Spontaneously formed closed rings of single-wall carbon nanotube bundles and their physical mechanism

In this paper we demonstrate that the closed SWNT rings formed on SiO2/Si substrate are in a host of different shapes, besides circular, that include ovals and even ribbon-like closed loops. Their formation mechanism may be related to the competition between surface tension, van der Waals attraction, and the elastic force during solution evaporation. Our investigations may provide a possible way to control the different shapes of CNT rings for physical and device applications and further yield insight into optimizing self-assembly technologies for CNT alignments and orientations based on wet chemistry.