Thermodynamic Explanation on Surface-Driven Capillary Flow of Working Liquids in the Microfluidic Devices Fabricated by Polymers

Abstract

In this experimental work, total 100 individual microfluidic devices are fabricated by polymers using author’s own hands-on completely. A set of straight microchannels, gradual expansion microchannels, sudden expansion microchannels and sudden contraction microchannels are fabricated by SU-8 using the maskless lithography and indirect bonding technique. Another set of straight microchannels, gradual expansion microchannels, sudden expansion microchannels and sudden contraction microchannels are fabricated by PMMA using the maskless lithography, hot embossing lithography and direct bonding technique. Dyed water and dyed ethylene glycol are prepared and used as dyed working liquids. Effects of channel aspect ratio, capillary pressure, liquid viscosity, and surface to volume ratio on the surface-driven capillary flow are experimentally found and analysed. The variation in diffusion coefficient is also studied. According to a strong and updated literature review (bibliography of this work), this present experimental work is logically supported by the theoretical and experimental findings existing in already published reports. This experimental work will be useful to fabricate the lab-on-a-chip systems for commercial bioengineering applications. Also, this work may be suitable as research-idea for the fabrication of nanofluidic systems in future.

Keywords: SU-8, PMMA, Water, Ethylene glycol, Capillary flow, Diffusion coefficient