1
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Shaik VA, Elfring GJ. Densitaxis: Active particle motion in density gradients. Proc Natl Acad Sci U S A 2024; 121:e2405466121. [PMID: 38935563 PMCID: PMC11228529 DOI: 10.1073/pnas.2405466121] [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: 03/15/2024] [Accepted: 05/31/2024] [Indexed: 06/29/2024] Open
Abstract
Organisms often swim through density-stratified fluids. Here, we investigate the dynamics of active particles swimming in fluid density gradients and report theoretical evidence of taxis as a result of these gradients (densitaxis). Specifically, we calculate the effect of density stratification on the dynamics of a force- and torque-free spherical squirmer and show that density gradients induce reorientation that tends to align swimming either parallel or normal to the gradient depending on the swimming gait. In particular, swimmers that propel by generating thrust in the front (pullers) rotate to swim parallel to gradients and hence display (positive or negative) densitaxis, while swimmers that propel by generating thrust in the back (pushers) rotate to swim normal to the gradients. This work could be useful to understand the motion of marine organisms in ocean or be leveraged to sort or organize a suspension of active particles by modulating density gradients.
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Affiliation(s)
- Vaseem A Shaik
- Department of Mechanical Engineering, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Gwynn J Elfring
- Department of Mechanical Engineering, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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2
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Liu Z, Chao Y, Zheng Z, Zhu L. Spontaneous oscillation of an active filament under viscosity gradients. SOFT MATTER 2024; 20:3845-3853. [PMID: 38651457 DOI: 10.1039/d4sm00095a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
We investigate the effects of uniform viscosity gradients on the spontaneous oscillations of an elastic, active filament in viscous fluids. Combining numerical simulations and linear stability analysis, we demonstrate that a viscosity gradient increasing from the filament's base to tip destabilises the system, facilitating its self-oscillation. This effect is elucidated through a reduced-order model, highlighting the delicate balance between destabilising active forces and stabilising viscous forces. Additionally, we reveal that while a perpendicular viscosity gradient to the filament's orientation minimally affects instability, it induces asymmetric ciliary beating, thus generating a net flow along the gradient. Our findings offer new insights into the complex behaviours of biological and artificial filaments in complex fluid environments, contributing to the broader understanding of filament dynamics in heterogeneous viscous media.
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Affiliation(s)
- Zhaorong Liu
- Department of Mechanical Engineering, National University of Singapore, 117575, Singapore.
| | - Youchuang Chao
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China
| | - Zhijun Zheng
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, 230027, China
| | - Lailai Zhu
- Department of Mechanical Engineering, National University of Singapore, 117575, Singapore.
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3
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Eswaran P, Mishra S. Synchronized rotations of active particles on chemical substrates. SOFT MATTER 2024; 20:2592-2599. [PMID: 38416156 DOI: 10.1039/d3sm00452j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Many microorganisms use chemical 'signaling' - a quintessential self-organizing strategy in non-equilibrium - that can induce spontaneous aggregation and coordinated motion. Using synthetic signaling as a design principle, we construct a minimal model of active Brownian particles (ABPs) having soft repulsive interactions on a chemically quenched patterned substrate. The interplay between chemo-phoretic interactions and activity is numerically investigated for a proposed variant of the Keller-Segel model for chemotaxis. Such competition not only results in a chemo-motility-induced phase-separated state, but also results in a new cohesive clustering phase with synchronized rotations. Our results suggest that rotational order can emerge in systems by virtue of activity and repulsive interactions alone without an explicit alignment interaction. These rotations can also be exploited by designing mechanical devices that can generate reorienting torques using active particles.
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Affiliation(s)
- Pathma Eswaran
- Department of Physics, Indian Institute of Technology (BHU), Varanasi, 221005, India.
| | - Shradha Mishra
- Department of Physics, Indian Institute of Technology (BHU), Varanasi, 221005, India.
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4
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Théry A, Chamolly A, Lauga E. Controlling Confined Collective Organization with Taxis. PHYSICAL REVIEW LETTERS 2024; 132:108301. [PMID: 38518318 DOI: 10.1103/physrevlett.132.108301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 11/30/2023] [Accepted: 01/31/2024] [Indexed: 03/24/2024]
Abstract
Biased locomotion is a common feature of microorganisms, but little is known about its impact on self-organization. Inspired by recent experiments showing a transition to large-scale flows, we study theoretically the dynamics of magnetotactic bacteria confined to a drop. We reveal two symmetry-breaking mechanisms (one local chiral and one global achiral) leading to self-organization into global vortices and a net torque exerted on the drop. The collective behavior is ultimately controlled by the swimmers' microscopic chirality and, strikingly, the system can exhibit oscillations and memorylike features.
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Affiliation(s)
- Albane Théry
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
- Department of Mathematics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Alexander Chamolly
- Institut Pasteur, Université de Paris, CNRS UMR3738, Developmental and Stem Cell Biology Department, F-75015 Paris, France
- Laboratoire de Physique de l'Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, F-75005 Paris, France
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
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5
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Mo C, Fu Q, Bian X. Chemotaxis of an elastic flagellated microrobot. Phys Rev E 2023; 108:044408. [PMID: 37978695 DOI: 10.1103/physreve.108.044408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/29/2023] [Indexed: 11/19/2023]
Abstract
Machine learning algorithms offer a tool to boost mobility and flexibility of a synthetic microswimmer, hence may help us design truly smart microrobots. In this work, we design a two-gait microrobot swimming in circular or helical trajectory. It utilizes the coupling between flagellum elasticity and resistive force to change the characteristics of swimming trajectory. Leveraging a deep reinforcement learning (DRL) approach, we show that the microrobot can self-learn chemotactic motion autonomously (without heuristics) using only several current and historical chemoattractant concentration and curvature information. The learned strategy is more efficient than a human-devised shortsighted strategy and can be further greatly improved in a stochastic environment. Furthermore, in the helical trajectory case, if additional heuristic information of direction is supplemented to evaluate the strategy during the learning process, then a highly efficient strategy can be discovered by the DRL. The microrobot can quickly align the helix vector to the gradient direction using just several smart sequential gait switchings. The success for the efficient strategies depends on how much historical information is provided and also the steering angle step size of the microrobot. Our results provide useful guidance for the design and smart maneuver of synthetic spermlike microswimmers.
