Capillary Gripping and Self-Alignment: A Route Toward Autonomous Heterogeneous Assembly

Abstract

Abstract-We present a pick-and-place approach driven by capillarity for highly precise and cost-effective assembly of mesoscopic components onto structured substrates. Based on competing liquid bridges, the technology seamlessly combines programmable capillary grasping, handling and passive releasing with capillary self-alignment of components onto pre-patterned assembly sites. The performance of the capillary gripper is illustrated by comparing the measured lifting capillary forces with those predicted by a hydrostatic model of the liquid meniscus. Two component release strategies, based on either axial or shear capillary forces, are discussed and experimentally validated. The releaseand-assembly process developed for a continuously moving assembly substrate provides a roll-to-roll-compatible technology for high-resolution and high-throughput component assembly.

Surface tension-driven self-alignment

“…65 The capillary self-alignment of 10 to 20 mm-sized plastic foil dies fed by pick-and-place onto silicon-based 64 and laser-scribed plastic substrates 48 was also demonstrated, the latter being also suitable for autonomous deployment onto moving webs. 75 Centimeter-sized components floating at the air/water interface were assembled onto matching hydrophilic receptors of hydrophobic substrates. 76 The substrate was pulled at an angle through the fluid interface, and unique pre-orientation of the components could also be enforced by using a magnetic template.…”

“…Besides vacuum grippers, other tools such as mechanical tweezers and capillary grippers are used. 60,75,130,131 The performance of single component pick-and-place can reach tens of assembled components per second, with an accuracy of e.g. 10 mm.…”

Rupture of a Liquid Bridge between a Cone and a Plane

“…Liquid bridges are encountered in nature and many industrial applications. The capillary forces that they generate have been used for micro gripping and self-alignment, [1][2][3] printing processes such as ink transfer or the printing of electrical circuits. 4,5 In a wet granular material, sub-millimeter liquid bridges between grains induce cohesion and increase the strength of the material, which keeps sandcastles standing for example.…”

Self-assembly of micro/nanosystems across scales and interfaces

“…For the purpose, we additionally developed an all-capillary autonomous assembly line on moving web, which made sequential use of capillary gripping and self-alignment of the components [35]; and demonstrated working electrical interconnections mediated by anisotropic conductive adhesives [31]. Advanced efforts are focusing on wafer-level chip-to-wafer integration and packaging by combining capillary selfalignment of sub-μm precision with solder microbumpsbased [30] and direct Cu-oxide bonding methods [36].…”