Highly Stretchable, Self-healing Ionic Elastomer for Magnetically Coupled Piezo-ionic Mechano-sensing

Abstract

Soft and stretchable electronic materials have recently attracted considerable attention as promising platforms for wearable sensing and biointegrated devices because of their ability to operate in mechanically dynamic and biologically relevant environments. However, many currently used electronic sensing systems still rely on rigid components and external power sources such as batteries, which increase device complexity and limit long-term autonomous operation in wearable applications. These limitations have motivated the development of soft materials capable of converting naturally available mechanical stimuli into electrical signals. In this work, a magnetically responsive ionic elastomer was developed by incorporating the magnetic ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate (Emim-FeCl4) into a polyurethane matrix synthesized through a prepolymer method. The resulting magneto-ionic elastomer combines the intrinsic elasticity of polyurethane with the ionic conductivity and magnetic responsiveness introduced by the ionic liquid. The successful formation of the polyurethane network and the homogeneous distribution of the magnetic ionic liquid within the elastomer matrix are confirmed by the structural and morphological characterizations. Mechanical testing reveals highly stretchable behaviour with elongation approaching ~960%, along with self-healing capability arising from dynamic intermolecular interactions within the polymer network. The elastomer exhibits a clear piezo-ionic response to mechanical bending, generating voltage signals as mobile ions redistribute across the film. Furthermore, magnetically induced deformation of the elastomer produces measurable electrical signals, demonstrating a magnetically coupled piezo-ionic response. These results highlight the potential of magneto-ionic polyurethane elastomers as soft, stretchable, and self-powered materials for flexible sensing systems, wearable electronics, and next-generation soft electronic devices.