1
|
Kumar M, Murali A, Subramaniam AG, Singh R, Thutupalli S. Emergent dynamics due to chemo-hydrodynamic self-interactions in active polymers. Nat Commun 2024; 15:4903. [PMID: 38851777 PMCID: PMC11162426 DOI: 10.1038/s41467-024-49155-7] [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: 12/24/2023] [Accepted: 05/24/2024] [Indexed: 06/10/2024] Open
Abstract
The field of synthetic active matter has, thus far, been led by efforts to create point-like, isolated (yet interacting) self-propelled objects (e.g. colloids, droplets, microrobots) and understanding their collective dynamics. The design of flexible, freely jointed active assemblies from autonomously powered sub-components remains a challenge. Here, we report freely-jointed active polymers created using self-propelled droplets as monomeric units. Our experiments reveal that the self-shaping chemo-hydrodynamic interactions between the monomeric droplets give rise to an emergent rigidity (the acquisition of a stereotypical asymmetric C-shape) and associated ballistic propulsion of the active polymers. The rigidity and propulsion of the chains vary systematically with their lengths. Using simulations of a minimal model, we establish that the emergent polymer dynamics are a generic consequence of quasi two-dimensional confinement and auto-repulsive trail-mediated chemical interactions between the freely jointed active droplets. Finally, we tune the interplay between the chemical and hydrodynamic fields to experimentally demonstrate oscillatory dynamics of the rigid polymer propulsion. Altogether, our work highlights the possible first steps towards synthetic self-morphic active matter.
Collapse
Affiliation(s)
- Manoj Kumar
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
| | - Aniruddh Murali
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | | | - Rajesh Singh
- Department of Physics, Indian Institute of Technology, Chennai, India.
| | - Shashi Thutupalli
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bangalore, India.
| |
Collapse
|
2
|
Singh K, Raman H, Tripathi S, Sharma H, Choudhary A, Mangal R. Pair Interactions of Self-Propelled SiO 2-Pt Janus Colloids: Chemically Mediated Encounters. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:7328-7343. [PMID: 38526954 DOI: 10.1021/acs.langmuir.3c03415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
Driven by the necessity to achieve a thorough comprehension of the bottom-up fabrication process of functional materials, this experimental study investigates the pairwise interactions or collisions between chemically active SiO2-Pt Janus colloids. These collisions are categorized based on the Janus colloids' orientations before and after they make physical contact. In addition to the hydrodynamic interactions, the Janus colloids are also known to affect each other's chemical field, resulting in chemophoretic interactions, which depend on the degree of surface anisotropy in reactivity of Janus colloid and the solute-surface interaction at play. Our study reveals that these interactions lead to a noticeable decrease in particle speed and changes in orientation that correlate with the contact duration and yield different collision types. Distinct configurations of contact during collisions were found, whose mechanisms and likelihood are found to be dependent primarily on the chemical interactions. Such estimates of collision and their characterization in dilute suspensions shall have a key impact in determining the arrangement and time scales of dynamical structures and assemblies of denser suspensions and potentially the functional materials of the future.
Collapse
Affiliation(s)
- Karnika Singh
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Harishwar Raman
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Shwetabh Tripathi
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Hrithik Sharma
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Akash Choudhary
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Rahul Mangal
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
| |
Collapse
|
3
|
Ray S, Roy A. Simple model for self-propulsion of microdroplets in surfactant solution. Phys Rev E 2023; 108:035102. [PMID: 37849129 DOI: 10.1103/physreve.108.035102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 08/23/2023] [Indexed: 10/19/2023]
Abstract
We propose a simple active hydrodynamic model for the self-propulsion of a liquid droplet suspended in micellar solutions. The self-propulsion of the droplet occurs by spontaneous breaking of isotropic symmetry and is studied using both analytical and numerical methods. The emergence of self-propulsion arises from the slow dissolution of the inner fluid into the outer micellar solution as filled micelles. We propose that the surface generation of filled micelles is the dominant reason for the self-propulsion of the droplet. The flow instability is due to the Marangoni stress generated by the nonuniform distribution of the surfactant molecules on the droplet interface. In our model, the driving parameter of the instability is the excess surfactant concentration above the critical micellar concentration, which directly correlates with the experimental observations. We consider various low-order modes of flow instability and show that the first mode becomes unstable through a supercritical bifurcation and is the only mode contributing to the swimming of the droplet. The flow fields around the droplet for these modes and their combined effects are also discussed.
Collapse
Affiliation(s)
- Swarnak Ray
- Soft Condensed Matter Group, Raman Research Institute, Bangalore 560080, India
| | - Arun Roy
- Soft Condensed Matter Group, Raman Research Institute, Bangalore 560080, India
| |
Collapse
|
4
|
Wang Z, Fang G, Gao Z, Liao Y, Gong C, Kim M, Chang GE, Feng S, Xu T, Liu T, Chen YC. Autonomous Microlasers for Profiling Extracellular Vesicles from Cancer Spheroids. NANO LETTERS 2023; 23:2502-2510. [PMID: 36926974 DOI: 10.1021/acs.nanolett.2c04123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Self-propelled micro/nanomotors are emergent intelligent sensors for analyzing extracellular biomarkers in circulating biological fluids. Conventional luminescent motors are often masked by a highly dynamic and scattered environment, creating challenges to characterize biomarkers or subtle binding dynamics. Here we introduce a strategy to amplify subtle signals by coupling strong light-matter interactions on micromotors. A smart whispering-gallery-mode microlaser that can self-propel and analyze extracellular biomarkers is demonstrated through a liquid crystal microdroplet. Lasing spectral responses induced by cavity energy transfer were employed to reflect the abundance of protein biomarkers, generating exclusive molecular labels for cellular profiling of exosomes derived from 3D multicellular cancer spheroids. Finally, a microfluidic biosystem with different tumor-derived exosomes was employed to elaborate its sensing capability in complex environments. The proposed autonomous microlaser exhibits a promising method for both fundamental biological science and applications in drug screening, phenotyping, and organ-on-chip applications.
