Biomimetic Multiscale Oriented PVA/NRL Hydrogel Enabled Multistimulus Responsive and Smart Shape Memory Actuator

Shape memory hydrogels provide a worldwide scope for functional soft materials. However, most shape memory hydrogels exhibit poor mechanical properties, leading to low actuation strength, which severely limits their applications in smart biomimetic devices. Herein, a strategy for muscle-inspired shape memory-oriented polyvinyl alcohol (PVA)-natural rubber latex (NRL) hydrogel (OPNH) with multiscale oriented structure is demonstrated. The shape memory function comes from the stretch-induced crystallization of natural rubber (NR), while PVA forms strong hydrogen bonding interactions with proteins and phospholipids on the surface of NRL particles. Meanwhile, the reconfigurable interactions of PVA and NR produce a multiscale-oriented structure during stretch-drying, improving the mechanical and shape memory properties. The resultant OPNH shows excellent interfacial compatibility, exhibiting outstanding mechanical performance (3.2 MPa), high shape fixity (≈80%) and shape recovery ratio (≈92%), high actuation strength (206 kPa), working capacity (105 kJ m^{- 3}), extremely short response time (≈2 s), low response temperature (28 °C) and smart thermal responsiveness. It can even maintain muscle-like working capacity when lifting a load equivalent to 372 times its weight, providing a new class shape memory material for the application in smart biomimetic muscles and multistimulus responsive devices.