Macro- and micro-wrinkled conductors and multi-scale wrinkled nanofibers for omnidirectional stretchable wearable triboelectric nanogenerators

The critical challenge of triboelectric nanogenerators (TENGs) as self-powered wearable devices is the lack of flexibility and more importantly stretchability. Hence, in this study, macro-micro-nano-wrinkles were fabricated in material structures that endow both electrode and active tribo-layers with high omnidirectional stretchability, improving the performance. The multi-scale wrinkled nanofibrous nylon/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film was fabricated using a layering strategy including the low-cost balloon-blowing method as a tribo-electrode layer. Furthermore, through a cost-effective and novel thermo-mechanical shrinkage method, macro-micro-wrinkled (MW) carbon-based electrodes/elastomer composite was generated as the other tribo-electrode layer, including MW-reduced graphene oxide (rGO)/polydimethylsiloxane (PDMS), MW-single-walled carbon nanotubes (SWCNTs)/PDMS, and MW-titanium carbide (MXene)/PDMS. This wrinkled structure preserved by the elastomer has omnidirectional stretchability due to an isotropic property of the shrinking process and increases the area for electron transfer leading to performance enhancement. Three fully flexible macro-micro-wrinkled stretchable TENGs (MW-STENGs) were developed to harvest biomotion. By optimizing the wrinkles, design, materials, and electrical and mechanical properties, it was concluded that MW-STENG with wrinkled nylon/PEDOT:PSS film and MW-MXene/PDMS composite has the best performance with a stretchability of 80 %. The effects of frequency (1–3 Hz), pressure (1–3 N), resistance (10 3 -10 9 Ω), and durability on the optimum MW-STENG were evaluated. Moreover, to study this MW-STENG as an energy harvester and a power source, its ability to charge capacitors (1, 4.7, and 10 μF) and illuminate an LED was studied. • Macro-micro wrinkled conductors/PDMS with an omnidirectional stretchability are fabricated by thermo-mechanical shrinkage. • Wrinkled nanofibrous nylon/PEDOT:PSS film is fabricated by balloon-blowing method. • Micro-nano wrinkles improve output and endow omnidirectional stretchability of 80 %. • Optimum TENG (wrinkled nylon/PEDOT:PSS/MXene/PDMS) is applied as a wearable device.