Nanoscale Mechanisms of Piezoelectric Enhancement in MXene-Fluoropolymer Composites.

Piezoelectric polymers have emerged as promising materials for flexible electronics, particularly in sensing and energy-harvesting applications. Their advantages over conventional inorganic piezoelectrics arise from their lower density, flexibility, ease of processing, and potentially lower costs. Many common piezoelectric polymers are bio-derived or biocompatible, making them ideal for applications in healthcare. The main disadvantage of piezoelectric polymers relative to inorganics is that their piezoelectric coefficients are usually a few orders of magnitude lower, and their low conductivity usually leads to piezoelectric nanogenerator (PENG) devices with very high output impedances, making interfacing with external circuits difficult. Among various strategies to improve the performance of piezoelectric polymers, the incorporation of two-dimensional MXenes as nanofillers has emerged as a versatile and effective approach. This Mini-Review summarizes the documented effects of MXenes on piezoelectric fluoropolymers, with a focus on electrospun nanofibers. We discuss spatially confined nanostructures and interfacial interactions that lead MXene/polymer composites to exhibit enhanced performance. We highlight some MXenes that are inherently piezoelectric, while also discussing how conventional MXenes promote piezoelectricity in polymers, in addition to improvements in other areas, such as dielectric properties, charge transport, and mechanical properties. Finally, we outline future research directions for further enhancement techniques for the piezoelectric performance of MXene-based polymer composites.