This Wearable, Flexible Laser Patch Beams Light Into Your Tissue to Listen To Your Biomolecules

Engineers at the University of California San Diego have developed a flexible, wearable skin-patch device, which can monitor hemoglobin and other biomolecules in deep tissue — without any invasive incisions or injections.

"The amount and location of hemoglobin in the body provide critical information about blood perfusion or accumulation in specific locations," explains corresponding author Sheng Xu, a professor of nanoengineering at UC San Diego, of the project's potential for health monitoring and disease diagnosis. "Our device shows great potential in close monitoring of high-risk groups, enabling timely interventions at urgent moments."

Being able to monitor blood perfusion — the flow of blood through tissue — inside the body provides early warning of issues ranging from heart attacks to malignant tumor growth, but continuous monitoring at a deep tissue level is challenging: traditional magnetic resonance imaging (MRI) and X-ray computing tomography scans require expensive and bulky equipment, making them suitable only for a point-in-time look at a patient.

"Continuous monitoring is critical for timely interventions to prevent life-threatening conditions from worsening quickly," explains Xiangjun Chen, co-author of the paper. "Wearable devices based on electrochemistry for biomolecules detection, not limited to hemoglobin, are good candidates for long-term wearable monitoring applications. However, the existing technologies only achieve the ability of skin-surface detection."

The team's patch, by contrast, needs only to be attached to the skin. Built from arrays of laser diodes and piezoelectric transducers, encased in a soft silicone matrix, the patch fires pulsed laser light into the wearer's tissues that are then absorbed by the target biomolecules — creating a sound, which can be picked up the the transducers.

The result is a non-invasive and intrinsically safe device, which can nevertheless provide continuous monitoring of biomolecules at depths of inches below the surface of the skin — and with the ability to expand from hemoglobin to other biomolecules simply by adding laser diodes with different wavelengths of light tuned to a particular target for monitoring. The team has also proven that the device can be expanded to three-dimensional core temperature monitoring, though Xu admits that this currently requires "interventional calibration."

The team's work is available under open-access terms in the journal Nature Communications.