Studies on Size and Lubricant Effects for Fluidic Self-Assembly of Microparts on Patterned Substrate Using Capillary Effect

Conventional pick-and-place technology platform in handling microscale component assembly processes has technical limitations in terms of capacity, efficiency, and accuracy. The fluidic self-assembly (FSA) approach employs a lubricant fluid carrying micropart flows over a target wafer patterned with binding sites, which results in part-substrate attachment. This technique transports microparts from one location to another with orientation control and parallel sorting. The present study demonstrates a FSA approach for fast, economic, and precise handling of microscale parts with square (few are in rectangular) shapes. The microparts fabricated from silicon-oxide wafers and ranging in size from $350×350×170μm3to1000×1000×440μm3$ aligned and filled to designated sites in the substrate under water. The effects of micropart sizes and lubricants on the FSA processes are compared. This study provides a fundamental analysis for achieving and optimizing the self-alignment. The polymer or solder adhesion force of the square-patterned micropart immobilized at the larger binding sites were estimated to be $117±15μN$ and $510±50μN$⁠, respectively, which results in higher assembly yield of up to 100% for these samples.