Programming Hydrogen Bonds for Reversible Elastic-Plastic Phase Transition in a Conductive Stretchable Hydrogel Actuator with Rapid Ultra-High-Density Energy Conversion and Multiple Sensory Properties

P Guo and ZX Zhang and CN Qian and RF Wang and L Cheng and Y Tian and HP Wu and SZ Zhu and AP Liu, ADVANCED MATERIALS, 36 (2024).

DOI: 10.1002/adma.202410324

Smart hydrogels have recently garnered significant attention in the fields of actuators, human-machine interaction, and soft robotics. However, when constructing large-scale actuated systems, they usually exhibit limited actuation forces (approximate to 2 kPa) and actuation speeds. Drawing inspiration from hairspring energy conversion mechanism, an elasticity-plasticity-controllable composite hydrogel (PCTA) with robust contraction capabilities is developed. By precisely manipulating intermolecular and intramolecular hydrogen-bonding interactions, the material's elasticity and plasticity can be programmed to facilitate efficient energy storage and release. The proposed mechanism enables rapid generation of high contraction forces (900 kPa) at ultra-high working densities (0.96 MJ m-3). Molecular dynamics simulations reveal that modifications in the number and nature of hydrogen bonds lead to a distinct elastic-plastic transition in hydrogels. Furthermore, the conductive PCTA hydrogel exhibits multimodal sensing capabilities including stretchable strain sensing with a wide sensing range (1-200%), fast response time (180 ms), and excellent linearity of the output signal. Moreover, it demonstrates exceptional temperature and humidity sensing capabilities with high detection accuracy. The strong actuation power and real-time sensory feedback from the composite hydrogels are expected to inspire novel flexible driving materials and intelligent sensing systems. Inspired by the energy conversion of hairspring, an intelligent hydrogel is developed to achieve reversible transformation between elasticity and plasticity through precise regulation of hydrogen bonds, enabling efficient energy storage and release. The hydrogel exhibits exceptional drive rate, high energy density output, and diversified sensing capability. This groundbreaking innovation paves the way for novel designs of smart hydrogel actuators. image

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