2020: Three different millimeter components can be self-assembled onto specific sites using pattern matching!

“Selective self-assembly of three-component system based on hydrophilic/hydrophobic patterning”
Published in T. Okuyama et al., Sensors and Actuators A: Physical, 312, 11214, 2020.

This paper presents a demonstration of the selective bonding of three different millimeter-scale components by using complementary patterning of hydrophilic and hydrophobic surfaces. The hydrophobic surface of millimeter-scale components fabricated from hydrophobic polydimethylsiloxane (PDMS) was made partially hydrophilic with a designed pattern by exposure to an excimer light through a stencil mask. The oil, as an adhesive, was only deposited on the hydrophobic surface. We prepared 30 components with 3 patterns, which were agitated in water by using a computer-controlled propeller stirrer. As a result, we obtained a significantly higher yield of correct bonds compared to erroneous bonds under an appropriate stirring condition. The result can be explained through the contrast in bonding strength between the correct and erroneous bonds. The design principle of using concentric patterns serves as a basic strategy for realizing programmed self-assembly with selective bonding patterns.