Direct adhesion contrast patterning on PDMS substrate by ArF excimer laser scanning for on-demand printing of functional layers

Abstract

Adhesion contrast planography (ACP) is a printing method wherein a difference in adhesion forces between a semi-dried ink layer and a polydimethylsiloxane (PDMS) surface is used to form fine patterns. In the present study, direct laser surface modification of PDMS surfaces by a 193-nm excimer laser aiming at the use as an ACP printing plate was investigated in order to realize on-demand printed electronics. Various processing parameters were investigated systematically, including laser energy, laser pulse repetition frequency, scanning rate, and a thin primer film composed of a silane coupling agent. The results showed that appropriate laser conditions for a subsequent ACP process were found such that a cumulative energy density given at silane coupling agent-mediated PDMS surfaces by laser irradiation was in the range of 8–11 mJ/mm2. Under such conditions, the adhesion force on the treated PDMS surface was changed from 2.3 to 3.8 μN against a silica probing sphere. Complementary atomic force microscopy measurements on the laser-treated and pristine PDMS surfaces showed a gradual increase of the surface stiffness of PDMS, validating the idea that laser irradiation induced a conversion of PDMS into a mineralized SiO2 network. To further test the applicability of the present process, several complicated shapes were also examined.