Simple home medical tests consist of a deck of various silicon chips coated in special film — one that could detect drugs in the blood, another for proteins in the urine indicating infection, and another for bacteria in water and the like. Add the bodily fluid to be tested, take a picture with a smartphone, and a special app shows if there’s a problem or not.
Low-cost, nanostructured thin films of silicon feature nanoscale holes that are a thousand times smaller than a strand of hair. They selectively capture molecules when pre-treated with the appropriate surface coating, darkening the silicon, which the app detects.
Similar technology being developed relies on expensive hardware that compliments the smartphone. The new system uses the phone’s flash as a light source and the researchers plans to develop an app that could handle all data processing necessary to confirm that the film simply darkened when fluid was added.
In the future, such a phone could replace a mass spectrometry system that costs thousands of dollars. The Transportation Security Administration (TSA) uses mass spectrometers at airports across the country where they are used to detect gunpowder on hand swabs.
Other home tests rely on a color change, which is a separate chemical reaction that introduces more room for error. In the new system, a biotin-streptavidin protein assay was used with an iPhone SE to test the silicon films. Accuracy was similar to that of bench-top measurement systems. A 3D-printed box stabilized the phone to get standardized measurements.