Statics and Dynamics of Triple Phase Contact Line Under Electric Field


Miniaturization is a necessity in today's world. Size reduction through the advent of microfluidics has facilitated integration and intensification of multiple processes over a single microfluidic chip. In droplet-based microfluidics, incorporation of external electric field provides control over mixing, transport and manipulation of droplets. Dynamics of sessile droplets is primarily governed by the dynamics of the triple phase contact line (TPCL).  We investigate the statics and dynamics of TPCL under electric field using a three-pronged approach including calculus of variation (CV), thin film modelling and molecular dynamics simulations. The work has implications in internal mixing at low Reynolds number, electrovariable optics, droplet actuation, and bioassays.

The method of calculus of variations is integral in the study of statics of TPCL at a continuum level. The classical Young-Dupre equation as well as the Young Lippmann equation for electrowetting can be derived using CV by constrained energy minimization. The utility of such a method to arrive at the statics of TPCL of different liquids and substrates differentiable on the basis of electrochemical and physical properties will be attempted. Non-linear dynamics of TPCL under electric field can be captured using WRIBL (Weighted Residual Integral Boundary Layer) theory. The role of bulk charges in a vast class of fluids such as electrolytes also remains largely unexplored. Electrowetting of nano-scale droplets, wherein the continuum description fails, requires understanding that can only be derived from molecular simulations. The role of electric field on contact angle saturation, contact line friction and contact line tension are key areas that warrant investigation. 

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