A skin patch engineered at the University of California San Diego is a true multitasking medical health monitor. The wearable tracks blood pressure, measures lactate, caffeine and alcohol in sweat, and gauges glucose levels in interstitial fluids.

The conformable device composed of stretchy polymers is expected to benefit users managing high blood pressure and diabetes, and could prove valuable in detecting the onset of sepsis as signaled by blood pressure drop and rapid elevation of lactate level. Equipped with a blood pressure sensor and two chemical sensors, the patch may also provide an alternative to the use of invasive catheters and multiple monitors for patients in intensive care units.

The blood pressure sensor placed near the center of the patch consists of small ultrasound transducers welded to the device by a conductive ink. A voltage applied to the transducers send ultrasound waves into the body when voltage is applied, and as waves bounce off an artery, the sensor detects the echoes and translates the signals into a blood pressure reading.

Two electrodes screen-printed on the patch from conductive ink form the chemical sensors. The element that senses lactate, caffeine and alcohol is printed on the right side of the patch and releases a drug called pilocarpine into the skin to induce sweat, which is analyzed for the biomarkers. The second electrode passes a mild electrical current through the skin to release interstitial fluid and to enable glucose detection.

Future iterations of the skin patch described in Nature Biomedical Engineering will include additional sensors in a wireless wearable.

Illustration of the placement of the sensor and the enzymatic chemical sensors for interstitial fluid and sweat. Source: Joseph Wang et al.Illustration of the placement of the sensor and the enzymatic chemical sensors for interstitial fluid and sweat. Source: Joseph Wang et al.

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