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Affiliation(s)
- Chaojie Mo
- Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo 315100, People's Republic of China and State Key Laboratory of Fluid Power and Mechatronic Systems, Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Qingfei Fu
- School of Astronautics, Beihang University, Beijing 100191, People's Republic of China and Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo 315100, People's Republic of China
| | - Xin Bian
- State Key Laboratory of Fluid Power and Mechatronic Systems, Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
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6
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Feng K, Ureña Marcos JC, Mukhopadhyay AK, Niu R, Zhao Q, Qu J, Liebchen B. Self-Solidifying Active Droplets Showing Memory-Induced Chirality. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2300866. [PMID: 37526332 PMCID: PMC10520641 DOI: 10.1002/advs.202300866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 05/20/2023] [Indexed: 08/02/2023]
Abstract
Most synthetic microswimmers do not reach the autonomy of their biological counterparts in terms of energy supply and diversity of motions. Here, this work reports the first all-aqueous droplet swimmer powered by self-generated polyelectrolyte gradients, which shows memory-induced chirality while self-solidifying. An aqueous solution of surface tension-lowering polyelectrolytes self-solidifies on the surface of acidic water, during which polyelectrolytes are gradually emitted into the surrounding water and induce linear self-propulsion via spontaneous symmetry breaking. The low diffusion coefficient of the polyelectrolytes leads to long-lived chemical trails which cause memory effects that drive a transition from linear to chiral motion without requiring any imposed symmetry breaking. The droplet swimmer is capable of highly efficient removal (up to 85%) of uranium from aqueous solutions within 90 min, benefiting from self-propulsion and flow-induced mixing. These results provide a route to fueling self-propelled agents which can autonomously perform chiral motion and collect toxins.
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Affiliation(s)
- Kai Feng
- Key Laboratory of Material Chemistry for Energy Conversion and StorageMinistry of EducationSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan430074China
| | | | - Aritra K. Mukhopadhyay
- Institut für Physik Kondensierter MaterieTechnische Universität Darmstadt64289DarmstadtGermany
| | - Ran Niu
- Key Laboratory of Material Chemistry for Energy Conversion and StorageMinistry of EducationSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan430074China
| | - Qiang Zhao
- Key Laboratory of Material Chemistry for Energy Conversion and StorageMinistry of EducationSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan430074China
| | - Jinping Qu
- Key Laboratory of Material Chemistry for Energy Conversion and StorageMinistry of EducationSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan430074China
| | - Benno Liebchen
- Institut für Physik Kondensierter MaterieTechnische Universität Darmstadt64289DarmstadtGermany
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Ureña Marcos JC, Liebchen B. Inverted Sedimentation of Active Particles in Unbiased ac Fields. PHYSICAL REVIEW LETTERS 2023; 131:038201. [PMID: 37540873 DOI: 10.1103/physrevlett.131.038201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 06/26/2023] [Indexed: 08/06/2023]
Abstract
Gaining control over the motion of active particles is crucial for applications ranging from targeted cargo delivery to nanomedicine. While much progress has been made recently to control active motion based on external forces, flows, or gradients in concentration or light intensity, which all have a well-defined direction or bias, little is known about how to steer active particles in situations where no permanent bias can be realized. Here, we show that ac fields with a vanishing time average provide an alternative route to steering active particles. We exemplify this route for inertial active particles in a gravitational field, observing that a substantial fraction of them persistently travels in the upward direction upon switching on the ac field, resulting in an inverted sedimentation profile at the top wall of a confining container. Our results offer a generic control principle that could be used in the future to steer active motion, direct collective behaviors, and purify mixtures.
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Affiliation(s)
- José Carlos Ureña Marcos
- Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstraße 8, 64289 Darmstadt, Germany
| | - Benno Liebchen
- Institut für Physik Kondensierter Materie, Technische Universität Darmstadt, Hochschulstraße 8, 64289 Darmstadt, Germany
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8
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Dhatt-Gauthier K, Livitz D, Wu Y, Bishop KJM. Accelerating the Design of Self-Guided Microrobots in Time-Varying Magnetic Fields. JACS AU 2023; 3:611-627. [PMID: 37006772 PMCID: PMC10052236 DOI: 10.1021/jacsau.2c00499] [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: 09/12/2022] [Revised: 02/23/2023] [Accepted: 02/24/2023] [Indexed: 06/19/2023]
Abstract
Mobile robots combine sensory information with mechanical actuation to move autonomously through structured environments and perform specific tasks. The miniaturization of such robots to the size of living cells is actively pursued for applications in biomedicine, materials science, and environmental sustainability. Existing microrobots based on field-driven particles rely on knowledge of the particle position and the target destination to control particle motion through fluid environments. Often, however, these external control strategies are challenged by limited information and global actuation where a common field directs multiple robots with unknown positions. In this Perspective, we discuss how time-varying magnetic fields can be used to encode the self-guided behaviors of magnetic particles conditioned on local environmental cues. Programming these behaviors is framed as a design problem: we seek to identify the design variables (e.g., particle shape, magnetization, elasticity, stimuli-response) that achieve the desired performance in a given environment. We discuss strategies for accelerating the design process using automated experiments, computational models, statistical inference, and machine learning approaches. Based on the current understanding of field-driven particle dynamics and existing capabilities for particle fabrication and actuation, we argue that self-guided microrobots with potentially transformative capabilities are close at hand.
