Observations of Nanobubble Formation on Carbon Nanotubes

We used an optical trap and a high-speed camera to image water bubble initiation on the surfaces of multiwalled carbon nanotubes. The laser wavelength was 1064nm and the average power was 100mW. This is the first demonstration of bubble formation on individual nanotubes. Most, but not all, nanotubes exhibited bubble formation. Bubbles both grew from and collapsed down to submicrometer size. Bubbles grew at the point where the laser heated a given nanotube. Transmission electron microscopy showed presence of amorphous coating and other structural defects on nanotube surface, which are most likely to act as bubble nucleation sites. No separation of the bubble from the nanotube surface was observed. (C) 2010 The Japan Society of Applied Physics