Optimising fundamental knitting parameters for wearable triboelectric nanogenerators

During the past decade, Triboelectric Nanogenerators (TENG) have demonstrated their potential as an energy harvesting and self-powered sensing technology for future wearable applications. Among various TENG architectures, knitted textile TENGs have become increasingly popular in recent times, as they provide advantages such as high electrical outputs, very good mechanical properties and excellent wearability. However, there is still a lack of understanding on how to engineer the knitting parameters to maximize the electrical output generation of knitted textile TENGs. Herein, for the first time, we bridge this gap by mapping the relationship between basic knit parameters and the fundamental TENG parameters which govern their electrical outputs. In this work, the loop length, yarn count, number of yarns per loop and the loop structure of a knitted textile TENG are empirically varied and its impact on the charge, current and voltage outputs is studied. The observed output trends are then analysed in-depth using the distance-dependent electric field theory, thus, explaining the root causes of the observed output trends. Consequently, several new strategies on the design and optimisation of more efficient knitted textile TENGs are uncovered. Further, the impact of these optimisation strategies on the wearable properties of the knitted textile TENGs is studied, paving the way for practically applicable textile TENG designs with balanced electrical output generation and long-term wearability.