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9
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Hosaka Y, Andelman D, Komura S. Pair dynamics of active force dipoles in an odd-viscous fluid. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:18. [PMID: 36947274 DOI: 10.1140/epje/s10189-023-00265-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
We discuss the lateral dynamics of two active force dipoles, which interact with each other via hydrodynamic interactions in a thin fluid layer that is active and chiral. The fluid layer is modeled as a two-dimensional (2D) compressible fluid with an odd viscosity, while the force dipole (representing an active protein or enzyme) induces a dipolar flow. Taking into account the momentum decay in the 2D fluid, we obtain analytically the mobility tensor that depends on the odd viscosity and includes nonreciprocal hydrodynamic interactions. We find that the particle pair shows spiral behavior due to the transverse flow induced by the odd viscosity. When the magnitude of the odd viscosity is large as compared with the shear viscosity, two types of oscillatory behaviors are seen. One of them can be understood as arising from closed orbits in dynamical systems, and its circular trajectories are determined by the ratio between the magnitude of the odd viscosity and the force dipole. In addition, the phase diagrams of the particle dipolar angles are obtained numerically. Our findings reveal that the nonreciprocal response leads to complex dynamics of active particles embedded in an active fluid with odd viscosity.
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Affiliation(s)
- Yuto Hosaka
- Max Planck Institute for Dynamics and Self-Organization (MPI DS), Am Faßberg 17, 37077, Göttingen, Germany
| | - David Andelman
- School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, 69978, Tel Aviv, Israel
| | - Shigeyuki Komura
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, 325001, Zhejiang, China.
- Oujiang Laboratory, Wenzhou, 325000, Zhejiang, China.
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Tokyo, 192-0397, Japan.
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10
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Nsamela A, Garcia Zintzun AI, Montenegro-Johnson TD, Simmchen J. Colloidal Active Matter Mimics the Behavior of Biological Microorganisms-An Overview. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2202685. [PMID: 35971193 DOI: 10.1002/smll.202202685] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/18/2022] [Indexed: 06/15/2023]
Abstract
This article provides a review of the recent development of biomimicking behaviors in active colloids. While the behavior of biological microswimmers is undoubtedly influenced by physics, it is frequently guided and manipulated by active sensing processes. Understanding the respective influences of the surrounding environment can help to engineering the desired response also in artificial swimmers. More often than not, the achievement of biomimicking behavior requires the understanding of both biological and artificial microswimmers swimming mechanisms and the parameters inducing mechanosensory responses. The comparison of both classes of microswimmers provides with analogies in their dependence on fuels, interaction with boundaries and stimuli induced motion, or taxis.
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Affiliation(s)
- Audrey Nsamela
- Chair of Physical Chemistry, TU Dresden, 01069, Dresden, Germany
- Elvesys SAS, 172 Rue de Charonne, Paris, 75011, France
| | | | | | - Juliane Simmchen
- Chair of Physical Chemistry, TU Dresden, 01069, Dresden, Germany
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11
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Ji F, Wu Y, Pumera M, Zhang L. Collective Behaviors of Active Matter Learning from Natural Taxes Across Scales. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2203959. [PMID: 35986637 DOI: 10.1002/adma.202203959] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/23/2022] [Indexed: 06/15/2023]
Abstract
Taxis orientation is common in microorganisms, and it provides feasible strategies to operate active colloids as small-scale robots. Collective taxes involve numerous units that collectively perform taxis motion, whereby the collective cooperation between individuals enables the group to perform efficiently, adaptively, and robustly. Hence, analyzing and designing collectives is crucial for developing and advancing microswarm toward practical or clinical applications. In this review, natural taxis behaviors are categorized and synthetic microrobotic collectives are discussed as bio-inspired realizations, aiming at closing the gap between taxis strategies of living creatures and those of functional active microswarms. As collective behaviors emerge within a group, the global taxis to external stimuli guides the group to conduct overall tasks, whereas the local taxis between individuals induces synchronization and global patterns. By encoding the local orientations and programming the global stimuli, various paradigms can be introduced for coordinating and controlling such collective microrobots, from the viewpoints of fundamental science and practical applications. Therefore, by discussing the key points and difficulties associated with collective taxes of different paradigms, this review potentially offers insights into mimicking natural collective behaviors and constructing intelligent microrobotic systems for on-demand control and preassigned tasks.
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Affiliation(s)
- Fengtong Ji
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, 999077, China
| | - Yilin Wu
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, 999077, China
| | - Martin Pumera
- Faculty of Electrical Engineering and Computer Science, VSB - Technical University of Ostrava, 17. listopadu 2172/15, Ostrava, 70800, Czech Republic
- Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea
| | - Li Zhang
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, 999077, China
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12
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Gong J, Shaik VA, Elfring GJ. Active particles crossing sharp viscosity gradients. Sci Rep 2023; 13:596. [PMID: 36631505 PMCID: PMC9834246 DOI: 10.1038/s41598-023-27423-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 12/29/2022] [Indexed: 01/13/2023] Open
Abstract
Active particles (living or synthetic) often move through inhomogeneous environments, such as gradients in light, heat or nutrient concentration, that can lead to directed motion (or taxis). Recent research has explored inhomogeneity in the rheological properties of a suspending fluid, in particular viscosity, as a mechanical (rather than biological) mechanism for taxis. Theoretical and experimental studies have shown that gradients in viscosity can lead to reorientation due to asymmetric viscous forces. In particular, recent experiments with Chlamydomonas Reinhardtii algae swimming across sharp viscosity gradients have observed that the microorganisms are redirected and scattered due to the viscosity change. Here we develop a simple theoretical model to explain these experiments. We model the swimmers as spherical squirmers and focus on small, but sharp, viscosity changes. We derive a law, analogous to Snell's law of refraction, that governs the orientation of active particles in the presence of a viscosity interface. Theoretical predictions show good agreement with experiments and provide a mechanistic understanding of the observed reorientation process.
