On Thermocapillary Propulsion of Microliquid Slug

Abstract

A liquid slug in a microchannel can be propelled by temperature difference between the ends of the slug. This study presents an analytical model to predict the velocity of such slug motion. The models thus far developed only considers very long slugs where the viscous dissipation near the contact line is negligible compared with the bulk dissipation. Therefore, here we develop a novel model to account for the shear stress near the contact line so that it can be applied to slugs of general configuration. It is shown that the bulk dissipation dominates when the slug length is much greater than the channel's hydraulic diameter. However, the wedge dissipation dominates when the slug length is much smaller than the hydraulic diameter. A simple experiment using a mineral oil microslug shows that our theory considering both the wedge and bulk dissipation agrees with the measurement results.

KEY WORDS:

• thermocapillary
• microchannel
• contact line
• contact angle

This work was supported by the Korea Research Foundation (Grant No. KRF-2005–003-D00033) funded by the Korea government (MOEHRD) through the Basic Research Promotion Fund.