Programmable Thermo-Responsive Actuation of Hydrogels via Light-Guided Surface Growth of Active Layers on Shape Memory Substrates.

Hydrogel shape memory and actuating functionalities are heavily pursued and have found great potential in various application fields. However, their combination for more flexible and complicated morphing behaviors is still challenging. Herein, it is reported that by controlling the light-initiated polymerization of active hydrogel layers on shape memory hydrogel substrates, advanced morphing behaviors based on programmable hydrogel shapes and actuating trajectories are realized.

Light-Guided Growth of Gradient Hydrogels with Programmable Geometries and Thermally Responsive Actuations.

Hydrogel actuators have gained considerable interest and experienced significant advancements in recent years. However, the programming of their actuating behaviors is still challenging. Herein, we report the development and regulation of gradient structures of hydrogels for programmable thermally responsive actuating behaviors.

Photoresponsive Shape Memory Hydrogels for Complex Deformation and Solvent-Driven Actuation.

A new design for photoresponsive shape memory hydrogels and their possible applications are demonstrated in the present study. We show that the photodissociable Fe-carboxylate coordination can be utilized as a molecular switch to realize photocontrol of shape memory on both macroscopic and microscopic scales and enable a number of functions. Indeed, Fe-carboxylate coordination can fix a large tensile strain (up to 680%) of the sodium alginate/polyacrylamide hydrogel through cross-linking of sodium alginate chains, and subsequent UV irradiation allows strain energy release in spatially selected regions through reduction of Fe to Fe.