Figure 5.

Digitalization of bioassays. (a) Analog bioassay. The relative concentration of the target in the analyte is estimated by the relative intensity of the signal generated from the target. Signal intensity is correlated with a concentration within the dynamic range. (b) Digital bioassay. Bioassay is compartmentalized either by microwell array or a microdroplet so that each compartment contains either 1 or 0 copy of the target. Then, the presence of the target in each compartment was detected, and statistics were collected. Digital bioassays allow for absolute quantification of the target in the analyte. (c) Digital–analog bioassays. More than 1 target was encapsulated in each compartment. Next, both the presence of the signal and the relative intensity of the signal generated from a target in each compartment were used to quantify the number of copies of the target. ☆ indicates target molecule, while other shapes indicate non-target molecules. Magenta indicates signal to be detected, which has been emitted by label molecule after reacting with target molecule.