Osmosis and pervaporation in polyimide submicron microfluidic channel structures
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(a) Top view of the polymide channel array used for pervaporation experiments. The permeation area is indicated by the dashed rectangle. (b) Cross section of one channel. Roof thickness is . (c) Schematic of the pervaporation experiment. Dots indicate dissolved . Pumping indicated by arrows coincides with a change in salt concentration measured as a change in channel conductance. (d) Change in channel conductance observed as a result of water pervaporation through the channel roof. The channel solution is refreshed at and , restoring original conductance.
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(a) Branched channel structure used for osmotic experiments. The permeation area is indicated by the dashed rectangle. The meniscus speed was observed at the location of the arrow [compare (c) and (d)]. (b) Schematic of the first osmosis experiments with water permeating out of the channel towards a NaCl solution on top of the permeation area. (c)–(d) Observed water meniscus movement; the indicated times are after addition of NaCl. (e) Schematic of the second osmosis experiments with water permeating into the channel towards an alcohol (isopropanol or ethanol). (f)–(g) Observed isopropanol meniscus movement; the indicated times are after placing a water drop on the exchange area.
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