Optical mapping surface
Fig. 3. Preparation of PDMS microchannels, as described in the text.
Silicon basic steps involve thorough mixing of the polymer components and catalyst, followed by degassing to remove air bubbles. The mixture is then poured onto silicon wafer master and allowed to cure at 65°C. After overnight incubation, the PDMS is fully cured and rigid enough to be peeled away from the silicon wafer. The fabricant is now hydrophobic and resistant to loading. To facilitate aqueous loadings, oxygen plasma treatment converts exposed PDMS surfaces into hydrophilic silica (Dimalanta et al., 2004). Since the contact angle affects capillary action used for loading, it is controlled to range between 5 and 10°. The plasma treatment is not permanent, and the PDMS will gradually become hydrophobic in air, however storage in water extends the lifetime of hydrophilic microchannels to 1 week.
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