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Ferreira VRA, Azenha MA. Recent Advances in Light-Driven Semiconductor-Based Micro/Nanomotors: Optimization Strategies and Emerging Applications. Molecules 2024; 29:1154. [PMID: 38474666 DOI: 10.3390/molecules29051154] [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: 01/15/2024] [Revised: 02/21/2024] [Accepted: 02/28/2024] [Indexed: 03/14/2024] Open
Abstract
Micro/nanomotors represent a burgeoning field of research featuring small devices capable of autonomous movement in liquid environments through catalytic reactions and/or external stimuli. This review delves into recent advancements in light-driven semiconductor-based micro/nanomotors (LDSM), focusing on optimized syntheses, enhanced motion mechanisms, and emerging applications in the environmental and biomedical domains. The survey commences with a theoretical introduction to micromotors and their propulsion mechanisms, followed by an exploration of commonly studied LDSM, emphasizing their advantages. Critical properties affecting propulsion, such as surface features, morphology, and size, are presented alongside discussions on external conditions related to light sources and intensity, which are crucial for optimizing the propulsion speed. Each property is accompanied by a theoretical background and conclusions drawn up to 2018. The review further investigates recent adaptations of LDSM, uncovering underlying mechanisms and associated benefits. A brief discussion is included on potential synergistic effects between different external conditions, aiming to enhance efficiency-a relatively underexplored topic. In conclusion, the review outlines emerging applications in biomedicine and environmental monitoring/remediation resulting from recent LDSM research, highlighting the growing significance of this field. The comprehensive exploration of LDSM advancements provides valuable insights for researchers and practitioners seeking to leverage these innovative micro/nanomotors in diverse applications.
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Affiliation(s)
- Vanessa R A Ferreira
- CIQUP-Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
| | - Manuel A Azenha
- CIQUP-Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
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Saud KT, Solomon MJ. Microdynamics of active particles in defect-rich colloidal crystals. J Colloid Interface Sci 2023; 641:950-960. [PMID: 36989821 DOI: 10.1016/j.jcis.2023.03.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/04/2023] [Accepted: 03/02/2023] [Indexed: 03/11/2023]
Abstract
HYPOTHESIS Because they are self-propulsive, active colloidal particles can interact with their environment in ways that differ from passive, Brownian particles. Here, we explore how interactions in different microstructural regions may contribute to colloidal crystal annealing. EXPERIMENTS We investigate active particles propagating in a quasi-2D colloidal crystal monolayer produced by alternating current electric fields (active-to-passive particle ratio ∼ 1:720). The active particle is a platinum Janus sphere propelled by asymmetric decomposition of hydrogen peroxide. Crystals are characterized for changes in void properties. The mean-squared-displacement of Janus particles are measured to determine how active microdynamics depend on the local microstructure, which is comprised of void regions, void-adjacent regions (defined as within three particle diameters of a void), and interstitial regions. FINDINGS At active particle energy EA = 2.55 kBT, the average void size increases as much as three times and the average void anisotropy increases about 40% relative to the passive case. The average microdynamical enhancement, <δ(t)>, of Janus particles in the crystal relative to an equivalent passive Janus particle is reduced compared to that of a free, active particle (<δ(t) > is 1.88 ± 0.04 and 2.66 ± 0.08, respectively). The concentration of active particles is enriched in void and void-adjacent regions. Active particles exhibit the greatest change in dynamics relative to the passive control in void-adjacent regions (<δ(t)> = 2.58 ± 0.06). The results support the conjecture that active particle microdynamical enhancement in crystal lattices is affected by local defect structure.
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Affiliation(s)
- Keara T Saud
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, United States; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
| | - Michael J Solomon
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States; Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, United States.