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Affiliation(s)
- Jiahao Gong
- Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, BC, V6T 1Z2, Canada
| | - Vaseem A Shaik
- Department of Mechanical Engineering, Institute of Applied Mathematics, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Gwynn J Elfring
- Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, BC, V6T 1Z2, Canada. .,Department of Mechanical Engineering, Institute of Applied Mathematics, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
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13
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Chepizhko O, Franosch T. Resonant Diffusion of a Gravitactic Circle Swimmer. PHYSICAL REVIEW LETTERS 2022; 129:228003. [PMID: 36493425 DOI: 10.1103/physrevlett.129.228003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 08/16/2022] [Accepted: 10/07/2022] [Indexed: 06/17/2023]
Abstract
We investigate the dynamics of a single chiral active particle subject to an external torque due to the presence of a gravitational field. Our computer simulations reveal an arbitrarily strong increase of the long-time diffusivity of the gravitactic agent when the external torque approaches the intrinsic angular drift. We provide analytic expressions for the mean-square displacement in terms of eigenfunctions and eigenvalues of the noisy-driven-pendulum problem. The pronounced maximum in the diffusivity is then rationalized by the vanishing of the lowest eigenvalues of the Fokker-Planck equation for the angular motion as the rotational diffusion decreases and the underlying classical bifurcation is approached. A simple harmonic-oscillator picture for the barrier-dominated motion provides a quantitative description for the onset of the resonance while its range of validity is determined by the crossover to a critical-fluctuation-dominated regime.
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Affiliation(s)
- Oleksandr Chepizhko
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria
| | - Thomas Franosch
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria
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14
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Abstract
Control of self-propelled particles is central to the development of many microrobotic technologies, from dynamically reconfigurable materials to advanced lab-on-a-chip systems. However, there are few physical principles by which particle trajectories can be specified and can be used to generate a wide range of behaviors. Within the field of ray optics, a single principle for controlling the trajectory of light─Snell's law─yields an intuitive framework for engineering a broad range of devices, from microscopes to cameras and telescopes. Here we show that the motion of self-propelled particles gliding across a resistance discontinuity is governed by a variant of Snell's law, and develop a corresponding ray optics for gliders. Just as the ratio of refractive indexes sets the path of a light ray, the ratio of resistance coefficients is shown to determine the trajectories of gliders. The magnitude of refraction depends on the glider's shape, in particular its aspect ratio, which serves as an analogue to the wavelength of light. This enables the demixing of a polymorphic, many-shaped, beam of gliders into distinct monomorphic, single-shaped, beams through a friction prism. In turn, beams of monomorphic gliders can be focused by spherical and gradient friction lenses. Alternatively, the critical angle for total internal reflection can be used to create shape-selective glider traps. Overall our work suggests that furthering the analogy between light and microscopic gliders may be used for sorting, concentrating, and analyzing self-propelled particles.
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Affiliation(s)
- Tyler D Ross
- Department of Computing and Mathematical Sciences, California Institute of Technology, Pasadena, California91125, United States
| | - Dino Osmanović
- Center for the Physics of Living Systems, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - John F Brady
- Divisions of Chemistry & Chemical Engineering and Engineering & Applied Science, California Institute of Technology, Pasadena, California91125, United States
| | - Paul W K Rothemund
- Department of Computing and Mathematical Sciences, California Institute of Technology, Pasadena, California91125, United States
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15
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Active Colloids on Fluid Interfaces. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2022.101629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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16
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A theoretical understanding of ionic current through a nanochannel driven by a viscosity gradient. J Colloid Interface Sci 2022; 628:545-555. [PMID: 36007419 DOI: 10.1016/j.jcis.2022.07.174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 11/24/2022]
Abstract
HYPOTHESIS Different thermodynamic forces owing to the gradient of temperature, electrical potential, or concentration can drive ionic current through charged membranes. It has been recently shown that a viscosity gradient can drive an electrical current through a negatively charged nanochannel (Wiener and Stein, arXiv: 1807.09106). A model description of this phenomenon, based on the Maxwell-Stefan equation will help unravel the dominating physical mechanisms in so-called visco-migration. THEORY To understand the physical mechanisms underlying this phenomenon, we employed the Maxwell-Stefan equation to develop a 1D model and obtain a relation between the flux of solvents and the driving forces. Viscosity gradients are known to drive transport, but the development of an electrical current has not been theoretically described prior to this work. FINDINGS Our 1D model shows that the ionic current depends on the ideality of the solvent, though both ideal and non-ideal scenarios demonstrated good agreement with experimental data. We employed the model to understand the impact of solution bulk ionic strength and pH on the drift of ionic species with same reservoirs solution properties. Our modeling results unveiled the significant impact of bulk solution properties on the drift of ions which is in agreement with the experiments. Moreover, we have shown that the diffusion gradient along the nanochannel contributes significantly into driving ionic species if we even apply a small ionic concentration gradient to both reservoirs. Our modeling results may pave the way for finding novel applications for drift of ions in a diffusion gradient, which can be induced by connecting reservoirs of different viscosity fluids.
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17
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Vuijk HD, Klempahn S, Merlitz H, Sommer JU, Sharma A. Active colloidal molecules in activity gradients. Phys Rev E 2022; 106:014617. [PMID: 35974656 DOI: 10.1103/physreve.106.014617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
We consider a rigid assembly of two active Brownian particles, forming an active colloidal dimer, in a gradient of activity. We show analytically that depending on the relative orientation of the two particles the active dimer accumulates in regions of either high or low activity, corresponding to, respectively, chemotaxis and antichemotaxis. Certain active dimers show both chemotactic and antichemotactic behavior, depending on the strength of the activity. Our coarse-grained Fokker-Planck approach yields an effective potential, which we use to construct a nonequilibrium phase diagram that classifies the dimers according to their tactic behavior. Moreover, we show that for certain dimers a higher persistence of the motion is achieved similar to the effect of a steering wheel in macroscopic devices. This work could be useful for designing autonomous active colloidal structures which adjust their motion depending on the local activity gradients.
