Scientists have created a skin patch that tracks multiple health markers simultaneously.
Worn on the neck, the stretchy device continuously monitors a wearer's blood pressure and heart rate, while also measuring their glucose, alcohol and caffeine levels.
The team behind the device, from the University of California San Diego, believe it could one day enable people with conditions like diabetes to keep on top of their health.
It could also be used as a non-invasive alternative in intensive care, where even babies have catheters fitted while being tethered to multiple monitors that continuously check their vital signs.
When tested on human volunteers, the patch "captured physiological effects of food intake and exercise", including the production of glucose after eating, rises in blood pressure and heart rate, and oxygen depletion following a workout.
It is unclear when the patch may be available. The existing prototype has to be hooked up to electronics, with the scientists hoping to one day make it wireless.
"The novelty here is we take completely different sensors and merge them together on a single small platform as small as a stamp," said study author Professor Joseph Wang.
"We can collect so much information with this one wearable and do so in a non-invasive way, without causing discomfort or interruptions to daily activity."
The creation is a combined effort from two laboratories, one focusing on a wearable device that monitors multiple signals simultaneously and the other developing a stretchy skin patch that specifically tracks blood pressure.
Made up of stretchy polymers, the thin patch conforms to the wearer's skin, the scientists wrote in the journal Nature Biomedical Engineering.
It is made up of a blood pressure sensor and two chemical sensors, one of which measures caffeine, alcohol and lactate; a substance produced by cells during exercise.
The second chemical sensor checks for blood sugar levels in interstitial fluid; the solution that surrounds cells.
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"Each sensor provides a separate picture of a physical or chemical change," said co-author Professor Sheng Xu.
"Integrating them all in one wearable patch allows us to stitch those different pictures together to get a more comprehensive overview of what's going on in our bodies."
The blood pressure sensor works via small ultrasound transducers; an electronic device that converts energy from one form to another.
When a voltage is applied to the transducers, ultrasound waves are sent into the body, bouncing off arteries. The sensor detects the echoes of this, translating it into a blood pressure reading.
The chemical sensors consist of two electrodes; conductors of electricity.
The electrode that senses lactate, caffeine and alcohol releases a drug called pilocarpine into the skin to induce sweat, from which chemical substances can be detected.
The electrode that looks for glucose passes a mild electrical current through the skin to release interstitial fluid, before measuring the sugar in that substance.
Watch: Skin patch monitors health
Together, these markers provide an indication of a person's blood pressure.
"Let's say you are monitoring your blood pressure, and you see spikes during the day and think something is wrong," said co-author Dr Juliane Sempionatto.
"But a biomarker reading could tell you if those spikes were due to an intake of alcohol or caffeine. This combination of sensors can give you that type of information."
The device could even detect the early signs of sepsis; characterised by a sudden drop in blood pressure alongside a rapid rise in lactate.
It may have been particularly useful amid the coronavirus outbreak, where some in-person medical appointments have been postponed.
"This type of wearable would be very helpful for people with underlying medical conditions to monitor their own health on a regular basis," said co-author Lu Yin, a PhD student.
"It would also serve as a great tool for remote patient monitoring, especially during the COVID-19 [the disease caused by the coronavirus] pandemic when people are minimising in-person visits to the clinic."
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The scientists are working on a new patch with more sensors.
"There are opportunities to monitor other biomarkers associated with various diseases," said Dr Sempionatto.
The team is also trying to shrink the electronics required for the blood pressure sensor, with the existing prototype having to be connected to a power source and a bench-top machine to show its readings.
The scientists hope to eventually put these on a wireless patch.
"We want to make a complete system that is fully wearable," said co-author Muyang Lin, a PhD student.
Watch: High blood pressure may cause irregular heart beat