Soluble smartwatch makes it easier to recycle electronics – sciencedaily
Small electronic devices, including smartwatches and fitness trackers, are not easy to take apart and recycle. So when a new model comes out, most users send the old devices to hazardous waste streams. To simplify the recycling of small electronic devices, researchers Applied materials and interfaces ACS have developed a two-metal nanocomposite for circuits that disintegrates when submerged in water. They demonstrated the circuitry in a prototype transient device, a functional smartwatch that dissolved in 40 hours.
Planned obsolescence and the rapid pace of technological innovation lead to new devices that constantly replace old versions, generating millions of tons of electronic waste per year. Recycling can reduce the volume of electronic waste and is mandatory in many places. However, it is often not worth recycling small consumer electronics, as their parts have to be collected by hand, and some processing steps, such as open combustion and acid leaching. , can cause health problems and environmental pollution. Soluble devices that break on demand could solve both of these problems. Previously, Xian Huang and his colleagues developed a zinc-based nanocomposite that dissolves in water for use in temporary circuits, but it was not conductive enough for consumer electronics. So they wanted to improve the electrical properties of their soluble nanocomposite while creating circuits tough enough to withstand everyday use.
The researchers modified the zinc-based nanocomposite by adding silver nanowires, making it very conductive. Then, they screen printed the metal solution onto pieces of polyvinyl alcohol – a polymer that degrades in water – and solidified the circuits by applying small water droplets that facilitate chemical reactions and then evaporate. With this approach, the team made a smartwatch with multiple nanocomposite circuit boards inside a 3D printed poly (vinyl alcohol) case. The smartwatch had sensors that accurately measured heart rate, blood oxygen levels, and step count, and sent the information to a cell phone app over a Bluetooth connection. The outer wrapper stood up to sweat, but after the entire device was completely submerged in water, the polymer casing and circuitry completely dissolved in 40 hours. Only the components of the watch remained, such as an organic light-emitting diode (OLED) display and microcontroller, as well as resistors and capacitors that had been built into the circuitry. The researchers say the two-metal nanocomposite can be used to produce transient devices that perform well in performance with commercial models, which could go a long way in solving the problems of small electronic waste.
The authors do not mention any source of funding for this study.
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