Investigation of Brownian Motion of Micro- and Nano-Bubble

In this paper, nanobubble shrunk from microbubble generated by electrolysis was observed by optical microscope in order to distinguish a bubble from impurities or contamination in the water. To keep microbubbles in focus, it is necessary to generate microbubble whose diameter is less than 5μm in focal position directly since its rising velocity is negligibly small and shrink rapidly. Therefore, diameter distribution of bubble generated by electrolysis was firstly investigated under the different configurations of electrode diameter, concentration of solution and voltage. In the result, when diameter of electrode was less than 1μm, distribution of bubble diameter was decreased to generate smaller bubble. Observation of Brownian motion of nanobubble was succeeded. Root mean square of displacement and diameter of nanobubble were simultaneously measured and compared with a behavior of the ZnO solid particle. As a consequence, root mean square of displacement of bubble is smaller than that of ZnO particle due to different structure of interface.