Collapse
Affiliation(s)
- Ziyihui Wang
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Guocheng Fang
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Zehang Gao
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai, 200050, China
- Department of Clinical Laboratory, Third Affiliated Hospital of Guangzhou Medical University, Guangdong 510150, China
| | - Yikai Liao
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Chaoyang Gong
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Munho Kim
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| | - Guo-En Chang
- Department of Mechanical Engineering and Advanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chiayi 62102, Taiwan
| | - Shilun Feng
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai, 200050, China
| | - Tianhua Xu
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
- School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Tiegen Liu
- School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
| | - Yu-Cheng Chen
- School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Ave., Singapore 639798, Singapore
| |
Collapse
|
5
|
Yoshiko T, Sato D, Yamamoto T. Fibrous self-assembly of liquid crystal made by self-organisation. LIQUID CRYSTALS TODAY 2023. [DOI: 10.1080/1358314x.2022.2179827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Affiliation(s)
- Takenaka Yoshiko
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - D. Sato
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
- Department of Applied Physics, Tokyo University of Science, Tokyo, Japan
| | - T. Yamamoto
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| |
Collapse
|
6
|
We the Droplets: A Constitutional Approach to Active and Self-Propelled Emulsions. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2022.101623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
7
|
|
8
|
Liu C, Chen C, Tu C, Hung S, Chao C. Structure colorants based on cross‐linked cholesteric liquid crystalline polymeric slices. J Appl Polym Sci 2022. [DOI: 10.1002/app.51717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Chun‐Yen Liu
- Department of Materials Science and Engineering National Cheng Kung University Tainan City Taiwan
| | - Cheng‐Chieh Chen
- Department of Chemical Engineering National Cheng Kung University Tainan City Taiwan
| | - Chia‐Ming Tu
- Department of Materials Science and Engineering National Cheng Kung University Tainan City Taiwan
| | - Sheng‐Chi Hung
- Department of Materials Science and Engineering National Cheng Kung University Tainan City Taiwan
| | - Chia‐Hui Chao
- Department of Materials Science and Engineering National Cheng Kung University Tainan City Taiwan
| |
Collapse
|
9
|
Bahr C. Lattice Boltzmann and Jones matrix calculations for the determination of the director field structure in self-propelling nematic droplets. Phys Rev E 2021; 104:044703. [PMID: 34781516 DOI: 10.1103/physreve.104.044703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 09/24/2021] [Indexed: 11/07/2022]
Abstract
Nematic droplets immersed in aqueous surfactant solutions can show a self-propelled motion induced by a Marangoni flow in the droplet surface. In addition to the self-propulsion, the Marangoni flow induces within the droplet a convective flow which considerably influences the nematic director field of the droplet. We report numerical simulations aiming at the determination of the director field in the self-propelling droplet. The convective flow and the resulting structure of director field are described by a lattice Boltzmann model. The reliability of the obtained structures is proved by subsequent Jones matrix calculations which enable the direct comparison of experimental polarizing microscopy images of self-propelling droplets with calculated images based on the simulated structures.
Collapse
Affiliation(s)
- Christian Bahr
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany
| |
Collapse
|
10
|
Chen H, Yan T, Zhang J, Pei X, Cui Z, Song B. Formation of asymmetric belt-like aggregates from a bio-based surfactant derived from dehydroabietic acid. SOFT MATTER 2021; 17:9950-9956. [PMID: 34694306 DOI: 10.1039/d1sm01375k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The morphology and physicochemical properties of ordered molecular aggregates are closely related to surfactant molecules. Herein, a rosin-based amine oxide surfactant containing a large hydrophobic group (abbreviated R-10-AO) was synthesized from dehydroabietic acid, which is an important derivative of rosin. Cryogenic transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) showed that at a concentration of ∼5 mM, R-10-AO molecules formed flexible nanobelts with a thickness of only 2-3 nm. The width of these nanobelts was 50-150 nm and the length was more than 1 μm. The formation of the stable nanobelts arose from the strong van der Waals forces of the bulky hydrophobic portions of R-10-AO in solution, facilitating the stability of the asymmetrical aggregates. Rheological tests showed that the formed nanobelts were thermodynamically stable. The entanglement of these nanobelts led to significant viscoelasticity of the solutions. The zero-shear viscosity (η0) of the R-10-AO solution reached 10 Pa s at a concentration of 5 mM, which is much greater than that of most wormlike micellar solutions. This work provides the inspirations of preparing aggregates with novel properties using natural products.
