Outer diameter Curvature effects in Multi-Walled carbon nanotubes on the twistron energy harvester

We describe an experimental and computational study of increased electrical double layer capacitance (EDLC) changes and improved harvesting performances in multi-walled carbon nanotube (MWCNT) yarn-based energy harvesters using smaller-diameter MWCNTs. Twisted MWCNT yarn-based energy harvesters convert tensile mechanical energy into electrical energy by utilizing changes in the EDLC on the surface of MWCNTs. The correlation of the variance in EDLC and open circuit voltage (OCV) of the coiled MWCNT yarn was investigated under the mechanical stretch applied to the twistron energy harvester, and both OCV and capacitance increased as the MWCNT diameter decreased. We performed molecular dynamics (MD) simulations to elucidate the mechanisms of the increasing EDLC and OCV of twistron energy harvesters, which were verified by experiment. The computational results elucidate the relationship between the decrease in MWCNT diameters and the increasing number density of interstitial spaces between multi-walled MWCNTs. The decrease in the total surface area of the interstitial spaces is an important factor in the capacitance change of the twistron energy harvester under longitudinal stretching. Such novel findings are a foundation for the development of a twistron harvester with significantly improved energy harvesting performance.