Custom-designed Android app displays test results on a smartphone screen. (Credit: UCSD)

Engineers have developed a smartphone case and app that will make it easier for patients to record and track their blood glucose readings, whether they’re at home or on the go.

The device, called GPhone, is a new proof-of-concept portable glucose sensing system. GPhone has two main parts. One is a slim, 3D printed case that fits over a smartphone and has a permanent, reusable sensor on one corner. The second part consists of small, one-time use, enzyme-packed pellets that magnetically attach to the sensor. The pellets are housed inside a 3D printed stylus attached to the side of the smartphone case.

To run a test, the user would first take the stylus and dispense a pellet onto the sensor — this step activates the sensor. The user would then drop a blood sample on top. The sensor measures the blood glucose concentration, then wirelessly transmits the data via Bluetooth to a custom-designed Android app that displays the numbers on the smartphone screen. The test takes about 20 seconds. Afterwards, the used pellet is discarded, deactivating the sensor until the next test. The stylus holds enough pellets for 30 tests before it needs to be refilled. A printed circuit board enables the whole system to run off a smartphone battery.

A key innovation in this design is the reusable sensor. In previous glucose sensors developed by the team, the enzymes were permanently built in on top of the electrodes. The problem was that the enzymes wore out after several uses. The sensor would no longer work and had to be completely replaced. Keeping the enzymes in separate pellets resolved this issue.