Collapse
Affiliation(s)
- Hao Chen
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| | - Tingting Yan
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| | - Jinpeng Zhang
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| | - Xiaomei Pei
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| | - Zhenggang Cui
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| | - Binglei Song
- The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, P. R. China.
| |
Collapse
|
11
|
Roh S, Tsuei M, Abbott NL. Using Liquid Crystals for In Situ Optical Mapping of Interfacial Mobility and Surfactant Concentrations at Flowing Aqueous-Oil Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:5810-5822. [PMID: 33950693 DOI: 10.1021/acs.langmuir.1c00133] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Flow-induced states of fluid interfaces decorated with amphiphiles underlie phenomena such as emulsification, foaming, and spreading. While past studies have shown that interfacial mass transfer, the kinetics of surfactant adsorption and desorption, interfacial mobility, and surfactant reorganization regulate the dynamic properties of surfactant-laden interfaces, few simple methods permit simultaneous monitoring of this interplay. Here, we explore the optical responses of micrometer-thick films of oils (4-cyano-4'-pentylbiphenyl, 5CB) with a liquid crystalline order in contact with flowing aqueous phases of soluble [e.g., sodium dodecyl sulfate (SDS)] or insoluble (e.g., 1,2-dilauroyl-sn-glycero-3-phosphocholine) amphiphiles. We observe the onset of flow of 0.5 mM SDS solutions within a millifluidic channel (area-average velocity of 200 mm/s) to transform a liquid crystal (LC) film with an alignment along the interface normal into a bright birefringent state (average LC tilt angle of 30°), consistent with an initially mobile interface that shears and thus tilts the LC along the flow direction. Subsequently, we observed the LC film to evolve to a steady state (over ∼10 s) with position-dependent optical retardance controlled by gradients in surfactant concentration and thus Marangoni stresses. For 0.5 mM SDS solutions, by using particle tracking and a simple hydrodynamic model, we reveal that the dominant role of the flow-induced interfacial surfactant concentration gradient is to change the mobility of the interface (and thus shear rate of LC) and not to change the easy axis (equilibrium orientation) or anchoring energy (orientation-dependent interfacial energy) of the LC. At lower surfactant concentrations (0.015 mM SDS), however, we show that the LC directly maps flow-induced interfacial surfactant concentration gradients via a change in the local easy axis of the LC. When combined with additional measurements obtained with simple salts and insoluble amphiphiles, these results hint that LC oils may offer the basis of general and facile methods that permit mapping of both interfacial mobilities and surfactant distributions at flowing interfaces.
Collapse
Affiliation(s)
- Sangchul Roh
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Michael Tsuei
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Nicholas L Abbott
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| |
Collapse
|
12
|
Abstract
Sudden onset of solubilization is observed widely around or below the critical micelle concentration (CMC) of surfactants. It has also been reported that micellization is induced by the solutes even below CMC and the solubilized solute increases the aggregation number of the surfactant. These observations suggest enhanced cooperativity in micellization upon solubilization. Recently, we have developed a rigorous statistical thermodynamic theory of cooperative solubilization. Its application to hydrotropy revealed the mechanism of cooperative hydrotropy: hydrotrope self-association enhanced by solutes. Here we generalize our previous cooperative solubilization theory to surfactants. We have shown that the well-known experimental observations, such as the reduction of CMC in the presence of the solutes and the increase of aggregation number, are the manifestations of cooperative solubilization. Thus, the surfactant self-association enhanced by a solute is the driving force of cooperativity and a part of a universal cooperative solubilization mechanism common to hydrotropes and surfactants at low concentrations.
Collapse
Affiliation(s)
- Seishi Shimizu
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | | |
Collapse
|
13
|
Wang X, Zhang R, Mozaffari A, de Pablo JJ, Abbott NL. Active motion of multiphase oil droplets: emergent dynamics of squirmers with evolving internal structure. SOFT MATTER 2021; 17:2985-2993. [PMID: 33596294 DOI: 10.1039/d0sm01873b] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Synthetic soft matter systems, when driven beyond equilibrium by active processes, offer the potential to achieve dynamical states and functions of a complexity found in living matter. Emulsions offer the basis of a simple yet versatile system for identification of the physicochemical principles underlying active soft matter, but how multiple internal phases within emulsion droplets (e.g., Janus morphologies) organize to impact emergent dynamics is not understood. Here, we create multiphase oil droplets with ultralow interfacial tensions but distinct viscosities, and drive them into motion in aqueous micellar solutions. Preferential solubilization of select components of the oil both drives the droplet motion and yields a progression of internal phase morphological states with distinct symmetries. We find the active droplets to exhibit five dynamical states during morphogenesis. By quantifying microscopic flow fields, we show that it is possible to map the diverse droplet behaviors to squirmer models of spherical microswimmers in Stokes flow, thus showing that multiphase droplets offer the basis of a versatile platform with which to study and engineer the hydrodynamics of microswimmers.
Collapse
Affiliation(s)
- Xin Wang
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
| | - Rui Zhang
- Institute for Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Ali Mozaffari
- Institute for Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Juan J de Pablo
- Institute for Molecular Engineering, University of Chicago, Chicago, IL, USA and Argonne National Laboratory, Chicago, IL, USA
| | - Nicholas L Abbott
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
| |
Collapse
|
14
|
Kree R, Zippelius A. Controlled locomotion of a droplet propelled by an encapsulated squirmer. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:6. [PMID: 33599874 PMCID: PMC7892747 DOI: 10.1140/epje/s10189-021-00018-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/13/2021] [Indexed: 05/08/2023]
Abstract
We work out the propulsion of a viscous drop which is driven by two mechanisms: the active velocity of an encapsulated squirmer and an externally applied force acting on the squirmer. Of particular interest is the existence of a stable comoving state of drop and squirmer, allowing for controlled manipulation of the viscous drop by external forcing. The velocities of droplet and squirmer, as well as the conditions for a stable comoving state are worked out analytically for the axisymmetric configuration with a general displacement of the squirmer from the center of the droplet.
