Low-entropy structured wearable film sensor with piezoresistive-piezoelectric hybrid effect for 3D mechanical signal screening

Continuous monitoring of physical signals such as stress and strain plays a crucial role in Internet of Thing and artificial intelligence, thus flexible mechanical sensors gain increasing attention due to their enormous application potential in wearable electronics, soft robots, human-machine interfaces, etc. Recently, significant progress has been made in mechanical sensors for trading off high sensitivity and wide range for low dimensional strain/force sensors, yet it is still of significant challenge to discriminate complicated three-dimensional (3D) mechanical signals in practical applications. Herein, a novel wearable film sensor capable of sensing multi-directional mechanical stimuli is developed by coating MXene onto low-entropy structured piezoelectric poly(vinylene fluoride-trifluoroethylene) (PVDF-TrFE) mat composed of aligned nanofibers. The resultant functional fiber mats give rise to an anisotropic in-plane conductive network for 2D in-plane strain sensing, and oriented ferroelectric crystals in nanofibers with piezoelectricity allow for out-of-plane dynamic pressure detection. Besides, the all-in-one flexible anisotropic sensor shows linear sensing properties and high sensitivities both in the plane strain and out of the plane pressure due to piezoresistive and piezoelectric mechanisms, respectively. Such sensors can effectively distinguish multi-directional mechanical stimuli for potential applications in human machine interfaces, healthcare, entertainment and other systems.