Photoacid catalyzed organic–inorganic hybrid inks for the manufacturing of inkjet-printed photonic devices

Abstract

Photoacid catalyzed jettable inks containing monomers with epoxy and silane functionalities have been successfully formulated. In contrast to inks based on conventional sol–gel processes, the hydrolysis and condensation processes in these materials are triggered after printing using UV light favoring the long-term stability of the ink, a prerequisite for industrial applications. UV light can trigger the photocuring reaction of the epoxy groups and the hydrolysis and condensation of the silane groups leading to a crosslinked organic–inorganic hybrid polymeric network. Advantageously, the inks use no solvents and therefore the deposited material can be polymerized immediately after the deposition step by exposure to UV light. No additional baking steps are required allowing the use of thermally sensitive substrates and notably simplifying the process to one single step. Deposits with excellent adhesion and good transparency can be obtained by proper selection of the curing conditions through this process. Planar and channel optical waveguides have been prepared using these formulations by inkjet printing technology on a variety of substrates. The waveguides support optical modes with propagation losses as low as 0.5 dB cm⁻¹, demonstrating the potential of these photoacid catalyzed organic–inorganic hybrid formulations and inkjet printing for the preparation of photonic devices.