A hierarchical core-shell tribopositive yarn TENG with electrospun polyethyleneimine (PEI) nanofibers for sustainable energy harvesting and human machine interface application

The rising demand for sustainable energy has led to significant interest in triboelectric yarns, which can be integrated into smart textiles with energy harvesting and sensing capabilities. While ongoing research on tribonegative yarns has advanced the development of triboelectric nanogenerators (TENGs); further progress is needed on fabricating tribopositive yarns that offer scalability, ease of fabrication, soft aesthetics, easy to be woven and knit with higher electrical outputs, and enhanced durability. Our work introduces a core-shell structured, flexible, durable and continuous scalable tribopositive yarn TENG (TPY), fabricated via conjugate electrospinning of polyacrylonitrile (PAN) possessing highly polar groups ⸺C ≡ N with flexible thermoplastic polyurethane (TPU) and increasing electron donating capability amine functional groups (⸺NH 2 ) rich polyethyleneimine (PEI). Due to the electron-withdrawing capability of the amine groups, the hierarchical TPY with 5 % PEI concentration exhibited antibacterial properties and generated an output voltage of 13.3 V in a 2.5 cm length, which is ∼183 % higher than the 4.7 V produced by the PAN-TPU TENG yarn. TPY was shaped into various woven and knitted electronic textiles (e-textiles) to study the impact of triboelectricity on designed fabrics structure where, 2/2 basket woven, and 1x1 rib knitted TENG showed power densities of 5.518 mW/m 2 and 4.504 mW/m 2 respectively. Maintaining durability and soft aesthetics, e-textiles withstood 4000 Martindale abrasion cycles. For practical applications, they were utilized as self-powered sensors to monitor body motions and differentiate objects through grasping and releasing. Additionally, they functioned as a human-machine interface (HMI) for PowerPoint slide transitions and as a smart switch to control power on/off functions. This work demonstrates an easy approach for designing durable tribopositive yarns with enhanced electrical output and opens new ways for practical applications of textile based TENGs.