Carbon Nanotubes as Heating Elements for Micro-Bubble Generation

Development and preliminary characterization on the performance of a micro-bubble generator using carbon nanotubes (CNTs) as heating elements are presented. Dielectrophoretic force was used to align CNTs between fabricated micro-electrodes. The contacts between the CNTs and electrodes were fixed by patterned SiO₂ thin film. Localized high temperature due to Joule-heating generated by an AC current of a few hundred muA (in general les100 Hz) in the carbon nanotubes vaporized surrounding water and generated micron sized bubbles (with diameter of 5 mum detectable under normal optical microscope). These experimental evidence indicate that exposed CNTs may function as a single nucleation site for bubble generation. The power required to generate these bubbles can be as small as 337 muW, which is with 1-2 order of magnitude smaller than that of typical metal or polysilicon based MEMS heaters. Precisely controlled micro bubble generation may find promising applications in ink-jet printing, micro-fluidic visualization, or micro-fluidic based bio-manipulation