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Affiliation(s)
- Hidde D Vuijk
- Leibniz-Institut für Polymerforschung Dresden, Institut Theory der Polymere, 01069 Dresden, Germany
| | - Sophie Klempahn
- Leibniz-Institut für Polymerforschung Dresden, Institut Theory der Polymere, 01069 Dresden, Germany
| | - Holger Merlitz
- Leibniz-Institut für Polymerforschung Dresden, Institut Theory der Polymere, 01069 Dresden, Germany
- School of Physical Science and Technology, Xiamen University, Xiamen 361005, People's Republic of China
| | - Jens-Uwe Sommer
- Leibniz-Institut für Polymerforschung Dresden, Institut Theory der Polymere, 01069 Dresden, Germany
- Technische Universität Dresden, Institut für Theoretische Physik, 01069 Dresden, Germany
| | - Abhinav Sharma
- Leibniz-Institut für Polymerforschung Dresden, Institut Theory der Polymere, 01069 Dresden, Germany
- Technische Universität Dresden, Institut für Theoretische Physik, 01069 Dresden, Germany
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18
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Yang Y, Yue C, Zhang C, Yuan J. Chemotactic response of Escherichia coli to polymer solutions. Phys Biol 2022; 19. [PMID: 35545074 DOI: 10.1088/1478-3975/ac6eb1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 05/11/2022] [Indexed: 11/12/2022]
Abstract
Polymers are important components of the complex fluid environment for microorganisms. The mechanical effects on bacterial motile behavior due to the viscous or viscoelastic properties of polymers were extensively studied, whereas possible chemical effects on bacterial motility through bacterial chemoreception of the polymers were unclear. Here we studied the chemotactic response of Escherichia coli to polymeric solutions by combining the bead assay and FRET measurements. We found that the wild-type E. coli strain exhibited an attractant response to widely used polymers such as Ficoll 400, PEG 20000 and PVP 360000, and the response amplitude from chemoreception was much larger than that from the load-dependence of motor switching due to viscosity change. The chemotactic response depended on the type of receptors and the chain length of the polymers. Our findings here provided novel ingredients for further studies of bacterial motile behavior in complex fluids.
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Affiliation(s)
- Yue Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, 96 Jinzhai Rd, Hefei, Anhui, 230026, CHINA
| | - Caijuan Yue
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, 96 Jinzhai Rd, Hefei, Anhui, 230026, CHINA
| | - Chi Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, 96 Jinzhai Rd, Hefei, Anhui, 230026, CHINA
| | - Junhua Yuan
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, 96 Jinzhai Rd, Hefei, Anhui, 230026, CHINA
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19
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Renner J, Schmidt M, Heras DDL. Shear and Bulk Acceleration Viscosities in Simple Fluids. PHYSICAL REVIEW LETTERS 2022; 128:094502. [PMID: 35302832 DOI: 10.1103/physrevlett.128.094502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Inhomogeneities in the velocity field of a moving fluid are dampened by the inherent viscous behavior of the system. Both bulk and shear effects, related to the divergence and the curl of the velocity field, are relevant. On molecular time scales, beyond the Navier-Stokes description, memory plays an important role. Using molecular and overdamped Brownian dynamics many-body simulations, we demonstrate that analogous viscous effects act on the acceleration field. This acceleration viscous behavior is associated with the divergence and the curl of the acceleration field, and it can be quantitatively described using simple exponentially decaying memory kernels. The simultaneous use of velocity and acceleration fields enables the description of fast dynamics on molecular scales.
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Affiliation(s)
- Johannes Renner
- Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Matthias Schmidt
- Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany
| | - Daniel de Las Heras
- Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany
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20
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Gerhard M, Jayaram A, Fischer A, Speck T. Hunting active Brownian particles: Learning optimal behavior. Phys Rev E 2021; 104:054614. [PMID: 34942812 DOI: 10.1103/physreve.104.054614] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 11/16/2021] [Indexed: 01/02/2023]
Abstract
We numerically study active Brownian particles that can respond to environmental cues through a small set of actions (switching their motility and turning left or right with respect to some direction) which are motivated by recent experiments with colloidal self-propelled Janus particles. We employ reinforcement learning to find optimal mappings between the state of particles and these actions. Specifically, we first consider a predator-prey situation in which prey particles try to avoid a predator. Using as reward the squared distance from the predator, we discuss the merits of three state-action sets and show that turning away from the predator is the most successful strategy. We then remove the predator and employ as collective reward the local concentration of signaling molecules exuded by all particles and show that aligning with the concentration gradient leads to chemotactic collapse into a single cluster. Our results illustrate a promising route to obtain local interaction rules and design collective states in active matter.
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Affiliation(s)
- Marcel Gerhard
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
| | - Ashreya Jayaram
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
| | - Andreas Fischer
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
| | - Thomas Speck
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
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21
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Shirke PU, Goswami H, Kumar V, Shah D, Beri S, Das S, Bellare J, Mayor S, Venkatesh KV, Seth JR, Majumder A. "Viscotaxis"- directed migration of mesenchymal stem cells in response to loss modulus gradient. Acta Biomater 2021; 135:356-367. [PMID: 34469788 DOI: 10.1016/j.actbio.2021.08.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 07/30/2021] [Accepted: 08/24/2021] [Indexed: 12/12/2022]
Abstract
Directed cell migration plays a crucial role in physiological and pathological conditions. One important mechanical cue, known to influence cell migration, is the gradient of substrate elastic modulus (E). However, the cellular microenvironment is viscoelastic and hence the elastic property alone is not sufficient to define its material characteristics. To bridge this gap, in this study, we investigated the influence of the gradient of viscous property of the substrate, as defined by loss modulus (G″) on cell migration. We cultured human mesenchymal stem cells (hMSCs) on a collagen-coated polyacrylamide gel with constant storage modulus (G') but with a gradient in the loss modulus (G″). We found hMSCs to migrate from high to low loss modulus. We have termed this form of directional cellular migration as "Viscotaxis". We hypothesize that the high loss modulus regime deforms more due to creep in the long timescale when subjected to cellular traction. Such differential deformation drives the observed Viscotaxis. To verify our hypothesis, we disrupted the actomyosin contractility with myosin inhibitor blebbistatin and ROCK inhibitor Y27632, and found the directional migration to disappear. Further, such time-dependent creep of the high loss material should lead to lower traction, shorter lifetime of the focal adhesions, and dynamic cell morphology, which was indeed found to be the case. Together, findings in this paper highlight the importance of considering the viscous modulus while preparing stiffness-based substrates for the field of tissue engineering. STATEMENT OF SIGNIFICANCE: While the effect of substrate elastic modulus has been investigated extensively in the context of cell biology, the role of substrate viscoelasticity is poorly understood. This omission is surprising as our body is not elastic, but viscoelastic. Hence, the role of viscoelasticity needs to be investigated at depth in various cellular contexts. One such important context is cell migration. Cell migration is important in morphogenesis, immune response, wound healing, and cancer, to name a few. While it is known that cells migrate when presented with a substrate with a rigidity gradient, cellular behavior in response to viscoelastic gradient has never been investigated. The findings of this paper not only reveal a completely novel cellular taxis or directed migration, it also improves our understanding of cell mechanics significantly.
