Bioinspired Sarcomeric Double-Network Hydrogels for Programmable Mechanics with Ultralow Hysteresis

Hysteresis is normally unavoidable in hydrogels under complex external loading conditions due to the intermolecular friction, which usually leads to fatigue. Here, we fabricate a sarcomere-inspired double-network hydrogel made from polyacrylamide, alginate and phytic acid, whose hysteresis can be effectively regulated by preloading. Particularly, due to the synergy of micellization, fibrillation and micro-lubrication, the as-prepared hydrogel displays an ultralow hysteresis (≤0.02%) after it experiences a pre-tensile process at a specific amplitude and strain rate, or even possesses negative hysteresis in the case of low tensile amplitudes or high strain rates. Interestingly, smart responses of the developed hydrogel to cyclic tensile loadingare similar to the mechanical behaviors of sarcomeres in vivo. Likewise, the derived hydrogel with ultralow hysteresis performs reliably even at temperatures as low as −20 °C. The ultralow hysteresis presented by the biomimetic hydrogel with ultralow hysteresis makes it suitable for many engineering fields like electrical sensing with superior reliability (the corresponding electrical signal (ΔR/R0) is stable even after 1000 stretching–unstretching cycles). Moreover, the design strategy of hydrogels with programmable hysteresis provides an innovative methodology for the future development of smart high-performance hydrogels.