Electrospun Polyvinylidene Fluoride Nanofiber Membrane-Based Flexible Capacitive Tactile Sensors for Biomedical Applications

Polyvinylidene fluoride (PVDF) is a high-performance polymer with excellent ferroelectric, piezoelectric and pyroelectric properties. The electrospun PVDF has gained much attention in the design of tactile sensors based on piezoelectricity. This study aims to develop piezocapacitive sensors for measuring static pressure, which cannot be done by piezoelectric sensors. Electrospun PVDF nanofiber membranes with relatively uniform morphology were prepared using an electrospinning technique. The surface morphology of the electrospun PVDF nanofibers was analyzed by scanning electron microscopy, and their microstructure was characterized by the Fourier transform infrared and Raman spectroscopies. Infrared vibrational spectroscopy data revealed a ferroelectric polar beta-phase in the as-fabricated and untreated membranes. It was demonstrated that the electrospinning technique can induce crystalline and polar beta-phase by applying an electric field to the PVDF polymer solution during solution jet stretching. The piezocapacitive membranes with full-face copper electrodes were fabricated and then sandwiched between Kapton polyimide films to form a sensing device. The results indicated a linear piezocapacitive-force behavior. Thus, PVDF electrospun membranes can be used to create highly flexible pressure sensors. Several potential biomedical applications of these PVDF nanofiber based membranes in the form of flexible capacitive pressure sensors are discussed.