A Simple Method to Produce a Piezoelectric Composite Membrane with Aligned and Crimped Nanofibers for Wearable Pressure Sensors.

Organic fiber-based pressure sensors are extensively used in smart wearable electronic devices due to their remarkable combination of wearability and sensitivity. However, enhancing their sensing and wearable performance has been hindered by complex processing parameters, use of toxic chemicals, and high costs. Herein, a simple, efficient, and green method is developed using wool lamination and ethanol treatment to prepare cross-scale sandwich-structured composite membranes that contain aligned yet crimped nanofibers. The proposed method significantly improves the permeability and mechanical properties of a poly(vinylidene fluoride) (PVDF) fiber-based membrane, increasing the pore size from 3.18 ± 0.69 to 3.91 ± 0.90 μm, tensile strength from 3.85 ± 0.22 to 8.28 ± 0.98 MPa, and ultimate strain from 60.2 ± 7.7 to 200 ± 30.3%, when compared to the PVDF nanofiber membrane produced without wool lamination or ethanol treatment. Furthermore, the piezoelectric coefficient and sensitivity increase by approximately 70 and 300% respectively, to 45.6 pC/N and 2.0 V/N. The feasibility of applying this method to other materials is demonstrated by testing polyacrylonitrile nanofibers. This work presents an effective method to produce functional structures in nanofiber composite membranes, endowing them with enhanced piezoelectricity and hence elevated potential in smart wearables.