bullets, and stripes, as well as the role of surface inhomogeneity and the strength of the applied field, are consistent with experimental findings presented here for nematic LCs confined between two chemically treated parallel plates.
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Affiliation(s)
- Noe Atzin
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
| | - Ali Mozaffari
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
- OpenEye, Cadence Molecular Sciences, Boston, Massachusetts 02114, USA
| | - Xingzhou Tang
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
| | - Soumik Das
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Nicholas L Abbott
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
- Center for Molecular Engineering, Argonne National Laboratory, Lemont, Illinois 60439, USA
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15
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Macías-Durán J, Duarte-Alaniz V, Híjar H. Active nematic liquid crystals simulated by particle-based mesoscopic methods. SOFT MATTER 2023; 19:8052-8069. [PMID: 37700612 DOI: 10.1039/d3sm00481c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Two Multi-particle collision dynamics algorithms that simulate nematic liquid crystals are generalised to reproduce active behaviour. One of the algorithms is due to Shendruk and Yeomans and is based on particles that carry an orientation vector ordered by a mean-field energy [T. N. Shendruk and J. M. Yeomans, Soft Matter, 2015, 11, 5101]. In the other algorithm, due to Mandal and Mazza, particles possess an order parameter tensor which evolves according to the Qian-Sheng model of nematohydrodynamics [S. Mandal and M. G. Mazza, Phys. Rev. E, 2019, 99, 063319]. For both methods activity is incorporated through a force proportional to the divergence of the local average order parameter tensor. Both implementations produce disclination curves in the nematic fluid that undergo nucleation and self-annihilation dynamics. Topological defects are found to be consistent with those observed in recent experiments of three-dimensional active nematics. Results permit to compare the length-scales over which the different nematic Multi-particle collision dynamics methods operate. The structure and dynamics of the orientation and flow fields agree with those obtained recently in numerical studies of continuum three-dimensional active nematics. Overall, our results open the opportunity to use mesoscopic particle-based approaches to study active liquid crystals in situations such as nonequilibrium states driven by flow or colloidal particles in active anisotropic solvents.
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Affiliation(s)
- Jesús Macías-Durán
- La Salle University Mexico, Benjamin Franklin 45, 06140, Mexico City, Mexico.
| | | | - Humberto Híjar
- La Salle University Mexico, Benjamin Franklin 45, 06140, Mexico City, Mexico.
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16
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Molaei M, Redford SA, Chou WH, Scheff D, de Pablo JJ, Oakes PW, Gardel ML. Measuring response functions of active materials from data. Proc Natl Acad Sci U S A 2023; 120:e2305283120. [PMID: 37819979 PMCID: PMC10589671 DOI: 10.1073/pnas.2305283120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 08/08/2023] [Indexed: 10/13/2023] Open
Abstract
From flocks of birds to biomolecular assemblies, systems in which many individual components independently consume energy to perform mechanical work exhibit a wide array of striking behaviors. Methods to quantify the dynamics of these so-called active systems generally aim to extract important length or time scales from experimental fields. Because such methods focus on extracting scalar values, they do not wring maximal information from experimental data. We introduce a method to overcome these limitations. We extend the framework of correlation functions by taking into account the internal headings of displacement fields. The functions we construct represent the material response to specific types of active perturbation within the system. Utilizing these response functions we query the material response of disparate active systems composed of actin filaments and myosin motors, from model fluids to living cells. We show we can extract critical length scales from the turbulent flows of an active nematic, anticipate contractility in an active gel, distinguish viscous from viscoelastic dissipation, and even differentiate modes of contractility in living cells. These examples underscore the vast utility of this method which measures response functions from experimental observations of complex active systems.
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Affiliation(s)
- Mehdi Molaei
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
| | - Steven A. Redford
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL60637
| | - Wen-Hung Chou
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL60637
| | - Danielle Scheff
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Department of Physics, University of Chicago, Chicago, IL60637
| | - Juan J. de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
| | - Patrick W. Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL60153
| | - Margaret L. Gardel
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL60637
- James Franck Institute, University of Chicago, Chicago, IL60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL60637
- Department of Physics, University of Chicago, Chicago, IL60637
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17
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Rønning J, Renaud J, Doostmohammadi A, Angheluta L. Spontaneous flows and dynamics of full-integer topological defects in polar active matter. SOFT MATTER 2023; 19:7513-7527. [PMID: 37493084 DOI: 10.1039/d3sm00316g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Polar active matter of self-propelled particles sustain spontaneous flows through the full-integer topological defects. We study theoretically the incompressible flow profiles around ±1 defects induced by polar and dipolar active forces. We show that dipolar forces induce vortical flows around the +1 defect, while the flow around the -1 defect has an 8-fold rotational symmetry. The vortical flow changes its chirality near the +1 defect core in the absence of the friction with a substrate. We show analytically that the flow induced by polar active forces is vortical near the +1 defect and is 4-fold symmetric near the -1 defect, while it becomes uniform in the far-field. For a pair of oppositely charged defects, this polar flow contributes to a mutual interaction force that depends only on the orientation of the defect pair relative to the background polarization, and that enhances defect pair annihilation. This is in contradiction with the effect of dipolar active forces which decay inversely proportional with the defect separation distance. As such, our analyses reveals a long-ranged mechanism for the pairwise interaction between topological defects in polar active matter.
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Affiliation(s)
- Jonas Rønning
- Department of Physics, Njord Centre, University of Oslo, P.O. Box 1048, 0316 Oslo, Norway.
| | - Julian Renaud
- École Normale Supérieure, PSL Research University, 45 rue d'Ulm, 75005 Paris, France
- Institute of Science and Technology Austria, Am Campus 1, A-3400 Klosterneuburg, Austria
| | - Amin Doostmohammadi
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen, Denmark.
| | - Luiza Angheluta
- Department of Physics, Njord Centre, University of Oslo, P.O. Box 1048, 0316 Oslo, Norway.
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18
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Zarei Z, Berezney J, Hensley A, Lemma L, Senbil N, Dogic Z, Fraden S. Light-activated microtubule-based two-dimensional active nematic. SOFT MATTER 2023; 19:6691-6699. [PMID: 37609884 DOI: 10.1039/d3sm00270e] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
We assess the ability of two light responsive kinesin motor clusters to drive dynamics of microtubule-based active nematics: opto-K401, a processive motor, and opto-K365, a non-processive motor. Measurements reveal an order of magnitude improvement in the contrast of nematic flow speeds between maximally- and minimally-illuminated states for opto-K365 motors when compared to opto-K401 construct. For opto-K365 nematics, we characterize both the steady-state flow and defect density as a function of applied light. We also examine the transient behavior as the system switches between steady-states upon changes in light intensities. Although nematic flows reach a steady state within tens of seconds, the defect density exhibits transient behavior for up to 10 minutes, showing a separation between small-scale active flows and system-scale structural states. Our work establishes an experimental platform that can exploit spatiotemporally-heterogeneous patterns of activity to generate targeted dynamical states.
