Design of a Photoactuator Based on a Photosalient Crystal Driven by Solid-State [2+2] Cycloaddition

Soft microrobots have become an emerging branch of materials science owing to their capability to perform critical tasks in inaccessible, compact, confined, and tiny spaces. This work highlights the fabrication of a soft photo-actuator by utilizing molecular motions of one of the two isostructural photosalient CdI₂ based metal complex, incorporated into a polyvinyl alcohol (PVA) matrix to achieve flexible, controlled macroscopic shape-dependent photomechanical motions. The actuator successfully performs light-controlled mechanical work, including mimicking bio-responses, silica-ball displacement. We performed the quantitative analysis of its motion as a function of time and displacement. The actuator's performance is strongly dependent on strength, thickness, and applied load. As the rate and magnitude of actuation depend on UV exposure, a theoretical model is developed to identify crucial parameters for optimized performance. The model quantitatively evaluates time-dependent light-induced deflection and the resulting photo-actuation force under no(with) load conditions, capturing an initial fast response followed by a slower regime governed by above parameters. The rapid conversion of photochemical energy into mechanical work is further demonstrated through a prototype photo-switch. Overall, this study advances the understanding of light-controlled actuation in composite films and contributes to the development of next-generation smart soft microrobots from both experimental and theoretical perspectives.