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Keywords = catalytic microswimmers

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19 pages, 4437 KB  
Review
Collective Behaviors of Isotropic Micromotors: From Assembly to Reconstruction and Motion Control under External Fields
by Kai Feng, Ling Chen, Xinle Zhang, Jiang Gong, Jinping Qu and Ran Niu
Nanomaterials 2023, 13(21), 2900; https://doi.org/10.3390/nano13212900 - 3 Nov 2023
Cited by 3 | Viewed by 3226
Abstract
Swarms of self-propelled micromotors can mimic the processes of natural systems and construct artificial intelligent materials to perform complex collective behaviors. Compared to self-propelled Janus micromotors, the isotropic colloid motors, also called micromotors or microswimmers, have advantages in self-assembly to form micromotor swarms, [...] Read more.
Swarms of self-propelled micromotors can mimic the processes of natural systems and construct artificial intelligent materials to perform complex collective behaviors. Compared to self-propelled Janus micromotors, the isotropic colloid motors, also called micromotors or microswimmers, have advantages in self-assembly to form micromotor swarms, which are efficient in resistance to external disturbance and the delivery of large quantity of cargos. In this minireview, we summarize the fundamental principles and interactions for the assembly of isotropic active particles to generate micromotor swarms. Recent discoveries based on either catalytic or external physical field-stimulated micromotor swarms are also presented. Then, the strategy for the reconstruction and motion control of micromotor swarms in complex environments, including narrow channels, maze, raised obstacles, and high steps/low gaps, is summarized. Finally, we outline the future directions of micromotor swarms and the remaining challenges and opportunities. Full article
(This article belongs to the Special Issue Advances in Micro-/Nanorobotics)
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10 pages, 406 KB  
Article
Accurate Solutions to Non-Linear PDEs Underlying a Propulsion of Catalytic Microswimmers
by Evgeny S. Asmolov, Tatiana V. Nizkaya and Olga I. Vinogradova
Mathematics 2022, 10(9), 1503; https://doi.org/10.3390/math10091503 - 1 May 2022
Cited by 4 | Viewed by 2744
Abstract
Catalytic swimmers self-propel in electrolyte solutions thanks to an inhomogeneous ion release from their surface. Here, we consider the experimentally relevant limit of thin electrostatic diffuse layers, where the method of matched asymptotic expansions can be employed. While the analytical solution for ion [...] Read more.
Catalytic swimmers self-propel in electrolyte solutions thanks to an inhomogeneous ion release from their surface. Here, we consider the experimentally relevant limit of thin electrostatic diffuse layers, where the method of matched asymptotic expansions can be employed. While the analytical solution for ion concentration and electric potential in the inner region is known, the electrostatic problem in the outer region was previously solved but only for a linear case. Additionally, only main geometries such as a sphere or cylinder have been favoured. Here, we derive a non-linear outer solution for the electric field and concentrations for swimmers of any shape with given ion surface fluxes that then allow us to find the velocity of particle self-propulsion. The power of our formalism is to include the complicated effects of the anisotropy and inhomogeneity of surface ion fluxes under relevant boundary conditions. This is demonstrated by exact solutions for electric potential profiles in some particular cases with the consequent calculations of self-propulsion velocities. Full article
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11 pages, 652 KB  
Article
Progress Report on pH-Influenced Photocatalysis for Active Motion
by Sandra Heckel, Julia Hübner, Anne Leutzgen, Gregor Jung and Juliane Simmchen
Catalysts 2021, 11(5), 599; https://doi.org/10.3390/catal11050599 - 6 May 2021
Cited by 13 | Viewed by 4077
Abstract
Living systems use catalysis to achieve chemical transformations to comply with their needs in terms of energy and building blocks. The pH is a powerful means to regulate such processes, which also influences synthetic systems. In fact, the pH sensitivity of artificial photocatalysts, [...] Read more.
Living systems use catalysis to achieve chemical transformations to comply with their needs in terms of energy and building blocks. The pH is a powerful means to regulate such processes, which also influences synthetic systems. In fact, the pH sensitivity of artificial photocatalysts, such as bismuth vanadate, bears the strong potential of flexibly influencing both the motion pattern and the speed of catalytic microswimmers, but it has rarely been investigated to date. In this work, we first present a comprehensive view of the motion behavior of differently shaped bismuth vanadate microswimmers, discuss influences, such as shape, pH, and conductivity of the solutions, and find that the motion pattern of the swimmers switches between upright and horizontal at their point of zero charge. We then apply an immobilizable hydroxypyrene derivative to our substrates to locally influence the pH of the solution by excited-state proton transfer. We find that the motion pattern of our swimmers is strongly influenced by this functionalization and a third motion mode, called tumbling, is introduced. Taking other effects, such as an increased surface roughness of the modified substrates, into account, we critically discuss possible future developments. Full article
(This article belongs to the Special Issue State of the Art and Future Trends in Nanostructured Biocatalysis)
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13 pages, 1742 KB  
Article
The Hydrodynamics of a Micro-Rocket Propelled by a Deformable Bubble
by Giacomo Gallino, Lailai Zhu and François Gallaire
Fluids 2019, 4(1), 48; https://doi.org/10.3390/fluids4010048 - 14 Mar 2019
Cited by 6 | Viewed by 4476
Abstract
We perform simulations to study the hydrodynamics of a conical-shaped swimming micro-robot that ejects catalytically produced bubbles from its inside. We underline the nontrivial dependency of the swimming velocity on the bubble deformability and on the geometry of the swimmer. We identify three [...] Read more.
We perform simulations to study the hydrodynamics of a conical-shaped swimming micro-robot that ejects catalytically produced bubbles from its inside. We underline the nontrivial dependency of the swimming velocity on the bubble deformability and on the geometry of the swimmer. We identify three distinct phases during the bubble evolution: immediately after nucleation the bubble is spherical and its inflation barely affects the swimming speed; then the bubble starts to deform due to the confinement gradient generating a force that propels the swimmer; while in the last phase, the bubble exits the cone, resulting in an increase in the swimmer velocity. Our results shed light on the fundamental hydrodynamics of the propulsion of catalytic conical swimmers and may help to improve the efficiency of these micro-machines. Full article
(This article belongs to the Special Issue Free surface flows)
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