Sometimes, the future arrives as a low-tech innovation that redefines simple technology from the past. It doesn’t get much simpler than a graphite pencil: a device widely used today that has barely deviated from its original design from the 1500s. What goes hand in hand with a pencil? Paper. Put them together, and you’ve got… a sensor!
A recent research paper demonstrates that drawings in pencil on paper can act as electrodes that sense a variety of skin-surface biometrics. Engineers at the University of Missouri created a series of hand-drawn wave patterns with a graphite pencil on commercial copy paper. When applied to the skin with a biocompatible adhesive, these drawings can detect body temperature, respiratory rate, electro-cardiac activity, and other biopotential factors. They can also identify chemical elements in sweat, such as pH, uric acid, and glucose.
What makes a super-basic sensor like this so revolutionary? Let’s begin with cost. A wearable health tracking device generally requires components such as metal alloys, LED and infrared sensors, impact-resistant glass, and machine cut zircon, sapphire, or diamond crystals. Compare that material complexity with a simple pencil, paper, and a wire that transmits the data to a computer. That kind of cost differential could eventually make personal health tracking devices accessible to users across the economic spectrum.
Then there are the ecological implications. Standard digital electronic devices eventually stop working; unfortunately, their components aren’t easily recycled. However, a biodegradable pencil-drawn sensor dissolves completely in water, meaning recycling both the paper and the graphite is fast and easy.
In the paper, the team cited an array of potential benefits of pencil-paper on-skin sensors. For example, low-cost remote health monitoring and scientific research can help with risk mitigation during the COVID-19 pandemic. And the devices could eventually monitor sleep and activity like traditional consumer wearables.
The team has plans for next-level studies to develop a wireless system and expand research in other areas of application. So the future, it seems, may be sitting on your desk now, right in front of you.