A Passive Wireless Flexible Strain Sensor With Reconfigurable Frequency Selectivity Inspired by Kirigami

ABSTRACT This paper presents a passive wireless flexible strain sensor with reconfigurable frequency selectivity inspired by kirigami. The sensor is composed of a rectangular complementary split‐ring resonator (CSRR) array and a polyimide (PI) kirigami sheet, using a standard horn antenna as the transceiver antenna to communicate with the resonator array. Nonlinear finite element analysis is performed on the kirigami structure to predict the mechanical responses of various kirigami designs and obtain the stress distribution on the kirigami structure surface after stretching. The electromagnetic simulation and circuit simulation of the designed element structure are carried out, verifying the validity of the equivalent circuit model and the consistency of unit performance by comparing the simulation results. The resonator array is mounted on a custom kirigami sheet, where under quasi‐axial stress, the kirigami design enables each resonant unit to shift and flip, thereby altering the overall electromagnetic properties of the surface. Experimental results show that when tensile force is applied to increase the strain level of the kirigami structure from 0% to 18%, the sensor exhibits a resonant frequency shift exceeding 30 MHz and a resonant amplitude shift exceeding 40 dB, with a sensitivity of 1.928 MHz/%. Additionally, the reflection coefficient changes by 172% within the strain range of 0%–8%. Compared with traditional strain sensors, this sensor has achieved noncontact and accurate strain measurement, expanding the application potential of strain sensors in monitoring structural deformation within complex engineering environments.