Scientists have developed an innovative technique to print biosensors, which can measure temperature, electrical heart signals and blood oxygen saturation, directly onto the skin at room temperature.

This advance, which was developed by US and Chinese researchers and led by Penn State University’s Larry (Huanyu) Cheng, is important because it has the potential to make long term, continuous monitoring of sick or fragile patients easier and more accurate.

“We are interested in applying this multifunctional, wearable sensing technology for diagnostic confirmation and timely treatments for cardiopulmonary diseases, including Covid-19, pneumonia, and fibrotic lung diseases,” explains Cheng.

In Covid-19 patients in particular, there could be value in using sensors like these as they can quickly inform healthcare professionals when a hospitalized patient’s condition is deteriorating.

These sensors also have great potential for continuous monitoring of health measures, such as heart rate and hydration level, that are of interest for professional athletes or people working in dangerous or remote environments. Cheng and his colleagues have also previously developed a wearable sweat monitor, which he says could be added as a component to the printed sensor if required.

A key advance developed by the researchers is that normally printing any kind of metal components for these sensors has to be done at a temperature too high to print on skin without causing burns.

Cheng and colleagues got round this problem by first painting a paste containing a key ingredient of peelable face masks, polyvinyl alcohol, calcium carbonate, onto the skin. The addition of other nanoparticles to this paste such as aluminium and magnesium oxides, metallic salts and copper, all helped to reduce the temperature needed to print the sensors.

They then printed the sensors, made from silver nanoparticles, onto this layer at room temperature, before completing the ‘bonding’ process by blowing cold air over the printed sensor to remove any residual water from the ink.

The biosensor is currently just at a prototype stage, but can already accurately measure body temperature, moisture change on the skin, blood oxygen and saturation, and electrophysiological signals from the heart such as those measured during an electrocardiogram (ECG) test. Cheng says it is possible to adapt the sensor to add particular components as needed in the future.


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