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Affiliation(s)
- Zahra Zarei
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
| | - John Berezney
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
| | - Alexander Hensley
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
| | - Linnea Lemma
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
- The Department of Chemical and Biological Engineering, Princeton, NJ 08544, USA
- Department of Physics, University of California, Santa Barbara, California 93106, USA
| | - Nesrin Senbil
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
| | - Zvonimir Dogic
- Department of Physics, University of California, Santa Barbara, California 93106, USA
- Biomolecular Science and Engineering, University of California, Santa Barbara, California 93106, USA
| | - Seth Fraden
- The Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts 02454, USA.
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19
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Golden M, Grigoriev RO, Nambisan J, Fernandez-Nieves A. Physically informed data-driven modeling of active nematics. SCIENCE ADVANCES 2023; 9:eabq6120. [PMID: 37406118 PMCID: PMC10321743 DOI: 10.1126/sciadv.abq6120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 05/31/2023] [Indexed: 07/07/2023]
Abstract
A continuum description is essential for understanding a variety of collective phenomena in active matter. However, building quantitative continuum models of active matter from first principles can be extremely challenging due to both the gaps in our knowledge and the complicated structure of nonlinear interactions. Here, we use a physically informed data-driven approach to construct a complete mathematical model of an active nematic from experimental data describing kinesin-driven microtubule bundles confined to an oil-water interface. We find that the structure of the model is similar to the Leslie-Ericksen and Beris-Edwards models, but there are appreciable and important differences. Rather unexpectedly, elastic effects are found to play no role in the experiments considered, with the dynamics controlled entirely by the balance between active stresses and friction stresses.
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Affiliation(s)
- Matthew Golden
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Roman O. Grigoriev
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Jyothishraj Nambisan
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Department of Condensed Matter Physics, University of Barcelona, Barcelona 08028, Spain
- Institute of Complex Systems (UBICS), University of Barcelona, Barcelona 08028, Spain
| | - Alberto Fernandez-Nieves
- Department of Condensed Matter Physics, University of Barcelona, Barcelona 08028, Spain
- Institute of Complex Systems (UBICS), University of Barcelona, Barcelona 08028, Spain
- ICREA-Institució Catalanade Recerca i Estudis Avançats, Barcelona 08010, Spain
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20
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Luo Y, Gu M, Park M, Fang X, Kwon Y, Urueña JM, Read de Alaniz J, Helgeson ME, Marchetti CM, Valentine MT. Molecular-scale substrate anisotropy, crowding and division drive collective behaviours in cell monolayers. J R Soc Interface 2023; 20:20230160. [PMID: 37403487 PMCID: PMC10320338 DOI: 10.1098/rsif.2023.0160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 06/13/2023] [Indexed: 07/06/2023] Open
Abstract
The ability of cells to reorganize in response to external stimuli is important in areas ranging from morphogenesis to tissue engineering. While nematic order is common in biological tissues, it typically only extends to small regions of cells interacting via steric repulsion. On isotropic substrates, elongated cells can co-align due to steric effects, forming ordered but randomly oriented finite-size domains. However, we have discovered that flat substrates with nematic order can induce global nematic alignment of dense, spindle-like cells, thereby influencing cell organization and collective motion and driving alignment on the scale of the entire tissue. Remarkably, single cells are not sensitive to the substrate's anisotropy. Rather, the emergence of global nematic order is a collective phenomenon that requires both steric effects and molecular-scale anisotropy of the substrate. To quantify the rich set of behaviours afforded by this system, we analyse velocity, positional and orientational correlations for several thousand cells over days. The establishment of global order is facilitated by enhanced cell division along the substrate's nematic axis, and associated extensile stresses that restructure the cells' actomyosin networks. Our work provides a new understanding of the dynamics of cellular remodelling and organization among weakly interacting cells.
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Affiliation(s)
- Yimin Luo
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mengyang Gu
- Department of Statistics and Applied Probability, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Minwook Park
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Xinyi Fang
- Department of Statistics and Applied Probability, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Younghoon Kwon
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Juan Manuel Urueña
- BioPACIFIC MIP, California NanoSystems Institute, Santa Barbara, CA 93106, USA
| | - Javier Read de Alaniz
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Matthew E. Helgeson
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Cristina M. Marchetti
- Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Megan T. Valentine
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
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21
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Ray S, Zhang J, Dogic Z. Rectified Rotational Dynamics of Mobile Inclusions in Two-Dimensional Active Nematics. PHYSICAL REVIEW LETTERS 2023; 130:238301. [PMID: 37354394 DOI: 10.1103/physrevlett.130.238301] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/14/2023] [Indexed: 06/26/2023]
Abstract
We investigate the dynamics of mobile inclusions embedded in 2D active nematics. The interplay between the inclusion shape, boundary-induced nematic order, and autonomous flows powers the inclusion motion. Disks and achiral gears exhibit unbiased rotational motion, but with distinct dynamics. In comparison, chiral gear-shaped inclusions exhibit long-term rectified rotation, which is correlated with dynamics and polarization of nearby +1/2 topological defects. The chirality of defect polarities and the active nematic texture around the inclusion correlate with the inclusion's instantaneous rotation rate. Inclusions provide a promising tool for probing the rheological properties of active nematics and extracting ordered motion from their inherently chaotic motion.
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Affiliation(s)
- Sattvic Ray
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Jie Zhang
- Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China (USTC), 230026 Hefei, China
- Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China (USTC), 230026 Hefei, China
| | - Zvonimir Dogic
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
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22
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Stam S, Gardel ML, Weirich KL. Direct detection of deformation modes on varying length scales in active biopolymer networks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.15.540780. [PMID: 37292666 PMCID: PMC10245561 DOI: 10.1101/2023.05.15.540780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Correlated flows and forces that emerge from active matter orchestrate complex processes such as shape regulation and deformations in biological cells and tissues. The active materials central to cellular mechanics are cytoskeletal networks, where molecular motor activity drives deformations and remodeling. Here, we investigate deformation modes in actin networks driven by the molecular motor myosin II through quantitative fluorescence microscopy. We examine the deformation anisotropy at different length scales in networks of entangled, cross-linked, and bundled actin. In sparsely cross-linked networks, we find myosin-dependent biaxial buckling modes across length scales. In cross-linked bundled networks, uniaxial contraction is predominate on long length scales, while the uniaxial or biaxial nature of the deformation depends on bundle microstructure at shorter length scales. The anisotropy of deformations may provide insight to regulation of collective behavior in a variety of active materials.