Collapse
Affiliation(s)
- R Kree
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
| | - A Zippelius
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| |
Collapse
|
15
|
Toyota T, Sugiyama H, Hiroi S, Ito H, Kitahata H. Chemically artificial rovers based on self-propelled droplets in micrometer-scale environment. Curr Opin Colloid Interface Sci 2020. [DOI: 10.1016/j.cocis.2020.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
16
|
Li M, Hosseinzadeh M, Pagonabarraga I, Seemann R, Brinkmann M, Fleury JB. Kinetics of active water/ethanol Janus droplets. SOFT MATTER 2020; 16:6803-6811. [PMID: 32627799 DOI: 10.1039/d0sm00460j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Droplets made of a water/ethanol mixture spontaneously self-propel in an oil/surfactant solution and, depending on the initial ethanol concentration at the time of production, may evolve in up to three stages. Upon self-propulsion the droplets absorb surfactant molecules during their continuous motion in the oily phase. In combination with the continuous loss of ethanol this mass exchange with the ambient phase may lead to a spontaneous phase separation of the water/ethanol mixture, and eventually to the formation of characteristic Janus droplets. Supported by experimental evidence, we propose a simple model that is able to explain the propulsion velocity and its scaling with the droplet radius in the last stage of the droplet evolution.
Collapse
Affiliation(s)
- Menglin Li
- Experimental Physics, Saarland University, 66123 Saarbrücken, Germany.
| | | | - Ignacio Pagonabarraga
- Department of Condensed Matter Physics, University of Barcelona, Carrer de Marti i Franques 1, Barcelona, Spain
| | - Ralf Seemann
- Experimental Physics, Saarland University, 66123 Saarbrücken, Germany.
| | - Martin Brinkmann
- Experimental Physics, Saarland University, 66123 Saarbrücken, Germany. and Smart Materials & Surfaces Laboratory, Faculty of Engineering & Environment, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
| | | |
Collapse
|
17
|
Nayani K, Córdova-Figueroa UM, Abbott NL. Steering Active Emulsions with Liquid Crystals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6948-6956. [PMID: 31804839 DOI: 10.1021/acs.langmuir.9b02975] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Colloids dispersed in liquid crystals (LCs) diffuse preferentially along the LC director because this direction of displacement generates the lowest hydrodynamic drag. In this article, we report on the active transport of micrometer-sized nematic droplets of 4'-pentyl-4-biphenylcarbonitrile (5CB) propelled through a continuous LC phase formed from aqueous solutions of disodium cromoglycate (DSCG) by Marangoni stresses (generated through the addition of sodium dodecyl sulfate (SDS)). We observe the nematic droplets to exhibit motion guided by the continuous LC phase, but in contrast to passive diffusion, the LC droplets move preferentially in a direction perpendicular to the continuous-phase LC director. Our results suggest that the LC droplets, with internal symmetry broken by the Marangoni flow, interact through orientation-dependent van der Waals forces with the LC continuous phase, biasing the orientation of the droplets and the direction of propulsion orthogonal to the far-field director of the continuous LC phase. This proposal is supported by measurements of the orientations of droplets of 5CB and 4-ethoxy-4'-(6-acryloyloxyhexyloxy) azobenzene (RM257) polymerized in a preradial director configuration, which reveal the polymerized droplets to adopt orientations that are biased toward the perpendicular of the far-field DSCG director. Additionally, we demonstrate that preferential motion parallel to the continuous-phase LC director is recovered when using self-propelled isotropic oil droplets. We also observe periodic changes in the instantaneous velocities of LC droplets. We show the changes to correlate with the formation and detachment of satellite droplets, consistent with the solubilization of the nematic oil into surfactant assemblies near the trailing edge of the droplets and their accumulation near a stagnation region downstream of the droplet. Overall, our results provide fundamental insights into ways in which LC ordering can change the dynamics of active colloidal systems and hint at principles by which the motion of active colloids can be steered.
Collapse
Affiliation(s)
- Karthik Nayani
- Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Ubaldo M Córdova-Figueroa
- Department of Chemical Engineering, University of Puerto Rico-Mayagüez, Mayagüez 00682, Puerto Rico, United States
| | - Nicholas L Abbott
- Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| |
Collapse
|
18
|
Dewangan NK, Conrad JC. Rotating oil droplets driven by motile bacteria at interfaces. SOFT MATTER 2019; 15:9368-9375. [PMID: 31693048 DOI: 10.1039/c9sm01570a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We show that oil droplets suspended near a liquid-solid interface can be driven to rotate by motile bacteria adhered to the droplet surface. Droplets rotate clockwise when viewed from the liquid side, due to symmetry-breaking hydrodynamic interactions of bacteria with the interface. The angular speed of rotation for droplets decreases as their size is increased. Differences in the speed of rotation driven by Escherichia coli, Shewanella haliotis, and Halomonas titanicae bacteria reflects differences in the number of bacteria adhered at the droplet surface and their interfacial affinity. Adding surfactant reduces the number of adherent bacteria and hence lowers the speed of rotation. Together, these results demonstrate that bacterial activity can be used to manipulate suspended droplets.
Collapse
Affiliation(s)
- Narendra K Dewangan
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204, USA.
| | - Jacinta C Conrad
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204, USA.
| |
Collapse
|
19
|
Kasuo Y, Kitahata H, Koyano Y, Takinoue M, Asakura K, Banno T. Start of Micrometer-Sized Oil Droplet Motion through Generation of Surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:13351-13355. [PMID: 31550892 DOI: 10.1021/acs.langmuir.9b01722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Self-propelled motion of micrometer-sized oil droplets in surfactant solution has drawn much attention as an example of nonlinear life-like dynamics under far-from-equilibrium conditions. The driving force of this motion is thought to be induced by Marangoni convection based on heterogeneity in the interfacial tension at the droplet surface. Here, to clarify the required conditions for the self-propelled motion of oil droplets, we have constructed a chemical system, where oil droplet motion is induced by the production of 1,2,3-triazole-containing surfactants through the Cu-catalyzed azide-alkyne cycloaddition reaction. From the results of the visualization and analysis of flow fields around the droplet, the motion of the droplets could be attributed to the formation of flow fields, which achieved sufficient strength caused by the in situ production of surfactants at the droplet surface.
