Manipulation of the Wettability of Surfaces on the 0.1 to 1-Micrometer Scale Through Micromachining and Molecular Self-Assembly

Micromachining allows the formation of micrometer-sized regions of bare gold on the surface of a gold film supporting a self-assembled monolayer (SAM) of alkanethiolate. A second SAM forms on the micromachined surfaces when the entire system-the remaining undisturbed gold-supported SAM and the micromachined features of bare gold-is exposed to a solution of dialkyl disulfide. By preparing an initial hydrophilic SAM from HS(CH$_2$)$_{15}$ COOH, micromachining features into this SAM, and covering these features with a hydrophobic SAM formed from [CH$_3$(CH$_2$)$_{11}$S]$_2$, it is possible to construct micrometer-scale hydrophobic lines in a hydrophilic surface. These lines provide new structures with which to manipulate the shapes of liquid drops.