A Novel Contactless DC Current Sensor Using a Highly Sensitive Thin-Film Lamb Wave Resonator With a Self-Aligned Micromagnet

This article presents a novel resonant current sensor designed for contactless, miniaturized, high-sensitivity, and high-precision static dc current measurement. The sensor features a cantilever structure integrated with a thin-film lithium niobate lamb wave resonator (LWR) and a micromagnet. The working principle of the sensor is based on the torque and force induced by the magnetic field of the measured current, which causes a resonant frequency shift of the LWR. To integrate a 30 µm thick cantilever with a 400 nm thick LWR, a dual-mask deep silicon etching process is employed. This process ensures that the structure can support the magnet while also maintaining the resonant region as a thin film that is favorable for LWR operation. Furthermore, to ensure precise magnet placement, a self-aligning process based on the attraction between the nickel layer and the magnet is introduced. Experimental results demonstrate a sensitivity of 2.2 kHz/A, a minimum current resolution of 0.6 A in open-loop testing, and a linear measurement range of up to 70 A for dc wire measurements. These results suggest that the proposed sensor has strong potential for applications in smart meters, battery management systems (BMS), and electric vehicle charging stations.