What do cameras, audio recorders, and music players have in common? They're all things that we no longer have to carry around separately, since they're built into smartphones. Diabetics may soon be able to add blood glucose-measuring kits to that list, as scientists from the University of California San Diego have created a phone case that does the job.

Known as the GPhone, the 3D-printed prototype device fits over a phone, running off of its battery. At one corner of the case is a reusable sensor, connected to a printed circuit board. Additionally, mounted along one side of the case is a removable stylus that's packed with single-use pellets, which it dispenses one at a time.

To take a reading, the user starts by using the stylus to put one of the pellets on the sensor, where it's held in place via a magnet. This powers the sensor up.

They then place a sample of their blood on the pellet. An enzyme within the pellet, known as glucose oxidase, reacts with glucose in the blood by generating an electric signal. That signal is in turn measured by the sensor's electrodes – the higher the glucose concentration, the greater the signal. The sensor then transmits the data to the phone via Bluetooth, where it's displayed onscreen as a numerical value on a custom Android app. Such readings could be stored to track the patient's progress over time, or to share with a physician.

It takes about 20 seconds to perform a test. Once the user is finished, they simply remove the pellet and throw it away, deactivating the sensor in the process.

The technology is still in the proof-of-concept phase, and it should be noted that the pellets would likely cost slightly more than the paper strips that are used in conventional test kits. Additionally, at least 12 drops of blood are currently required for each test, although the researchers are hoping to reduce that to the amount that's usually extracted from a finger prick. It's additionally hoped that in the future, the system could be built right into smartphones.

The GPhone is being developed by a team led by professors Patrick Mercier and Joseph Wang, and is described in a paper that was recently published in the journal Biosensors and Bioelectronics.

For other approaches to smartphone-based glucose-checking tech, check out One Drop and the Dario Meter.

View gallery - 2 images