Dynamics of gas micronuclei formed on a flat hydrophobic surface, the predecessors of decompression bubbles

Abstract

It is a long-standing hypothesis that the bubbles which evolve as a result of decompression have their origin in stable gas micronuclei. In a previous study (Arieli and Marmur, 2011), we used hydrophilic and monolayer-covered hydrophobic smooth silicon wafers to show that nanobubbles formed on a flat hydrophobic surface may be the gas micronuclei responsible for the bubbles that evolve to cause decompression sickness. On decompression, bubbles appeared only on the hydrophobic wafers. The purpose of the present study was to examine the dynamics of bubble evolution. The numbers of bubbles after decompression were greater with increasing hydrophobicity. Bubbles appeared after decompression from 150kPa, and their density increased with elevation of the exposure pressure (and supersaturation), up to 400kPa. The normal force of attraction between the hydrophobic surface and the bubble, as determined from the volume of bubbles leaving the surface of the wafer, was 38×10−5N and the tangential force was 20×10−5N. We discuss the correlation of these results with previous reports of experimental decompression and bubble formation, and suggest to consider appropriate modification of decompression models.