Highly flexible and conductive stainless-steel thread based piezoelectric coaxial yarn nanogenerators via solution coating and touch-spun nanofibers coating methods

The concept of nanogenerators (NGs) based on textiles was introduced to impart functional attributes to textiles for developing smart textiles and integrating wearable electronics of various functionalities. The human body can generate sufficient mechanical energy that can be harvested by the piezoelectric NGs (PENGs) and used to power up low power consuming wearable electronics. Two simple and easy approaches for coating a highly conductive weave-able metal electrode with polyvinylidene fluoride (PVDF) piezoelectric polymer to construct two different types of coaxial yarn-based PENGs (Y-PENGs) are presented in this paper. The proposed techniques result in the in-situ formation of the β phase of the PVDF. The Y-PENGs are based on facile solution coating and touchspun nanofibers (TSNFs) coating of the inner electrode. The solution-coated Y-PENG (SC-YPENG) showed 5.12 V of peak open-circuit voltage (V _oc) and 41.25 nA of peak short circuit current (I _sc). Whereas the TSNFs coated Y-PENG (NFC-YPENG) showed 5.08 V of peak V _oc and 29.1 nA of peak I _sc. In a series connection, the average peak V _oc were synergized by ∼2.53 and ∼2.4 factor respectively for the SC-YPENG and the NFC-YPENG. The Y-PENGs were able to charge capacitors and run LEDs. Additionally, our coated inner electrode shows great flexibility, thereby it could be knitted or woven into smart textiles to run wearable electronics sustainably.