Wireless Human Motion Monitoring by a Wearable 3D Spiral Liquid Metal Sensor with a Spinning Top‐Shaped Structure

Abstract Flexible wireless pressure sensors based on the LC resonance principle have emerged for critical applications in wearable devices. However, the challenge remains to promote the sensing performance while maintaining good wearability of the devices. Herein, a 3D spiral liquid metal sensor (3D‐SLMS) is reported with a spinning top‐shaped structure for wireless human motion detection. The device is composed of only liquid metals embedded in Ecoflex elastomer, thus being highly flexible. The study develops a unique method to fabricate 3D‐SLMS by integration of mask‐assisted spraying of liquid metals and virtual molding tuned by vacuum. Under an external load, the deformation of the spinning top‐shaped structure leads to changes in both inductance and capacitance, offering a detectable shift in the resonant frequency of the sensor. The 3D‐SLMS technology allows for a high sensitivity of −0.502 MHz N ⁻¹ , a limit of detection as low as 0.71 mN, fast response time of 0.6 s, and stretchability up to 158% without device failure. As a proof‐of‐concept, the wireless pressure detection of various human motions such as arm bending, fisting, boxing, coughing, and flatfoot diagnosis is successfully implemented, thus promising translation of wearable electronics for sport monitoring and medical rehabilitation.