Photons provide an efficient way to transport energy, but there is a lack of “engines” that can use photons as a fuel.  One way to directly transform light into mechanical work is to utilize molecular photoisomerization reactions.  When photochromic molecules are organized in a crystal, photochemistry can generate macroscopic motions as the reactant crystal transforms into the product crystal.  Photomechanical crystals that undergo deformations like expansion, bending, twisting, peeling and coiling provide a path to actuators that can be scaled down to micro- or nanoscale dimensions.  In this talk we will review various types of photomechanical crystals, emphasizing the importance of morphology, from intermolecular interactions in the crystal to overall crystal size and shape.  By looking at the photoinduced mechanical change as the outcome of a polymorphic crystal transition, we show that a quantitative understanding of these motions is possible, opening the door to rational design of these materials.  From a practical standpoint, the hierarchical organization of nano-scale and micro-scale crystals in a macroscopic actuator structure, using either templated growth or electron beam lithography, has led to the development of composite organic-inorganic actuators with unprecedented power-to-weight ratios:  under light illumination, less than 1 mg of crystalline material can move a 100 g mass.  The combination of crystal engineering and photochemistry provides a promising approach to making light-responsive materials with high work outputs.

Using photochemical crystal-to-crystal transitions to create light-powered actuators

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.