With people worldwide increasingly concerned about keeping the planet inhabitable for this generation and future ones, there are ongoing efforts to make electronics more sustainable by elevating their recyclability potential. Although researchers don’t expect to replace silicon-based components, there’s continual interest in making electronics that cut down on e-waste and keep the planet’s future in mind.
A team at Duke University recently developed the first entirely recyclable printable electronics, and graphene was a key part of the effort. They made a transistor with three carbon-based inks. The graphene inks produced conductors made with an aerosol jet printer. The research group also relied on nanocellulose, a biodegradable material that unlocked the recyclability potential.
People already know that nanocellulose has potential as an insulator in electronics. However, this was the first effort of using it to increase sustainability. The team’s recycling process involved submerging the parts in a series of baths, using sound waves to vibrate them and centrifuging the solution afterward. That process led to an average 100% recovery yield rate for the graphene, with very little performance loss. The graphene could also be used in the same printing process.
Better Marketability for Electronics
Electronics engineers push to overcome known problems with items on the market and make products more appealing to consumers. Graphene helps them do that. MSI Global is a graphics card company that replaced the plastic backplates in some of its products with ones made from graphene. This decision gave the components four times the strength, and they performed 20 times better at heat dissipation.
Gigabyte also has two graphics cards that use graphene as a lubricant. It more than doubles the fan’s lifetime and also makes it quieter. These examples show graphene’s potential for nonflexible components manufactured with methods other than printing.
However, recent work at Kansas State University revealed that a graphene additive manufacturing process could solve the problem of slow-charging batteries in electronics. Researchers hope to eventually replace conventional batteries with supercapacitors to accelerate charging speeds.
The Kansas State University team is developing micro-supercapacitors made from graphene-based nano inks. Materials are printed onto flexible substrates. The group has put the components through 10,000 charge and discharge cycles to evaluate their feasibility.
Suprem Das, a research leader for the project, noted, ”When you think about the best materials and wish to make the best devices, it is not simple and straightforward. One needs to then understand the underpinning physics and chemistry involved in devices.”
Additive manufacturing processes also speed the crucial task of designing prototypes and assessing what works well and which designs require revisions. Some computer-aided design modeling tools use scripting to automate repetitive tasks and create whole parts to a person’s specifications.
Enhanced Sensors for More Accurate Monitoring
Flexible electronics could be instrumental in more precise monitoring, particularly for human subjects. Doctors are increasingly interested in solutions that provide them with more data than a single office appointment would. Many patients have complaints that manifest at home, but not during the limited times they see their physicians.
The combination of flexibility and high sensitivity could result in sensors that give doctors dependable results and make patients willing to wear them consistently. A team at Trinity College Dublin developed printed graphene sensors that are 50 times more sensitive than current industry standards and outperform comparable products.
The researchers’ printing process allows depositing graphene inks onto flexible materials, including bandages. The group developed strain sensors, which measure things like pulse rate changes and how well a recovering stroke patient can swallow.
Another recent development concerned printable electronics made from graphene that measure food freshness and indicate safety. A project at Iowa State University allowed detecting histamine at 3.41 parts per million, much better than federal regulations requiring methods that find it at 50 parts per million in fish.
An aerosol-jet-printing process provided the required precision for creating high-resolution electrodes. The basic approach was to print graphene electrodes onto a flexible polymer, then use chemical binding to attach histamine antibodies to them. That step gave the electrodes the necessary sensing capabilities.
More Comfort and Durability for Wearables
Physical therapists and elite athletes are interested in wearable products that could give more insight into the body's biomechanics and how to improve performance or everyday functionality. Flexible electronics offer numerous advantages over the hard materials often used for wearables today. Comfort is one of the main perks. However, people also want assurance that the electronics will withstand frequent use and washing cycles.
A multiorganization effort led by the University of Cambridge resulted in researchers printing graphene directly onto fabric. This approach created sensors that were breathable, stretchable and suitable for up to 20 machine washing cycles. The group experimented with single transistors and fully integrated circuits. They also discovered that modifying the fabric's roughness changed how the printed devices performed.
Dr. Felice Torrisi of the Cambridge Graphene Centre noted, “Other inks for printed electronics normally require toxic solvents and are not suitable to be worn, whereas our inks are both cheap, safe and environmentally friendly, and can be combined to create electronic circuits by simply printing different two-dimensional materials on the fabric.”
Professor Roman Sordan of Politecnico di Milano also spoke of how the achievement could lead to other breakthroughs. “Although we demonstrated very simple integrated circuits, our process is scalable, and there are no fundamental obstacles to the technological development of wearable electronic devices, both in terms of their complexity and performance.“
Graphene Additive Manufacturing Shows Promise
It’s not yet common practice for people to combine graphene with additive manufacturing to get flexible and printable electronics. However, these examples show why doing so is a worthwhile effort. Many of the results mentioned here may take years to prove themselves commercially viable. Even so, it’s still fascinating to see how engineers could work with graphene in ways that create high-tech electronics free from many of the downsides that some products on the market have now.