ABSTRACT
This chapter focused on the interplay of geometry and chemistry in determining wetting behavior and the implications for passive control of fluids in microfluidic systems where immiscible fluids meet. The chapter revisits the fundamentals of surface wettability with respect to ideal and nonideal surfaces, metastable wetting behavior, and wetting dynamics. It gives several approaches to modifying microchannel wettability. It also provides a discussion of several key applications of wetting in microfluidic devices and structures. The characteristic angle measured through the droplet phase between the solid–liquid interface and the plane of the liquid–vapor interface at the contact line is referred to as the contact angle and is the primary measure of wettability. The chapter focuses on the passive applications of wetting in microfluidics, including capillary-driven flow, valves, flow guides, and multiphase flow stability. It also shows how the wettability of the solid can be employed as a major driver for the microhandling of fluids.
