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Activity-induced propulsion of a vesicle

Peng, Zhiwei and Zhou, Tingtao and Brady, John F. (2022) Activity-induced propulsion of a vesicle. Journal of Fluid Mechanics, 942 . Art. No. A32. ISSN 0022-1120. doi:10.1017/jfm.2022.398.

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Modern biomedical applications such as targeted drug delivery require a delivery system capable of enhanced transport beyond that of passive Brownian diffusion. In this work, an osmotic mechanism for the propulsion of a vesicle immersed in a viscous fluid is proposed. By maintaining a steady-state solute gradient inside the vesicle, a seepage flow of the solvent (e.g. water) across the semipermeable membrane is generated, which in turn propels the vesicle. We develop a theoretical model for this vesicle–solute system in which the seepage flow is described by a Darcy flow. Using the reciprocal theorem for Stokes flow, it is shown that the seepage velocity at the exterior surface of the vesicle generates a thrust force that is balanced by the hydrodynamic drag such that there is no net force on the vesicle. We characterize the motility of the vesicle in relation to the concentration distribution of the solute confined inside the vesicle. Any osmotic solute is able to propel the vesicle so long as a concentration gradient is present. In the present work, we propose active Brownian particles (ABPs) as a solute. To maintain a symmetry-breaking concentration gradient, we consider ABPs with spatially varying swim speed, and ABPs with constant properties but under the influence of an orienting field. In particular, it is shown that at high activity, the vesicle velocity is U ~ [K_⊥/(ηₑℓₘ)]∫Π^(swim)₀ndΩ, where Π^(swim)₀ is the swim pressure just outside the thin accumulation boundary layer on the vesicle interior surface, n is the unit normal vector of the vesicle boundary, K_⊥ is the membrane permeability, ηₑ is the viscosity of the solvent, and ℓₘ is the membrane thickness.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Peng, Zhiwei0000-0002-9486-2837
Zhou, Tingtao0000-0002-1766-719X
Brady, John F.0000-0001-5817-9128
Additional Information:© The Author(s), 2022. Published by Cambridge University Press. Received 11 December 2021; revised 9 March 2022; accepted 2 May 2022. Published online by Cambridge University Press: 23 May 2022. This work is supported by the National Science Foundation under grant no. CBET 1803662. The authors report no conflict of interest.
Funding AgencyGrant Number
Subject Keywords:active matter, colloids, suspensions
Record Number:CaltechAUTHORS:20220119-233953357
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Official Citation:Peng, Z., Zhou, T., & Brady, J. (2022). Activity-induced propulsion of a vesicle. Journal of Fluid Mechanics, 942, A32. doi:10.1017/jfm.2022.398
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113007
Deposited By: George Porter
Deposited On:20 Jan 2022 18:50
Last Modified:07 Jun 2022 22:50

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