Towards optimal designs for self-alignment in surface tension driven micro-assembly

Fluidic self-assembly driven by surface tension force has demonstrated the capability of assembling micro parts to binding sites in parallel with high efficiency and accuracy. In this paper, we focus on the binding site design for this technique, as it is a critical factor not only for accurate assembly, but also to achieve unique alignment position and orientation. To find optimal designs, we use a first-order approximation model to evaluate a series of patterns including disks, rings and offset rings. From this analysis, optimal patterns assuring unique alignment are determined to be offset rings with specific geometric constraints. For comparison, experiments with different shapes are performed, and results matching with the simulations are observed.