New Microprinting Technique Improves Nanoscale Fabrication

A new technique called micro-displacement printing, which makes possible the highly precise placement of molecules during the fabrication of nanoscale components for electronic and sensing devices has been developed by a research team at Penn State University.

(Left) A schematic of the microdisplacement printing process, using a 1-admantanethiolate self-assembled monolayer as the weakly bound film and 11-mercaptoundecanoic acid as the displacing ink molecules on a striped stamp. (Right) Lateral force microscopy images of a sample made by the microdisplacement printing. The higher friction (shown as light) stripes are the ink. The lower friction (shown as dark) stripes are the remaining, undisplaced 1-adamantanethiolate regions.

The new micro-displacement technique is based on a widely used patterning method known as micro-contact printing--a simple way of fabricating chemical patterns that does not require clean rooms and other kinds of special and expensive environments. Both methods involve "inking" a patterned rubber-like stamp with a solution of molecules, then applying the inked stamp to a surface.

One of the limitations of micro-contact printing is that its precision is limited at the edges of a stamped pattern by the tendency of the applied molecules to skitter across the stamped surface, blurring or obliterating the applied pattern and destroying its usefulness. The team’s improved micro-displacement technique solves this problem by applying a self-assembled-monolayer film--a single ordered layer of spherical adamantanethiolate molecules -- to keep the stamped molecules in place on the surface. The molecules inked on the stamp replace the adamantanethiolate molecules wherever they touch the monolayer film, but the surrounding molecules in the film remain attached to the surface to prevent the applied molecules from wandering.

In addition to providing more control over the precision of stamped patterns, the new micro-displacement technique also relaxes the requirements in precisely positioning a series of stamps used to apply consecutive patterns with different molecular inks. Each successive layer of molecules either will displace or will not displace the already-applied molecules, depending on their relative bonding strengths with the underlying surface.

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