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Prajapati SD, Bhatnagar A, Gupta A. Effect of the background flow on motility-induced phase separation. SOFT MATTER 2025. [PMID: 40396309 DOI: 10.1039/d5sm00362h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2025]
Abstract
We simulate active Brownian particles (ABPs) with soft-repulsive interactions subjected to a four-roll-mill flow. In the absence of flow, this system exhibits motility-induced phase separation (MIPS). To investigate the interplay between MIPS and flow-induced mixing, we introduce dimensionless parameters: a scaled time, τ, and a scaled speed, V, characterizing the ratio of ABP to fluid time and speed scales, respectively. The parameter space defined by τ and V reveals three distinct ABP distribution regimes. At low speeds, V ≪ 1, flow dominates, leading to a homogeneous mixture. Conversely, at high speeds, V ≫ 1, motility prevails, resulting in MIPS. In the intermediate regime (V ∼ 1), the system's behavior depends on τ. For τ < 1, a moderately mixed homogeneous phase emerges, while for τ > 1, a novel phenomenon, termed flow-induced phase separation (FIPS), arises due to the combined effects of flow topology and ABP motility and size. To characterize these phases, we analyze drift velocity, diffusivity, mean-squared displacement, giant number fluctuations, radial distribution function, and cluster-size distribution.
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Affiliation(s)
- Soni D Prajapati
- Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad 502284, India.
| | - Akshay Bhatnagar
- Department of Physics, Indian Institute of Technology Palakkad, Palakkad 678623, Kerala, India.
- Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India
| | - Anupam Gupta
- Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad 502284, India.
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Kumar M, Sane S, Murali A, Thutupalli S. Temperature switchable self-propulsion activity of liquid crystalline microdroplets. SOFT MATTER 2025; 21:3782-3788. [PMID: 40242986 DOI: 10.1039/d4sm01382d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2025]
Abstract
We report on a switchable emulsion droplet microswimmer by utilizing a temperature-dependent transition of the droplet phase. The droplets, made from a liquid crystalline (LC) smectic phase material (T = 25 °C), self-propel only in their nematic and isotropic phases at elevated temperatures (T ≥ 33.5 °C). This transition between motile and non-motile states is fully reversible - in the motile state, the droplets exhibit persistent motion and directional memory over multiple heating-cooling cycles. Furthermore, we distinguish the state of rest from the state of motion by characterizing the chemical and hydrodynamic fields of the droplets. Next, we map the motility behaviour of the droplets across varying surfactant concentrations and temperatures, observing that swimming occurs only at sufficiently high surfactant concentrations and temperatures above the smectic-nematic phase transition temperature i.e. T ≥ 33.5 °C. Our work envisions the potential of LC emulsion droplets as temperature tunable microswimmers.
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Affiliation(s)
- Manoj Kumar
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India.
| | - Siddharth Sane
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India.
| | - Aniruddh Murali
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India.
| | - Shashi Thutupalli
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India.
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Hoskote Village, Bangalore, India
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3
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Ramesh P, Chen Y, Räder P, Morsbach S, Jalaal M, Maass CC. Frozen by Heating: Temperature Controlled Dynamic States in Droplet Microswimmers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2025; 37:e2416813. [PMID: 40040287 PMCID: PMC12004900 DOI: 10.1002/adma.202416813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2024] [Revised: 02/15/2025] [Indexed: 03/06/2025]
Abstract
Self-propelling active matter relies on the conversion of energy from the undirected, nanoscopic scale to directed, macroscopic motion. One of the challenges in the design of synthetic active matter lies in the control of dynamic states, or motility gaits. Here, an experimental system of self-propelling droplets with thermally controllable and reversible dynamic states is presented, from unsteady over meandering to persistent to arrested motion. These states are known to depend on the Péclet number of the molecular process powering the motion, which can now be tuned by using a temperature sensitive mixture of surfactants as propulsion fuel. The droplet dynamics are quantified by analyzing flow and chemical fields for the individual states, comparing them to canonical models for autophoretic particles. In the context of these models, in situ, the fundamental first broken symmetry that translates an isotropic, immotile base state to self-propelled motility, is experimentally demonstrated.
