Osmotic propulsion: the osmotic motor

A model for self-propulsion of a colloidal particle--the osmotic motor--immersed in a dispersion of "bath" particles is presented. The nonequilibrium concentration of bath particles induced by a surface chemical reaction creates an osmotic pressure imbalance on the motor causing it to move...

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Bibliographic Details
Published in:Physical review letters 2008-04, Vol.100 (15), p.158303-158303, Article 158303
Main Authors: Córdova-Figueroa, Ubaldo M, Brady, John F
Format: Article
Language:English
Subjects:
Colloids - chemistry
Kinetics
Models, Chemical
Nanotechnology - methods
Osmosis
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Summary:A model for self-propulsion of a colloidal particle--the osmotic motor--immersed in a dispersion of "bath" particles is presented. The nonequilibrium concentration of bath particles induced by a surface chemical reaction creates an osmotic pressure imbalance on the motor causing it to move. The ratio of the speed of reaction to that of diffusion governs the bath particle distribution which is employed to calculate the driving force on the motor, and from which the self-induced osmotic velocity is determined. For slow reactions, the self-propulsion is proportional to the reaction velocity. When surface reaction dominates over diffusion the osmotic velocity cannot exceed the diffusive speed of the bath particles. Implications of these features for different bath particle volume fractions and motor sizes are discussed. Theoretical predictions are compared with Brownian dynamics simulations.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.100.158303