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Affiliation(s)
- Samantha Stam
- Biophysical Sciences Graduate Program, University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
- Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
- James Franck Institute, University of Chicago, Chicago, IL 60637
- Department of Physics, University of Chicago, Chicago, IL 60637
| | - Kimberly L Weirich
- James Franck Institute, University of Chicago, Chicago, IL 60637
- Department of Materials Science & Engineering, Clemson University, Clemson, SC 29634
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23
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Lemma LM, Varghese M, Ross TD, Thomson M, Baskaran A, Dogic Z. Spatio-temporal patterning of extensile active stresses in microtubule-based active fluids. PNAS NEXUS 2023; 2:pgad130. [PMID: 37168671 PMCID: PMC10165807 DOI: 10.1093/pnasnexus/pgad130] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 02/27/2023] [Accepted: 04/03/2023] [Indexed: 05/13/2023]
Abstract
Microtubule-based active fluids exhibit turbulent-like autonomous flows, which are driven by the molecular motor powered motion of filamentous constituents. Controlling active stresses in space and time is an essential prerequisite for controlling the intrinsically chaotic dynamics of extensile active fluids. We design single-headed kinesin molecular motors that exhibit optically enhanced clustering and thus enable precise and repeatable spatial and temporal control of extensile active stresses. Such motors enable rapid, reversible switching between flowing and quiescent states. In turn, spatio-temporal patterning of the active stress controls the evolution of the ubiquitous bend instability of extensile active fluids and determines its critical length dependence. Combining optically controlled clusters with conventional kinesin motors enables one-time switching from contractile to extensile active stresses. These results open a path towards real-time control of the autonomous flows generated by active fluids.
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Affiliation(s)
- Linnea M Lemma
- Department of Physics, Brandeis University, 415 South St., Waltham, 02453 MA, USA
- Department of Physics, University of California, Santa Barbara, 93106 CA, USA
| | - Minu Varghese
- Department of Physics, Brandeis University, 415 South St., Waltham, 02453 MA, USA
| | - Tyler D Ross
- Department of Computing and Mathematical Sciences, California Institute of Technology, 1200 E California Blvd. Pasadena, 91125 CA, USA
| | - Matt Thomson
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, 91125 CA, USA
| | - Aparna Baskaran
- Department of Physics, Brandeis University, 415 South St., Waltham, 02453 MA, USA
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24
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Rønning J, Marchetti MC, Angheluta L. Defect self-propulsion in active nematic films with spatially varying activity. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221229. [PMID: 36816847 PMCID: PMC9929493 DOI: 10.1098/rsos.221229] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 01/24/2023] [Indexed: 06/18/2023]
Abstract
We study the dynamics of topological defects in active nematic films with spatially varying activity and consider two set-ups: (i) a constant activity gradient and (ii) a sharp jump in activity. A constant gradient of extensile (contractile) activity endows the comet-like +1/2 defect with a finite vorticity that drives the defect to align its nose in the direction of decreasing (increasing) gradient. A constant gradient does not, however, affect the known self-propulsion of the +1/2 defect and has no effect on the -1/2 that remains a non-motile particle. A sharp jump in activity acts like a wall that traps the defects, affecting the translational and rotational motion of both charges. The +1/2 defect slows down as it approaches the interface and the net vorticity tends to reorient the defect polarization so that it becomes perpendicular to the interface. The -1/2 defect acquires a self-propulsion towards the activity interface, while the vorticity-induced active torque tends to align the defect to a preferred orientation. This effective attraction of the negative defects to the wall is consistent with the observation of an accumulation of negative topological charge at both active/passive interfaces and physical boundaries.
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Affiliation(s)
- Jonas Rønning
- Njord Centre, Department of Physics, University of Oslo, PO Box 1048, Oslo 0316, Norway
| | - M. Cristina Marchetti
- Department of Physics and Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Luiza Angheluta
- Njord Centre, Department of Physics, University of Oslo, PO Box 1048, Oslo 0316, Norway
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25
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Fazli Z, Naji A. Rectification of polymer translocation through nanopores by nonchiral and chiral active particles. Phys Rev E 2023; 107:024602. [PMID: 36932605 DOI: 10.1103/physreve.107.024602] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/16/2023] [Indexed: 06/18/2023]
Abstract
We study translocation of a flexible polymer chain through a membrane pore under the influence of active forces and steric exclusion using Langevin dynamics simulations within a minimal two-dimensional model. The active forces on the polymer are imparted by nonchiral and chiral active particles that are introduced on one side or both sides of a rigid membrane positioned across the midline of a confining box. We show that the polymer can translocate through the pore to either side of the dividing membrane in the absence of external forcing. Translocation of the polymer to a given side of the membrane is driven (hindered) by an effective pulling (pushing) exerted by the active particles that are present on that side. The effective pulling results from accumulation of active particles around the polymer. This crowding effect signifies persistent motion of active particles causing prolonged detention times for them close to the confining walls and the polymer. The effective pushing that hinders the translocation, on the other hand, results from steric collisions that occur between the polymer and active particles. As a result of the competition between these effective forces, we find a transition between two rectified cis-to-trans and trans-to-cis translocation regimes. This transition is identified by a sharp peak in the average translocation time. The effects of active particles on the transition is studied by analyzing how the translocation peak is regulated by the activity (self-propulsion) strength of these particles, their area fraction, and chirality strength.
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Affiliation(s)
- Zahra Fazli
- School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19538-33511, Iran
- School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19538-33511, Iran
| | - Ali Naji
- School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19538-33511, Iran
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26
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Joshi C, Ray S, Lemma LM, Varghese M, Sharp G, Dogic Z, Baskaran A, Hagan MF. Data-Driven Discovery of Active Nematic Hydrodynamics. PHYSICAL REVIEW LETTERS 2022; 129:258001. [PMID: 36608242 DOI: 10.1103/physrevlett.129.258001] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 11/14/2022] [Indexed: 06/17/2023]
Abstract
Active nematics can be modeled using phenomenological continuum theories that account for the dynamics of the nematic director and fluid velocity through partial differential equations (PDEs). While these models provide a statistical description of the experiments, the relevant terms in the PDEs and their parameters are usually identified indirectly. We adapt a recently developed method to automatically identify optimal continuum models for active nematics directly from spatiotemporal data, via sparse regression of the coarse-grained fields onto generic low order PDEs. After extensive benchmarking, we apply the method to experiments with microtubule-based active nematics, finding a surprisingly minimal description of the system. Our approach can be generalized to gain insights into active gels, microswimmers, and diverse other experimental active matter systems.
