PDMS through-hole fabrication by soft lithography using CH4/He atmospheric RF plasma surface treatment

This paper presents a PDMS micro through-hole molding method by simple soft lithography process in which the surface of a master mold and a substrate is treated by atmospheric CH₄/He RF plasma to feature hydrophobic property on the surface. Rectangular and circular-shaped PDMS micro through-hole layers are made by the proposed fabrication method. As one of the applications of the PDMS micro through-hole layer for multi-layered systems, a radial concentration gradient generator including a micro through-hole layer is constructed and its performance is tested. The micro through-holes fabricated by the proposed method are well-defined. The concentration gradients measured in radial directions are in a similar level. Also, the tearing problem, which is often happened in spin-coating and lift-off molding methods, is not observed during the fabrication process of the PDMS micro through-holes. Therefore, we believe that the proposed fabrication method contributes to improve the technology for PDMS through-hole fabrication.