Design and Fabrication of a Hierarchical Structured Pressure Sensor Based on BaTiO3/PVDF Nanofibers via Near-Field Electrospinning

Herein, a simple and low-cost fabrication method for flexible piezoelectric pressure sensors with hierarchical structures over large areas is presented. First, polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3, BTO) composite membranes are fabricated through near-field electrospinning, and the hierarchical structured membrane (HSM) is obtained by spreading the flat membrane on the designed mold and drying. Then, the effect of encapsulation schemes on the piezoelectric properties of the sensor is investigated by combining different membranes with different PDMS substrates. The output voltage under periodic loads shows that the encapsulation scheme of "the hierarchical structured membrane with a hierarchical structured substrate" (HHS) can provide the highest peak voltage attributed to its largest contact area, which increases the active area (deformation area) for piezoelectricity generation. Also, the HHS with a bulge of 2 mm can produce a maximum output voltage of 2.32 V under a periodic load of 2 N, 2.5 Hz. Finally, the HHS pressure sensors are used for monitoring human motions, including joint bending, walking, and jumping, and the results show that the presented hierarchically microstructured flexible piezoelectric pressure sensor has great potential for applications of for human-activity monitoring and wearable bioelectronic devices.