Micro-channel filling flow considering surface tension effect

Abstract

Understanding filling flow into micro-channels is important in designing micro-injection molding, micro-fluidic devices and an MIMIC (micromolding in capillaries) process. In this paper, we investigated, both experimentally and numerically, 'transient filling' flow into micro-channels, which differs from steady-state completely 'filled' flow in micro-channels. An experimental flow visualization system was devised to facilitate observation of flow characteristics in filling into micro-channels. Three sets of micro-channels of various widths of different thicknesses (20, 30, and 40 µm) were fabricated using SU-8 on the silicon substrate to find a geometric effect with regard to pressure gradient, viscous force and, in particular, surface tension. A numerical analysis system has also been developed taking into account the surface tension effect with a contact angle concept. Experimental observations indicate that surface tension significantly affects the filling flow to such an extent that even a flow blockage phenomenon was observed at channels of small width and thickness. A numerical analysis system also confirms that the flow blockage phenomenon could take place due to the flow hindrance effect of surface tension, which is consistent with experimental observation. For proper numerical simulations, two correction factors have also been proposed to correct the conventional hydraulic radius for the filling flow in rectangular cross-sectioned channels.

Modeling, analysis and design of centrifugal force driven transient filling flow into rectangular microchannel

“…(It might be noted here that surface tension becomes important in the microscale transient flow (Duffy et al 1999;Kim et al 2002;Madou et al 2001;Gyrosä Microlaboratory, http://www.gyros.com) depending upon the surface properties. However, it may be reasonable to neglect surface tension effect when a polymer substrate of which the contact angle of a sample fluid is almost 90°.…”

Modeling, analysis and design of centrifugal force-driven transient filling flow into a circular microchannel

“…(It might be noted here that surface tension becomes an important parameter for the microscale transient flow (Duffy et al 1999;Kim et al 2002;Tseung et al 2002;Madou et al 2001; Gyros Microlaboratory) depending upon the surface properties. However, it may be reasonable to neglect the surface tension effect when a polymer substrate of which the contact angle of a sample fluid is almost 90°.…”

MEMS-Based Boiler Operation from Low Temperature Heat Transfer and Thermal Scavenging

“…Boilers were fabricated with a range of channel depths as part of this work. Previous work established the ability to vary capillary pumping rates as a function of capillary channel height and width dimensions [12,18]. Due to this effect, multiple channel heights were fabricated to fully characterize boiler behavior as a result of capillary pumping variations.…”