A phenomenological model of dynamic contact angle

Electroosmotically driven capillary transport of typical non-Newtonian biofluids in rectangular microchannels

“…Most of the above-mentioned studies, however, assumed constant contact angles between the advancing liquid front and the capillary wall, despite the fact that experimental observations had revealed strong dependences of the contact angle on the rate of capillary meniscus advancement [8,9]. Considering the dynamic evolution of the contact angle, several empirical or semi-empirical correlations were subsequently introduced into the literature for prescribing the contact angle as functions of time [10][11][12][13]. However, most of these considerations 0003-2670/$ -see front matter © 2007 Elsevier B.V. All rights reserved.…”

Numerical modeling of electrowetting transport processes for digital microfluidics

“…The main challenges are related to the dynamics of the liquid-gas interface, dynamic contact angle as well as the contact angle hysteresis (CAH). Since classical fluid dynamics methods (based on solving partial differential equations and a continuum description of the liquid) either leads to (1) stress singularities and multivalued velocity fields especially near the contact line (Sciffer 2000;Seppecher 1996) or (2) involve empirical relations with unknown parameters which can only be determined by fittings with experimental data (Sciffer 2000), alternative and promising numerical scheme based on discrete (atomistic) description of the liquid (molecular dynamics simulations) have been recently developed (He and Hadjiconstantinou 2003;Samsonov and Ratnikov 2007) but the necessary computational load for modeling real amounts of liquids in microfluidic devices is too large. One way to circumvent this difficulty and model larger systems while taking advantages from both continuum and discrete approaches is to use hybrid methods (Yasuda and Yamamoto 2008) obtained by coupling classical fluid computation schemes with molecular dynamics algorithms.…”

A generalized analysis of capillary flows in channels

“…Several empirical relations are available to describe the dynamic contact angle as a function of time [14][15][16][17]. The Hoffman function [14] can be applied to the case of capillary flow in horizontal channels where the effects of the inertial force and gravity are negligible.…”