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Affiliation(s)
- Pallavi Uday Shirke
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Hiya Goswami
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Vardhman Kumar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Darshan Shah
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Sarayu Beri
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India
| | - Siddhartha Das
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Jayesh Bellare
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India
| | - K V Venkatesh
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Jyoti R Seth
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India.
| | - Abhijit Majumder
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India.
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22
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Tan Z, Calandrini V, Dhont JKG, Nägele G, Winkler RG. Hydrodynamics of immiscible binary fluids with viscosity contrast: a multiparticle collision dynamics approach. SOFT MATTER 2021; 17:7978-7990. [PMID: 34378623 DOI: 10.1039/d1sm00541c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We present a multiparticle collision dynamics (MPC) implementation of layered immiscible fluids A and B of different shear viscosities separated by planar interfaces. The simulated flow profile for imposed steady shear motion and the time-dependent shear stress functions are in excellent agreement with our continuum hydrodynamics results for the composite fluid. The wave-vector dependent transverse velocity auto-correlation functions (TVAF) in the bulk-fluid regions of the layers decay exponentially, and agree with those of single-phase isotropic MPC fluids. In addition, we determine the hydrodynamic mobilities of an embedded colloidal sphere moving steadily parallel or transverse to a fluid-fluid interface, as functions of the distance from the interface. The obtained mobilities are in good agreement with hydrodynamic force multipoles calculations, for a no-slip sphere moving under creeping flow conditions near a clean, ideally flat interface. The proposed MPC fluid-layer model can be straightforwardly implemented, and it is computationally very efficient. Yet, owing to the spatial discretization inherent to the MPC method, the model can not reproduce all hydrodynamic features of an ideally flat interface between immiscible fluids.
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Affiliation(s)
- Zihan Tan
- Biomacromolecular Systems and Processes, Institute of Biological Information Processing, Forschungszentrum Jülich, 52428 Jülich, Germany.
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23
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Breoni D, Löwen H, Blossey R. Active noise-driven particles under space-dependent friction in one dimension. Phys Rev E 2021; 103:052602. [PMID: 34134234 DOI: 10.1103/physreve.103.052602] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/14/2021] [Indexed: 12/24/2022]
Abstract
We study a Langevin equation describing the stochastic motion of a particle in one dimension with coordinate x, which is simultaneously exposed to a space-dependent friction coefficient γ(x), a confining potential U(x) and nonequilibrium (i.e., active) noise. Specifically, we consider frictions γ(x)=γ_{0}+γ_{1}|x|^{p} and potentials U(x)∝|x|^{n} with exponents p=1,2 and n=0,1,2. We provide analytical and numerical results for the particle dynamics for short times and the stationary probability density functions (PDFs) for long times. The short-time behavior displays diffusive and ballistic regimes while the stationary PDFs display unique characteristic features depending on the exponent values (p,n). The PDFs interpolate between Laplacian, Gaussian, and bimodal distributions, whereby a change between these different behaviors can be achieved by a tuning of the friction strengths ratio γ_{0}/γ_{1}. Our model is relevant for molecular motors moving on a one-dimensional track and can also be realized for confined self-propelled colloidal particles.
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Affiliation(s)
- D Breoni
- Institut für Theoretische Physik II: Weiche Materie, Heinrich Heine-Universität Düsseldorf, Universitässtraße 1, 40225 Düsseldorf, Germany
| | - H Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich Heine-Universität Düsseldorf, Universitässtraße 1, 40225 Düsseldorf, Germany
| | - R Blossey
- University of Lille, UGSF CNRS UMR8576, 59000 Lille, France
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24
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Sukhov A, Hubert M, Grosjean G, Trosman O, Ziegler S, Collard Y, Vandewalle N, Smith AS, Harting J. Regimes of motion of magnetocapillary swimmers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:59. [PMID: 33895914 PMCID: PMC8068718 DOI: 10.1140/epje/s10189-021-00065-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/31/2021] [Indexed: 05/26/2023]
Abstract
The dynamics of a triangular magnetocapillary swimmer is studied using the lattice Boltzmann method. We extend on our previous work, which deals with the self-assembly and a specific type of the swimmer motion characterized by the swimmer's maximum velocity centred around the particle's inverse viscous time. Here, we identify additional regimes of motion. First, modifying the ratio of surface tension and magnetic forces allows to study the swimmer propagation in the regime of significantly lower frequencies mainly defined by the strength of the magnetocapillary potential. Second, introducing a constant magnetic contribution in each of the particles in addition to their magnetic moment induced by external fields leads to another regime characterized by strong in-plane swimmer reorientations that resemble experimental observations.
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Affiliation(s)
- Alexander Sukhov
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Straße 248, 90429, Nuremberg, Germany.