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Affiliation(s)
- Chaitanya Joshi
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
- Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155, USA
| | - Sattvic Ray
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Linnea M Lemma
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Minu Varghese
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 USA
| | - Graham Sharp
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Zvonimir Dogic
- Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Aparna Baskaran
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Michael F Hagan
- Department of Physics, Brandeis University, Waltham, Massachusetts 02453, USA
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27
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Topological defect-mediated morphodynamics of active-active interfaces. Proc Natl Acad Sci U S A 2022; 119:e2122494119. [PMID: 36469777 PMCID: PMC9897450 DOI: 10.1073/pnas.2122494119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/10/2022] Open
Abstract
Physical interfaces widely exist in nature and engineering. Although the formation of passive interfaces is well elucidated, the physical principles governing active interfaces remain largely unknown. Here, we combine simulation, theory, and cell-based experiment to investigate the evolution of an active-active interface. We adopt a biphasic framework of active nematic liquid crystals. We find that long-lived topological defects mechanically energized by activity display unanticipated dynamics nearby the interface, where defects perform "U-turns" to keep away from the interface, push the interface to develop local fingers, or penetrate the interface to enter the opposite phase, driving interfacial morphogenesis and cross-interface defect transport. We identify that the emergent interfacial morphodynamics stems from the instability of the interface and is further driven by the activity-dependent defect-interface interactions. Experiments of interacting multicellular monolayers with extensile and contractile differences in cell activity have confirmed our predictions. These findings reveal a crucial role of topological defects in active-active interfaces during, for example, boundary formation and tissue competition that underlie organogenesis and clinically relevant disorders.
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28
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Vafa F. Defect dynamics in active polar fluids vs. active nematics. SOFT MATTER 2022; 18:8087-8097. [PMID: 36239265 DOI: 10.1039/d2sm00830k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Topological defects play a key role in two-dimensional active nematics, and a transient role in two-dimensional active polar fluids. Using a variational method, we study both the transient and long-time behavior of defects in two-dimensional active polar fluids in the limit of strong order and overdamped, compressible flow, and compare the defect dynamics with the corresponding active nematics model studied recently. One result is non-central interactions between defect pairs for active polar fluids, and by extending our analysis to allow orientation dynamics of defects, we find that the orientation of +1 defects, unlike that of ±1/2 defects in active nematics, is not locked to defect positions and relaxes to asters. Moreover, using a scaling argument, we explain the transient feature of active polar defects and show that in the steady state, active polar fluids are either devoid of defects or consist of a single aster. We argue that for contractile (extensile) active nematic systems, +1 vortices (asters) should emerge as bound states of a pair of +1/2 defects, which has been recently observed. Moreover, unlike the polar case, we show that for active nematics, a linear chain of equally spaced bound states of pairs of +1/2 defects can screen the activity term. A common feature in both models is the appearance of +1 defects (elementary in polar and composite in nematic) in the steady state.
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Affiliation(s)
- Farzan Vafa
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, MA 02138, USA.
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29
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Gouveia B, Kim Y, Shaevitz JW, Petry S, Stone HA, Brangwynne CP. Capillary forces generated by biomolecular condensates. Nature 2022; 609:255-264. [PMID: 36071192 DOI: 10.1038/s41586-022-05138-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 07/25/2022] [Indexed: 12/21/2022]
Abstract
Liquid-liquid phase separation and related phase transitions have emerged as generic mechanisms in living cells for the formation of membraneless compartments or biomolecular condensates. The surface between two immiscible phases has an interfacial tension, generating capillary forces that can perform work on the surrounding environment. Here we present the physical principles of capillarity, including examples of how capillary forces structure multiphase condensates and remodel biological substrates. As with other mechanisms of intracellular force generation, for example, molecular motors, capillary forces can influence biological processes. Identifying the biomolecular determinants of condensate capillarity represents an exciting frontier, bridging soft matter physics and cell biology.
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Affiliation(s)
- Bernardo Gouveia
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
| | - Yoonji Kim
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | | | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA. .,The Howard Hughes Medical Institute, Princeton, NJ, USA.
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30
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Vafa F, Mahadevan L. Active Nematic Defects and Epithelial Morphogenesis. PHYSICAL REVIEW LETTERS 2022; 129:098102. [PMID: 36083666 DOI: 10.1103/physrevlett.129.098102] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 04/11/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Inspired by recent experiments that highlight the role of nematic defects in the morphogenesis of epithelial tissues, we develop a minimal framework to study the dynamics of an active curved surface driven by its nematic texture. Allowing the surface to evolve via relaxational dynamics leads to a theory linking nematic defect dynamics, cellular division rates, and Gaussian curvature. Regions of large positive (negative) curvature and positive (negative) growth are colocalized with the presence of positive (negative) defects. In an ex-vivo setting of cultured murine neural progenitor cells, we show that our framework is consistent with the observed cell accumulation at positive defects and depletion at negative defects. In an in-vivo setting, we show that the defect configuration consisting of a bound +1 defect state, which is stabilized by activity, surrounded by two -1/2 defects can create a stationary ring configuration of tentacles, consistent with observations of a basal marine invertebrate Hydra.
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Affiliation(s)
- Farzan Vafa
- Department of Physics, University of California Santa Barbara, Santa Barbara, California 93106, USA
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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31
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Pawale T, Yi S, Wang X, Zhang R, Li X. The fate of liquid crystal topological defects on chemically patterned surfaces during phase transitions. SOFT MATTER 2022; 18:5939-5948. [PMID: 35861160 DOI: 10.1039/d2sm00566b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Controlling topological defects in liquid crystals (LCs) is an essential element in the development of areas such as directed self-assembly and micropatterning materials. However, during the phase transition on confined patterned surfaces, how the morphologies in one liquid crystalline phase change from deformations or defects into another phase is much less known. Here, we examine the fate of defects in a LC confined on a patterned surface during smectic-A-nematic and nematic-isotropic phase transitions, using experiments and simulation analyses. Upon heating from smectic-A to nematic, a Toric focal conical domain (TFCD) melts into a +1 converging boojum defect, which then transitioned into a concentric configuration as temperature increases, attributed to a steeper decrease of the bend and twist modulus compared to splay modulus. During cooling, TFCDs are developed from two distinct pathways depending on the cooling rates. Our continuum simulation recapitulates these transformations and provides elastic constant-based explanations for the two pathways. Although the phase transition pathways of defects are independent of the geometry of the confined patterns, the arrangement of FCDs is highly dependent on the size and shape of the patterns. Taken together, this simple approach offers promising opportunities for tuning the micro- or nano-patterning of topological defects in liquid crystals.
