An Efficient Two-Photon-Generated Photoacid Applied to Positive-Tone 3D Microfabrication

Abstract

A two-photon–activatable photoacid generator, based on a bis [(diarylamino) styryl]benzene core with covalently attached sulfonium moieties, has been synthesized. The photoacid generator has both a large two-photon absorption cross section (δ = 690 × 10 −50 centimeter 4 second per photon) and a high quantum yield for the photochemical generation of acid (φ H + = 0.5). Under near-infrared laser irradiation, the molecule produces acid after two-photon excitation and initiates the polymerization of epoxides at an incident intensity that is one to two orders of magnitude lower than that needed for conventional ultraviolet-sensitive initiators. This photoacid generator was used in conjunction with a positive-tone chemically amplified resist for the fabrication of a three-dimensional (3D) microchannel structure.