Experimental and numerical investigation of capillary flow in SU8 and PDMS microchannels with integrated pillars |
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| Authors: | Auro Ashish Saha Sushanta K Mitra Mark Tweedie Susanta Roy Jim McLaughlin |
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| Affiliation: | (1) Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, India;(2) Department of Mechanical Engineering, University of Alberta, Edmonton, Canada;(3) Nanotechnology and Integrated BioEngineering Centre, University of Ulster, Jordanstown, Northern Ireland; |
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| Abstract: | Microfluidic channels with integrated pillars are fabricated on SU8 and PDMS substrates to understand the capillary flow.
Microscope in conjunction with high-speed camera is used to capture the meniscus front movement through these channels for
ethanol and isopropyl alcohol, respectively. In parallel, numerical simulations are conducted, using volume of fluid method,
to predict the capillary flow through the microchannels with different pillar diameter to height ratio, ranging from 2.19
to 8.75 and pillar diameter to pitch ratio, ranging from 1.44 to 2.6. The pillar size (diameter, pitch and height) and the
physical properties of the fluid (surface tension and viscosity) are found to have significant influence on the capillary
phenomena in the microchannel. The meniscus displacement is non-uniform due to the presence of pillars and the non-uniformity
in meniscus displacement is observed to increase with decrease in pitch to diameter ratio. The surface area to volume ratio
is observed to play major roles in the velocity of the capillary meniscus of the devices. The filling speed is observed to
change more dramatically under different pillar heights upto 120 μm and the change is slow with further increase in the pillar
height. The details pertaining to the fluid distribution (meniscus front shapes) are obtained from the numerical results as
well as from experiments. Numerical predictions for meniscus front shapes agree well with the experimental observations for
both SU8 and PDMS microchannels. It is observed that the filling time obtained experimentally matches very well with the simulated
filling time. The presence of pillars creates uniform meniscus front in the microchannel for both ethanol and isopropyl alcohol.
Generalized plots in terms of dimensionless variables are also presented to predict the performance parameters for the design
of these microfluidic devices. The flow is observed to have a very low Capillary number, which signifies the relative importance
of surface tension to viscous effects in the present study. |
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