On-demand control of pH in microfluidic droplets

In this paper, we propose a strategy to form on-demand droplets with specific pH values. We analyzed the principle of our technique, designed and fabricated the microfluidic devices. The droplet-on-demand system is based on a T-junction microchannel for droplet emulsion and a pulsed pressure to trigger the onset of droplet injection. The pH control is based on electrolysis of water in the microchannel, and the produced hydrogen and hydroxyl ions are separated and confined in individual containers during the droplet generation. By tuning the applied voltages and pressure pulses, we can on-demand control the pH value in a droplet