Over the past decade and a half, human reliance on technology and the Internet has increased exponentially as computing power has made it possible to take the World Wide Web everywhere in the palm of your hand. Apple, Samsung, Google, Microsoft and all the chip makers are constantly pushing the boundaries of what was previously thought possible when it comes to new technologies. Unfortunately, this constant push to upgrade or develop new technology (as well as the human propensity to accidentally drop and destroy these devices) has an environmental impact, leaving behind vast quantities of discarded or broken devices.
Millions of pounds of electronics are disposed of every year, but the United Nations estimates that less than a quarter of the material can be recycled. This continues to be a problem, especially as a potential 5G upgrade supercycle looms. Phones and computers contain dozens of components like glass screens, copper wires and metal cases that are theoretically recyclable, but which are actually difficult to recycle in practice because of the way they are assembled. Workers in factories do their best to break down electronics for recycling, but they are often left with little more than a few scraps of metal for their efforts.
Even more troubling is the fact that the brain of most electronic devices—its silicon chip—is not recyclable at all. There are conceivably millions of working microchips left sitting in old smartphones. Those could sure come in handy right about now as the world faces a massive shortage of chips that has become so severe that used cars are appreciating in value.
Engineers at Duke University believe they may be close to reaching a breakthrough in the way electronics can be manufactured with only carbon-based inks. The team at Duke has developed a method to print ink-based transistors on paper or flexible surfaces.
“Silicon-based computer components are probably never going away, and we don’t expect easily recyclable electronics like ours to replace the technology and devices that are already widely used,” said Aaron Franklin, the Addy Professor of Electrical and Computer Engineering at Duke. “But we hope that by creating new, fully recyclable, easily printed electronics and showing what they can do, that they might become widely used in future applications.”
The transistors that Franklin and his team have developed can work thanks to the use of an ink derived from wood fibers and nanocellulose. This is the first use in this application of nanocellulose as a printable ink for the electronics industry. Transistors are printed with the nanocellulose, graphene and carbon nanotubes and are fully recyclable. The nanocellulose is the key factor in making the components nearly 100 percent recyclable.
Recycling the printed electronics is a fairly simple process. First, the devices are submerged and vibrated gently with sound waves. Next, the solution is centrifuged with the carbon nanotubes and graphene being recovered. Finally, the nanocellulose and the paper it was printed on are recycled like any other piece of paper.
Franklin realizes that his team’s new technology won’t completely disrupt the trillion-dollar global electronics industry but believes it is commercially viable for simple applications like environmental sensors that do not require a lot of power. Small, single-use biosensing patches are another potential application for these printed sensors.
“Recyclable electronics like this aren’t going to go out and replace an entire half-trillion-dollar industry by any means, and we’re certainly nowhere near printing recyclable computer processors,” said Franklin. “But demonstrating these types of new materials and their functionality is hopefully a stepping-stone in the right direction for a new type of electronics lifecycle.”
Developing this new method of printing electronics is an excellent first step in addressing the never-ending supply of tech waste across the globe. Fully recyclable sensors will also make it easier and cheaper to monitor environmental conditions, reduce energy consumption or track bodily functions. The first step is developing the method. Next comes applying it, and it appears there are already several promising use cases.