There are three separate detectors in our project. We used pH test paper which can change color to detect pH in saliva between pH 5.0 and pH 8.0, and used modified bacteria carrying plasmids with genes to detect CSP and lactate separately. These bacteria will be attached to test paper and freeze dried to preserve them until use. These test papers lie between two pieces of glass that not only avoid bacterial escape to environment but also protect the bacteria from contamination.
How does the device work? The test papers and glass will be built into a holder. Before you want to use the machine, you put the holder into the machine and set the time that you expected to use it. The machine will take a series of actions to activate the bacteria before you spit saliva into the machine. Bacteria will interact with a specific substance and produce GFP (green fluorescence protein). The system detects the strength of the excited light and uses Bluetooth to upload the data, first to a cellphone and then to a server. The data are input into a model calculated by machine learning, and the results sent back to the user’s cellphone to show the risk of cavities.