Glass Substrates for Microfluidic Applications
Date
2004
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Alfred University. Faculty of Ceramic Engineering. Kazuo Inamori School of Engineering
Abstract
Various glass compositions, including a soda-lime, float, binary sodium silicate, and phosphate glass, were treated using five aqueous solutions combined with ultraviolet light exposure. The goal of the work was to find a glass substrate that would be suitable for microfluidic applications. In order to be a suitable substrate, the masked channel on the glass surface must be able to support fluid migration when an external potential is applied. Contact angle analysis and grazing angle infrared spectroscopy measurements were the primary tools used in the characterization of the hydrophilic nature of the surfaces. Impedance and electrokinetics were used to test the channel conductivity and fluid flow. When glass is exposed to aqueous solutions, surface bonds, such as Si-O-Si, are exploited to form a gel layer on the surface. The gel layer possesses a more open structure than the original glass which gives it the ability to support electrical current flow and fluid migration. Contact angle data that was collected suggests that the water plasma treatment that was used to clean the surfaces made them hydrophilic. Low, wetting contact angles were measured on the surface using water. However, infrared spectroscopy did not show activity in the hydroxyl region of the spectra. As the treatments progressed the contact angle increased, suggesting that the surface was becoming less hydrophilic. The hydroxyl groups present on surface are reactive, meaning that any contamination that contacted the surface may have become an adsorbed species thus making the surface more hydrophobic. Again, infrared spectroscopy did not pick up any contamination present on the surface. The fact that neither hydroxyl nor contamination layers were observed can be explained if the incident angle of the infrared light is considered. Of the compositions that were tested, phosphate glass immersed in Laemmli buffer performed the best in the electrophoresis experiments. The combination represented a moderately non-durable phosphate glass treated and a moderately high pH Laemmli buffer. The success of the phosphate glass and Laemmli buffer treatment could be an effect of the surface charge that resulted from a high pH treatment.
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Keywords
Microfluidic applications, Glasses