Figure 3

Hermetic sealing test of the device. The hermetic seal of the assembled microchambers was validated for oxygen (a) and proton (H⁺, (b)) leak by purging outside media with a mixture of gas containing different concentrations of oxygen and nitrogen or using buffers with different pH values, respectively. The lack of change in emission intensity of each of the corresponding sensors indicates hermetically sealed microchambers. We note that the minor (about 10%) increase in the oxygen sensor intensity in some of the microchambers over a time period of 35 minutes after oxygen concentration in the gas mixture was reduced to zero is negligible and can be corrected, as the sensor response during an assay is typically 100–150% in comparable period.