Dynamics of two interacting active Janus particles.

Starting from a microscopic model for a spherically symmetric active Janus particle, we study the interactions between two such active motors. The ambient fluid mediates a long range hydrodynamic interaction between two motors. This interaction has both direct and indirect hydrodynamic contributions. The direct contribution is due to the propagation of fluid flow that originated from a moving motor and affects the motion of the other motor. The indirect contribution emerges from the re-distribution of the ionic concentrations in the presence of both motors. Electric force exerted on the fluid from this ionic solution enhances the flow pattern and subsequently changes the motion of both motors. By formulating a perturbation method for very far separated motors, we derive analytic results for the translation and rotational dynamics of the motors. We show that the overall interaction at the leading order modifies the translational and rotational speeds of motors which scale as O[1/D](3) and O[1/D](4) with their separation, respectively. Our findings open up the way for studying the collective dynamics of synthetic micro-motors.

[1]  Sirilak Sattayasamitsathit,et al.  Rapid delivery of drug carriers propelled and navigated by catalytic nanoshuttles. , 2010, Small.

[2]  Yanyan Cao,et al.  Catalytic nanomotors: autonomous movement of striped nanorods. , 2004, Journal of the American Chemical Society.

[3]  Shin‐Hyun Kim,et al.  Light-activated self-propelled colloids , 2014, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[4]  Clemens Bechinger,et al.  Active Brownian motion tunable by light , 2011, Journal of physics. Condensed matter : an Institute of Physics journal.

[5]  A. Najafi,et al.  Two-sphere low-Reynolds-number propeller. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[6]  Samuel Sanchez,et al.  Catalytic Janus motors on microfluidic chip: deterministic motion for targeted cargo delivery. , 2012, ACS nano.

[7]  Ehud Yariv,et al.  Electrokinetic self-propulsion by inhomogeneous surface kinetics , 2011, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[8]  Yuan Gao,et al.  How half-coated janus particles enter cells. , 2013, Journal of the American Chemical Society.

[9]  Allen Pei,et al.  Water-driven micromotors. , 2012, ACS nano.

[10]  Ryan Pavlick,et al.  Intelligent, self-powered, drug delivery systems. , 2013, Nanoscale.

[11]  A. Najafi,et al.  Rheological properties of a dilute suspension of self-propelled particles , 2014, 1408.4345.

[12]  J. Posner,et al.  Locomotion of electrocatalytic nanomotors due to reaction induced charge autoelectrophoresis. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[13]  Francesco Zerbetto,et al.  Synthetic molecular motors and mechanical machines. , 2007, Angewandte Chemie.

[14]  R. Goldstein,et al.  Self-concentration and large-scale coherence in bacterial dynamics. , 2004, Physical review letters.

[15]  A. Najafi,et al.  Propulsion at low Reynolds number , 2005 .

[16]  Gary J. Dunderdale,et al.  Electrokinetic effects in catalytic platinum-insulator Janus swimmers , 2013, 1312.6250.

[17]  Sirilak Sattayasamitsathit,et al.  Self-propelled activated carbon Janus micromotors for efficient water purification. , 2015, Small.

[18]  J. Ralston,et al.  Phoretic motion of spheroidal particles due to self-generated solute gradients , 2010, The European physical journal. E, Soft matter.

[19]  Wilson Poon,et al.  Ionic effects in self-propelled Pt-coated Janus swimmers. , 2013, Soft matter.

[20]  A. Najafi,et al.  General aspects of hydrodynamic interactions between three-sphere low-Reynolds-number swimmers. , 2012, Physical review. E, Statistical, nonlinear, and soft matter physics.

[21]  Dongqing Li,et al.  Micro-valve using induced-charge electrokinetic motion of Janus particle. , 2011, Lab on a chip.

[22]  Ramin Golestanian,et al.  Self-motile colloidal particles: from directed propulsion to random walk. , 2007, Physical review letters.