| | - Maxime Hubert
- PULS Group, Department of Physics, Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany
| | - Galien Grosjean
- GRASP Lab, CESAM Research Unit, Université de Liège, Allée du 6 Août 19, 4000, Liège, Belgium
- IST Austria, Lab Building West, Am Campus 1, 3400, Klosterneuburg, Austria
| | - Oleg Trosman
- PULS Group, Department of Physics, Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany
| | - Sebastian Ziegler
- PULS Group, Department of Physics, Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany
| | - Ylona Collard
- GRASP Lab, CESAM Research Unit, Université de Liège, Allée du 6 Août 19, 4000, Liège, Belgium
| | - Nicolas Vandewalle
- GRASP Lab, CESAM Research Unit, Université de Liège, Allée du 6 Août 19, 4000, Liège, Belgium
| | - Ana-Sunčana Smith
- PULS Group, Department of Physics, Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany
- Group for Computational Life Sciences, Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, P.P. 180, Zagreb, 10002, Croatia
| | - Jens Harting
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Straße 248, 90429, Nuremberg, Germany
- Department of Chemical and Biological Engineering and Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fürther Straße 248, 90429, Nuremberg, Germany
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25
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Dou Y, Tzelios PM, Livitz D, Bishop KJM. Programmable topotaxis of magnetic rollers in time-varying fields. SOFT MATTER 2021; 17:1538-1547. [PMID: 33331388 DOI: 10.1039/d0sm01443e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We describe how spatially uniform, time-periodic magnetic fields can be designed to power and direct the migration of ferromagnetic spheres up (or down) local gradients in the topography of a solid substrate. Our results are based on a dynamical model that considers the time-varying magnetic torques on the particle and its motion through the fluid at low Reynolds number. We use both analytical theory and numerical simulation to design magnetic fields that maximize the migration velocity up (or down) an inclined plane. We show how "topotaxis" of spherical particles relies on differences in the hydrodynamic resistance to rotation about axes parallel and perpendicular to the plane. Importantly, the designed fields can drive multiple independent particles to move simultaneously in different directions as determined by gradients in their respective environments. Experiments on ferromagnetic spheres provide evidence for topotactic motions up inclined substrates. The ability to program the autonomous navigation of driven particles within anisotropic environments is relevant to the design of colloidal robots.
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Affiliation(s)
- Yong Dou
- Department of Chemical Engineering, Columbia University, New York, NY, USA.
| | - Peter M Tzelios
- Department of Chemical Engineering, Columbia University, New York, NY, USA.
| | - Dimitri Livitz
- Department of Chemical Engineering, Columbia University, New York, NY, USA.
| | - Kyle J M Bishop
- Department of Chemical Engineering, Columbia University, New York, NY, USA.
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26
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Abstract
We study the behaviour of the green alga Chlamydomonas reinhardtii (CR) in the presence of neighbouring regions of different viscosity. We show that the velocity and angular diffusion of the algae decreases when the viscosity of the surrounding medium is increased. We report on a phenomenon occurring when the algae try to cross from a region of low viscosity to a highly viscous one, which causes CR to re-orient and scatter away from the interface if it is approached at a sufficiently small angle. We highlight that the effect does not occur for CR crossing from high to low viscosity regions. Lastly we show that algae do not concentrate in the region of high viscosity despite them swimming slower there. On the contrary, they concentrate in the region of low viscosity or maintain a uniform concentration profile, depending on the viscosity ratio between the two regions.
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27
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Tainio O, Sohrabi F, Janarek N, Koivisto J, Puisto A, Viitanen L, Timonen JVI, Alava M. Chlamydomonas reinhardtii swimming in the Plateau borders of 2D foams. SOFT MATTER 2021; 17:145-152. [PMID: 33155584 DOI: 10.1039/d0sm01206h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Unicellular Chlamydomonas reinhardtii micro-algae cells were inserted into a quasi-2D Hele-Shaw chamber filled with saponin foam. The movement of the algae along the bubble borders was then manipulated and tracked. These self-propelled particles generate flow and stresses in their surrounding matter. In addition, the algae possess the capability of exerting forces that alter bubble boundaries while maintaining an imminent phototactic movement. We find that by controlling the gas fraction of the foam we can change the interaction of the algae and bubbles. Specifically, our data expose three distinct swimming regimes for the algae with respect to the level of confinement due to the Plateau border cross-section: unlimited bulk, transition, and overdamped regimes. At the transition regime we find the speed of the algae to be modeled by a simple force balance equation emerging from the shear inside the Plateau border. Thus, we have shown that it is possible to create an algae-friendly foam while controlling the algae motion. This opens doors to multiple applications where the flow of nutrients, oxygen and recirculation of living organisms is essential.
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Affiliation(s)
- Oskar Tainio
- Department of Applied Physics, Aalto University, 00076 Aalto, Finland.
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28
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Doherty RP, Varkevisser T, Teunisse M, Hoecht J, Ketzetzi S, Ouhajji S, Kraft DJ. Catalytically propelled 3D printed colloidal microswimmers. SOFT MATTER 2020; 16:10463-10469. [PMID: 33057565 DOI: 10.1039/d0sm01320j] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Synthetic microswimmers are widely employed model systems in the studies of out-of-equilibrium phenomena. Unlike biological microswimmers which naturally occur in various shapes and forms, synthetic microswimmers have so far been limited almost exclusively to spherical shapes. Here, we exploit 3D printing to produce microswimmers with complex shapes in the colloidal size regime. We establish the flexibility of 3D printing by two-photon polymerisation to produce particles smaller than 10 microns with a high-degree of shape complexity. We further demonstrate that 3D printing allows control over the location of the active site through orienting the particles in different directions during printing. We verify that particles behave colloidally by imaging their motion in the passive and active states and by investigating their mean square displacement. In addition, we find that particles exhibit shape-dependant behavior, thereby demonstrating the potential of our method to launch a wide-range of in-depth studies into shape-dependent active motion and behaviour.
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Affiliation(s)
- Rachel P Doherty
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
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29
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Sprenger AR, Shaik VA, Ardekani AM, Lisicki M, Mathijssen AJTM, Guzmán-Lastra F, Löwen H, Menzel AM, Daddi-Moussa-Ider A. Towards an analytical description of active microswimmers in clean and in surfactant-covered drops. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2020; 43:58. [PMID: 32920676 DOI: 10.1140/epje/i2020-11980-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/10/2020] [Indexed: 05/24/2023]
Abstract
Geometric confinements are frequently encountered in the biological world and strongly affect the stability, topology, and transport properties of active suspensions in viscous flow. Based on a far-field analytical model, the low-Reynolds-number locomotion of a self-propelled microswimmer moving inside a clean viscous drop or a drop covered with a homogeneously distributed surfactant, is theoretically examined. The interfacial viscous stresses induced by the surfactant are described by the well-established Boussinesq-Scriven constitutive rheological model. Moreover, the active agent is represented by a force dipole and the resulting fluid-mediated hydrodynamic couplings between the swimmer and the confining drop are investigated. We find that the presence of the surfactant significantly alters the dynamics of the encapsulated swimmer by enhancing its reorientation. Exact solutions for the velocity images for the Stokeslet and dipolar flow singularities inside the drop are introduced and expressed in terms of infinite series of harmonic components. Our results offer useful insights into guiding principles for the control of confined active matter systems and support the objective of utilizing synthetic microswimmers to drive drops for targeted drug delivery applications.