Collapse
Affiliation(s)
- Yui Kasuo
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Hiroyuki Kitahata
- Department of Physics, Graduate School of Science , Chiba University , 1-33 Yayoi-cho , Inage-ku, Chiba 263-8522 , Japan
| | - Yuki Koyano
- Department of Physics , Tohoku University , 6-3 Aramaki-Aza-Aoba , Aoba-ku, Miyagi 980-8578 , Japan
| | - Masahiro Takinoue
- Department of Computer Science , Tokyo Institute of Technology , 4259 Nagatsuta-cho , Midori-ku , Yokohama 226-8502 , Japan
| | - Kouichi Asakura
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Taisuke Banno
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| |
Collapse
|
20
|
Morozov M, Michelin S. Orientational instability and spontaneous rotation of active nematic droplets. SOFT MATTER 2019; 15:7814-7822. [PMID: 31517379 DOI: 10.1039/c9sm01076a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In experiments, an individual chemically-active liquid crystal (LC) droplet submerged in the bulk of a surfactant solution may self-propel along a straight, helical, or random trajectory. In this paper, we develop a minimal model capturing all three types of self-propulsion trajectories of a drop in the case of a nematic LC with homeotropic anchoring at the LC-fluid interface. We emulate the director field within the drop by a single preferred polarization vector that is subject of two reorientation mechanisms, namely, the internal flow-induced displacement of the hedgehog defect and the droplet's rotation. Within this reduced-order model, the coupling between the nematic ordering of the drop and the surfactant transport is represented by variations of the droplet's interfacial properties with nematic polarization. Our analysis reveals that a novel mode of orientational instability emerges from the competition of the two reorientation mechanisms and is characterized by a spontaneous rotation of the self-propelling drop responsible for helical self-propulsion trajectories. In turn, we also show that random trajectories in isotropic and nematic drops alike stem from the advection-driven transition to chaos. The succession of the different propulsion modes is consistent with experimentally-reported transitions in the shape of droplet trajectories as the drop size is varied.
Collapse
Affiliation(s)
- Matvey Morozov
- LadHyX Département de Mécanique, CNRS École Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France.
| | | |
Collapse
|
21
|
Sakai Y, Sohn WY, Katayama K. Optical motion control of liquid crystalline droplets by host-guest molecular interaction. SOFT MATTER 2019; 15:7159-7165. [PMID: 31410429 DOI: 10.1039/c9sm01265f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Photo-induced motion is demonstrated for a photo-responsive dye-doped liquid crystal (LC) droplet in a surfactant solution. The LC droplets started rolling on a substrate during UV irradiation and moved either toward or away from the UV light, depending on the functional groups of the guest dyes. The mechanism is explained by the Marangoni flow caused by the photo-isomerization-induced adsorption and desorption of the dye molecules to and from the LC/solution interfaces.
Collapse
Affiliation(s)
- Yota Sakai
- Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
| | | | | |
Collapse
|
22
|
Sharma A, Jampani VSR, Lagerwall JPF. Realignment of Liquid Crystal Shells Driven by Temperature-Dependent Surfactant Solubility. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:11132-11140. [PMID: 31356088 PMCID: PMC7217602 DOI: 10.1021/acs.langmuir.9b00989] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 07/12/2019] [Indexed: 05/31/2023]
Abstract
We investigate dynamic director field variations in shells of the nematic liquid crystal (LC) compound, 4-cyano-4'-pentylbiphenyl, suspended in and containing immiscible aqueous phases. The outer and inner shell interfaces are stabilized by the cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), and by the water soluble polymer, poly(vinyl alcohol) (PVA), respectively. PVA and surfactant solutions normally promote tangential and orthogonal alignments, respectively, of the LC director. The rather high Krafft temperature of CTAB, TK ≈ 25 °C, means that its solubility in water is below the critical micelle concentration at room temperature in most labs. Here, we study the effect of cooling/heating past TK on the LC shell director configuration. Within a certain concentration range, CTAB in the outer aqueous phase (and PVA in the inner) switches the LC director field from hybrid to uniformly orthogonal upon cooling below TK. We argue that the effect is related to the migration of the surfactant through the fluid LC membrane into the initially surfactant-free aqueous PVA solution, triggered by the drastically reduced water solubility of CTAB at T < TK. The results suggest that LC shells can detect solutes in the continuous phase, provided there is sufficient probability that the solute migrates through the LC into the inner aqueous phase.
Collapse
|
23
|
Dogishi Y, Sakai Y, Sohn WY, Katayama K. Optically induced motion of liquid crystalline droplets. SOFT MATTER 2018; 14:8085-8089. [PMID: 30209505 DOI: 10.1039/c8sm01426d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The controlled motion of a liquid crystalline active droplet was demonstrated in a surfactant solution and by irradiation with UV light. The droplet could be induced to roll on a glass substrate toward the UV light source. This was explained by the Marangoni flow induced by the UV-induced desorption of surfactants.
