The research was carried out by scientists at China's Tianjin University, who had previously developed a novel type of zinc-based nanocomposite material that could be dissolved in water. The idea was that the material could be used for temporary electronic circuits, but the team found it wasn't quite conductive enough for use in consumer devices.

Looking to address this shortcoming, the team modified the zinc-based nanocomposite by adding silver nanowires, which in turn made them highly conductive. This concoction was then screen-printed onto a degradable polymer called polyvinyl alcohol, and the circuits were solidified through chemical reactions triggered by droplets of water.

This formed nanocomposite circuit boards that were then packed inside casings made of more polyvinyl alcohol, while sensors to measure a person's heart rate, blood oxygen levels and step count were added to complete the smartwatch design. In testing, the prototype wearable hit a sweet spot by enduring sweat, but succumbing perfectly in water.

When the entire device was entirely submersed, the polymer casing and the circuits completely dissolved within 40 hours. What was left for simple retrieval was the OLED screen and its microcontroller, along with resistors and capacitors incorporated into the circuits. The prototype is a long way from the type of smartwatch you'd see wrapped around the wrist of your typical wearables enthusiast, but the scientists do believe they've laid the groundwork for a transient device with a comparable performance.

The research was published in the journal ACS Applied Materials & Interfaces.