Highly sensitive and stretchable liquid-free ionic conductive elastomers for soft Ionotronics

Soft ionic conductors are essential for developing stretchable, transparent ionotronic devices such as ionic skins, human-machine interfaces, and soft luminescent devices. However, traditional ionic conductors based on hydrogels and ionogels face challenges due to the inherent limitations of their liquid components, such as freezing, evaporation, and leakage, which restrict their use in varied and complex environments. In this study, we synthesized a liquid-free ionic conductive elastomer (ICE) by integrating lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with an ethylene glycol methyl ether acrylate (MEA) and butyl acrylate (BA) blend followed by photoinduced copolymerization to overcome these obstacles. The ICEs exhibited excellent electro-mechanical characteristics, including remarkable stretchability up to 754 %, Young's modulus up to 1.18 MPa, conductivity up to 1.6 × 10⁻² S m⁻¹ and sensitivity (gauge factor) up to 2.51 within 0–200 % strain. Importantly, the absence of liquid components significantly enhanced the durability and lifespan of the device based on the ICE, thus addressing the drawbacks of traditional ionic conductors. We have also developed several ICE-based sensors with high gauge factors to detect human body movements like finger bending or elbow rotation. Moreover, a 3 × 3 sensor array demonstrates exceptional performance in accurately identifying the locations of touch pressure, highlighting the potential of ICE for the design of advanced soft electronic devices.