Small modern-day electronics, such as fitness trackers and smartwatches, are challenging to dismantle and recycle. On top of that, most users send their old devices into hazardous waste streams when a new model comes out. As a result, many millions of tons of electronic waste are generated each year. However, recent research by scientists at China’s Tianjin University demonstrates how we could chip away at this problem by having main components disintegrate when submerged in water.
The scientists had previously developed a zinc-based nanocomposite material that could dissolve in water to make temporary electronic circuits. Still, the team found that its conductivity wasn’t sufficient for use in consumer devices.
The team added silver nanowires to the zinc-based nanocomposite to address this shortcoming, making them highly conductive. This mixture was subsequently screen-printed onto a degradable polymer known as polyvinyl alcohol, and the circuits were solidified via chemical reactions triggered by water droplets.
This led to nanocomposite circuit boards which were then placed inside casings made from the degradable polymer. Finally, sensors to measure a person’s blood oxygen levels, heart rate, and step count were included to complete the smartwatch design.
You may wonder, would a dissolvable fitness tracker hold up in sweat if it just disintegrates in water? It would! During testing, the prototype wearable proved to endure sweat. However, when the device was entirely submerged, the circuits and the polymer casing wholly dissolved within 40 hours. The only remaining materials were the resistors and capacitors integrated into the circuits, the OLED screen, and its microcontroller.
The prototype is far from the kind of smartwatch you’d see a wearable enthusiast wearing on their wrist. Instead, the scientists believe their research lays the groundwork for temporary easy-to-recycle devices with comparable performance – but better for the environment. The study was published on July 5, 2021, in ACS Applied Materials & Interfaces.