Collapse
Affiliation(s)
- Yoshiharu Dogishi
- Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
| | - Yota Sakai
- Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
| | - Woon Yong Sohn
- Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan.
| | - Kenji Katayama
- Department of Applied Chemistry, Chuo University, Tokyo 112-8551, Japan. and PRESTO, Japan Science and Technology Agency (JST), Saitama 332-0012, Japan
| |
Collapse
|
24
|
Hirono A, Toyota T, Asakura K, Banno T. Locomotion Mode of Micrometer-Sized Oil Droplets in Solutions of Cationic Surfactants Having Ester or Ether Linkages. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:7821-7826. [PMID: 29878786 DOI: 10.1021/acs.langmuir.8b01352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Micrometer-sized self-propelled oil droplets under a far-from-equilibrium condition have drawn much attention because of their potential as a dynamic model for the chemical machinery in living organisms. To clarify the effect of interactions between the system components (surfactant, oil, and water) on the locomotion mode of droplets, we investigated the behaviors of oil droplets composed of n-heptyloxybenzaldehyde (HBA) in solutions of cationic surfactants having or not having an ester or an ether linkage. It was observed that in solutions of cationic surfactants having an ester or an ether linkage, spherical HBA droplets self-propelled by changing their direction frequently. On the other hand, when this functional group is absent, a slow self-propelled motion of the oil droplets concurrent with the evolution of aggregates on their surface was observed. From the results of measurement of interfacial tension and assessment of self-emulsification, we determined that the attractive interactions of cationic surfactants without an ester or an ether linkage with HBA are stronger than those having the linkage. The difference in the locomotion mode of oil droplets is probably explained from the viewpoint of the interactions among the system components.
Collapse
Affiliation(s)
- Ayana Hirono
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Taro Toyota
- Department of Basic Science, Graduate School of Arts and Sciences , The University of Tokyo , 3-8-1 Komaba , Meguro-ku, Tokyo 153-8902 , Japan
| | - Kouichi Asakura
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Taisuke Banno
- Department of Applied Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| |
Collapse
|
25
|
Suga M, Suda S, Ichikawa M, Kimura Y. Self-propelled motion switching in nematic liquid crystal droplets in aqueous surfactant solutions. Phys Rev E 2018; 97:062703. [PMID: 30011466 DOI: 10.1103/physreve.97.062703] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Indexed: 06/08/2023]
Abstract
The self-propelled motions of micron-sized nematic liquid crystal droplets in an aqueous surfactant solution have been studied by tracking individual droplets over long time periods. Switching between self-propelled modes is observed as the droplet size decreases at a nearly constant dissolution rate: from random to helical and then straight motion. The velocity of the droplet decreases with its size for straight and helical motions but is independent of size for random motion. The switching between helical and straight motions is found to be governed by the self-propelled velocity, and is confirmed by experiments at various surfactant concentrations. The helical motion appears along with a shifting of a point defect from the self-propelled direction of the droplet. The critical velocity for this shift of the defect position is found to be related with the Ericksen number, which is defined by the ratio of the viscous and elastic stresses. In a thin cell whose thickness is smaller than that of the initial droplet size, the droplets show more complex trajectories, including "figure-8s" and zigzags. The appearance of those characteristic motions is attributed to autochemotaxis of the droplet.
Collapse
Affiliation(s)
- Mariko Suga
- Department of Physics, School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Saori Suda
- Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Masatoshi Ichikawa
- Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yasuyuki Kimura
- Department of Physics, School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| |
Collapse
|
26
|
Yesil F, Suwa M, Tsukahara S. Anchoring Energy Measurements at the Aqueous Phase/Liquid Crystal Interface with Cationic Surfactants Using Magnetic Fréedericksz Transition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:81-87. [PMID: 29202240 DOI: 10.1021/acs.langmuir.7b03005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We constructed the apparatus to observe the Fréedericksz transition of liquid crystal in contact with water. The Fréedericksz transition is a distortion of nematic liquid crystals (LCs) induced by external fields. In the present system, sweeping homogeneous magnetic field was applied to the sample, and the distortion of the LC was visualized with a polarized light microscope with the crossed Nichols configuration. The anchoring energy (WAQ/LC) at the aqueous phase/LC interface was measured in the presence of surfactant from the threshold magnetic field of the Fréedericksz transition. We studied two cationic surfactants: dodecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide. A nematic LC, 4-cyano-4'-pentylbiphenyl (5CB), was examined, which was confined in a copper grid on an octadecyltrichlorosilane-treated microscope glass plate. Measured WAQ/LC were reproducible and showed consistence with the reported region for the water/LC interface. Interfacial excess of surfactants was also measured by the pendant drop method, and the relationship between the obtained WAQ/LC and the interfacial excess was investigated. Experiments showed that an increase in the anchoring energy depends on the surfactant and its interfacial excess. The region of the interfacial coverage, at which WAQ/LC increases, varied with the chain length of the surfactant. The measurement of the anchoring energy will provide new fundamental information on aqueous phase/LC interface.
Collapse
Affiliation(s)
- Fatma Yesil
- Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Masayori Suwa
- Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Satoshi Tsukahara
- Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| |
Collapse
|
27
|
Sumer Z, Striolo A. Manipulating molecular order in nematic liquid crystal capillary bridgesviasurfactant adsorption: guiding principles from dissipative particle dynamics simulations. Phys Chem Chem Phys 2018; 20:30514-30524. [DOI: 10.1039/c8cp04492a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Effect of surfactant tail length on the orientation of liquid crystals is investigated with dissipative particle dynamics (DPD) simulations.
Collapse
Affiliation(s)
- Zeynep Sumer
- Department of Chemical Engineering
- University College London
- London WC1E 7JE
- UK
| | - Alberto Striolo
- Department of Chemical Engineering
- University College London
- London WC1E 7JE
- UK
| |
Collapse
|
28
|
Abstract
Chemotaxis and autochemotaxis play an important role in many essential biological processes. We present a self-propelling artificial swimmer system that exhibits chemotaxis as well as negative autochemotaxis. Oil droplets in an aqueous surfactant solution are driven by interfacial Marangoni flows induced by micellar solubilization of the oil phase. We demonstrate that chemotaxis along micellar surfactant gradients can guide these swimmers through a microfluidic maze. Similarly, a depletion of empty micelles in the wake of a droplet swimmer causes negative autochemotaxis and thereby trail avoidance. We studied autochemotaxis quantitatively in a microfluidic device of bifurcating channels: Branch choices of consecutive swimmers are anticorrelated, an effect decaying over time due to trail dispersion. We modeled this process by a simple one-dimensional diffusion process and stochastic Langevin dynamics. Our results are consistent with a linear surfactant gradient force and diffusion constants appropriate for micellar diffusion and provide a measure of autochemotactic feedback strength vs. stochastic forces. This assay is readily adaptable for quantitative studies of both artificial and biological autochemotactic systems.
