  In this article, we show a novel approach to implementing valving action in a
dynamically evolving capillary filling process, by exploiting alternating
current electrothermal (ACET) mechanism. The surfaces of the top and bottom
walls of the capillary are asymmetrically patched with two different
wettabilities. Our observations reveal that by exploiting an intricate
interplay of the electrothermal effects and interfacial tension modulation, the
acceleration-deceleration motion of the interface and interface pinning at
specific locations may be delicately tuned. This, in turn, modulates the flow
speed and residence time of the interface at designated locations, with a
simple tuning of the frequency of the electrical signal. The present study,
thus, unveils a novel micro valving mechanism achieved via effective
manoeuvring of the interfacial electrochemistry where active and passive
control mechanisms can be utilized simultaneously to achieve control over the
interfacial motion of the two-phase system. This may bear far-reaching
consequence in optimizing several applications in the bio-microfluidic domain,
including devising novel miniaturized platforms for locally investigating
reaction chemistries.