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Affiliation(s)
- Prashanth Ramesh
- Physics of Fluids GroupMax Planck Center for Complex Fluid Dynamics and J. M. Burgers Center for Fluid DynamicsUniversity of TwentePO Box 217Enschede7500AENetherlands
- Max Planck Institute for Dynamics and Self‐OrganizationAm Faßberg 1737077GöttingenGermany
| | - Yibo Chen
- Physics of Fluids GroupMax Planck Center for Complex Fluid Dynamics and J. M. Burgers Center for Fluid DynamicsUniversity of TwentePO Box 217Enschede7500AENetherlands
- Max Planck Institute for Dynamics and Self‐OrganizationAm Faßberg 1737077GöttingenGermany
| | - Petra Räder
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Svenja Morsbach
- Max Planck Institute for Polymer ResearchAckermannweg 1055128MainzGermany
| | - Maziyar Jalaal
- University of AmsterdamScience Park 904Amsterdam1098 XHNetherlands
| | - Corinna C. Maass
- Physics of Fluids GroupMax Planck Center for Complex Fluid Dynamics and J. M. Burgers Center for Fluid DynamicsUniversity of TwentePO Box 217Enschede7500AENetherlands
- Max Planck Institute for Dynamics and Self‐OrganizationAm Faßberg 1737077GöttingenGermany
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Shenoy SA, Chaithanya K, Dayal P. Shear-induced dynamics of an active Belousov-Zhabotinsky droplet. SOFT MATTER 2025; 21:1957-1969. [PMID: 39967401 DOI: 10.1039/d4sm01464b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2025]
Abstract
Controlled navigation of self-propelled active matter in complex biological environments has remained a significant challenge in engineering owing to a multitude of interactions that persist in the process. Active droplets, being some of the several synthetic active matters, have garnered significant attention owing to their ability to exhibit dynamic shape changes, self-sustained motion, interact with external stimuli such as flows, and mimic biological active matter. Here, we explore the dynamics of a self-propelled active droplet powered by the oscillatory Belousov-Zhabotinsky (BZ) reaction in the presence of a shear flow. We adapt a multicomponent lattice Boltzmann method (LBM) in conjunction with the phase-field model to simulate the droplet's interaction with the surrounding fluid. We unravel the collective effect of droplet deformation, reaction kinetics, and strength of the surrounding shear flow on droplet dynamics. Our findings depict that the shear flow disrupts the initial isotropic surface tension, and produces concentration nucleation spots in the droplet. The asymmetry thus generated produces Marangoni flow that ultimately propels the droplet. Our findings provide valuable insights into the mechanisms governing active droplet behavior and open new avenues for designing controllable synthetic active matter systems with potential applications in microfluidics, targeted delivery, and biomimetic technologies. In addition, our framework can potentially be integrated with the physics-informed machine learning framework to develop more efficient mesh-free methods.
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Affiliation(s)
- Shreyas A Shenoy
- Polymer Engineering Research Lab (PERL), Department of Chemical Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, 382355, India.
| | - Kvs Chaithanya
- Polymer Engineering Research Lab (PERL), Department of Chemical Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, 382355, India.
| | - Pratyush Dayal
- Polymer Engineering Research Lab (PERL), Department of Chemical Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, 382355, India.
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Buness CM, Rana A, Maass CC, Dey R. Electrotaxis of Self-Propelling Artificial Swimmers in Microchannels. PHYSICAL REVIEW LETTERS 2024; 133:158301. [PMID: 39454145 DOI: 10.1103/physrevlett.133.158301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 09/11/2024] [Indexed: 10/27/2024]
Abstract
Biological microswimmers alter their swimming trajectories to follow the direction of an applied electric field, exhibiting electrotaxis. We show that synthetic active droplet microswimmers also autonomously change swimming trajectories in microchannels, even undergoing "U-turns," in response to an electric field, mimicking electrotaxis. We exploit such electrotaxis, in the presence of an external flow, to robustly tune the swimming trajectory of active droplets between wall-adjacent, oscillatory, and channel centerline swimming. A general hydrodynamic model demonstrates that the electrotactic dynamics is governed by the electrical effects due to the swimmer's inherent surface charge, besides its motility, hydrodynamic wall interactions, and relative orientations of the electric field and imposed flow. Our study demonstrates a simple method for controlling active agents in complex geometries for microrobotic applications, like autonomous cargo delivery.
