Patterning Self-Assembled Monolayers: Applications in Materials Science

Self-assembled monolayers (SAMs) form when organic molecules spontaneously chemisorb on the surfaces of solids (e.g. organic thiols and disulfides on gold, silver, and copper or carboxylic acids on the surface of alumina).1'2 The most robust and best characterized SAMs are those comprising alkanethiolates on gold.l By variation of the length of the alkane chain and the identityof the functional group at its terminus, the thickness of the organic layer and the chemical properties of the exposed interface can be controlled with great precision. We and others have used these SAMs for studies in tribology,t adhesion,a wetting,s and other fields.6 In this paper, we describe a technique for patterning the formation of SAMs, using an elastomeric stamp, that can routinely produce patterns with dimensions from 1 to 100 lrm;7 features as small as 0.2 mm (200 nm) have been generated using this procedure, although these very small features are not always easily reproduced. These patterned surfaces have geometrically well-defined regions with different chemical and physical properties. We demonstrate a number of uses for them.