Spatiotemporal toughness modulation in hydrogels through on-demand cross-linking
2025-10-10
Tough hydrogels are promising for soft robotics, bioelectronics, and tissue adhesives due to their exceptional resilience and biocompatibility, yet precise spatiotemporal control of their mechanics remains challenging. Here, we present a hydrogel platform that enables spatiotemporal modulation of toughness through a latent ionic cross-linking mechanism. By embedding calcium carbonate (CaCO 3 ) microparticles in alginate/polyacrylamide double-network hydrogels, we create a system where localized calcium release and thus ionic cross-linking can be programmed in both space and time. Spatial control is achieved by direct ink writing of CaCO 3 , while temporal activation is triggered by glucono-δ-lactone, a biocompatible acidifier that releases calcium on demand. This strategy allows user-defined tuning of stiffness and toughness, enabling fabrication of three-dimensional (3D) hydrogels with tailored mechanical profiles. The resulting materials offer a versatile platform for anisotropic impact shielding, directional strain sensing, and 3D-printed tissue adhesives, representing a paradigm shift for adaptive, reconfigurable, and multifunctional soft materials.