Self-assembled monolayers (SAMs) on gold derived from the direct adsorption of thioacetic acid S-decyl ester (C10SAc) and thioacetic acid S-octadecyl ester (C18SAc) were compared to the corresponding SAMs derived from the analogous adsorption n-decanethiol (C10SH) and n-octadecanethiol (C18SH). All SAMs were characterized using ellipsometry, contact angle goniometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). The comparison revealed that the SAMs generated from the thioacetates are not as densely packed and well ordered as the SAMs generated from the thiols. Furthermore, studies of the kinetics of adsorption found that the thioacetates adsorb more slowly than the corresponding thiols.

We report the development of laser-scanning lithography (LSL), which employs a laser-scanning confocal microscope to pattern photoresists that can be utilized, for example, in the fabrication of masters for use in soft lithography. This convenient technique provides even exposure across the entire view field and facilitates accurate alignment of successive photoresist exposures. Features on the scale of 3 microm have been achieved to date with a 10x objective (NA 0.45). Virtual masks, instructions for laser irradiation, were drawn using the Region of Interest (ROI) function of a Zeiss LSM 510 microscope. These regions were then exposed to a 458 nm argon laser for 32 micros (0.9 mW/microm(2)). Differential interference contrast (DIC) imaging was utilized with a non-destructive 514 nm argon laser as an immediate quality check of each exposure, to align successive exposures, and to reduce chromatic aberration between imaging and exposure. Developed masters were replica-molded with poly(dimethylsiloxane) (PDMS); these masters were then utilized for microcontact printing of cell-adhesive self-assembled monolayers (SAMs) to demonstrate the utility of this process. Initial studies confirmed that human dermal fibroblast adhesion and spreading were limited to cell-adhesive SAM areas. LSL is a rapid, flexible, and readily available technique that will accelerate master design and preparation; moreover, it can be applied to additional forms of photolithography and photopolymerization for studies in cell biology, biomaterials design and evaluation, materials science, and surface chemistry.

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