Billions of discarded CDs end up in landfills across the world with negative environmental consequences. Now, new research offers a second life for CDs by turning them into flexible biosensors that are inexpensive and easy to manufacture, and can monitor various health conditions and markers.

Researchers at Binghamton University (Binghamton, NY, USA) have shown how a gold CD’s thin metallic layer can be separated from the rigid plastic and fashioned into sensors to monitor electrical activity in human hearts and muscles as well as lactose, glucose, pH and oxygen levels. The sensors can communicate with a smartphone via Bluetooth. The fabrication is completed in 20 to 30 minutes without releasing toxic chemicals or needing expensive equipment, and it costs about USD 1.50 per device.

The researchers initially began by investigating previous research on biosensors made from CDs, but found that those sensors retained a rigid structure and had a more limited number of applications than they hoped to achieve. The first step was removing the metallic coating from the plastic beneath using a chemical process and adhesive tape. The researchers loosened the layer of metals from the CD and then picked up that metal layer with tape, so they could just peel it off. That thin layer is then processed and flexible.

To create the sensors, the researchers used a Cricut cutter, an off-the-shelf machine for crafters that generally cuts designs from materials like paper, vinyl, card stock and iron-on transfers. The flexible circuits then would be removed and stuck onto a person. With the help of a smartphone app, medical professionals or patients could get readings and track progress over time. The researchers are thrilled to see something they speculated could be possible almost a decade ago is now a reality, and have ideas about how the CD-to-sensor technology could be improved.

“We used gold CDs, and we want to explore silver-based CDs, which I believe are more common,” said Matthew Brown, PhD ’22. “How can we upcycle those types of CDs with the same kind of process? We also want to look at if we can utilize laser engraving rather than using the fabric-based cutter to improve the upcycling speed even further.” 

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