Microassembly combining pick-and-place and water mist

This paper reports a novel and versatile hybrid microassembly technique that applies water mist on the surface of microparts to assist alignment of microchips. This technique combines the traditional robotic pick-and-place technique and self-assembly technique. Two different approaches are studied: 1) mist-last where a 200μm × 200μm × 70μm SU-8 chip is placed roughly on another chip of the same size using a microgripper and then water mist is delivered to achieve self-alignment; 2) mist-first where water mist is delivered before the releasing of a chip near the target. The second approach is further studied to examine the maximum tolerance of placement error and placement of chips on hydrophilic/hydrophobic patterns. The experimental results indicate the proposed technique is reliable and versatile for stacking and assembling microchips. a 200μm × 200μm × 70μm SU-8 chip was assembled on the top of another SU-8 chip of the same dimensions, where the success rate can reach 75% with bias as high as 180μm. Microparts of size 200μm × 200μm × 70μm can be successfully assembled on hydrophilic/hydrophobic patterns.