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Jahangiri AR, Ziarati N, Dadkhah E, Bucak MN, Rahimizadeh P, Shahverdi A, Sadighi Gilani MA, Topraggaleh TR. Microfluidics: The future of sperm selection in assisted reproduction. Andrology 2024; 12:1236-1252. [PMID: 38148634 DOI: 10.1111/andr.13578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 11/03/2023] [Accepted: 12/10/2023] [Indexed: 12/28/2023]
Abstract
BACKGROUND Obtaining functional sperm cells is the first step to treat infertility. With the ever-increasing trend in male infertility, clinicians require access to effective solutions that are able to single out the most viable spermatozoa, which would max out the chance for a successful pregnancy. The new generation techniques for sperm selection involve microfluidics, which offers laminar flow and low Reynolds number within the platforms can provide unprecedented opportunities for sperm selection. Previous studies showed that microfluidic platforms can provide a novel approach to this challenge and since then researchers across the globe have attacked this problem from multiple angles. OBJECTIVE In this review, we seek to provide a much-needed bridge between the technical and medical aspects of microfluidic sperm selection. Here, we provide an up-to-date list on microfluidic sperm selection procedures and its application in assisted reproductive technology laboratories. SEARCH METHOD A literature search was performed in Web of Science, PubMed, and Scopus to select papers reporting microfluidic sperm selection using the keywords: microfluidic sperm selection, self-motility, non-motile sperm selection, boundary following, rheotaxis, chemotaxis, and thermotaxis. Papers published before March 31, 2023 were selected. OUTCOMES Our results show that most studies have used motility-based properties for sperm selection. However, microfluidic platforms are ripe for making use of other properties such as chemotaxis and especially rheotaxis. We have identified that low throughput is one of the major hurdles to current microfluidic sperm selection chips, which can be solved via parallelization. CONCLUSION Future work needs to be performed on numerical simulation of the microfluidics chip prior to fabrication as well as relevant clinical assessment after the selection procedure. This would require a close collaboration and understanding among engineers, biologists, and medical professionals. It is interesting that in spite of two decades of microfluidics sperm selection, numerical simulation and clinical studies are lagging behind. It is expected that microfluidic sperm selection platforms will play a major role in the development of fully integrated start-to-finish assisted reproductive technology systems.
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Affiliation(s)
- Ali Reza Jahangiri
- NanoLund, Lund University, Lund, Sweden
- Materials Science and Applied Mathematics, Malmö University, Malmö, Sweden
| | - Niloofar Ziarati
- Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Ehsan Dadkhah
- Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
- Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
| | - Mustafa Numan Bucak
- Department of Reproduction and Artificial Insemination, Faculty of Veterinary Medicine, Selcuk University, Konya, Turkey
| | - Pegah Rahimizadeh
- Division of Experimental Surgery, McGill University, Montreal, Quebec, Canada
- Cancer Research Program, The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Abdolhossein Shahverdi
- Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Mohammad Ali Sadighi Gilani
- Department of Andrology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Tohid Rezaei Topraggaleh
- Reproductive Health Research Center, Clinical Research Institute, Urmia University of Medical Sciences, Urmia, Iran
- Department of Anatomical Sciences, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
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Kumar P, Dwivedi P, Ashraf S, Pillai D, Mangal R. Motility and pairwise interactions of chemically active droplets in one-dimensional confinement. Phys Rev E 2024; 110:024612. [PMID: 39295064 DOI: 10.1103/physreve.110.024612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 08/09/2024] [Indexed: 09/21/2024]
Abstract
Self-propelled droplets serve as ideal model systems to delve deeper into understanding the motion of biological microswimmers by simulating their motility. Biological microorganisms are renowned for showcasing a diverse array of dynamic swimming behaviors when confronted with physical constraints. This study aims to elucidate the impact of physical constraints on swimming characteristics of biological microorganisms. To achieve this, we present observations on the individual and pairwise behavior of micellar solubilized self-propelled 4-cyano-4'-pentyl-biphenyl (5CB) oil droplets in a square capillary channel filled with a surfactant trimethyl ammonium bromide aqueous solution. To explore the effect of the underlying Péclet number of the swimming droplets, the study is also performed in the presence of additives such as high molecular weight polymer polyethylene oxide and molecular solute glycerol. The capillary confinement restricts droplet to predominantly one-dimensional motion, albeit with noticeable differences in their motion across the three scenarios. Through a characterization of the chemical and hydrodynamic flow fields surrounding the droplets, we illustrate that the modification of the droplets' chemical field due to confinement varies significantly based on the underlying differences in the Péclet number in these cases. This alteration in the chemical field distribution notably affects the individual droplets' motion. Moreover, these distinct chemical field interactions between the droplets also lead to variations in their pairwise motion, ranging from behaviors like chasing to scattering.
