Micro-bubble generation with micro-watt power using Carbon Nanotubes heating elements

The generation of micro-bubbles using localized μ watt heating of Carbon Nanotubes (CNTs) is presented in this paper. Dielectrophoretic force is used to form CNTs between micro metal electrodes. The contact of the metal electrodes and the CNTs is fixed by a thin film of SiO2. The localized heat generation by CNTs is provided by a DC current which induces a temperature increase due to resistive heating. The bubble diameter grew as the transduction of electrical energy into Joule-heating occurs continuously across the CNT heater. Similar to typical boiling phenomenon, the micron scale bubbles are generated using the CNTs as the nucleation site. Our experiments showed that the power required to generate bubbles was lower than ~113μW, which is only ~1 to 10% of the metal heaters as reported by other researchers. Experiments also showed that total input energy could be as small as ~2mJ to initiate bubble generation. As the maximum diameter of bubbles is around 100 microns and also the speed of the expansion of the diameter is controllable, this novel CNT heating element can be used in various application areas which require low energy consumption, such as hand-held ink-jet printing.