Methacrylated gelatin-based conductive self-healing hydrogels: a dual-scale approach for micro- and macro-sized soft materials.

Soft robotic microsystems, inspired by the flexibility of biological structures, have gained significant research interest due to their ability to navigate complex environments with high adaptability. Electroconductive hydrogels (ECHs) have emerged as promising materials for these systems, offering intrinsic softness, biocompatibility, and electrical conductivity. Here, we present an electroconductive hydrogel with multifunctionality developed using a dual-component conductive strategy, incorporating polyaniline (PANI)-silver (Ag) nanoparticles into a methacrylated gelatin (GelMa) network. The hydrogel was fabricated at two different length scales using complementary fabrication techniques. UV crosslinking was employed to produce macroscale hydrogels, while two-photon lithography was used to demonstrate the feasibility of fabricating microscale structures from the same material system. In addition to their structural versatility, the hydrogels exhibited self-healing behavior that enables autonomous recovery of both mechanical and electrical functionalities after damage, which is important for long-term operation in dynamic environments. Comprehensive characterization, including morphological, electrical, mechanical, and biological tests, confirmed the conductivity, cytocompatibility, and tunable mechanical properties of the hydrogel. The results suggest that this biopolymer-based, electroconductive hydrogel with self-healing ability is a highly promising candidate for next-generation soft robotic systems, offering a durable, adaptable, and bio-integrated solution for further soft robotic applications at both macro- and micro-scales.