Boundary Effects on Osmophoresis: motion of a vesicle in an arbitrary direction with respect to a plane wall

✍ Scribed by Huan J. Keh; Fong R. Yang

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 811 KB
• Volume: 48
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(93)85011-d

✦ Synopsis

The problem of the osmophoretic motion of a spherical vesicle in the presence of a nearby plane wall is analyzed in the quasi-steady limit of negligible Reynolds and Peclet numbers. The solute concentration gradient in the surrounding fluid is uniform in the undisturbed state and is oriented at an arbitrary angle relative to the plane wall. The solution of conservative equations for the solute species and fluid momentum applicable to the system is constructed by superposing solutions of the corresponding problems of motion normal to the plane and motion parallel to it. Using the spherical bipolar coordinate system, the translational and angular velocities of the osmophoretic vesicle are solved for various cases. Interestingly, the osmophoretic mobility of the vesicle increases monotonically as it approaches the wall. The interaction between the boundary and the vesicle can be very strong when the gap thickness gets close to zero. The direction of motion of the vesicle is, in general, different from that of the solute concentration gradient. The plane wall exerts the greatest influence on the vesicle in the case of parallel osmophoresis, and the weakest in the case of motion normal to it. In addition to the translational migration, the osmophoretic vesicle rotates at the same time in the direction opposite to that which would occur if the spherical particle sedimented parallel to a plane wall. The ratio of rotational-to-translational speeds of the sphere is, in general, much larger for osmophoresis than for sedimentation.