Effect of dynamic PVA surface coating on protein separation. Sample: a). Cytochrome b, pI 9.5–10.2, b). Carbonic anhydrase I, pI 6.6 and c). β-lactoglobulin A, pI 5.1. Buffer: 8M Urea, 2M Thiourea, 4% CHAPS, 2% Amphyolytes, 0.1% Methyl red. Applied voltage: 1,800V. Current: 1.4 mA. Flow rate: 10 µL/min. [Total protein]: 0.2 mg/mL. Electric field: 370 V/cm. A)-G) increasing PVA concentrations in PMDS devices with glass bottoms. H) All PDMS channel with 4% PVA.