Parameter Sensitivity in Microsphere Impact and Capture

In the presence of adhesion and under certain conditions a microsphere will be captured during a low speed impact with a substrate. The sensitivity of the capture velocity (the largest initial normal velocity at which capture occurs) to five physical factors is analyzed in this paper. The factors are the Hertzian stiffness, Dupré surface energy, the microsphere radius, a damping coefficient associated with adhesion dissipation, and one associated with material dissipation. The sensitivity is determined by examining the effects of the factors on the capture velocity using a two-level, fractional factorial design layout. Capture velocities are determined using analytical models. Results indicate that the Dupré surface energy and the microsphere radius by far play the greatest role in the capture process. The Hertzian stiffness and the dissipation coefficient associated with adhesion affect capture to a lesser extent; an interaction of the surface energy and the adhesion energy dissipation can also play a small role.