A magnetized microneedle-array based flexible triboelectric-electromagnetic hybrid generator for human motion monitoring

Most triboelectric-electromagnetic hybrid generators (TEHGs) are not suitable for monitoring human motions as wearable self-powered sensors owing to the rigid, complicated and bulky structures. In this work, we developed a novel magnetized microneedle-array (MA) based flexible TEHG for monitoring human motions. The magnetic-field-induced spray self-assembly method with electro-magnetizing technique was firstly proposed to cost-effectively fabricate magnetized microneedles for TEHG. The magnetized microneedles in TEHG simultaneously serve as the frictional layer of triboelectric generator (TEG) and bendable magnetic poles of electromagnetic generator (EMG). TEG utilized the closed bending-friction-restoring behavior of microneedles to generate triboelectricity while EMG used the rotation of magnetized microneedles to produce the induced electromotive force. TEG could output the open-circuit voltage (V-OC) of 10 V and the EMG could generate the short-circuit current (I-SC) of 80 mu A under the 30 N and 1 Hz compressing-releasing operations. We demonstrated that the MA-based TEHG, integrated in insole and attached on elbow as the self-powered sensors, could exactly detect triggering frequency of human motions. Considering the unique advantages, including flexibility, small dimension, light weight, and easy scale up, further applications of TEHG in wearable electronics, self-powered sensors, and healthcare monitoring system are promising.