Engineers from University of California, San Diego’s Center for Wearable Centers have developed a wearable patch that tracks both biochemical and electrical signals in the human body.
The Chem-Phys patch is the subject of a new study published in Nature Communications. The device monitors and records electrocardiogram (EKG) signals and tracks lactate levels.
“Flexible, wearable sensing devices can yield important information about the underlying physiology of a human subject for applications in real-time health and fitness monitoring,” wrote the researchers. “Despite significant progress in fabrication of flexible biosensors that naturally comply with the epidermis, most designs measure only a small number of physical or electrophysiological parameters, and neglect the rich chemical information available from biomarkers.”
And that’s where the Chem-Phys patch comes in.
Placed at the base of the sternum, the patch, in experiments, was worn by three male test subjects for between 15 to 30 minutes while they performed rigorous activity on a stationary bike. Two of the test subjects wore a commercial wristband meant to monitor heart rate. The EKG information collected by the Chem-Phys patch matched the wristband data. Simultaneously, the information collected by the lactate biosensor resembled “the expected sweat-lactate profile for increasing intensity workouts,” according to the researchers.
“One of the overarching goals of our research is to build a wearable tricorder-like device that can measure simultaneously a whole suite of chemical, physical, and electrophysiological signals continuously throughout the day,” said study author Patrick Mercier, an electrical engineering professor, in a statement. “This research represents an important first step to show this may be possible.”
The screen printed patch is comprised of an electrode for the lactate biosensor, and two EKG electrodes, which flank the lactate biosensor. During fabrication, the researchers discovered that placing the EKG electrodes around four centimeters apart was crucial to avoiding signal interference.
Additionally, the researchers had to ensure the two different sensors were isolated. The lactate biosensor “works by applying a small voltage and measuring electric current across its electrodes,” according to the University of California, San Diego. “This current can pass through sweat, which is slightly conductive, and can potentially disrupt EKG measurements.” The researchers added a soft water-repelling silicone rubber to keep sweat away from the EKG electrodes.
The electrodes are connected by a circuit board outfitted with a microcontroller and Bluetooth low energy chip, which wirelessly transfers the data to a smartphone or computer.
The researchers hope to improve the device’s overall design, and add sensors for other chemical devices.