Role of step-shape structures and critical failure bubble volume in micro bubble constraint

Micro fluid devices using micro bubbles have attracted much attention for their special advantages. In many cases, the bubbles must be constrained to a certain position so as to grow or shrink under control. In this paper, we discuss the effect of step-shape structures in constraining bubbles against the surface force, which plays a dominant role on the micro scale. We fabricate specimens with a step and electrodes and carry out electrolysis experiments in water to observe bubble growth. We observe the constraining effect of steps as well as failure phenomena. Based on numerical simulations and theoretical analysis, we introduce the critical failure bubble volume and present the analytic solution in a 2-D model. Using step-shape structures is an easy method of constraining bubbles within the critical failure volume..