Tech 

Old CDs can be converted into new biosensors

While only gold CDs are currently being reworked in the rework process, a solution using other types of CDs may soon emerge.

The use of old golden CDs for the production of biosensors | photo: Binghamton University

Digital music files (including streaming services) have virtually dominated the music market, so compact discs (CDs) are slowly becoming an obsolete medium. However, some existing CDs may still be useful as their gold foil can be used to make biosensors for wearable devices. Although CDs are made primarily of polycarbonate, they contain a thin layer of reflective film. This foil is aluminum on most CDs, although gold is used for (possibly) better performance on gold compact discs.

Usually, when gold CDs are thrown away, this gold foil goes to the landfill along with the rest of the CD. Since thin layers of gold are also used in flexible skin-bonded biosensors, scientists at Binghamton University in New York wondered if they could save gold from CDs for this purpose.

PhD student Matthew Brown and prof. Ahyeon Koh developed a technique where the gold CDs were initially soaked in acetone for 90 seconds – this would shatter the polycarbonate, loosening the bond between it and the foil. A sheet of polyimide tape was then applied to the foil, and both the foil and the gold were peeled away from the underlying polycarbonate.

Using a commercially available Cricut fabric cutting machine (typically used by crafters), the gold foil and its ribbon backing were then cut into flexible circuits that could be applied and removed multiple times. occasions of human skin. In combination with other electronic devices, these biosensors can be used to monitor electrical activity in the heart and muscles, and are also capable of measuring lactose, glucose, pH and oxygen levels. All data can be transferred to the smartphone via Bluetooth.

Biosensor made from an old CD
Biosensor made from an old CD | photo: Binghamton University

The entire recycling and manufacturing process would only take 20-30 minutes, requires no expensive equipment, and costs around $1.50 per sensor. Although acetone is used in the process, no toxic chemicals are released into the waste stream.

We have used gold CDs and want to explore the possibilities of using silver based discs which are more common said Brown. We also want to see if we can use laser engraving instead of using a knife to further increase the speed of upcycling.

The research was described in a recent journal article Nature Communication.

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Source: Binghamton University | New Atlas

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