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Affiliation(s)
- Tejal Pawale
- Materials Science and Engineering Department, University of North Texas, Denton, USA.
| | - Shengzhu Yi
- Department of Physics, The Hongkong University of Science and Technology, Hongkong, China.
- Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Xiaowei Wang
- Materials Science and Engineering Department, University of North Texas, Denton, USA.
| | - Rui Zhang
- Department of Physics, The Hongkong University of Science and Technology, Hongkong, China.
| | - Xiao Li
- Materials Science and Engineering Department, University of North Texas, Denton, USA.
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32
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Vafa F, Zhang GH, Nelson DR. Defect absorption and emission for p-atic liquid crystals on cones. Phys Rev E 2022; 106:024704. [PMID: 36109947 DOI: 10.1103/physreve.106.024704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
We investigate the ground-state configurations of two-dimensional liquid crystals with p-fold rotational symmetry (p-atics) on fixed curved surfaces. We focus on the intrinsic geometry and show that isothermal coordinates are particularly convenient as they explicitly encode a geometric contribution to the elastic potential. In the special case of a cone with half-angle β, the apex develops an effective topological charge of -χ, where 2πχ=2π(1-sinβ) is the deficit angle of the cone, and a topological defect of charge σ behaves as if it had an effective topological charge Q_{eff}=(σ-σ^{2}/2) when interacting with the apex. The effective charge of the apex leads to defect absorption and emission at the cone apex as the deficit angle of the cone is varied. For total topological defect charge 1, e.g., imposed by tangential boundary conditions at the edge, we find that for a disk the ground-state configuration consists of p defects each of charge +1/p lying equally spaced on a concentric ring of radius d=(p-1/3p-1)^{1/2p}R, where R is the radius of the disk. In the case of a cone with tangential boundary conditions at the base, we find three types of ground-state configurations as a function of cone angle: (i) for sharp cones, all of the +1/p defects are absorbed by the apex; (ii) at intermediate cone angles, some of the +1/p defects are absorbed by the apex and the rest lie equally spaced along a concentric ring on the flank; and (iii) for nearly flat cones, all of the +1/p defects lie equally spaced along a concentric ring on the flank. Here the defect positions and the absorption transitions depend intricately on p and the deficit angle, which we analytically compute. We check these results with numerical simulations for a set of commensurate cone angles and find excellent agreement.
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Affiliation(s)
- Farzan Vafa
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Grace H Zhang
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - David R Nelson
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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33
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Kumar N, Zhang R, Redford SA, de Pablo JJ, Gardel ML. Catapulting of topological defects through elasticity bands in active nematics. SOFT MATTER 2022; 18:5271-5281. [PMID: 35789364 DOI: 10.1039/d2sm00414c] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Active materials are those in which individual, uncoordinated local stresses drive the material out of equilibrium on a global scale. Examples of such assemblies can be seen across scales from schools of fish to the cellular cytoskeleton and underpin many important biological processes. Synthetic experiments that recapitulate the essential features of such active systems have been the object of study for decades as their simple rules allow us to elucidate the physical underpinnings of collective motion. One system of particular interest has been active nematic liquid crystals (LCs). Because of their well understood passive physics, LCs provide a rich platform to interrogate the effects of active stress. The flows and steady state structures that emerge in an active LCs have been understood to result from a competition between nematic elasticity and the local activity. However most investigations of such phenomena consider only the magnitude of the elastic resistance and not its peculiarities. Here we investigate a nematic liquid crystal and selectively change the ratio of the material's splay and bend elasticities. We show that increases in the nematic's bend elasticity specifically drives the material into an exotic steady state where elongated regions of acute bend distortion or "elasticity bands" dominate the structure and dynamics. We show that these bands strongly influence defect dynamics, including the rapid motion or "catapulting" along the disintegration of one of these bands thus converting bend distortion into defect transport. Thus, we report a novel dynamical state resultant from the competition between nematic elasticity and active stress.
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Affiliation(s)
- Nitin Kumar
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
- Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India
| | - Rui Zhang
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
| | - Steven A Redford
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
- Graduate Program in Biophysical Sciences, The University of Chicago, Chicago, Illinois 60637, USA
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
- Institute for Molecular Engineering, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Margaret L Gardel
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
- Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA
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34
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Lemma B, Mitchell NP, Subramanian R, Needleman DJ, Dogic Z. Active Microphase Separation in Mixtures of Microtubules and Tip-Accumulating Molecular Motors. PHYSICAL REVIEW. X 2022; 12:031006. [PMID: 36643940 PMCID: PMC9835929 DOI: 10.1103/physrevx.12.031006] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Mixtures of filaments and molecular motors form active materials with diverse dynamical behaviors that vary based on their constituents' molecular properties. To develop a multiscale of these materials, we map the nonequilibrium phase diagram of microtubules and tip-accumulating kinesin-4 molecular motors. We find that kinesin-4 can drive either global contractions or turbulentlike extensile dynamics, depending on the concentrations of both microtubules and a bundling agent. We also observe a range of spatially heterogeneous nonequilibrium phases, including finite-sized radial asters, 1D wormlike chains, extended 2D bilayers, and system-spanning 3D active foams. Finally, we describe intricate kinetic pathways that yield microphase separated structures and arise from the inherent frustration between the orientational order of filamentous microtubules and the positional order of tip-accumulating molecular motors. Our work reveals a range of novel active states. It also shows that the form of active stresses is not solely dictated by the properties of individual motors and filaments, but is also contingent on the constituent concentrations and spatial arrangement of motors on the filaments.
