3D-printed smartphone attachment enables low-cost blood pressure monitoring

Engineers at the University of California San Diego have developed a simple, inexpensive clip that uses a smartphone’s camera and flash to monitor blood pressure at the user’s fingertip. The clip, which works with a special smartphone app, currently costs about 80 cents to manufacture. The researchers estimate that the cost could drop to 10 cents each if mass produced.

The technology, described in the journal Scientific Reports, could help make regular blood pressure monitoring simple, affordable and accessible to people in resource-poor communities.

The clip is a 3D-printed plastic attachment that fits over a smartphone’s camera and flash. It features an optical design similar to that of a pinhole camera. When the user presses the clip, the smartphone’s flash illuminates the fingertip. This light is then projected onto the camera through a hole-sized channel as an image of a red circle. A spring in the clip allows the user to press with different levels of pressure. The harder the user presses, the larger the red circle appears on the camera.

The smartphone app extracts two main pieces of information from the red circle. By looking at the size of the circle, the app can measure the pressure applied by the user’s fingertip. And by looking at the brightness of the circle, the app can measure the volume of blood flowing in and out of the fingertip. An algorithm converts that information into systolic and diastolic blood pressure readings.

The researchers tested the clip on 24 volunteers from UC San Diego Medical Center. The results were comparable to those obtained with a blood pressure cuff. While the team has only proven the solution on a single smartphone model so far, the clip’s current design should theoretically work on other phone models.

Next steps include improving the usability of the technology, verifying accuracy on different skin tones, and creating a more universal design.