Rectification of self-propelled particles in entropic barriers: finite size effects (Q2878622)

In the last years, the study of physical and biological systems has focused on the transport of particles, which is confined to narrow channels. Some of the investigations were concerned with energy barriers (see [\textit{M. Bier}, \textit{M. Kostur}, \textit{I. Derényi} and \textit{A. D. Astumian}, ``Nonlinearly coupled flows'', Phys. Rev. E 61, 7184 (2000; \url{doi:10.1103/PhysRevE.61.7184})]) and some others with entropic barriers (see [\textit{D. Reguera} and \textit{J. M. Rubí}, ``Kinetic equations for diffusion in the presence of entropic barriers'', Phys. Rev. E 64, 061106 (2001; \url{doi:10.1103/PhysRevE.64.061106})]).NEWLINENEWLINE In these studies, the size of particles was ignored, by considering the particles as points.NEWLINENEWLINE Recently, \textit{B.-Q. Ai} and \textit{J.-C. Wu} [``Transport of finite size particles in confined narrow channels: diffusion, coherence, and particle separation'', J. Chem. Phys. 139, No. 3, 034114 (2013; \url{doi:10.1063/1.4813798})] took into account the particle sizes in transport properties and presented a particle separation mechanism based on the antagonism between the spatial asymmetry and temporal asymmetry. We note that all the particles involved in the previous models are passive Brownian particles.NEWLINENEWLINE In opposition, by the study of bacteria and spermatozoa motions and artificial colloidal microswimmers in the attraction of researchers appear the self-propelled particles (see [\textit{W. R. DiLuzio}, \textit{L. Turner}, \textit{M. Mayer}, \textit{P. Garsteck}, \textit{D. B. Weibel}, \textit{H. C. Berg} and \textit{G. M. Whitesides}, ``Escherichia coli swim on the right-hand side'', Nature 435, 1271--1274 (2005; \url{doi:10.1038/nature03660})]).NEWLINENEWLINE Here, the authors extend the study of finite size passive particles to the case of self-propelled particles, and focus on finding the dependence of average velocity of the self-propelled particles on the key parameters (the spatial asymmetry, the rotational diffusion rate, the self-propelled speed etc.).