Low-Cost Smartphone Finger Clip Measures Blood Pressure

Engineers at the University of California San Diego have developed a low-cost cuffless blood pressure monitor. The device is a clip that attaches over a smartphone camera and flash. The user presses their finger against the clip, and the system can infer the amount of blood passing through the finger, and the amount of pressure being exerted on the clip by the finger. A smartphone app then uses algorithms to interpret these data and estimate the blood pressure. At present, the clip costs only 80 cents to produce, providing a low-cost method for people in low-resource areas to monitor their blood pressure. With mass production, the researchers claim that the clip could cost just 10 cents to make.

Blood pressure measurements are crucial to ensure good health over our lifetime. However, for those who live far away from a medical clinic, or who don’t have access to reliable diagnostic technology, tracking their blood pressure is haphazard. Developing low-cost solutions is crucial for such patients. These researchers have achieved just that, with individual units potentially costing only pennies.

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One of the clever features of the technology is that it does not need to be calibrated against a blood pressure cuff. Other cuffless blood pressure monitoring systems that have been developed, such as smartwatches, frequently need to be calibrated against blood pressure cuff data. However, the new clip is ready to go from the outset. “This is what distinguishes our device from other blood pressure monitors,” said Wang. “Our is a calibration-free system, meaning you can just use our device without touching another blood pressure monitor to get a trustworthy blood pressure reading.”

The 3D printed clip fits over the phone camera and flash. A spring within the clip allows a user to apply varying pressure to it. A small aperture in the clip functions as a pinhole camera, and the camera visualizes a red dot when a user’s fingers is pressed against it. The size of the dot is proportional to the pressure exerted on the clip while the brightness of the dot is proportional to the amount of blood flowing into the fingertip. The system uses an algorithm to combine these measurements into an estimation of blood pressure.

“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 Alison Moore, another researcher involved in the study

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