Synergistic Effect of Polyurethane in Polyurethane-Poly(vinylidene fluoride) Nanofiber-Based Stretchable Piezoelectric Nanogenerators (S-PENGs)

Poly(vinylidene fluoride) (PVDF)-based piezoelectric nanogenerators, though flexible, exhibit poor stretchability and mechanical stability. This limits their application for harvesting energy from repeated deformations arising from human articular motions. Herein, we propose a simple and cost-effective approach to overcome the above issues while simultaneously enhancing the piezoelectric effect of PVDF by mixing a small amount of polyurethane (PU) in PVDF-PU nanofibers. The presence of PU in PVDF could enhance electroactive phases by up to 46%, as measured by Fourier transform infrared (FTIR) spectroscopy. Interestingly, an addition of 21% of PU in PVDF exhibited both an increase in the d(33) value from 3.02 to 7.064 pm/V and stretchability to 90%. For developing a stretchable piezoelectric nanogenerator (S-PENG) device, stretchable electrodes with a 4.5 gauge factor at 100% strain were fabricated by spin-coating of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS):graphene nanoplates on a prestrained PU substrate. SPENG produced 3.8 V, 0.65 mu A, and 0.48 mu W/cm(2) peak open-circuit voltage, short-circuit current, and power density during cyclic deformation, respectively, with electrical and mechanical stability for at least 2000 cycles. Its performance was demonstrated for various human articular motions related to the knee, elbow, and foot by integrating it with wearables. The generated energy from the S-PENG could readily charge capacitors up to similar to 650 mV in just 100 s. The designed S-PENGs showed great potential in harvesting energy from simple human motions.

Automated summary

This study proposes a simple and cost-effective method to enhance the piezoelectric effect of PVDF by mixing a small amount of PU in PVDF-PU nanofibers. This method improves the stretchability and mechanical stability of PVDF-based piezoelectric nanogenerators, making them more suitable for harvesting energy from human articular motions. By integrating stretchable electrodes with the S-PENG device, the designed nanogenerator demonstrates excellent electrical and mechanical stability.