Low-Power Laser Micro-Shaping of Dye-Volatile Cocrystals: The Gentle Cutting Edge of Photoresponsive Materials

Abstract

Cocrystallisation of a fluorinated azobenzene with volatile cocrystal components dioxane or pyrazine yields halogen-bonded cocrystals that can be cut, carved or engraved with low-powered visible laser light. This process, termed cocrystal laser micro-shaping (CLMS), is enabled by cocrystallisation of a visible light dye with a volatile component, giving rise to materials that can be selectively disassembled with micrometer precision using gentle, non-burning irradiation in a commercial confocal microscope setup. The ability to shape and even machine cocrystals in 3D using laser powers between 0.5 and 20 mW, which are 2-4 orders of magnitude lower compared to laser powers used for machining metals, ceramics or polymers, is rationalized by CLMS targeting the disruption of weak supramolecular interactions between cocrystal components, rather than the breaking of covalent bonds in polymers or disruption of ionic structures required for conventional laser beam or focused ion beam machining processes, mainly by high-power laser heating.<br>