Radial gradient characteristics formed by the interstitial space of MWCNT yarn owing to twisting

The interstitial space of a multiwalled carbon nanotube (MWCNT) yarn is key to creating electric double-layer capacitance for harvesting energy. Despite various fabrication methods for MWCNT yarns, the formation mechanism of the interstitial space inside the yarns is poorly understood. Herein, the twisting process of a cylindrical MWCNT bundle into a yarn was simulated using the mesoscale coarse-grained particle dynamics model. A larger fraction of interstitial space was observed in the sheath region of the yarn, where large-diameter MWCNTs were mainly distributed. Small-diameter MWCNTs first swirled toward the inner core during the twisting process, causing the large-diameter MWCNTs to be sparsely distributed throughout the sheath region. The proposed methodology and its results can be applied to the geometric design of twisted MWCNT bundles to maximize the fraction of the interstitial space therein.