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The aim of this study was to improve the biocompatibility of poly(methyl methacrylate) (PMMA) substrates for possible applications in corneal prostheses or in micro-carrier cell culture systems. PMMA substrates were exposed to radio-frequency (RF) argon and nitrogen plasmas for 5 and 10 min each. The PMMA films were examined by Fourier transform infrared (FT-IR) spectroscopy, to characterize the surface changes after plasma exposure. Plasma treatment in general was found to decrease the water contact angle of PMMA, thus increasing its hydrophilicity. There was also an associated increase in the work of adhesion of plasma-treated PMMA substrates. PMMA substrates exhibited differential properties towards endothelial cell (CPA-47) growth. The untreated PMMA surface did not support endothelial growth, compared with both polystyrene (TCPS) and plasma-treated PMMA, while plasma (PL): PMMA exhibited growth rates slightly lower than the TCPS control, as assessed by [3H]thymidine incorporation profiles. The compatibility and growth supportive properties of PL : PMMA were further confirmed by an MTT assay, which showed preserved cellular viability and mitochondrial activity of the cells. Confocal microscopic visualization of cells with fluorescence-labeled vimentin showed normal organization of the cytoskeletal fibers, indicating appropriate attachment to the substrate. Cells growing on PL: PMMA maintained their functionality, as seen from Factor VIII expression. Taken collectively, the findings of this study point out the suitability of RF plasma treatment in inducing desirable changes in PMMA substrates, so as to improve their ability to support the growth and attachment of endothelial cells.

Polymers can be very good alternatives to SiOz and Si3N4, which are normally used to mask the anisotropic etching of silicon in anisotropic etchants like KOH. An adherent PMMA layer can be conxeniently used as a mask material as it is cheaper easily deposited and removed. In this regard a comparative study of spin coated PMMA with sputtered PMMA as an etch mask for silicon micromachining is carried out. The maximum masking time of 32min in 80°C 20wt% KOH was obtained for spin coated PMMA samples, which were prebaked at 90°C. As this masking time is insufficient for fabrication of various MEMS structures, sputter deposition of PMMA films was carried out in which a masking time of 300min as against 32min was obtained under similar conditions.

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