Collapse
|
29
|
Siebert JT, Letz J, Speck T, Virnau P. Phase behavior of active Brownian disks, spheres, and dimers. SOFT MATTER 2017; 13:1020-1026. [PMID: 28083593 DOI: 10.1039/c6sm02622b] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In this paper we provide high precision estimates of the phase diagram of active Brownian particles. We extract coexisting densities from simulations of phase separated states in an elongated box (slab geometry) which minimizes finite-size effects and allows for precise determination of points on the binodal lines. Using this method, we study the influence of both shape and dimensionality on the two-phase region. Active spheres and dimers of active particles are compared to the known phase diagram of active Brownian disks. In the case of dimers, both correlated and uncorrelated propulsion of the two beads are studied. The influence of correlations is discussed through a simple mapping.
Collapse
|
30
|
Krüger C, Klös G, Bahr C, Maass CC. Curling Liquid Crystal Microswimmers: A Cascade of Spontaneous Symmetry Breaking. PHYSICAL REVIEW LETTERS 2016; 117:048003. [PMID: 27494501 DOI: 10.1103/physrevlett.117.048003] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Indexed: 06/06/2023]
Abstract
We report curling self-propulsion in aqueous emulsions of common mesogenic compounds. Nematic liquid crystal droplets self-propel in a surfactant solution with concentrations above the critical micelle concentration while undergoing micellar solubilization [Herminghaus et al., Soft Matter 10, 7008 (2014)]. We analyzed trajectories both in a Hele-Shaw geometry and in a 3D setup at variable buoyancy. The coupling between the nematic director field and the convective flow inside the droplet leads to a second symmetry breaking which gives rise to curling motion in 2D. This is demonstrated through a reversible transition to nonhelical persistent swimming by heating to the isotropic phase. Furthermore, autochemotaxis can spontaneously break the inversion symmetry, leading to helical trajectories in 3D.
Collapse
Affiliation(s)
- Carsten Krüger
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
| | - Gunnar Klös
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
| | - Christian Bahr
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
| | - Corinna C Maass
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
| |
Collapse
|
31
|
Krüger C, Bahr C, Herminghaus S, Maass CC. Dimensionality matters in the collective behaviour of active emulsions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:64. [PMID: 27342105 DOI: 10.1140/epje/i2016-16064-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 06/02/2016] [Indexed: 06/06/2023]
Abstract
The behaviour of artificial microswimmers consisting of droplets of a mesogenic oil immersed in an aqueous surfactant solution depends qualitatively on the conditions of dimensional confinement; ranging from only transient aggregates in Hele-Shaw geometries to hexagonally packed, convection-driven clusters when sedimenting in an unconfined reservoir. We study the effects of varying the swimmer velocity, the height of the reservoir, and the buoyancy of the droplet swimmers. Two simple adjustments of the experimental setting lead to a suppression of clustering: either a decrease of the reservoir height below a certain value, or a match of the densities of droplets and surrounding phase, showing that the convection is the key mechanism for the clustering behaviour.
Collapse
Affiliation(s)
- Carsten Krüger
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077, Göttingen, Germany.
| | - Christian Bahr
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077, Göttingen, Germany
| | - Stephan Herminghaus
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077, Göttingen, Germany
| | - Corinna C Maass
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077, Göttingen, Germany
| |
Collapse
|
32
|
Jeong J, Gross A, Wei WS, Tu F, Lee D, Collings PJ, Yodh AG. Liquid crystal Janus emulsion droplets: preparation, tumbling, and swimming. SOFT MATTER 2015; 11:6747-6754. [PMID: 26171829 DOI: 10.1039/c5sm01053e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study introduces liquid crystal (LC) Janus droplets. We describe a process for the preparation of these droplets, which consist of nematic LC and polymer compartments. The process employs solvent-induced phase separation in emulsion droplets generated by microfluidics. The droplet morphology was systematically investigated and demonstrated to be sensitive to the surfactant concentration in the background phase, the compartment volume ratio, and the possible coalescence of multiple Janus droplets. Interestingly, the combination of a polymer and an anisotropic LC introduces new functionalities into Janus droplets, and these properties lead to unusual dynamical behaviors. The different densities and solubilities of the two compartments produce gravity-induced alignment, tumbling, and directional self-propelled motion of Janus droplets. LC Janus droplets with remarkable optical properties and dynamical behaviors thus offer new avenues for applications of Janus colloids and active soft matter.
Collapse
Affiliation(s)
- Joonwoo Jeong
- School of Natural Science, Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.
| | | | | | | | | | | | | |
Collapse
|
33
|
Vitek M, Muševič I. Nanosecond control and optical pulse shaping by stimulated emission depletion in a liquid crystal. OPTICS EXPRESS 2015; 23:16921-16932. [PMID: 26191703 DOI: 10.1364/oe.23.016921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study anisotropic Stimulated Emission Depletion (STED) from dye molecules, which are collectively ordered in a host liquid crystal. Due to the ordering of fluorescent emitters, the STED efficiency depends on the polarization of the depletion beam and time-delay of the STED pulse. The depletion efficiency is highest at lower temperatures in the highly ordered smectic-A phase and deteriorates in the higher temperature nematic and isotropic phases. We demonstrate by temporal tuning of STED that it is possible to generate an arbitrary sequence of nanosecond fluorescent pulses with variable width and variable delay. Our results show that the STED mechanism in principle allows for very fast (GHz) and efficient control of light by light, which could in the future be used for all-optical control of the flow of light in photonic microdevices based on liquid crystals. Using STED anisotropy and time-control, new modalities of STED imaging in liquid crystals could be developed.
