Microfluidic synthesis of monodisperse PDMS microbeads as discrete oxygen sensors

We describe the creation of monodisperse microbeads of polydimethylsiloxane (PDMS) via a microfluidic approach. Using a flow-focusing configuration, a PDMS precursor solution is dispersed into microdroplets within an aqueous continuous phase. These droplets are collected and thermally cured off-chip into solid microbeads. Our microfluidic technique allows for direct integration of payloads into the PDMS microbeads. Specifically, we integrate an oxygen-sensitive porphyrin dye into the beads and show that the resulting structures can function as non-invasive and real-time oxygen microsensors utilizing a simple optical readout at the single-particle level.