New gel that stretches 4600%, heals itself can be used in robotics

Researchers in Taiwan have developed an innovative stretchable, self-healing gel that changes color under mechanical stress or temperature variations, potentially transforming wearable technology and soft robotics. This gel combines exceptional elasticity—able to stretch up to 4600% of its original length—with toughness and self-repair capabilities, addressing a common trade-off in soft materials that typically sacrifice either durability, healing, or sensing functions. The key to this breakthrough lies in the gel’s molecular design, which incorporates mechanically interlocked rotaxane molecules arranged in daisy chains, enabling spring-like expansion and contraction. These molecules are chemically bonded within a polyurethane gel reinforced by cellulose nanocrystals, which facilitate self-healing through reversible hydrogen bonds. A special fluorescent unit called DPAC is attached to the rotaxanes, shifting its glow from orange to blue when the gel is stretched or cooled, thus providing a visible indication of stress distribution and temperature changes. This dual-sensing capability allows the gel to act as both a structural material and a built