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Activity-induced propulsion of a vesicle

Peng, Zhiwei and Zhou, Tingtao and Brady, John F. (2021) Activity-induced propulsion of a vesicle. . (Unpublished)

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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 which 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_⊥/(η_eℓ_m)]∫Π^(swim)₀ndΩ, where Π^(swim)₀ is the swim pressure just outside the thin accumulation boundary layer on the interior vesicle surface, n is the unit normal vector of the vesicle boundary, K_⊥ is the membrane permeability, η_e is the viscosity of the solvent, and ℓ_m is the membrane thickness.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Peng, Zhiwei0000-0002-9486-2837
Zhou, Tingtao0000-0002-1766-719X
Brady, John F.0000-0001-5817-9128
Additional Information:Attribution 4.0 International (CC BY 4.0). This work is funded by NSF under Grant No. CBET 1803662.
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Record Number:CaltechAUTHORS:20220119-233953357
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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:20 Jan 2022 18:50

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