Model for micropart planarization in capillary-based microassembly

This paper describes a quantitative model for the planarization of microparts after their capture on capillary binding sites. We have found that three distinct processes (tilt correction, squeeze-film settling, and force stabilization) contribute to the equilibrium position of a micropart that has been assembled using capillary forces. The three processes affecting micropart planarization are a function of the pressure profile underneath the micropart, which can be determined by the radius of curvature at the capillary/assembly fluid interfaces. The tilt correction and squeeze-film settling processes, which planarize the micropart, may or may not occur by capillary fluid flow depending on the force stabilization process. We present a two-dimensional model used to describe the equilibrium settling time of the micropart as a function of all three processes, part size, capillary fluid volume, viscosity, and surface tension.