Nanogenerators of acid-functionalized multiwalled carbon nanotubes incorporated poly(vinylidene fluoride) nanocomposites with enhanced piezoelectric performance towards bio-mechanical motion energy harvesting

Polymer-based piezoelectric nanocomposites, enhanced with nanofillers, offer a scalable solution for efficient energy harvesting. In this work, we incorporated acid-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) in poly(vinylidene fluoride) (PVDF) matrix to understand the influence of MWCNTs-COOH in enhancing the overall structural, morphological, dielectric, and piezoelectric properties of the PVDF/MWCNTs-COOH nanocomposites. The PVDF/MWCNTs-COOH nanocomposites were prepared by melt-mixing followed by solution casting, and the concentration of MWCNTs-COOH was varied from 0 to 3 wt%. MWCNTs-COOH served as a heterogeneous nucleating agent to form the polar crystalline polymorph of PVDF. The incorporation of 1.5 wt% of MWCNTs-COOH led to the highest polar phase content of ~ 89% owing to the uniform dispersion of MWCNTs-COOH in the PVDF matrix. Similarly, the highest piezoelectric coefficient (d₃₃) of ~ 49.2 pm/V was observed in the PVDF nanocomposite with 1.5 wt% of MWCNTs-COOH. The fabricated optimized piezoelectric nanogenerator with 1.5 wt% of MWCNTs-COOH exhibited the highest piezoelectric response with a sensitivity of ~ 11.4 V/N and an open circuit voltage of ~ 59.2 V, an open circuit current of ~ 3 μA, and a maximum power density of ~ 19.8 μW/cm². The optimized device was found to exhibit high durability, which was confirmed by performing the durability test for 3 months consecutively. The fabricated device can be used as a sensor as well as an energy harvesting device for various bio-mechanical motions. Highlights: PVDF/MWCNTs-COOH nanocomposites were used to fabricate nanogenerators. Higher extents of interfacial interactions enhanced piezoelectric performance. Nanocomposite of 1.5 wt% MWCNTs-COOH showed a polar phase content of ~ 89%. Nanocomposite of 1.5 wt% MWCNTs-COOH exhibited a d₃₃ value of ~ 49.2 pm/V. Nanogenerator utilized as a bio-mechanical motion energy harvester.