FIGURE 2.

CO₂ sensor fabrication. (A) A thin basal membrane of PDMS is deposited and pre-cured in 30 min or less (1); then a second layer of PDMS is deposited onto the first (2); next, the sensing solution comprised of HPTS dye, NaOH, and glycerol is deposited onto uncured PDMS (3), causing it to sink into the uncured polymer matrix, which is finally cured (4). (B) Representative video frames from Supplementary Video S1 showing the deposition of the sensing droplets over time. The interface between cured and uncured PDMS can be observed, notably in the final frame once the sensor droplets reach the cured layer.