Shock wave induced interaction of microbubbles and boundaries

In the present study we experimentally investigate bubble dynamics after laser induced shock wave exposure in the vicinity of salt crystals suspended in water. High-speed microscopic images show aspherical collapse and rebound of single and multiple bubbles with initial radii between 5 and 150 μm. Radius time curves of bubbles close to one boundary are compared to the bubble dynamics of a spherical model. The bubble dynamics strongly depends on the position of neighboring bubbles and on the number of boundaries given by the surrounding salt grains. After excitation bubbles are drawn to the closest particles in their vicinity. Subsequent application of shock waves leads to jet formation against the rigid boundaries. The bubbles often tend to form in or migrate into cracks on the crystal surfaces and sometimes lead to the breakage of particles due to rapid bubble dynamics. Similar behavior may occur in other cases where material damage is induced by shock waves in liquids such as lithotripsy or shock wave cleaning applications.