Microdroplet targeting induced by substrate curvature

doi:10.1088/1674-1056/27/9/096801

Abstract Fundamental understanding of the wettability of curved substrates is crucial for the applications of microdroplets in colloidal science, microfluidics, and heat exchanger technologies. Here we report via lattice Boltzmann simulations and energetic analysis that microdroplets show an ability of transporting selectively to appropriate substrates solely according to substrate shape (curvature), which is called the substrate-curvature-dependent droplet targeting because of its similarity to protein targeting by which proteins are transported to the appropriate destinations in the cell. Two dynamic pathways of droplet targeting are identified:one is the Ostwald ripening-like liquid transport between separated droplets via evaporating droplets on more curved convex (or less curved concave) surfaces and growing droplets on less curved convex (or more curved concave) surfaces, and the other is the directional motion of a droplet through contacting simultaneously substrates of different curvatures. Then we demonstrate analytically that droplet targeting is a thermodynamically driven process. The driving force for directional motion of droplets is the surface-curvature-induced modulation of the work of adhesion, while the Ostwald ripening-like transport is ascribed to the substrate-curvature-induced change of droplet curvature radius. Our findings of droplet targeting are potentially useful for a tremendous range of applications, such as microfluidics, thermal control, and microfabrication.

Keywords: droplet targeting substrate curvature lattice Boltzmann simulation

Received: 26 February 2018
Revised: 07 May 2018
Accepted manuscript online:

PACS:	68.08.Bc	(Wetting)
	68.18.Jk	(Phase transitions in liquid thin films)
	82.65.+r	(Surface and interface chemistry; heterogeneous catalysis at surfaces)

Fund: Project supported by the National Natural Science Foundation of China (Grant No. 91434204).

Corresponding Authors: Xianren Zhang
E-mail: zhangxr@mail.buct.edu.cn

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Hongguang Zhang(张红光), Zhenjiang Guo(郭振江), Shan Chen(陈珊), Bo Zhang(张博), Xianren Zhang(张现仁) Microdroplet targeting induced by substrate curvature 2018 Chin. Phys. B 27 096801

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Microdroplet targeting induced by substrate curvature

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