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Affiliation(s)
- Bezia Lemma
- Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
| | - Noah P. Mitchell
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
| | - Radhika Subramanian
- Molecular Biology Department, Massachusetts General Hospital Boston, Massachusetts 02114, USA
- Genetics Department, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Daniel J. Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Molecular and Cellular Biology Department, Harvard University, Cambridge, Massachusetts 02138, USA
- Center for Computational Biology, Flatiron Institute, New York, New York 10010, USA
| | - Zvonimir Dogic
- Physics Department, Brandeis University, Waltham, Massachusetts 02453, USA
- Physics Department, University of California, Santa Barbara, California 93106, USA
- Biomolecular Science and Engineering Department, University of California, Santa Barbara, California 93106, USA
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35
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Ardaševa A, Mueller R, Doostmohammadi A. Bridging microscopic cell dynamics to nematohydrodynamics of cell monolayers. SOFT MATTER 2022; 18:4737-4746. [PMID: 35703313 DOI: 10.1039/d2sm00537a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
It is increasingly being realized that liquid-crystalline features can play an important role in the properties and dynamics of cell monolayers. Here, we present a cell-based model of cell layers, based on the phase-field formulation, that connects cell-cell interactions specified at the single cell level to large-scale nematic and hydrodynamic properties of the tissue. In particular, we present a minimal formulation that reproduces the well-known bend and splay hydrodynamic instabilities of the continuum nemato-hydrodynamic formulation of active matter, together with an analytical description of the instability threshold in terms of activity and elasticity of the cells. Furthermore, we provide a quantitative characterisation and comparison of flows and topological defects for extensile and contractile stress generation mechanisms, and demonstrate activity-induced heterogeneity and spontaneous formation of gaps within a confluent monolayer. Together, these results contribute to bridging the gap between cell-scale dynamics and tissue-scale collective cellular organisation.
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Affiliation(s)
| | - Romain Mueller
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, UK
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36
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Sultan SA, R Nejad M, Doostmohammadi A. Quadrupolar active stress induces exotic patterns of defect motion in compressible active nematics. SOFT MATTER 2022; 18:4118-4126. [PMID: 35579323 DOI: 10.1039/d1sm01683k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A wide range of living and artificial active matter exists in close contact with substrates and under strong confinement, where in addition to dipolar active stresses, quadrupolar active stresses can become important. Here, we numerically investigate the impact of quadrupolar non-equilibrium stresses on the emergent patterns of self-organisation in non-momentum conserving active nematics. Our results reveal that beyond having stabilising effects, the quadrupolar active forces can induce various modes of topological defect motion in active nematics. In particular, we find the emergence of both polar and nematic ordering of the defects, as well as new patterns of self-organisation that comprise topological defect chains and transient topological defect asters. The results contribute to further understanding of emergent patterns of collective motion and non-equilibrium self-organisation in active matter.
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Affiliation(s)
- Salik A Sultan
- The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| | - Mehrana R Nejad
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, UK
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37
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Zhang DQ, Li ZY, Li B. Self-rotation regulates interface evolution in biphasic active matter through taming defect dynamics. Phys Rev E 2022; 105:064607. [PMID: 35854599 DOI: 10.1103/physreve.105.064607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Chirality can endow nonequilibrium active matter with unique features and functions. Here, we explore the chiral dynamics in biphasic active nematics composed of self-rotating units that continuously inject energy and angular momentum at the microscale. We show that the self-rotation of units can regularize the boundaries between two phases, rendering sinusoidal-like interfaces, which allow lateral wave propagation and are characterized by chains of ordered antiferromagnetic cross-interface flow vortices. Through the spontaneous coordination of counter-rotating units across the interfaces, topological defects excited by activity are sorted spatiotemporally, where positive defects are locally trapped at the interfaces but, unexpectedly, are transported laterally in a unidirectional rather than wavy mode, whereas inertial negative defects remain spinning in the bulks. Our findings reveal that individual chirality could be harnessed to modulate interfacial morphodynamics in active systems and suggest a potential approach toward controlling topological defects for programmable microfluidics and logic operations.
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Affiliation(s)
- De-Qing Zhang
- Institute of Biomechanics and Medical Engineering, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Zhong-Yi Li
- Institute of Biomechanics and Medical Engineering, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Bo Li
- Institute of Biomechanics and Medical Engineering, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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38
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Sarfati G, Maitra A, Voituriez R, Galas JC, Estevez-Torres A. Crosslinking and depletion determine spatial instabilities in cytoskeletal active matter. SOFT MATTER 2022; 18:3793-3800. [PMID: 35521993 DOI: 10.1039/d2sm00130f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Active gels made of cytoskeletal proteins are valuable materials with attractive non-equilibrium properties such as spatial self-organization and self-propulsion. At least four typical routes to spatial patterning have been reported to date in different types of cytoskeletal active gels: bending and buckling instabilities in extensile systems, and global and local contraction instabilities in contractile gels. Here we report the observation of these four instabilities in a single type of active gel and we show that they are controlled by two parameters: the concentrations of ATP and depletion agent. We demonstrate that as the ATP concentration decreases, the concentration of passive motors increases until the gel undergoes a gelation transition. At this point, buckling is selected against bending, while global contraction is favored over local ones. Our observations are coherent with a hydrodynamic model of a viscoelastic active gel where the filaments are crosslinked with a characteristic time that diverges as the ATP concentration decreases. Our work thus provides a unified view of spatial instabilities in cytoskeletal active matter.
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Affiliation(s)
- Guillaume Sarfati
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin, (LJP), F-75005 Paris, France.
| | - Ananyo Maitra
- Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, CY Cergy Paris, Université, F-95302 Cergy-Pontoise Cedex, France
| | - Raphael Voituriez
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin, (LJP), F-75005 Paris, France.
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, (LPTMC), F-75005 Paris, France
| | - Jean-Christophe Galas
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin, (LJP), F-75005 Paris, France.
| | - André Estevez-Torres
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin, (LJP), F-75005 Paris, France.
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39
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Guillamat P, Blanch-Mercader C, Pernollet G, Kruse K, Roux A. Integer topological defects organize stresses driving tissue morphogenesis. NATURE MATERIALS 2022; 21:588-597. [PMID: 35145258 PMCID: PMC7612693 DOI: 10.1038/s41563-022-01194-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 01/03/2022] [Indexed: 05/05/2023]
Abstract
Tissues acquire function and shape via differentiation and morphogenesis. Both processes are driven by coordinating cellular forces and shapes at the tissue scale, but general principles governing this interplay remain to be discovered. Here we report that self-organization of myoblasts around integer topological defects, namely spirals and asters, suffices to establish complex multicellular architectures. In particular, these arrangements can trigger localized cell differentiation or, alternatively, when differentiation is inhibited, they can drive the growth of swirling protrusions. Both localized differentiation and growth of cellular vortices require specific stress patterns. By analysing the experimental velocity and orientational fields through active gel theory, we show that integer topological defects can generate force gradients that concentrate compressive stresses. We reveal these gradients by assessing spatial changes in nuclear volume and deformations of elastic pillars. We propose integer topological defects as mechanical organizing centres controlling differentiation and morphogenesis.
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Affiliation(s)
- Pau Guillamat
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Carles Blanch-Mercader
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
- Department of Theoretical Physics, University of Geneva, Geneva, Switzerland
| | | | - Karsten Kruse
- Department of Biochemistry, University of Geneva, Geneva, Switzerland.
