Microfluidic fabrication using cyclic olefin copolymer and hydrocarbon solvents

Abstract

Cyclic olefin copolymer (COC) is a promising material in microfluidic applications due to their unique physical, chemical, and optical properties. This study implements a new and versatile fabrication process to fabricate COC microchannels, combining the fabrication and bonding processes in a single step, taking advantage of COCs’ swelling behavior in linear non-polar hydrocarbon solvents and their chemical compatibility with photolithography. Dodecane was selected as the hydrocarbon solvent based on the degree of swelling and Flory-Huggins interaction parameter, which resulted in the highest degree of swelling and affinity to COC. The effect of dodecane immersion time on the COC microchannel height was investigated, achieving a maximum average height of 50 ± 3 µm after 180 min. Bonding quality was quantified by a leakage test (maximum flow rate of 1730 ± 205 µL/min (Re = 237)), and a tensile test (800 ± 90 kPa). Furthermore, the effectiveness of the implemented process was demonstrated through the successful execution of three highly diverse microfluidic applications. These applications included a serpentine microchannel featuring semicircular obstacles that facilitated passive mixing, pinched flow fractionation which enabled the separation of a system of three different sizes of microparticles, and droplet microfluidics that allowed for the efficient generation of water in oil droplets.