Microscale pH regulation by splitting water

We present a simple, flexible approach for pH regulation in micro-chambers by injecting controllable amounts of protons and hydroxide ions via field-enhanced dissociation of water molecules. Under a DC voltage bias, the polymeric bipolar membranes integrated in microfluidics devices generate and separate H(+) and OH(-) ions without gas production or contaminant generation resulting from electron-transfer reactions. Robust local on-chip pH and pH gradients are sustained with no need of additional acidic∕basic solutions that dilute analyte concentrations. The method could provide a better strategy for pH control in microfluidics.