Microcontact Printing Techniques

Abstract

Three elements come together to constitute the microcontact printing technique. The first is the capability of a class of molecules to self-assemble, i.e. to arrange spontaneously, as a dense, ordered and stable monolayer on suitable surfaces. Generally, these molecules contain a chemically reactive head that anchors onto the surface, and a linear flexible chain of methyl groups which orients itself approximately with the normal to the surface as the most convenient packing configuration in the monolayer. The second element is that such a monolayer, about 2–3 nm thick, represents a barrier to the permeation of several chemical species from the environment (both in air and in aqueous solution), providing an effective protection against oxidation and corrosion of the underlying surface. The third element is due to the intuition of Xia and Whitesides who invented the μCP technique.¹ Besides known methods of inducing molecules to self-assemble onto a surface from the liquid or vapor phase, they discovered that self-assembly can also occur when a polymeric membrane impregnated with the same kind of molecules is brought into contact with a convenient substrate. The membrane, acting as a reservoir of molecules, allows their localized delivery to the contacted areas of the substrate.