Selective Surface Modification and Patterning on Self-Assembled Monolayers by a Micro-Plasma Discharge

In this paper, we will demonstrate a selective surface patterning method by a micro-plasma discharge. In this method, argon plasma is ignited through a hole of copper clad polyimide microstructure electrodes. As an illustration, experiments were performed in which an octadecanethiol (CH₃(CH₂)₁₇SH) self-assembled monolayer (SAM) on a gold film is exposed to a microdischarge and subsequently followed by immersion into the 16-mercaptohexadecanoic acid (COOH(CH₂)₁₅SH) solution. The octadecanethiol SAM is desorbed upon Ar plasma exposure, allowing the formation of a second SAM on the damaged region [Chai et al, App. Phys. Lett., 86, 034107 (2005)]. The patterned samples are viewed by using optical microscope and scanning electron microscopy. The advantage of this approach is that it is noncontact and eliminates the need of photolithography. The patterned samples can be employed to microfluidic self-propelled movement.