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Bag P, Nayak S, Debnath T, Ghosh PK. Directed Autonomous Motion and Chiral Separation of Self-Propelled Janus Particles in Convection Roll Arrays. J Phys Chem Lett 2022; 13:11413-11418. [PMID: 36459443 DOI: 10.1021/acs.jpclett.2c03193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Self-propelled Janus particles exhibit autonomous motion thanks to engines of their own. However, due to the randomly changing direction of such motion they are of little use for emerging nanotechnological and biomedical applications. Here, we numerically show that the motion of chiral active Janus particles can be directed, subjecting them to a linear array of convection rolls. The rectification power of self-propulsion motion here can be made to be more than 60%, which is much larger than earlier reports. We show that rectification of a chiral Janus particle's motion leads to conspicuous segregation of dextrogyre and levogyre active particles from a racemic binary mixture. Further, we demonstrate how efficiently the rectification effect can be exploited to separate dextrogyre and levogyre particles when their intrinsic torques are distributed with Gaussian statistics.
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Affiliation(s)
- Poulami Bag
- Department of Chemistry, Presidency University, Kolkata700073, India
| | - Shubhadip Nayak
- Department of Chemistry, Presidency University, Kolkata700073, India
| | - Tanwi Debnath
- Department of Chemistry, University of Calcutta, Kolkata700009, India
| | - Pulak K Ghosh
- Department of Chemistry, Presidency University, Kolkata700073, India
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Madden IP, Wang L, Simmchen J, Luijten E. Hydrodynamically Controlled Self-Organization in Mixtures of Active and Passive Colloids. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2107023. [PMID: 35304973 DOI: 10.1002/smll.202107023] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 02/04/2022] [Indexed: 06/14/2023]
Abstract
Active particles are known to exhibit collective behavior and induce structure in a variety of soft-matter systems. However, many naturally occurring complex fluids are mixtures of active and passive components. The authors examine how activity induces organization in such multi-component systems. Mixtures of passive colloids and colloidal micromotors are investigated and it is observed that even a small fraction of active particles induces reorganization of the passive components in an intriguing series of phenomena. Experimental observations are combined with large-scale simulations that explicitly resolve the near- and far-field effects of the hydrodynamic flow and simultaneously accurately treat the fluid-colloid interfaces. It is demonstrated that neither conventional molecular dynamics simulations nor the reduction of hydrodynamic effects to phoretic attractions can explain the observed phenomena, which originate from the flow field that is generated by the active colloids and subsequently modified by the aggregating passive units. These findings not only offer insight into the organization of biological or synthetic active-passive mixtures, but also open avenues to controlling the behavior of passive building blocks by means of small amounts of active particles.
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Affiliation(s)
- Ian P Madden
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Linlin Wang
- Department of Physical Chemistry, TU Dresden, Zellescher Weg 19, 01062, Dresden, Germany
| | - Juliane Simmchen
- Department of Physical Chemistry, TU Dresden, Zellescher Weg 19, 01062, Dresden, Germany
| | - Erik Luijten
- Departments of Materials Science and Engineering, Engineering Sciences and Applied Mathematics, Chemistry, Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA
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Zhu J, Wang H, Zhang Z. Shape-Tunable Janus Micromotors via Surfactant-Induced Dewetting. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:4964-4970. [PMID: 33861610 DOI: 10.1021/acs.langmuir.1c00340] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The ability to tune shapes of micromotors is challenging yet crucial for creating intelligent and functional micromachines with shape-dependent dynamics. Here, we demonstrate a facile strategy to synthesize Janus micromotors in large quantity whose shapes can be precisely tuned by a surfactant-induced dewetting strategy. The Janus micromotor is composed of a TiO2 microparticle partially encapsulated within a polysiloxane microsphere. A range of particle shapes, from approximately spherical to snowman, is achieved, and the shape-tunable dynamics of the micromotors are quantified. Our strategy is versatile and can be applicable to other photoactive materials, such as ZnO and Fe2O3 nanoparticles, demonstrating a general approach to synthesize Janus micromotors with controllable shapes. Such shape-tunable micromotors provide colloidal model systems for fundamental research on active matter, as well as building blocks for the fabrication of micromachines.
