Researchers at the University of Missouri (MU) have conducted a new study that reveals the potential of pencil and paper for creating electronic devices.
Pencil drawn devices could potentially be used to monitor personal health. Image used courtesy of the University of Missouri
Specifically, the researchers found that something so commonplace as a graphite pencil can create bioelectric devices that attach to the skin.
Using Friction Energy From Graphite Pencils
In recent years, researchers have found ways to power a number of devices with the energy of pencil-on-paper friction, including sensors, microfluidics, energy storage, and microanalytical devices. Paper is a useful option as a substrate for electronic circuits and sensors because it is both inexpensive and environmentally friendly.
Researchers can now use the passive and active roles of a pencil-trace by harvesting the energy of a 90% graphite pencil on paper. Dr. Zheng Yan, who led the team of MU researchers, expounds that pencils containing more than 90% graphite are able to conduct a high amount of energy created from the friction between paper and pencil when drawing or writing.
Temperature, biopotential, glucose, and pH sensors are part of a variety of pencil-on-paper electronic devices that are being explored. Image used courtesy of Dr. Zheng Yan’s research group at MU
Specifically, the researchers found pencils with 93% graphite were the best for creating a variety of on-skin bioelectronic devices drawn on commercial office copy paper. These drawing materials are often dispersed in liquids and deposit traces on papers after the solvent evaporates.
Pencil-on-Paper vs. Commercial On-Skin Biomedical Devices
Many existing commercial on-skin biomedical devices contain two major components: a biomedical tracking component and a surrounding flexible material, such as plastic, to provide a supportive structure for the component to maintain an on-skin connection.
In contrast, the pencil-on-paper approach develops a sensing platform where devices can be fabricated in minutes using nothing more than common office supplies. According to researchers Cheng-Wei Lin et. al, pencil traces are considered conductive thin films made of percolated graphite particle network on paper. This method is quite stable against moisture, chemicals, and UV irradiation as well.
A graphite pencil is a far more cost-effective solution than current on-skin based electronic devices. Dr. Yan explains, “Our approach is low-cost and very simple. We can make a similar device using widely available pencils and paper.”
What Can the Pencil-on-Paper-Powered Device Do?
The research concluded that a biocompatible spray-on adhesive could also be applied to the paper to help it stick better to a person’s skin. One single-unit device (0.87 cm2) can generate a sustained voltage of up to 480 mV.
A bilayer chemiresistor with multiple pencil trace layers. Image used courtesy of Cheng-Wei Lin et. al
The enabled devices can perform real-time, continuous, and high-fidelity monitoring of a range of virtual biophysical and biochemical signals from human bodies. This includes skin temperatures, instantaneous heart rates, respiratory rates, and delivering programmed thermal stimulations.
This MU research study indicates that this technology could have a broad future of applications, from home-based personalized health care to remote scientific research garnered for the COVID-19 pandemic. Dr. Zheng posits that pencil-on-paper developments could also help monitor a person’s sleep levels.
With continuing research into pencil-and-paper-powered electronics, this method could allow individuals to monitor their own health conditions by simply picking up a pencil and paper.