Unidirectional Moisture-Wicking PAN/BTO-PVDF/ZnO All Fibrous Bilayer Breathable Electronic Skin for Health Sensing

All fibrous electronic skin based on excellent flexibility and piezoelectric properties could be widely applied in monitoring and healthcare sensing. The accumulative moisture during application scenarios, just as violent sweat or a damp environment, can affect the stability and sensitivity of the piezoelectric signal. Here, a bilayer piezoelectric sensor was fabricated using a layer-by-layer electrospinning technique. The inner layer is composed of hydrophobic piezoelectric polyvinylidene fluoride (PVDF)-zinc oxide (ZnO) nanofibers, while the outer layer consists of hydrophilic piezoelectric polyacrylonitrile (PAN)-barium titanate (BTO) nanofibers. The unidirectional moisture-wicking performance based on the hydrophilic-hydrophobic gradient of PVDF/ZnO-PAN/BTO nanofiber membranes (PZ-PBNF) could conduct liquid within 1 s. Incorporating inorganic ZnO and BTO nanoparticles provides a practical approach to enhancing the piezoelectric output performance (277.5 mV). These fibrous PZ-PBNF membranes also exhibit excellent stretchability properties (breaking elongation of 110%) and air permeability (12.065 mm/s). This innovative electronic skin with directional water transport and sensing functions could ensure long-term wear comfort for practical application in emerging wearable technologies and all healthcare ranges.