Wearables

Pencil tattoos could be the most natural wearable sensors yet

Pencil tattoos could be the mo...
Pencil drawings might be the sensors of the future
Pencil drawings might be the sensors of the future
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Pencil drawings might be the sensors of the future
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Pencil drawings might be the sensors of the future

Applying the wearable sensors of the future could be as simple as sketching out a shape on your arm, according to new research that investigates the potential for bioelectronics to be applied through graphite pencil lead and ordinary office copy paper.

While the idea is still some way from being made into a practical reality, you can imagine the possibilities: drawing a shape on your arm to monitor your sleep overnight, or using a small sketch to keep tabs on your heart rate during the day.

The most important part of the setup is the pencil lead. The University of Missouri team behind the new study found that a 93-percent graphite mix was best for the job – the patterns this pencil lead creates can then act as sensing electrodes picking up signals from the skin, with the paper given the role of a flexible, supporting substrate.

Some form of biocompatible spray-on adhesive, or another similar material or frame, could be used to keep the paper in place. When the sensor is no longer needed, pencil and paper are of course very biodegradable and easy to recycle – you could simply peel the sensor off like a plaster.

In testing, such a setup produced results and fidelity comparable to existing wearable sensors, the researchers claim. The whole setup is self-powered through the use of ambient humidity, though in its current form another device needs to be connected in order to read data from the sensors.

"The conventional approach for developing an on-skin biomedical electronic device is usually complex and often expensive to produce," says Asst. Prof. Zheng Yan. "In contrast, our approach is low-cost and very simple. We can make a similar device using widely available pencils and paper."

Potentially, the sensors could be used to measure skin temperatures, respiratory rates, sweat acidity, glucose levels, heart rates and more. Extra power or sensing capability can be added with extra sheets of paper.

As for the squiggly designs of the graphite electrodes, it helps to keep them functioning on the skin, which can curve and stretch. Through the course of the research, the scientists were able to come up with several working designs for sensors.

There's still plenty of work to do before you'll be replacing your Fitbit with something like this, but as a proof-of-concept it's impressive. The team intends to do further research with different biomedical components, and wants to add wireless capabilities too.

The beauty of the setup is in the simplicity – it can be applied quickly, using inexpensive and commonly available materials, in hospitals or in the home. If this ends up being the future of wearable sensors, remember where you heard it first.

A paper on the research was published in the journal Proceedings of the National Academy of Sciences.

Source: University of Missouri

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