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Wang D, Gao C, Si T, Li Z, Guo B, He Q. Near-infrared light propelled motion of needlelike liquid metal nanoswimmers. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2020.125865] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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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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Ketzetzi S, de Graaf J, Kraft DJ. Diffusion-Based Height Analysis Reveals Robust Microswimmer-Wall Separation. PHYSICAL REVIEW LETTERS 2020; 125:238001. [PMID: 33337216 DOI: 10.1103/physrevlett.125.238001] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 10/08/2020] [Indexed: 06/12/2023]
Abstract
Microswimmers typically move near walls, which can strongly influence their motion. However, direct experimental measurements of swimmer-wall separation remain elusive to date. Here, we determine this separation for model catalytic microswimmers from the height dependence of the passive component of their mean-squared displacement. We find that swimmers exhibit "ypsotaxis," a tendency to assume a fixed height above the wall for a range of salt concentrations, swimmer surface charges, and swimmer sizes. Our findings indicate that ypsotaxis is activity induced, posing restrictions on future modeling of their still-debated propulsion mechanism.
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Affiliation(s)
- Stefania Ketzetzi
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, Netherlands
| | - Joost de Graaf
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands
| | - Daniela J Kraft
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, Netherlands
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Landry B, Girgis V, Gibbs JG. Controlling the Speed of Light-Activated Colloids with a Constant, Uniform Magnetic Field. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2003375. [PMID: 32761789 DOI: 10.1002/smll.202003375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 06/17/2020] [Indexed: 05/23/2023]
Abstract
It is demonstrated how the strength of activation for photocatalytic, self-propelled colloids can be enhanced with a constant, uniform magnetic field. When exposed to ultraviolet light and hydrogen peroxide, the titanium dioxide-based colloids become actively propelled. Due to the iron oxide core, a uniform field oriented perpendicular to the surface where motion takes place causes the asymmetrically shaped particles to rotate, which consequently leads to an increase in activity. The field-dependent dynamics of self-propulsion is quantified, and a qualitative description of how this effect arises is proposed. Since the application of the field is easily reversible, modulating the field on-and-off serves as a de facto "switch" that controls particle behavior.
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Affiliation(s)
- Brad Landry
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Victoria Girgis
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - John G Gibbs
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, AZ, 86011, USA
- Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, AZ, 86011, USA
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Huang T, Gobeil S, Wang X, Misko V, Nori F, De Malsche W, Fassbender J, Makarov D, Cuniberti G, Baraban L. Anisotropic Exclusion Effect between Photocatalytic Ag/AgCl Janus Particles and Passive Beads in a Dense Colloidal Matrix. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:7091-7099. [PMID: 32011149 DOI: 10.1021/acs.langmuir.0c00012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Synthetic nano- and micromotors interact with each other and their surroundings in a complex manner. Here, we report on the anisotropy of active-passive particle interaction in a soft matter system containing an immobile yet photochemical Ag/AgCl-based Janus particle embedded in a dense matrix of passive beads in pure water. The asymmetry in the chemical gradient around the Janus particle, triggered upon visible light illumination, distorts the isotropy of the surrounding electric potential and results in the repulsion of adjacent passive beads to a certain distance away from the Janus particle. This exclusion effect is found to be anisotropic with larger distances to passive beads in front of the Ag/AgCl cap of the Janus particle. We provide insight into this phenomenon by performing the angular analysis of the radii of exclusion and tracking their time evolution at the level of a single bead. Our study provides a novel fundamental insight into the collective behavior of a complex mixture of active and passive particles and is relevant for various application scenarios, e.g., particle transport at micro- and nanoscale and local chemical sensing.
