Photochemical Patterning and Characterization of Mechanical Properties on Soft Materials

Although different chemistries for the spatio-temporal localization of molecules and gradients of chemical signals within soft materials are now available, the achievement of spatio-temporal patterns of mechanical properties in such materials and their characterization remain considerable challenges. This study presents the syntheses of two novel photo-sensitive and thermoresponsive hydrogel systems, a photo-stiffening and a photo-softening hydrogel. Their potential for fabricating soft materials with patterned mechanical properties is then demonstrated by fabricating an actuator whose higher-order bending properties can be switched on with light, and by encoding mechanical properties for digital information encryption and storage. Microindentation and a custom-made data analysis software are essential for the characterization of all the materials. From a general perspective, this work opens a route to the fabrication of soft materials with patterned mechanical properties, addressing an important emerging challenge in soft materials science with applications in soft robotics and information encryption and storage.