Effects of pin-to-plate plasma on the TENG properties of electrospun PCL-Ag/PA6,6 core-sheath yarns

As the demand for self-powered wearable electronics and smart textiles accelerates, the development of high-performance, flexible, lightweight, energy harvesting materials with optimized electroactive surface properties has become a critical focus. Electrospun nanofibrous yarns became a promising candidate for such applications due to their high surface area-to-volume ratio and inherent flexibility. However, their surface chemistry and morphology often limit charge generation and transfer efficiency. For more efficient and responsive energy harvesting materials, surface modification of electrospun fibers is critical. Plasma treatment offers a solvent-free, tuneable, and scalable approach to modifying surface functionalities with nanoscale precision without compromising the bulk integrity of the fibers. In this study, we present a novel TENG architecture based on electrospun polycaprolactone (PCL)-Ag/polyamide 6,6 (PA6,6) core-sheath yarns, with property enhanced through a pin-to-plate plasma (PTP) surface treatment applied for the first time to this material system. A modified funnel-based electrospinning technique (NanoTwist Spinning) was employed to fabricate core-sheath yarns, in which a conductive Ag/PA6,6 core was encapsulated within a dielectric sheath of PCL fibers. These yarns were subsequently plasma-treated systematically investigate the TENG performance varying voltage parameters and treatment time. Comprehensive surface characterisation via FE-SEM, Raman, ATR-FTIR, and XPS revealed increased surface roughness, oxidation, and polymer crystallinity with longer plasma exposure. This nanoscale modifications directly translated to improved TENG performance, with the PTP-15 sample achieving a peak output of 113.6 V at a force of frequency of 10 Hz and a force of 20 N, a substantial enhancement over untreated samples (65.9 V). Plasma treatments can also have a noticeable impact on current measurements depending on treatment times. The findings demonstrate the effectiveness of plasma treatment in optimising the electrospun nanofiber materials for next-generation energy harvesting fabrics demonstrated by the lighting of LEDs. Beyond TENG applications, this approach opens new avenues for scalable, flexible, and eco-friendly power sources in wearable electronics and smart textile systems.