- Department of Theoretical Physics, University of Geneva, Geneva, Switzerland.
- NCCR for Chemical Biology, University of Geneva, Geneva, Switzerland.
| | - Aurélien Roux
- Department of Biochemistry, University of Geneva, Geneva, Switzerland.
- NCCR for Chemical Biology, University of Geneva, Geneva, Switzerland.
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40
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Zhang GH, Nelson DR. Fractional defect charges in liquid crystals with p-fold rotational symmetry on cones. Phys Rev E 2022; 105:054703. [PMID: 35706319 DOI: 10.1103/physreve.105.054703] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 03/30/2022] [Indexed: 06/15/2023]
Abstract
Conical surfaces, with a δ function of Gaussian curvature at the apex, are perhaps the simplest example of geometric frustration. We study two-dimensional liquid crystals with p-fold rotational symmetry (p-atics) on the surfaces of cones. For free boundary conditions at the base, we find both the ground state(s) and a discrete ladder of metastable states as a function of both the cone angle and the liquid crystal symmetry p. We find that these states are characterized by a set of fractional defect charges at the apex and that the ground states are in general frustrated due to effects of parallel transport along the azimuthal direction of the cone. We check our predictions for the ground-state energies numerically for a set of commensurate cone angles (corresponding to a set of commensurate Gaussian curvatures concentrated at the cone apex), whose surfaces can be polygonized as a perfect triangular or square mesh, and find excellent agreement with our theoretical predictions.
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Affiliation(s)
- Grace H Zhang
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - David R Nelson
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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41
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Bickmann J, Bröker S, Jeggle J, Wittkowski R. Analytical approach to chiral active systems: suppressed phase separation of interacting Brownian circle swimmers. J Chem Phys 2022; 156:194904. [DOI: 10.1063/5.0085122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We consider chirality in active systems by exemplarily studying the phase behavior of planar systems of interacting Brownian circle swimmers with a spherical shape. For this purpose, we derive a predictive field theory that is able to describe the collective dynamics of circle swimmers. The theory yields a mapping between circle swimmers and noncircling active Brownian particles and predicts that the angular propulsion of the particles leads to a suppression of their motility-induced phase separation, being in line with recent simulation results. In addition, the theory provides analytical expressions for the spinodal corresponding to the onset of motility-induced phase separation and the associated critical point as well as for their dependence on the angular propulsion of the circle swimmers. We confirm our findings by Brownian dynamics simulations. The agreement between results from theory and simulations is found to be good.
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Affiliation(s)
- Jens Bickmann
- Westfälische Wilhelms-Universität Münster Fachbereich 11 Physik, Germany
| | - Stephan Bröker
- Westfälische Wilhelms-Universität Münster Fachbereich 11 Physik, Germany
| | - Julian Jeggle
- Westfälische Wilhelms-Universität Münster Fachbereich 11 Physik, Germany
| | - Raphael Wittkowski
- Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster Fachbereich 11 Physik, Germany
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42
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Balasubramaniam L, Mège RM, Ladoux B. Active nematics across scales from cytoskeleton organization to tissue morphogenesis. Curr Opin Genet Dev 2022; 73:101897. [DOI: 10.1016/j.gde.2021.101897] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/07/2021] [Accepted: 12/21/2021] [Indexed: 11/28/2022]
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Filopodia rotate and coil by actively generating twist in their actin shaft. Nat Commun 2022; 13:1636. [PMID: 35347113 PMCID: PMC8960877 DOI: 10.1038/s41467-022-28961-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 02/10/2022] [Indexed: 12/19/2022] Open
Abstract
Filopodia are actin-rich structures, present on the surface of eukaryotic cells. These structures play a pivotal role by allowing cells to explore their environment, generate mechanical forces or perform chemical signaling. Their complex dynamics includes buckling, pulling, length and shape changes. We show that filopodia additionally explore their 3D extracellular space by combining growth and shrinking with axial twisting and buckling. Importantly, the actin core inside filopodia performs a twisting or spinning motion which is observed for a range of cell types spanning from earliest development to highly differentiated tissue cells. Non-equilibrium physical modeling of actin and myosin confirm that twist is an emergent phenomenon of active filaments confined in a narrow channel which is supported by measured traction forces and helical buckles that can be ascribed to accumulation of sufficient twist. These results lead us to conclude that activity induced twisting of the actin shaft is a general mechanism underlying fundamental functions of filopodia. The authors show how tubular surface structures in all cell types, have the ability to twist and perform rotary sweeping motion to explore the extracellular environment. This has implications for migration, sensing and cell communication.
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44
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Schimming CD, Viñals J. Singularity identification for the characterization of topology, geometry, and motion of nematic disclination lines. SOFT MATTER 2022; 18:2234-2244. [PMID: 35234228 DOI: 10.1039/d1sm01584b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We introduce a characterization of disclination lines in three dimensional nematic liquid crystals as a tensor quantity related to the so called rotation vector around the line. This quantity is expressed in terms of the nematic tensor order parameter Q, and shown to decompose as a dyad involving the tangent vector to the disclination line and the rotation vector. Further, we derive a kinematic law for the velocity of disclination lines by connecting this tensor to a topological charge density as in the Halperin-Mazenko description of defects in vector models. Using this framework, analytical predictions for the velocity of interacting line disclinations and of self-annihilating disclination loops are given and confirmed through numerical computation.
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Affiliation(s)
- Cody D Schimming
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Jorge Viñals
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
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45
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Zhang R, Mozaffari A, de Pablo JJ. Logic operations with active topological defects. SCIENCE ADVANCES 2022; 8:eabg9060. [PMID: 35196084 PMCID: PMC8865799 DOI: 10.1126/sciadv.abg9060] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 12/30/2021] [Indexed: 05/31/2023]
Abstract
Logic operations performed by semiconductor-based transistors are the basis of modern computing. There is considerable interest in creating autonomous materials systems endowed with the capability to make decisions. In this work, we introduce the concept of using topological defects in active matter to perform logic operations. When an extensile active stress in a nematic liquid crystal is turned on, +1/2 defects can self-propel, in analogy to electron transport under a voltage gradient. By relying on hydrodynamic simulations of active nematics, we demonstrate that patterns of activity, when combined with surfaces imparting certain orientations, can be used to control the formation and transport of +1/2 defects. We further show that asymmetric high- and low-activity patterns can be used to create effective defect gates, tunnels, and amplifiers. The proposed active systems offer the potential to perform computations and transmit information in active soft materials, including actin-, tubulin-, and cell-based systems.
