Hyperelastic Starch Hydrogel Configures Edible and Biodegradable All-Components for Soft Robots

Developing edible and biodegradable structural materials is a promising solution to the increasing risk of plastic pollution. Starch has been widely used in foods such as noodles, and puddings for thousands of years, but with low mechanical performance. Here, a starch chain phase separation strategy is proposed in synthesizing starch-based hydrogel to simultaneously enhance its strength and toughness, by the tunable interplay of glycerol/water (as -good solvent) and ethanol (as antisolvent). The mechanical performance of starch hydrogel, composed of starch, bound water, and glycerol, is widely tuned with maximum strains: 194.4-361.4%; maximum tensile stresses: 34-192 kPa; and Young's moduli: 36.0-205.8 kPa. Modulating the glycerol/ethanol ratio governs phase separation dynamics during the structural formation of starch hydrogel: lower glycerol/ethanol ratios bring higher maximum strain and maximum tensile stress, correlating with reconfigured starch crystallization and dynamic hydrogen-bonding network. Notably, the hyperelastic starch hydrogel achieves complete soil degradation within 24 days and is constructed for a pneumatic soft gripper. This work pioneers a green and sustainable hydrogel platform that harmonizes high performance with edibility and biodegradability, offering transformative potential for eco-friendly soft robotics and transient wearable systems.