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Jin C, Sengupta A. Microbes in porous environments: from active interactions to emergent feedback. Biophys Rev 2024; 16:173-188. [PMID: 38737203 PMCID: PMC11078916 DOI: 10.1007/s12551-024-01185-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/27/2024] [Indexed: 05/14/2024] Open
Abstract
Microbes thrive in diverse porous environments-from soil and riverbeds to human lungs and cancer tissues-spanning multiple scales and conditions. Short- to long-term fluctuations in local factors induce spatio-temporal heterogeneities, often leading to physiologically stressful settings. How microbes respond and adapt to such biophysical constraints is an active field of research where considerable insight has been gained over the last decades. With a focus on bacteria, here we review recent advances in self-organization and dispersal in inorganic and organic porous settings, highlighting the role of active interactions and feedback that mediates microbial survival and fitness. We discuss open questions and opportunities for using integrative approaches to advance our understanding of the biophysical strategies which microbes employ at various scales to make porous settings habitable.
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Affiliation(s)
- Chenyu Jin
- Physics of Living Matter Group, Department of Physics and Materials Science, University of Luxembourg, 162 A, Avenue de la Faïencerie, Luxembourg City, L-1511 Luxembourg
| | - Anupam Sengupta
- Physics of Living Matter Group, Department of Physics and Materials Science, University of Luxembourg, 162 A, Avenue de la Faïencerie, Luxembourg City, L-1511 Luxembourg
- Institute for Advanced Studies, University of Luxembourg, 2 Avenue de l’Université, Esch-sur-Alzette, L-4365 Luxembourg
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Schiltz-Rouse E, Row H, Mallory SA. Kinetic temperature and pressure of an active Tonks gas. Phys Rev E 2023; 108:064601. [PMID: 38243499 DOI: 10.1103/physreve.108.064601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 11/06/2023] [Indexed: 01/21/2024]
Abstract
Using computer simulation and analytical theory, we study an active analog of the well-known Tonks gas, where active Brownian particles are confined to a periodic one-dimensional (1D) channel. By introducing the notion of a kinetic temperature, we derive an accurate analytical expression for the pressure and clarify the paradoxical behavior where active Brownian particles confined to 1D exhibit anomalous clustering but no motility-induced phase transition. More generally, this work provides a deeper understanding of pressure in active systems as we uncover a unique link between the kinetic temperature and swim pressure valid for active Brownian particles in higher dimensions.
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Affiliation(s)
- Elijah Schiltz-Rouse
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Hyeongjoo Row
- Department of Chemical and Biomolecular Engineering, UC Berkeley, Berkeley, California 94720, USA
| | - Stewart A Mallory
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Wan KY. Active oscillations in microscale navigation. Anim Cogn 2023; 26:1837-1850. [PMID: 37665482 PMCID: PMC10769930 DOI: 10.1007/s10071-023-01819-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/27/2023] [Accepted: 08/12/2023] [Indexed: 09/05/2023]
Abstract
Living organisms routinely navigate their surroundings in search of better conditions, more food, or to avoid predators. Typically, animals do so by integrating sensory cues from the environment with their locomotor apparatuses. For single cells or small organisms that possess motility, fundamental physical constraints imposed by their small size have led to alternative navigation strategies that are specific to the microscopic world. Intriguingly, underlying these myriad exploratory behaviours or sensory functions is the onset of periodic activity at multiple scales, such as the undulations of cilia and flagella, the vibrations of hair cells, or the oscillatory shape modes of migrating neutrophils. Here, I explore oscillatory dynamics in basal microeukaryotes and hypothesize that these active oscillations play a critical role in enhancing the fidelity of adaptive sensorimotor integration.
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Affiliation(s)
- Kirsty Y Wan
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK.
- Department of Mathematics and Statistics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
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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]
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