An electrical patch to monitor hemoglobin in tissue

An electrical patch to monitor hemoglobin in tissue.


A team of engineers at the University of California, San Diego have developed an electronic patch that can monitor biomolecules in deep tissue, including hemoglobin. This gives doctors access to crucial information that could help pinpoint life-threatening conditions, such as malignancies, organ dysfunction, brain or intestinal hemorrhages, and more.


“The amount and location of hemoglobin in the body provide critical information about blood perfusion or accumulation in specific locations. Our device shows great potential in closely monitoring high-risk groups, enabling timely intervention at urgent times,” said Sheng Xu, professor of nanoengineering at UC San Diego and corresponding author of the study. The article is published in Nature Communications.

Poor blood perfusion within the body can cause severe organ dysfunction and is associated with a number of ailments, including heart attacks and vascular disease of the extremities. At the same time, an abnormal accumulation of blood in areas such as the brain or abdomen may indicate bleeding in the brain or visceral veins or malignancies. Continuous monitoring can help the diagnosisof these conditions and facilitate timely and potentially life-saving interventions. The new sensor overcomes some significant limitations of existing methods for monitoring biomolecules. Magnetic resonance imaging (MRI) and X-ray computed tomography rely on bulky equipment that can be hard to find and usually only provide information about the immediate state of the molecule, making them unsuitable for long-term monitoring.

The new patch

The new, wearable, flexible patch attaches comfortably to the skin, allowing for non-invasive, long-term monitoring. It can perform three-dimensional mapping of hemoglobin with submillimeter spatial resolution in deep tissue, up to several centimeters under the skin, compared to other wearable electrochemical devices that only detect biomolecules on the skin surface. Thanks to its optical selectivity, it can broaden the range of detectable molecules by integrating different laser diodes with different wavelengths, adding to its potential clinical applications.


The plaster is equipped with laser diodes and piezoelectric transducers (a particular electronic device which has the task of transforming electrical energy into vibrational mechanical energy or vice versa) in its soft silicone polymer matrix . The biomolecules present in the tissue absorb optical energy and radiate acoustic waves into the surrounding media. “Piezoelectric transducers receive the acoustic waves, which are processed in an electrical system to reconstruct the spatial mapping of the wave-emitting biomolecules,” said Xiaoxiang Gao, a researcher in Xu’s lab and co-author of the study. “With its low-power laser pulses, it’s also much safer than x-ray techniques that have ionizing radiation.”

Based on the success achieved so far, it is planned to explore the potential of the wearable device for monitoring core temperature. “Because the amplitude of the photoacoustic signal is proportional to the temperature, we have demonstrated core temperature monitoring in ex-vivo experiments,” Xu said. “However, validating temperature monitoring on the human body requires interventional calibration.”

The researchers are continuing to work with physicians to pursue other potential clinical applications.



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