Figure 7.

(a) Schematic of the micro flow patterning and micro contact printing techniques to pattern a planar Nafion membrane on a glass substrate.¹⁹ (b) PDMS preconcentrator chip with surface-patterned ion-selective membrane.¹⁹ (c) Preconcentration of β-phycoerythrin versus electrokinetic trapping time. This result shows that one can achieve a preconcentration factor of ~10⁵ in 20 min. Fluorescence images of 4 nM protein shown next to the graph prove an increase in the concentrated plug in size and concentration with trapping time.¹⁹