Liquid metal strain sensors based on flexible frequency-selective surfaces

This paper proposes and demonstrates a flexible strain sensor based on a liquid metal-filled frequency selective surface (FSS). The sensing mechanism relies on a resonant frequency shift induced by strain-driven changes in the effective inductance and capacitance of the FSS structure. Full-wave simulations and experimental measurements confirm the sensor's strain sensitivity of up to 582 MHz/mm, with excellent stability and repeatability over multiple loading cycles. These results demonstrate the feasibility of combining liquid metal with a flexible FSS design to achieve high-performance strain sensing and robust mechanical compliance.