High-Strength Shape-Memory Ionogels with Controllable Metastable State for High-Work-Density Actuation

Polymer gels are promising materials for smart actuators because of their softness and stimulus diversity. However, conventional stimuli-responsive polymer gels have limited work density due to the low deliverable force when applied as actuators. Here, we propose a strategy to prepare high-work-density soft actuators based on the phase separation strengthening mechanism. By constructing a liquid–liquid phase separation intercepted by the glass transition of the polymer, we report an ultrastrong metastable ionogel (E ∼ 650 MPa, σ ∼ 24 MPa) with wide-range switchable stiffness from 10⁴ to 10⁸ Pa. Benefitting from the excellent mechanical duality of these metastable ionogels we design an elastic-driven actuator that features programmable actuating behaviors with a contractile force and work density up to 238 kPa and 161.5 kJ/m³, respectively, outperforming current gel actuators and even biological muscles. These nonvolatile ionogels with tunable metastable state hold great promise in advanced engineering fields such as smart constructs, soft robotics, and artificial muscles where require both high mechanical strength and good formability.