Microstructure to substrate self-assembly using capillary forces

Abstract

Abstract-We have demonstrated the fluidic self-assembly of micromachined silicon parts onto silicon and quartz substrates in a preconfigured pattern with submicrometer positioning precision. Self-assembly is accomplished using photolithographically defined part and substrate binding sites that are complementary shapes of hydrophobic self-assembled monolayers. The patterned substrate is passed through a film of hydrophobic adhesive on water, causing the adhesive to selectively coat the binding sites. Next, the microscopic parts, fabricated from silicon-on-insulator wafers and ranging in size from 150 150 15 m 3 to 400 400 50 m 3 , are directed toward the substrate surface under water using a pipette. Once the hydrophobic pattern on a part comes into contact with an adhesive-coated substrate binding site, shape matching occurs spontaneously due to interfacial free energy minimization. In water, capillary forces of the adhesive hold the parts in place with an alignment precision of less than 0.2 m. Permanent bonding of the parts onto quartz and silicon is accomplished by activating the adhesive with heat or ultraviolet light. The resulting rotational misalignment is within 0.3 . Using square sites, 98-part arrays have been assembled in less than 1 min with 100% yield. The general microassembly approach described here may be applied to parts ranging in size from the nano-to milliscale, and part and substrate materials including semiconductors, glass, plastics, and metals. [602]

Beyond molecules: Self-assembly of mesoscopic and macroscopic components

“…However, another form of macroscopic self-assembly, the fluidic self-assembly pioneered by Jeh and Smith (43) and Howe and coworkers (44), is being developed commercially (Alien Technology, Morgan Hill, CA, www. alientechnology.com͞technology͞over-view.html).…”

Osmocapillary phase separation

“…1b). This capillary condensation has important consequence for micro-electro-mechanical systems [17][18][19], self-assembly [20][21][22], and atomic force microscopes [23][24][25].…”

Re-engineering artificial muscle with microhydraulics

“…Prior to movement, phases 1 and 2 were activated to execute a hold step, which acts to pull the water droplets into close contact with the electrode array. The hold step also causes the two parts to self-align 21 , both in rotation and translation. Actuation proceeds after the hold step by activating the electrodes in a cyclic manner.…”