Fabrication method of round-shaped cross sectional channel using a difference between adsorption and cohesion of PDMS

A novel PDMS process to fabricate a microchannel with round cross-section has been developed. The adsorption of liquid PDMS (soft PDMS) on solidified PDMS (hard PDMS) is stronger than the atomic cohesion force (interaction force) of liquid PDMS. Therefore, when the solidified PDMS contacts on the surface of the liquid PDMS, a meniscus is formed around the liquid PDMS like the surface of liquid in a glass tube driven by surface tension. From the experiments with various conditions, we found that the shape of the cross-section can be under control like the simple 'U' shape, elliptical shape, semicircular, and circular shape and that the novel technique is very useful in the development of LOC (lab on a chip) or various microfluidic devices.