Abstract: The influences of micro-pits, hydrophobic coating and electrolysis specifications on the growth behaviors and resident stability of the electrolyzed microbubbles are analyzed to achieve the adaptive start-stop control and stable residence of electrolyzed microbubble. The electrolytic test pieces with polyimide insulation surface and Pt bottom electrode were manufactured, and the observational experiments of electrolyzed microbubbles with normal and hydrophobic wall surfaces in the static water were made. The research results show that the adaptive start-stop control and stable residence of electrolyzed microbubbles in the micro-pits on electrolytic test piece can be achieved. The electrolyzed microbubbles start generating at the nucleation points, and more nucleation points are formed on the hydrophobic surface to accelerate the microbubble growth. The increased NaCl concentration from 0.5 % to 3.5 % would reduce the voltages of starting microbubble electrolysis on normal and hydrophobic wall surfaces by 4.43% and 2.31%, respectively. The increased NaCl concentration from 0.5 % to 2.5 % would also reduce the voltages of filling micro-pits on normal and hydrophobic wall surfaces, but the voltages of filling micro-pits turn to be constant as the NaCl concentration is greater than 2.5 %. The electrolytic voltage is increased to directly stimulate the combinations of H ions and electrons, thus significantly accelerating the electrolyzed microbubbles to inflate to the stable diameter. Under the same experimental conditions, the hydrophobic surface would lead to the greater stable diameter of microbubble to shorten the time to reach the stable diameter, and the resident stability of microbubble is improved using a greater contact angle θ.

Key words: microbubble, electrolysis, nucleationpoint, hydrophobicity, contactangle, residentstability