As online music services become more popular, CDs are falling out of favor. However, there are still applications for some of them, as the gold foil contained in them can be used in the manufacture of wearable biosensors.

Although CDs are mainly made of polycarbonate, they contain a thin layer of foil. Most CDs use this aluminum foil, although some use gold.

Because thin layers of gold are also used in flexible skin-adhesive biosensors, scientists at Binghamton University in New York wondered whether gold from the discs could be used for these purposes.

Led by graduate student Matthew Brown and associate professor Ahion Koch, they developed a method in which gold CDs are first soaked in acetone for 90 seconds, which breaks up the polycarbonate, weakening the bond between it and the foil, followed by a layer of polyimide adhesive. tape was applied to the foil and then the foil and gold were peeled off the polycarbonate.

Using a commercially available cloth cutting machine, the gold foil and ribbon backing were cut into flexible patterns that can be repeatedly applied to and removed from human skin. Along with other electronics, these biosensors can be used to monitor the electrical activity of the user’s heart and muscles, as well as measure lactose, glucose, pH and oxygen levels. All data can be sent to a smartphone via Bluetooth.

The entire fabrication process reportedly takes only 20-30 minutes, requires no expensive equipment, and costs around $1.50 per sensor.