Abstract
It is known fine bubbles with micro-or nano meter order diameters exhibit diameter-dependent unique characteristics, and some related applications has been developed. Development of further applications requires much detailed understanding of size effect on their fundamental properties. Here we propose an application of carbn nanotubes (CNTs) for a tool of generate and operate individual bubbles with selective size. Generally production of finebubbles for application use is conducted by top down approach such as mechanical sharing of large bubbles in liquid, so that the bubbles are obtained as a suspension with rather wide diameter distribution. In our study, individual CNTs work as a electrodes for water electrolysis, therefore the proposed device enable us to generate individual bubbles at CNT tip. If individual CNTs hold isolated bubbles at tip continuously, array of size-controlled bubbles can be realized applicable to various size-selective measurements. To realize such a device using vertically aligned CNTs, some technical problems should be solved such as aggression of neighboring CNTs by capillary action in water. Therefore, we fabricated CNT/resin composites as the electrode. Tips of individual CNTs are isolated on the surface of composite, so that they can work independently as the electrodes. Atomic Force Microscopy (AFM) revealed that numerous protrusions consisting if CNT tips existed on their surface and bubbles selectively generated at such protrusions by electrolysis with 5% sodium chloride solution. In situ AFM also showed time-dependent growth of nanobubbles in 10 seconds order to be certain size and, and gradual shrinking in 10 hours.
