Synergistic Two-Color Photochemical Polymer Network Formation and Lithography

Abstract

We introduce synergistic two-color lithography as an advanced wavelength-gated strategy for spatially and temporally controlling polymer network formation. Our photoresist entails two photoswitches, i.e., diarylindenone epoxide (DIO) and strained azobenzene (SA), each activated at a judiciously selected wavelength, i.e., 375 or 430 nm. Under specific conditions of photon flux, simultaneous irradiation at both wavelengths induces a (3 + 2) cycloaddition between the photoactivated DIO′ and SA′ species, generating covalently crosslinked networks, whereas under these specifically determined conditions, single-wavelength exposure does not induce solidification. Kinetic analysis highlights the potential of synergistic activation to enable advanced additive manufacturing. We implemented the two-color activated covalent bond forming system in a dual-laser lithographic platform enabling the fabrication of well-defined structures, including segmented ring and butterfly architectures by simply activating and deactivating one of the colors of light.