The circuit board for the biosensor. (Credit: Minghan Xian, et al.)

Made of graphene, a cuffless device is worn on the underside of the wrist and can measure blood pressure with comparable accuracy to a standard blood pressure cuff. While the technology is still in its early stages, the researchers envision that the monitor will be worn 24/7.

The application involves placing the device — which is attached to a thin strip of paper — onto the skin, dampening the paper with water, and then gently removing the paper, leaving the blood pressure monitor behind.

The tattoos don’t measure blood pressure directly. Instead, the tattoos rely on bioimpedance — a measure of how the body resists an electrical current. They contain tiny electrodes that apply a small current to an artery in the wrist and then sense how that current is affected by the artery. These bioimpedance measurements can then be converted into blood pressure readings using machine learning.

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