At the turn of the century, compact discs were the dominant media for music consumption.
Since then, CD sales have plummeted as the physical format was supplanted first by digital download and then by music streaming services.
They haven’t enjoyed the luxury item resurgence of vinyl records and, while not yet obsolete, they seem to be heading that way.
Now, new research has found a way to upcycle unwanted CDs into flexible biosensors that can be used to monitor a number of health conditions and markers.
CDs are composed mostly of a clear polycarbonate plastic substrate, but they also feature a reflective metallic layer beneath a clear protective coating of acrylic plastic.
The researchers, from the Department of Biomedical Engineering at Binghamton University in New York, demonstrated that gold could be extracted from the thin metallic layer of certain CDs and turned into the sensors.
These flexible sensors can monitor valuable metrics and markers such as electrical activity in the human heart and muscles, as well as levels of lactate, glucose, pH and oxygen.
Fabrication of the sensors is relatively quick and inexpensive
Describing the process in a paper published in the journal Nature Communications, the researchers reported that the sensor devices could be fabricated in half an hour or less, with each device costing around $1.50 to make.
Furthermore, the process did not release toxic chemicals and did not require any expensive equipment.
The paper called it a “sustainable approach for upcycling electronic waste” that did not require “cutting-edge microfabrication facilities, expensive materials or high-calibre engineering skills”.
Researchers Ahyeon Koh and Matthew Brown explored previous research on turning materials from CDs into sensors, but found that those devices were rigid, which reduced their potential applications.
The new approach involves removing the metallic coating from the plastic using a combination of chemicals and adhesive tape.
The metallic layer removed from the disc is then processed to retain flexibility.
For the sensors themselves, they used a commercially available die-cutting machine, commonly used by crafters, known as a Cricut cutter.
The completed flexible circuits can be affixed to a person’s body and, when linked to a smartphone app, can enable readings to be taken and sent to medical professionals.
For now, the process has only extracted gold from gold-based CDs, but the researchers hope to apply it to more common silver-based CDs in the future.
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