Branched Polyethylenimine-Reinforced Positive Polarity Polyamide 6 Nanofiber Membranes for Flexible Triboelectric Nanogenerator

Abstract Polyamide 6 nanofibers (PA6 NFs) have been widely explored as a friction layer in triboelectric nanogenerators (TENGs), but their intrinsically low dielectric constant severely limits charge storage and retention, resulting in suboptimal electrical output. Herein, PA6 NFs are activated by plasma treatment to enhance surface reactivity and subsequently functionalized via dip-grafting with branched polyethylenimine (PEI), resulting in PA6-PEI NFs with significantly enhanced triboelectric performance. Specifically, at the optimized PEI concentration of 3 wt %, the introduced amine-rich surface functionality enhances surface polarity and dielectric permittivity in the low-frequency region, thereby promoting more efficient charge generation and retention during contact electrification. Consequently, a TENG constructed with PA6-PEI NFs as the positive triboelectric layer delivers a high open-circuit voltage of 311.88 V and a power density of 0.57 W/m2. Furthermore, the device exhibits stable mechanical cycling performance under ambient laboratory conditions by efficiently harvesting low-frequency mechanical energy to power capacitors and diodes, while its skin-mounted flexibility enables Morse-code transmission through finger bending. Finally, the effective surface engineering strategy presented in this study provides an innovative design framework for the development of high-performance PA6-based TENGs.