Intrinsically Temperature-Insensitive and Highly Sensitive Flexible Wireless Strain Sensor

Accurate strain monitoring in environments with coexisting mechanical deformation and temperature fluctuations─such as solid rocket propellants, battery enclosures, and human ligaments─remains a longstanding challenge for flexible electronics. Conventional strain sensors suffer from significant thermal drift due to the intrinsic temperature dependence of their sensing materials, limiting their reliability in wireless and implantable applications. Here, we report an intrinsically temperature-insensitive, highly sensitive, wireless flexible strain sensor based on near-field communication technology. We innovatively design and demonstrate a flexible strain sensor that simultaneously achieves low temperature drift, high sensitivity, and passive wireless functionality. By combining two engineered materials with opposing temperature coefficients of resistance, the device achieves self-compensated thermal stability with a minimal temperature drift of 160 × 10^-6 °C^-1, eliminating the need for external calibration. It exhibits an exceptionally high gauge factor of 2415.76 across a wide strain range (0-80%), and enables wireless, battery-free strain readout over a distance of 3 cm. We demonstrate the sensor's robust performance across three thermo-mechanically coupled scenarios: (1) strain monitoring within solid rocket motor propellant grains, (2) detection of volumetric deformation in lithium-ion batteries, and (3) ligament strain sensing in the human knee joint. This work provides a generalizable strategy for achieving thermal invariance in high-performance flexible strain sensors and expands the utility of passive wireless sensing in harsh and dynamic environments.