Radiation‐Crosslinked Relaxor Ferroelectric Elastomers for Fully Organic Stretchable Capacitive Strain Sensors

The adaptation of capacitors to wearable electronics requires dielectric materials that combine high permittivity with well resilience. Fully organic stretchable capacitive strain sensors are particularly attractive, but their performance is often limited by the lack of suitable elastic high-k dielectrics. Relaxor ferroelectric polymers offer intrinsically high dielectric constants; however, conventional elastification approaches, such as thermal and photo-crosslinking, are constrained by harsh processing conditions and residual chemical species. Here, we present a simple and effective radiation-crosslinking strategy to convert a relaxor ferroelectric polymer into an elastic dielectric without the need for initiators or elevated temperatures. By employing poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) in combination with poly(ethylene glycol) diacrylate (PEGDA) as a crosslinking sensitizer, a stable crosslinked network is formed under mild irradiation conditions. The resulting material exhibits a high dielectric constant (∼37 at 25°C and 1 kHz) together with excellent elastic recovery (∼80%), thereby achieving a desirable balance between dielectric performance and resilience. When integrated with stretchable electrodes, the resulting fully organic capacitive device exhibits reproducible capacitance variation to tensile strain, demonstrating its potential for fully organic stretchable capacitive strain sensing. This work establishes a practical strategy for developing high-permittivity dielectric elastomers and advances the design of stretchable electronic devices.