Magnetic flexible sensor with randomly distributed pine-branch microstructure for bidirectional recognition

Flexible sensors have been widely used in smart wearable devices, in which the multifunctional selectivity and mechanical property receive the main attention. However, a simple process for preparing sensors which can recognize different forms of mechanical stimuli is still a challenge. This paper reports a magnetic thin-film sensor (MP-Ag-MP) consisting of magnetic PDMS matrix and conductive Ag nanowires film with pine-branch microstructure by using sandpaper as an abrasive template. Due to its upper and lower asymmetric microstructures, the sensor has diametrically opposed electrical signal responses to bending stimuli in different directions, thus enabling the differentiated monitoring of in-plane and out-plane bending, and the sensitivities can respectively reach −9.04 × 10⁻²/mm and 12.87 × 10⁻²/mm in the sensing range. Moreover, it can also respond promptly to different magnetic field directions and intensities, which demonstrates excellent magnetic sensing performance. The sensor can be applied to monitor various human joint motions and construct a Morse code encryption-decryption system. Furthermore, a stress-magnetic bi-functional control system integrated with Bluetooth transmission function can be designed to wirelessly control the motion of the smart cart. As a result, this randomly distributed pine-branch microstructure endows the wonderful bi-directional sensing function and provides high potential application in smart wearable devices.