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Affiliation(s)
- Rui Zhang
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
| | - Ali Mozaffari
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- OpenEye Scientific Software, Inc., 9 Bisbee Court Suite D, Santa Fe, New Mexico 87508, USA
| | - Juan J. de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
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46
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Rønning J, Marchetti CM, Bowick MJ, Angheluta L. Flow around topological defects in active nematic films. Proc Math Phys Eng Sci 2022; 478:20210879. [PMID: 35153617 PMCID: PMC8791053 DOI: 10.1098/rspa.2021.0879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 12/22/2021] [Indexed: 11/14/2022] Open
Abstract
We study the active flow around isolated defects and the self-propulsion velocity of +1/2 defects in an active nematic film with both viscous dissipation (with viscosity η) and frictional damping Γ with a substrate. The interplay between these two dissipation mechanisms is controlled by the hydrodynamic dissipation length ℓd=η/Γ that screens the flows. For an isolated defect, in the absence of screening from other defects, the size of the shear vorticity around the defect is controlled by the system size R. In the presence of friction that leads to a finite value of ℓd, the vorticity field decays to zero on the lengthscales larger than ℓd. We show that the self-propulsion velocity of +1/2 defects grows with R in small systems where R<ℓd, while in the infinite system limit or when R≫ℓd, it approaches a constant value determined by ℓd.
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Affiliation(s)
- Jonas Rønning
- Njord Centre, Department of Physics, University of Oslo, PO Box 1048, Oslo 0316, Norway
| | - Cristina M Marchetti
- Department of Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mark J Bowick
- Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Luiza Angheluta
- Njord Centre, Department of Physics, University of Oslo, PO Box 1048, Oslo 0316, Norway
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47
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Del Junco C, Estevez-Torres A, Maitra A. Front speed and pattern selection of a propagating chemical front in an active fluid. Phys Rev E 2022; 105:014602. [PMID: 35193207 DOI: 10.1103/physreve.105.014602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 11/24/2021] [Indexed: 01/18/2023]
Abstract
Spontaneous pattern formation in living systems is driven by reaction-diffusion chemistry and active mechanics. The feedback between chemical and mechanical forces is often essential to robust pattern formation, yet it remains poorly understood in general. In this analytical and numerical paper, we study an experimentally motivated minimal model of coupling between reaction-diffusion and active matter: a propagating front of an autocatalytic and stress-generating species. In the absence of activity, the front is described by the well-studied Kolmogorov, Petrovsky, and Piskunov equation. We find that front propagation is maintained even in active systems, with crucial differences: an extensile stress increases the front speed beyond a critical magnitude of the stress, while a contractile stress has no effect on the front speed but can generate a periodic instability in the high-concentration region behind the front. We expect our results to be useful in interpreting pattern formation in active systems with mechanochemical coupling in vivo and in vitro.
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Affiliation(s)
- Clara Del Junco
- Department of Chemistry and Department of Sociology, University of Chicago, Chicago, Illinois 60637, USA and Wesleyan University Library, Middletown, Connecticut 06459, USA
| | - André Estevez-Torres
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin (LJP), F-75005, Paris
| | - Ananyo Maitra
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin (LJP), F-75005, Paris and Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, CY Cergy Paris Université, F-95302 Cergy-Pontoise Cedex, France
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48
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Senoussi A, Galas JC, Estevez-Torres A. Programmed mechano-chemical coupling in reaction-diffusion active matter. SCIENCE ADVANCES 2021; 7:eabi9865. [PMID: 34919433 PMCID: PMC8682988 DOI: 10.1126/sciadv.abi9865] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Embryo morphogenesis involves a complex combination of self-organization mechanisms that generate a great diversity of patterns. However, classical in vitro patterning experiments explore only one self-organization mechanism at a time, thus missing coupling effects. Here, we conjugate two major out-of-equilibrium patterning mechanisms—reaction-diffusion and active matter—by integrating dissipative DNA/enzyme reaction networks within an active gel composed of cytoskeletal motors and filaments. We show that the strength of the flow generated by the active gel controls the mechano-chemical coupling between the two subsystems. This property was used to engineer a synthetic material where contractions trigger chemical reaction networks both in time and space, thus mimicking key aspects of the polarization mechanism observed in C. elegans oocytes. We anticipate that reaction-diffusion active matter will promote the investigation of mechano-chemical transduction and the design of new materials with life-like properties.
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49
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Thijssen K, Kusters GLA, Doostmohammadi A. Activity-induced instabilities of brain organoids. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:147. [PMID: 34874504 PMCID: PMC8651611 DOI: 10.1140/epje/s10189-021-00149-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 11/15/2021] [Indexed: 05/07/2023]
Abstract
We present an analytical and numerical investigation of the activity-induced hydrodynamic instabilities in model brain organoids. While several mechanisms have been introduced to explain the experimental observation of surface instabilities in brain organoids, the role of activity has been largely overlooked. Our results show that the active stress generated by the cells can be a, previously overlooked, contributor to the emergence of surface deformations in brain organoids.
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Affiliation(s)
- Kristian Thijssen
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Rd, CB2 1EW, Cambridge, UK.
| | - Guido L A Kusters
- Department of Applied physics, Eindhoven University of Technology, Eindhoven, The Netherlands
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Abstract
Colloidal self-assembly refers to a solution-processed assembly of nanometer-/micrometer-sized, well-dispersed particles into secondary structures, whose collective properties are controlled by not only nanoparticle property but also the superstructure symmetry, orientation, phase, and dimension. This combination of characteristics makes colloidal superstructures highly susceptible to remote stimuli or local environmental changes, representing a prominent platform for developing stimuli-responsive materials and smart devices. Chemists are achieving even more delicate control over their active responses to various practical stimuli, setting the stage ready for fully exploiting the potential of this unique set of materials. This review addresses the assembly of colloids into stimuli-responsive or smart nanostructured materials. We first delineate the colloidal self-assembly driven by forces of different length scales. A set of concepts and equations are outlined for controlling the colloidal crystal growth, appreciating the importance of particle connectivity in creating responsive superstructures. We then present working mechanisms and practical strategies for engineering smart colloidal assemblies. The concepts underpinning separation and connectivity control are systematically introduced, allowing active tuning and precise prediction of the colloidal crystal properties in response to external stimuli. Various exciting applications of these unique materials are summarized with a specific focus on the structure-property correlation in smart materials and functional devices. We conclude this review with a summary of existing challenges in colloidal self-assembly of smart materials and provide a perspective on their further advances to the next generation.
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Affiliation(s)
- Zhiwei Li
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Qingsong Fan
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Yadong Yin
- Department of Chemistry, University of California, Riverside, California 92521, United States
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