Biotech, Biomaterials and Biomedical: TechConnect Briefs 2015Biotech, Biomaterials and Biomedical TechConnect Briefs 2015

Micro, Nano & Bio Fluidics Chapter 4

On the dynamic contact angle in spontaneous capillary flow

J. Berthier, D. Gosselin, G. Delapierre
CEA-Leti, France

pp. 218 - 221

Keywords: spontaneous capillary flow (SCF), capillarics, capillary velocity, dynamic and static contact angles

Capillary actuation of fluids is an interesting solution when the gravitational forces are small: this is the case in space , or in microfluidic systems where gravity is negligible. The onset of spontaneous capillary flow (SCF) and its dynamics have been widely investigated, first in the years 1920s, then more recently with the development of microfluidic systems for biotechnology. Most of the time, the interpretation of the dynamics of the flow is performed using a constant contact angle. Although the study of the dynamic contact angle on the dynamics of wetting has been the subject of many investigations, the effect of the dynamic contact angle during a sponaneous capillary flow is still unclear. In this work, we propose a correction to the capillary velocity that takes into account the dynamic contact angle, based on correlations reported in the literature. Comparison between static and dynamic velocities are presented.. It is concluded that the dynamic contact angle has an importance only on the few first millimeters of the channel. The length scale of the device is then of utmost importance. A non-dimensional number characterizing the effect of the dynamic contact angle is proposed