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Affiliation(s)
- Alexander R Sprenger
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany.
| | - Vaseem A Shaik
- School of Mechanical Engineering, Purdue University, 47907, West Lafayette, IN, USA
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, 47907, West Lafayette, IN, USA
| | - Maciej Lisicki
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland
| | - Arnold J T M Mathijssen
- Department of Bioengineering, Stanford University, 443 Via Ortega, 94305, Stanford, CA, USA
- Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, 19104, Philadelphia, PA, USA
| | - Francisca Guzmán-Lastra
- Centro de Investigación DAiTA Lab, Facultad de Estudios Interdisciplinarios, Universidad Mayor, Av. Manuel Montt 367, Providencia, Santiago de Chile, Chile
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany
| | - Andreas M Menzel
- Institut für Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany
| | - Abdallah Daddi-Moussa-Ider
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225, Düsseldorf, Germany
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30
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Datt C, Elfring GJ. Active Particles in Viscosity Gradients. PHYSICAL REVIEW LETTERS 2019; 123:158006. [PMID: 31702312 DOI: 10.1103/physrevlett.123.158006] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Indexed: 06/10/2023]
Abstract
Microswimmers in nature often experience spatial gradients of viscosity. In this Letter we develop theoretical results for the dynamics of active particles, biological or otherwise, swimming through viscosity gradients. We model the active particles using the squirmer model, and show how viscosity gradients lead to viscotaxis for squirmers, and how the effects of viscosity gradients depend on the swimming gait of the microswimmers. We also show how such gradients in viscosity can be used to control active particles and suggest a mechanism to sort them based on their swimming style.
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Affiliation(s)
- Charu Datt
- Department of Mechanical Engineering and Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Gwynn J Elfring
- Department of Mechanical Engineering and Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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31
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32
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Hoell C, Löwen H, Menzel AM. Multi-species dynamical density functional theory for microswimmers: Derivation, orientational ordering, trapping potentials, and shear cells. J Chem Phys 2019. [DOI: 10.1063/1.5099554] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Christian Hoell
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
| | - Andreas M. Menzel
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
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33
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Abstract
We study the dynamics of active Janus particles that self-propel in solution by light-activated catalytic decomposition of chemical "fuel." We develop an analytical model of a photo-active self-phoretic particle that accounts for "self-shadowing" of the light by the opaque catalytic face of the particle. We find that self-shadowing can drive "phototaxis" (rotation of the catalytic cap toward the light source) or "anti-phototaxis," depending on the properties of the particle. Incorporating the effect of thermal noise, we show that the distribution of particle orientations is captured by a Boltzmann distribution with a nonequilibrium effective potential. Furthermore, the mean vertical velocity of phototactic (anti-phototactic) particles exhibits a superlinear (sublinear) dependence on intensity. Overall, our findings show that photo-active particles exhibit a rich "tactic" response to light, which could be harnessed to program complex three-dimensional trajectories.
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Affiliation(s)
- W E Uspal
- Department of Mechanical Engineering, University of Hawai'i at Manoa, 2540 Dole Street, Holmes 302, Honolulu, Hawaii 96822, USA
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Abstract
The ability to navigate in chemical gradients, called chemotaxis, is crucial for the survival of microorganisms. It allows them to find food and to escape from toxins. Many microorganisms can produce the chemicals to which they respond themselves and use chemotaxis for signaling, which can be seen as a basic form of communication, allowing ensembles of microorganisms to coordinate their behavior, for example, during embryogenesis, biofilm formation, or cellular aggregation. For example, Dictyostelium cells use signaling as a survival strategy: when starving, they produce certain chemicals toward which other cells show taxis. This leads to aggregation of the cells resulting in a multicellular aggregate that can sustain long starvation periods. Remarkably, the past decade has led to the development of synthetic microswimmers, which can self-propel through a solvent, analogously to bacteria and other microorganisms. The mechanism underlying the self-propulsion of synthetic microswimmers like camphor boats, droplet swimmers, and in particular autophoretic Janus colloids involves the production of certain chemicals. As we will discuss in this Account, the same chemicals (phoretic fields) involved in the self-propulsion of a (Janus) microswimmer also act on other ones and bias their swimming direction toward (or away from) the producing microswimmer. Synthetic microswimmers therefore provide a synthetic analogue to motile microorganisms interacting by taxis toward (or away from) self-produced chemical fields. In this Account, we review recent progress in the theoretical description of synthetic chemotaxis mainly based on simulations and field theoretical descriptions. We will begin with single motile particles leaving chemical trails behind with which they interact themselves, leading to effects like self-trapping or self-avoidance. Besides these self-interactions, in ensembles of synthetic motile particles each particle also responds to the chemicals produced by other particles, inducing chemical (or phoretic) cross-interactions. When these interactions are attractive, they commonly lead to clusters, even at low particle density. These clusters may either proceed toward macrophase separation, resembling Dictyostelium aggregation, or, as shown very recently, lead to dynamic clusters of self-limited size (dynamic clustering) as seen in experiments in autophoretic Janus colloids. Besides the classical case where chemical interactions are attractive, this Account discusses, as its main focus, repulsive chemical interactions, which can create a new and less known avenue to pattern formation in active systems leading to a variety of pattern, including clusters which are surrounded by shells of chemicals, traveling waves and more complex continuously reshaping patterns. In all these cases "synthetic signalling" can crucially determine the collective behavior of synthetic microswimmer ensembles and can be used as a design principle to create patterns in motile active particles.
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Affiliation(s)
- Benno Liebchen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
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Hoell C, Löwen H, Menzel AM. Particle-scale statistical theory for hydrodynamically induced polar ordering in microswimmer suspensions. J Chem Phys 2018; 149:144902. [DOI: 10.1063/1.5048304] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Christian Hoell
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Andreas M. Menzel
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
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