Controlled manipulation of floating objects on deformed fluid interfaces and conditions for stable equilibria

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• 作者：Jose M. Carballo ; Qi Ni ; Jose Vasquez ; Nathan B. Crane ; ^{ncrane@usf.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Capillarity ; Electrowetting ; Interfacial assembly ; Capillary charge ; Semi-immersed rod
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：512
• 期：Complete
• 页码：118-128
• 全文大小：2184 K

文摘

At the millimeter scale, interactions between floating and semi-immersed objects are significant. The local curvature of the interface is modified by the weight/buoyancy forces of floating objects, and by the surface properties of semi-immersed objects. The curvature changes generate attractive (or repulsive) interactions between floating parts, and semi-immersed objects. This work demonstrates how electrowetting can manipulate these interactions in order to position, align, assemble and transport parts attached to the fluid interface. This demonstrates one way in which fluid interfaces can provide an alternative to standard pick and place technology for part positioning/assembly. Typically, the part/rod forces are purely attractive or repulsive, but under some conditions, floating objects reach a stable equilibrium with a finite gap between the floating and semi- immersed bodies. Stable equilibrium positions were measured for rectangular prisms suspended on a water/oil interface and a fixed cylindrical rod. Measurements showed that the equilibrium position depends on the ratio of $\frac{▵\rho t}{w}$where t is the part thickness; w   is its width, and ▵ρ$▵\rho$ the part/fluid density difference. The stable equilibrium position provides for repeatable positioning without risk of parts sticking to the semi-immersed bodies.