INDUSTRY NEWS

Self-assembly required

You're a process engineer. How much easier would your life be if you could spray a device directly onto a flexible silicon sheet? Using just an ink-jet printer. That's what the future possibly holds in store with a process called "surfactant-templated silica mesophases," according to researchers at Sandia National Laboratories. The tongue-twisting moniker describes "intelligent" spray-on materials that assemble themselves into circuits.

Project leader Jeff Brinker says that adding ligands capable of molecular recognition to the materials has allowed researchers to jet-spray instant sensor arrays on a silicon substrate. The process makes use of the tendency of detergent-type molecules to both repel and dissolve in water. The molecules form pores during evaporation. When dry, a drop of the material forms a hollow, domelike structure, and a line of the material forms a hollow tubelike structure with a flat bottom. Sprayed in a line on a silicon substrate, the pores spontaneously form a waveguide measuring only 25 Å diam. Slightly heated, the pores become a solid structure. For the moment, the research team is focusing on fluids and gases for existing sensor chips in devices such as handheld chemical analyzers.

In the future the team foresees using color-sensitive ligands to spray computer displays onto a flexible silicon sheet with an ink-jet printer and color composition software. The software will be used to mix the materials into 64,000 combinations for different circuit components. More immediately, the team hopes to create passive circuits for devices with dielectric constants lower than those made using conventional lithography.

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