In situ observation of dewetting-induced deformation of vertically aligned single-walled carbon nanotubes

Abstract We investigated dynamical processes of capillary-mediated deformation of vertically aligned single-walled carbon nanotubes (VA-SWCNTs) via in situ observation of their wetting and dewetting behaviors using an environmental scanning electron microscope (ESEM). Three types of wetting behaviors on a VA-SWCNT sample were confirmed, including conical shaped water aggregates, spherical droplets on tips of conical shaped water aggregates, and extensively distributed water layers. While the former two types both resulted in dimples on the VA-SWCNT surface and failed to induce large-scale deformation of VA-SWCNTs, the latter caused the formation of wall-like structures and crack propagation in the VA-SWCNT film during the dewetting process due to directional retraction of vapor-liquid interfaces. This dewetting-induced large-scale deformation that was confirmed by the in situ ESEM observation for the first time represented initial stages of capillary processes, leading to the self-organization of VA-SWCNTs reported in recent literatures. Compared to the previous studies based on ex situ observations of dried samples, our in situ observation successfully captured temporal evolution of the dewetting-induced deformation, facilitating the more precise construction of predictive models of final morphologies of VA-SWCNT films after capillary-mediated densification.