[23]  D. Prieve,et al.  Motion of a particle generated by chemical gradients. Part 2. Electrolytes , 1982, Journal of Fluid Mechanics.

[24]  Qiang He,et al.  Self-propelled polymer multilayer Janus capsules for effective drug delivery and light-triggered release. , 2014, ACS applied materials & interfaces.

[25]  E. Lauga,et al.  Phoretic self-propulsion at finite Péclet numbers , 2014, Journal of Fluid Mechanics.

[26]  Hiroyuki Ohshima,et al.  Theory of Colloid and Interfacial Electric Phenomena , 2006 .

[27]  Walter F Paxton,et al.  Catalytic nanomotors: remote-controlled autonomous movement of striped metallic nanorods. , 2005, Angewandte Chemie.

[28]  Thomas Powers,et al.  Life at low Reynolds' number revisited , 2012 .

[29]  Huiru Ma,et al.  Autonomous motion and temperature-controlled drug delivery of Mg/Pt-poly(N-isopropylacrylamide) Janus micromotors driven by simulated body fluid and blood plasma. , 2014, ACS applied materials & interfaces.

[30]  Wall effects on self-diffusiophoretic Janus particles: a theoretical study , 2013, Journal of Fluid Mechanics.

[31]  S. Balasubramanian,et al.  Chemical sensing based on catalytic nanomotors: motion-based detection of trace silver. , 2009, Journal of the American Chemical Society.

[32]  E. Yariv,et al.  Osmotic self-propulsion of slender particles , 2015 .

[33]  J. Howse,et al.  Direct observation of the direction of motion for spherical catalytic swimmers. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[34]  J. Happel,et al.  Low Reynolds number hydrodynamics , 1965 .

[35]  Aditya S. Khair,et al.  Dynamics of a self-diffusiophoretic particle in shear flow. , 2014, Physical review. E, Statistical, nonlinear, and soft matter physics.

[36]  J. Koplik,et al.  Diffusiophoretic self-propulsion of colloids driven by a surface reaction: The sub-micron particle regime for exponential and van der Waals interactions , 2013 .

[37]  Ayusman Sen,et al.  Catalytic motors for transport of colloidal cargo. , 2008, Nano letters.

[38]  J. Brady,et al.  Osmotic propulsion: the osmotic motor. , 2008, Physical review letters.

[39]  T. Lubensky,et al.  Statistical mechanics and hydrodynamics of bacterial suspensions , 2009, Proceedings of the National Academy of Sciences.

[40]  A. Najafi,et al.  Simple swimmer at low Reynolds number: three linked spheres. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[41]  J. Yeomans,et al.  Hydrodynamic interaction between two swimmers at low Reynolds number. , 2007, Physical review letters.

[42]  Liangfang Zhang,et al.  Artificial Micromotors in the Mouse’s Stomach: A Step toward in Vivo Use of Synthetic Motors , 2014, ACS nano.

[43]  F. Jülicher,et al.  Comment on "Osmotic propulsion: the osmotic motor". , 2009, Physical review letters.

[44]  T. Powers,et al.  The hydrodynamics of swimming microorganisms , 2008, 0812.2887.

[45]  S. Childress,et al.  Pattern formation in a suspension of swimming microorganisms: equations and stability theory , 1975, Journal of Fluid Mechanics.

[46]  Sriram Ramaswamy,et al.  Rheology of active-particle suspensions. , 2003, Physical review letters.

[47]  M. Tasinkevych,et al.  Self-propulsion of a catalytically active particle near a planar wall: from reflection to sliding and hovering. , 2014, Soft matter.

[48]  Samuel Sanchez,et al.  Self-Propelled Micromotors for Cleaning Polluted Water , 2013, ACS nano.

[49]  A. Najafi,et al.  Hydrodynamic interactions of spherical particles in a fluid confined by a rough no-slip wall. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[50]  Weihong Tan,et al.  A Single DNA Molecule Nanomotor , 2002 .