CDs upcycled into flexible biosensors

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Gold compact discs are being given a second life in the US by being turned into flexible biosensors that are inexpensive and easy to manufacture.

Flexible biosensor on skin
Flexible biosensor on skin - Matthew Brown

In a paper published in Nature Communications, Matthew Brown, PhD ’22, and Assistant Professor Ahyeon Koh from the Department of Biomedical Engineering at Binghamton University, State University of New York, show how a gold CD’s thin metallic layer can be separated from the rigid plastic and turned into sensors to monitor electrical activity in human hearts and muscles, plus lactate, glucose, pH and oxygen levels. The sensors can communicate with a smartphone via Bluetooth.

The fabrication is said to be completed in 20 to 30 minutes without releasing toxic chemicals or needing expensive equipment, and it costs around $1.50 per device. According to the paper, “this sustainable approach for upcycling electronic waste provides an advantageous research-based waste stream that does not require cutting-edge microfabrication facilities, expensive materials or high-calibre engineering skills.”

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Koh first considered the idea of converting the CDs into sensors while doing postdoctoral research at the University of Illinois.

“I had an idea: Maybe we could harvest the critical material from the CD and then upcycle to sensing systems,” she said in a statement. “I talked to Matt about my idea during the early stage of his dissertation research, and he wanted to continue this research.”

Brown investigated previous research on biosensors made from CDs, but found that those sensors retained a rigid structure and had a more limited number of applications.

The first step is removing the metallic coating from the plastic beneath using a chemical process and adhesive tape.

“We loosen the layer of metals from the CD and then pick up that metal layer with tape, so we just peel it off,” said Koh. “That thin layer is then processed and flexible.”

To create the sensors, Binghamton researchers used a Cricut cutter, an off-the-shelf machine used by crafters. The flexible circuits are then 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.

Brown has 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 Brown. “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.”