A fundamental study of the modification of elastomeric poly(dimethylsiloxane) and silicon surfaces using polymers and their applications in patterning

A fundamental study of the polymer functionalization of flat elastomeric poly(dimethylsiloxane) (PDMS) and Silcon wafers is described. Using polymer grafting methodologies such as "grafting onto" and "grafting from" a functional substrate, the development of a novel pattern miniaturization protocol and method for nanoparticle patterning was achieved. Currently, a general strategy for the poly(ethylene glycol) (PEG) functionalization of Silastic RTV elastomeric substrates does not exist in the literature. Our preliminary attempts with the functionalization of elastomeric PDMS suffered from a lack of effective surface functionalization control, primarily as a result of literature inconsistencies and inadequate surface characterization. Therefore, we performed in-depth and quantitative surface analysis of the surface functionality of the elastic PDMS substrates that were used to adopt a modified functionalization strategy. The end result was the development of a dynamic material where the surface energy could be manipulated through simple mechanical stretching.;A new miniaturization protocol, referred to as high-efficiency stepwise contraction and adsorption nanolithography (hSCAN), was demonstrated. A thin film of elastomeric precursor was first cast on a stretched substrate. A designed microstructure was then imprinted and the precursor layer was subsequently cured. The microstructure was miniaturized after the substrate relaxed to its original length. The miniaturized structures can be used as stamps to transfer materials onto a designated support or as molds to produce the structure on another stretched substrate for further miniaturization. The patterning of materials by microcontact printing has been improved with the development of hSCAN. Optical disc media polycarbonate discs were used as master molds in the hSCAN miniaturization protocol with promising results. CD's, DVD's and even Blue-ray polycarbonate discs were miniaturized, and < 100 nm features were observed. Additionally using imprint lithography techniques, we developed a novel approach to selectively adhere light-emitting CdSe nanoparticles to Au surfaces in small and well defined patterns. Using microcontact printing techniques, we prepared a patterned self-assembled monolayer (SAM) of thiol ligands on a gold substrate in which the reactive portion of the patterned substrate presented regions of carboxylate functionality. These served as the adhesive domain to bind CdSe nanoparticles through a novel adhesion mechanism.