3D printing enhanced piezoelectricity of MXene/P(VDF-TrFE) composites for energy harvesting and force sensing

In pursuit of advanced self-powered wearable devices, piezoelectric materials have aroused great attention due to their stable energy harvesting ability from surroundings. However, traditional piezoelectric polymer-based nanogenerators necessitate a high-energy process to align the dipoles of the polymer, which is cumbersome, expensive, and could even lead to material deterioration. To address this challenge, we present a composite strategy with self-poling capability enabled by the extrusion-based 3D printing. MXene nanosheets were introduced into the fluoropolymer poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) to provide strong hydrogen bonding as anchors. Under the shear stress generated by the extrusion process, the alignment of the dipoles was realized without additional treatment. The resulting piezoelectric nanogenerator exhibits an open-circuit voltage of 5.5 V, a short-circuit current of 1.1 μA, and the output power density of 68 μWcm⁻³ under the force of 22 N and a frequency of 2 Hz. A self-powered sensor was assembled and demonstrated high sensitivity for human motions and facial expressions. Moreover, the 3D-printed piezoelectric composites present good flexibility, which is a crucial property for wearable devices. With the free design capabilities of the 3D printing technology, this strategy may pave the way for customized and feasible processing of high-performance piezoelectric nanogenerators and force sensors.