In a hospital, blood from a finger prick usually goes to the lab, and the result comes back the next day. The new method promises to cut that wait to a few minutes. Instead of catching light reflected off a sample, it reads the electrical voltage that arises at the boundary between two media, like the faint tingle you feel when you touch a battery with wet fingers. This signal turned out to be surprisingly stable and accurate.
The researchers tested the method on a wide range of assays. The hormones estradiol, progesterone, and luteinizing hormone were measured in blood plasma with accuracy nearly indistinguishable from large laboratory machines (correlation coefficient greater than 0.97). Glucose was detected at concentrations below one microgram per deciliter. The human immunodeficiency virus protein was caught at 44.8 femtograms per milliliter: that's like finding a single grain of sand in an Olympic-sized swimming pool. And the hepatitis B virus was detected in five minutes.
This approach sidesteps the main problem with portable analyzers: previously, compact electrochemical sensors were distorted by sample composition, while optical ones required bulky optics. Now the signal can be read from an ordinary test strip, like a pharmacy pregnancy test, but with laboratory-grade accuracy. This opens the door to diagnostics in remote areas, at home, and in the field — without sacrificing quality.
A femtogram is one billionth of a milligram. To get 44.8 femtograms of salt, you'd have to take a grain and split it into twenty-three trillion parts.