Ultrasensitive Multifunctional Magnetoresistive Strain Sensor Based on Hair-Like Magnetization-Induced Pillar Forests

An ultrasensitive multifunctional sensor which integrates tactile sensing and magnetism sensing together in one device is presented. The sensor, dubbed L-MPF, consists of two interlocking hair-like magnetization-induced pillar forests, which are self-formed under a magnetic field and a loading pressure. An L-MPF endows intelligent electronics with magnetic field reception, which is the sense of bacteria, birds, and whales, rather than human beings. It is found that the L-MPF precisely detects the magnitude and the loading path of the dynamic load, including pressure, shear, and magnetic field, with fast response, high reversibility, excellent sensitivity, and high stability. The sensitivity coefficient can reach 1965, 1.6, and 240% T-1 under 50-60% compressive strain, 0-3.4 degrees shear strain, and 21-170 mT magnetic field. Additionally, the strain sensitivity coefficient can be set by the external magnetic field, which affords a potential approach to realize different sensing requirements in various circumstances. For a detailed insight into the sensing element's behavior, the magnetic-mechanic-electric coupling response is also described by simplified model simulation and theoretical analysis. Furthermore, a 4 x 4 L-MPF array exhibits contactless gesture sensing, which provides a new way for next-generation human-electronics interface devices and artificial electronic skin.