| Abstract
| - Nanoliter-sized liquid drops can be accurately meteredinside hydrophilic microchannels using a combination ofhydrophobic surface treatment and air pressure. Thetechnique involves spontaneously filling the microchannels up to a hydrophobic region and splitting a liquid dropby injecting air through a hydrophobic side channel. Thehydrophobic regions are fabricated by using a patternedmetal mask on a substrate. The patterned substrate isimmersed in an isooctane solution containing 1H,1H,2H,2H-per-fluorodecyltrichlorosilane to form hydrophobicpatches on the exposed surface. Stripping the metal maskleaves the hydrophobic patches and restores the hydrophilic substrate surface. Precise and accurate liquidvolumes, ranging from 0.5 to 125 nanoliters, have beenmetered using this technique. Theoretical predictions ofthe pressure needed to meter drops compare well withthe experimental values.
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