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. Author manuscript; available in PMC: 2009 Sep 24.
Published in final edited form as: Anal Chem. 2008 Mar 22;80(9):3198–3204. doi: 10.1021/ac800362e

Figure 1.

Figure 1

(a) Optical image and (b) operation of PDMS preconcentration chip as a reaction enhancing tool for low-abundance enzyme assay. The microchannel in the center (red) is loaded with enzyme/substrate mixture and the side channel (green) is filled with a buffer solution. To concentrate the premixed solution of enzyme/substrate, a potential difference is applied across the middle and the side channel in combination with an electrokinetic flow. In the depletion mode, the depletion region is formed due to the concentration polarization and then in the trapping mode, the molecules driven with an electroosmotic flow are electrokinetically trapped in front of the depletion region, resulting in increased concentration.