Ultrathin Biocompatible Electrospun Fiber Films for Self-Powered Human Motion Sensor

In recent years, triboelectric nanogenerator (TENG) has been proven to be an effective and simple solution for self-powered wearable sensing, and a wide variety of materials and methods have been applied to TENG based sensors. In this study, an ultrathin fiber film with nanoporous brain-like structure (BUF) was obtained by cold-pressing the electrospun biocompatible fiber mats, and a wearable TENG sensor based on the BUF films that could sensitively detect human motion was demonstrated. This simply designed self-powered sensor was composed of Kapton as the shell and ultrathin, biocompatible poly L-lactic acid and ethyl cellulose (EC) fiber films as the triboelectric layers, prepared by convenient electrospinning method and cold-pressing. Compared to as-spun fiber mats, cold-pressed fiber membranes not only acquire overall compact structure but also remained porous surface morphology, which improved the triboelectric outputs and operational stability of TENG. Three TENGs were fabricated to evaluate the effects of different triboelectric layers on triboelectric outputs, and the BUF-TENG had the maximum triboelectric outputs (19 V, 630 nA at 3.5 Hz) and longer life than as-spun fiber mats based TENG. The BUF-TENG had linear relationship between triboelectric outputs and frequency, and sensitivities of 32.4, 0.94 and 0.22 V Hz(-1)in the range of 0.1-0.35, 0.35-2 and 2-3.5 Hz, respectively. Moreover, a self-powered sensor based on the BUF-TENG was proposed to sensitively detect human walking state and limbs motion. With convenient preparation process and biocompatible materials, the BUF-TENG sensor could be a potential self-powered wearable and portable sensor in future health care and monitoring field.