University of California San Diego engineers have prototyped an inexpensive device that clips onto a smartphone to monitor a user’s blood pressure.
The 3D-printed device uses the smartphone’s camera and flash paired with an algorithm on an app to take systolic and diastolic blood pressure readings.
“We’ve created an inexpensive solution to lower the barrier to blood pressure monitoring,” study first author Yinan (Tom) Xuan, an electrical and computer engineering Ph.D. student at UCSD, said in a news release.
Xuan published the team’s findings this week in Scientific Reports with senior author and electrical and computer engineering professor Edward Wang, who’s also director of the UCSD Digital Health Lab.
“Because of their low cost, these clips could be handed out to anyone who needs them but cannot go to a clinic regularly,” Wang said. “A blood pressure monitoring clip could be given to you at your checkup, much like how you get a pack of floss and toothbrush at your dental visit.”
In testing on 24 volunteers, results were comparable to a blood pressure cuff, the researchers said.
“Using a standard blood pressure cuff can be awkward to put on correctly, and this solution has the potential to make it easier for older adults to self-monitor blood pressure,” said study co-author and medical collaborator Alison Moore, chief of UCSD School of Medicine’s Division of Geriatrics.
The researchers noted their prototype does not require calibration with a blood pressure cuff, unlike other cuffless systems in development.
“This is what distinguishes our device from other blood pressure monitors,” Wang said.
How the smartphone blood pressure monitor works
The plastic, 3D-printed device clips onto a smartphone over the rear-facing camera and flash.
“When the user presses on the clip, the smartphone’s flash lights up the fingertip. That light is then projected through a pinhole-sized channel to the camera as an image of a red circle. A spring inside the clip allows the user to press with different levels of force. The harder the user presses, the bigger the red circle appears on the camera,” UCSD explained in the news release. “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 amount of pressure that the user’s fingertip applies. And by looking at the brightness of the circle, the app can measure the volume of blood going in and out of the fingertip. An algorithm converts this information into systolic and diastolic blood pressure readings.”
Wang and co-author Colin Barry, a UCSD electrical and computer engineering student, co-founded Billion Labs to further develop and commercialize the technology.
So far they’ve only tested the device on a Google Pixel 4, but they believe the design should work on other smartphones.
They plan to make the system easier to use, particularly for older adults. They also want to test its accuracy on different skin tones and create a more universal design.
The plastic clip currently costs about 80 cents to manufacture, which the team thinks could drop to 10 cents per device at scale.