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Affiliation(s)
- Tao Huang
- Max Bergmann Center of Biomaterials and Institute for Materials Science, Technische Universität Dresden, 01062 Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Sophie Gobeil
- Max Bergmann Center of Biomaterials and Institute for Materials Science, Technische Universität Dresden, 01062 Dresden, Germany
| | - Xu Wang
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Vyacheslav Misko
- Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wako shi, Saitama 351-0198, Japan
- μFlow group, Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Franco Nori
- Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wako shi, Saitama 351-0198, Japan
- Physics Department, University of Michigan, Ann Arbor, Michigan 48109-1040, United States
| | - Wim De Malsche
- μFlow group, Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jürgen Fassbender
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Denys Makarov
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Gianaurelio Cuniberti
- Max Bergmann Center of Biomaterials and Institute for Materials Science, Technische Universität Dresden, 01062 Dresden, Germany
| | - Larysa Baraban
- Max Bergmann Center of Biomaterials and Institute for Materials Science, Technische Universität Dresden, 01062 Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
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11
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Gibbs JG. Shape- and Material-Dependent Self-Propulsion of Photocatalytic Active Colloids, Interfacial Effects, and Dynamic Interparticle Interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6938-6947. [PMID: 31738561 DOI: 10.1021/acs.langmuir.9b02866] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Active colloids powered by self-generated, local chemical concentration gradients exhibit dynamics that are a function of the particles' morphology and material properties. These characteristics also govern how the active colloids interact with surfaces, including other particles and nearby walls. Thus, by targeted design, the dynamic behavior, on average, can be engineered, despite a lack of "external" control such as an applied magnetic field. This allows for the development of new applications and the investigation of novel effects that arise when self-propelled active colloids have complex shapes and material composition. Here, we explore some of our recent work on this topic including the dynamics and interactions of photoactivated, self-propelled colloids with such multifaceted properties. We also delve into some special cases, such as a new variety of active particle-particle interaction that we recently developed, in which direct contact between the active colloids is forbidden, and the direction of propulsion for pairs of particles is correlated. The unifying theme of the work highlighted herein is the relationship between the physical, chemical, and material properties of active colloids and their motive behavior, the understanding of which opens up a wide range of new possibilities as we move toward the ultimate goal of realizing functional, man-made micro- and nanomachinery.
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Ketzetzi S, de Graaf J, Doherty RP, Kraft DJ. Slip Length Dependent Propulsion Speed of Catalytic Colloidal Swimmers near Walls. PHYSICAL REVIEW LETTERS 2020; 124:048002. [PMID: 32058791 DOI: 10.1103/physrevlett.124.048002] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 09/06/2019] [Indexed: 06/10/2023]
Abstract
Catalytic colloidal swimmers that propel due to self-generated fluid flows exhibit strong affinity for surfaces. Here, we report experimental measurements of a significant dependence of such microswimmers' speed on the nearby substrate material. We find that speeds scale with the solution contact angle θ on the substrate, which relates to the associated hydrodynamic substrate slip length, as V∝(cosθ+1)^{-3/2}. We show that such dependence can be attributed to osmotic coupling between swimmers and substrate. Our work points out that hydrodynamic slip at nearby walls, though often unconsidered, can significantly impact microswimmer self-propulsion.
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Affiliation(s)
- Stefania Ketzetzi
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Joost de Graaf
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Rachel P Doherty
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Daniela J Kraft
- Soft Matter Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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13
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Gendelman O, Frenkel M, Binks BP, Bormashenko E. Cherenkov-Like Surface Thermal Waves Emerging from Self-Propulsion of a Liquid Marble. J Phys Chem B 2020; 124:695-699. [PMID: 31931572 DOI: 10.1021/acs.jpcb.9b11100] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We explore the thermal field related to the self-propulsion of floating liquid marbles filled with aqueous ethanol. Cherenkov-like thermal waves arising from self-propulsion are registered. The opening angle of the thermal field Cherenkov triangle is governed by the inter-relation between the velocity of self-propulsion and the phase velocity of the capillary waves. The self-propulsion is driven by soluto-capillarity accompanied by thermo-capillarity. A semiquantitative analysis of the effect is presented. The empirical selection rule for capillary waves responsible for the mass, momentum, and heat transfer is outlined. The soluto-capillarity leads to much stronger spatial variations of the surface tension than the thermo-capillarity.
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Affiliation(s)
- Oleg Gendelman
- Technion, Israel Institute of Technology , Faculty of Mechanical Engineering , Haifa , 3200003 , Israel
| | - Mark Frenkel
- Ariel University , Engineering Faculty, Chemical Engineering Department , P.O.B. 3, 407000 , Ariel , Israel
| | - Bernard P Binks
- Department of Chemistry and Biochemistry , University of Hull , Hull HU67RX , U.K
| | - Edward Bormashenko
- Ariel University , Engineering Faculty, Chemical Engineering Department , P.O.B. 3, 407000 , Ariel , Israel
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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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