For many, these are days at the seaside, and many are choosing a smartwatch to do outdoor exercises. Maybe for long swims, as long as they are water resistant. What if I told you that they are bringing out a smartwatch that can dissolve in water? A “soluble” smartwatch?
Researchers at Tianjin University used a two-metal nanocomposite material to create a fully functional smartwatch prototype which dissolves when immersed in water.
But why?
According to the paper published in ACS Applied Materials & Interfaces, wearable and dissolvable devices could be a solution to combat electronic waste. While larger electronics can be disassembled to recycle parts, smaller devices like smartwatches and fitness bands require a much more difficult process. The components must be recovered by hand and this can involve dangerous processes such as open burning or acid leaching.
Following this line of thinking, the researchers speculated that a soluble smartwatch could solve these problems.
Soluble but long lasting
The challenge here is that smartwatches and fitness bands need to be durable. While not all of them are safe for the pool or shower, most claim to withstand things like washing dishes, training sessions (with associated sweats), and thunderstorms.
The researchers modified a previously used zinc-based nanocomposite material to create a temporary soluble circuit. To make the material conductive enough for consumer electronics, the researchers added silver nanowires. They then printed the solution onto a water-degradable polymer and “solidified the circuits by applying small drops of water that facilitate chemical reactions and then evaporate.”
How is the soluble smartwatch made?
Using this method, the researchers created multiple circuit boards then housed inside a 3D-printed polyvinyl alcohol case. (Polyvinyl alcohol is a water-soluble, biodegradable material.) The prototype smartwatch also included sensors that could read heart rate, step count, and blood oxygen levels. It was also able to connect to a phone app via Bluetooth. A smartwatch, I said. In full order.
During testing, researchers found that the device was capable of accurately recording biometric data, as well as sending emojis, caller ID, and messages from a paired phone. It was also able to resist splashes from water droplets, indicating that the smartwatch could tolerate a (small?) degree of humidity. However, when it was immersed for 40 hours in water, the prototype completely disintegrated. Soluble, I have already said this too. All that was left behind were components like the OLED screen and the microcontroller.
Electronic waste: a “legitimate alibi”
In 2019, the world has generated 53,6 million tons of electronic waste, of which only 17,4% was recycled. And already a few years earlier, the amount of global electronic waste it was enough to build 4.500 Eiffel Towers. The problem is only getting worse thanks to planned obsolescence. As companies quickly add new features to gadgets every year or stop updating older ones, consumers are incentivizedto throw away perfectly functioning devices.
Sure, tech giants have been making a big splash in recent years (very greenwashing) on their sustainability efforts and 2020 saw a reduction in e-waste due to the pandemic, but that's not enough. Dissolvable electronics won't be hitting shelves anytime soon, but perhaps one day they could help make recycling a little easier.