Collapse
|
34
|
Wang X, Miller DS, de Pablo JJ, Abbott NL. Reversible Switching of Liquid Crystalline Order Permits Synthesis of Homogeneous Populations of Dipolar Patchy Microparticles. ADVANCED FUNCTIONAL MATERIALS 2014; 24:6219-6226. [PMID: 25484850 PMCID: PMC4251523 DOI: 10.1002/adfm.201400911] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The spontaneous positioning of colloids on the surfaces of micrometer-sized liquid crystalline droplets and their subsequent polymerization offers the basis of a general and facile method for the synthesis of patchy microparticles. The existence of multiple local energetic minima, however, can generate kinetic traps for colloids on the surfaces of the liquid crystal (LC) droplets and result in heterogeneous populations of patchy microparticles. To address this issue, here we demonstrate that adsorbate-driven switching of the internal configurations of LC droplets can be used to sweep colloids to a single location on the LC droplet surfaces, thus resulting in the synthesis of homogeneous populations of patchy microparticles. The surface-driven switching of the LC can be triggered by addition of surfactant or salts, and permits the synthesis of dipolar microparticles as well as "Janus-like" microparticles. By using magnetic colloids, we illustrate the utility of the approach by synthesizing magnetically-responsive patchy microdroplets of LC with either dipolar or quadrupolar symmetry that exhibit distinct optical responses upon application of an external magnetic field.
Collapse
Affiliation(s)
- Xiaoguang Wang
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Daniel S. Miller
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Juan J. de Pablo
- Institute for Molecular Engineering, University of Chicago, 5801 South Ellis Avenue Chicago, Illinois 60637, United States
| | - Nicholas L. Abbott
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| |
Collapse
|
35
|
Herminghaus S, Maass CC, Krüger C, Thutupalli S, Goehring L, Bahr C. Interfacial mechanisms in active emulsions. SOFT MATTER 2014; 10:7008-22. [PMID: 24924906 DOI: 10.1039/c4sm00550c] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Active emulsions, i.e., emulsions whose droplets perform self-propelled motion, are of tremendous interest for mimicking collective phenomena in biological populations such as phytoplankton and bacterial colonies, but also for experimentally studying rheology, pattern formation, and phase transitions in systems far from thermal equilibrium. For fuelling such systems, molecular processes involving the surfactants which stabilize the emulsions are a straightforward concept. We outline and compare two different types of reactions, one which chemically modifies the surfactant molecules, the other which transfers them into a different colloidal state. While in the first case symmetry breaking follows a standard linear instability, the second case turns out to be more complex. Depending on the dissolution pathway, there is either an intrinsically nonlinear instability, or no symmetry breaking at all (and hence no locomotion).
Collapse
Affiliation(s)
- Stephan Herminghaus
- Max-Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.
| | | | | | | | | | | |
Collapse
|
36
|
Peddireddy K, Kumar P, Thutupalli S, Herminghaus S, Bahr C. Myelin structures formed by thermotropic smectic liquid crystals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15682-15688. [PMID: 24274621 DOI: 10.1021/la4038588] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on transient structures, formed by thermotropic smectic-A liquid crystals, resembling the myelin figures of lyotropic lamellar liquid crystals. The thermotropic myelin structures form during the solubilization of a smectic-A droplet in an aqueous phase containing a cationic surfactant at concentrations above the critical micelle concentration. Similar to the lyotropic myelin figures, the thermotropic myelins appear in an optical microscope as flexible tubelike structures growing at the smectic/aqueous interface. Polarizing microscopy and confocal fluorescence microscopy show that the smectic layers are parallel to the tube surface and form a cylindrically bent arrangement around a central line defect in the tube. We study the growth behavior of this new type of myelins and discuss similarities to and differences from the classical lyotropic myelin figures.
Collapse
Affiliation(s)
- Karthik Peddireddy
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 Goettingen, Germany
| | | | | | | | | |
Collapse
|
37
|
Peddireddy K, Jampani VSR, Thutupalli S, Herminghaus S, Bahr C, Muševič I. Lasing and waveguiding in smectic A liquid crystal optical fibers. OPTICS EXPRESS 2013; 21:30233-30242. [PMID: 24514602 DOI: 10.1364/oe.21.030233] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a new class of soft matter optical fibers, which are self-assembled in a form of smectic-A liquid crystal microtubes grown in an aqueous surfactant dispersion of a smectic-A liquid crystal. The diameter of the fibers is highly uniform and the fibers are highly birefringent. They are characterized by a line topological defect in the core of the fiber with an optical axis pointing from the defect core towards the surface. We demonstrate guiding of light along the fiber and Whispering Gallery Mode (WGM) lasing in a plane perpendicular to the fiber. The light guiding as well as the lasing threshold are significantly dependent on the polarization of the excitation beam. The observed threshold for WGM lasing is very low (≈ 75μJ/cm(2)) when the pump beam polarization is perpendicular to the direction of the laser dye alignment and is similar to the lasing threshold in nematic droplets. The smectic-A fibers are soft and flexible and can be manipulated with laser tweezers demonstrating a promising approach for realization of soft photonic circuits.
Collapse
|