MICRO- pH CONTROL BY BREAKING WATER AND ITS APPLICATIONS

A novel strategy is demonstrated for pH regulation in microscale environments by injecting controllable amounts of protons and hydroxide ions via field-enhanced dissociation of water molecules. The dissociation occurs at the ion-depleted junction of reverse-biased bipolar membranes, fabricated by photo-patterning ion-exchange polymers into microfluidic chips. The bipolar membrane generates and separates H+ and OH- ions without gas production or contaminant generation of electrontransfer reactions. Furthermore, it effects pH changes with no need of additional acidic/basic solutions that dilute analyte concentrations. Combining with properly designed microchannel configurations, the approach allows us to sustain robust local on-chip pH and pH gradients to improve several microfluidic operations, such as micro-reactors and molecular separation in microfluidic chips.