5 minute read
Sustainable electronics
from IM20213EN
After two months buried in the soil, the capacitor has disintegrated, leaving only a few visible carbon particles (Image: Gian Vaitl/Empa)
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The number of data-transmitting microdevices, for instance in packaging and transport logistics, will increase sharply in the coming years. All these devices need energy, but the amount of batteries would have a major impact on the environment. Empa researchers have developed a biodegradable mini-capacitor that can solve the problem. It consists of carbon, cellulose, glycerin and table salt. They used a conventional, modified, commercially available 3D printer. The real innovation is therefore not the device, but lies within the recipe for the gelatinous inks this printer can dispense onto a surface. The mixture consists of cellulose nanofibers and cellulose nanocrystallites, plus carbon in the form of carbon black, graphite and activated carbon. To liquefy all this, the researchers use glycerin, water, two different types of alcohol and a pinch of table salt for ionic conductivity.
To build a functioning supercapacitor from these ingredients, four layers are needed, all made by the 3D printer one after the other: a flexible substrate, a conductive layer, the electrode and finally the electrolyte. These layers then are arranged in a sandwich structure, with the electrolyte in the center. This creates a kind of mini capacitor that can store electricity for hours and is now capable of supplying power to a small digital clock. It can withstand thousands of charge and discharge cycles and years of storage, even in freezing temperatures, and is resistant to pressure and shock. And last but not least, at the end of lifetime it is easily compostable. After two months, the capacitor will have disintegrated, leaving only a few visible carbon particles.
According to EMPA, the bio-capacitor could soon become a key component for the Internet of Things. Such capacitors could be briefly charged using an electromagnetic field, for example, then they could provide power for a sensor
or a microtransmitter for hours. This could be used, for instance, to check the contents of individual packages during shipping. Powering sensors in environmental monitoring or agriculture is also conceivable - there’s no need to collect these batteries again, as they could be left in nature to degrade.
More at EMPA>
Video The biodegradable battery consists of four layers, all made by a 3D printer. Its folded like a sandwich, with the electrolyte in the center (Image: Gian Vaitl/Empa)
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Sustainable electronics (2) A battery that degrades on demand
The introduction of lithium-ion (Li-ion) batteries has revolutionized technology as a whole, leading to major advances in consumer goods across nearly all sectors. But the popularity of the batteries also creates problems in terms of sustainability and environmental impact. Current Li-ion batteries use significant amounts of metals loke cobalt and are responsible for a substantial environmental impact. Only a very small percentage of Li-ion batteries are recycled, increasing the demand for cobalt and other strategic elements.
A multidisciplinary team of Texas A&M University (TAMU)-researchers developed a new metal-free battery platform that could lead to more sustainable, recyclable batteries. In an article published in the May issue of Nature, they outline their research into a new battery technology platform that is completely metal-free, by using a polypeptide organic radical construction.
According to the researchers, these polypeptide batteries are degradable, they are recyclable, they are non-toxic and they are safer across the board. The all-polypeptide organic radical batte-
Metal-free, recyclable, polypeptide battery (Source: Texas A&M Engineering)
ry composed of redox-active amino-acid macromolecules also solves the problem of recyclability. The components of the new device can be degraded on demand in acidic conditions to generate amino acids, other building blocks and degradation products. The development of a metal-free, allpolypeptide organic radical battery that degrade on demand, marks significant progress toward sustainable, recyclable batteries that minimize dependence on strategic metals.
Much more at TAMU>
The article is online>
A 3D rendering of the first fully recyclable, printed transistor (Duke)
Engineers at Duke University have developed the world’s first fully recyclable printed electronics. By demonstrating a carbon based transistor, the researchers hope to inspire a new generation of recyclable electronics to help fight the growing global problem of electronic waste. The work was published on April 26 in the journal Nature Electronics, titled ‘Printable and recyclable carbon electronics using crystalline nanocellulose dielectrics.’ Part of the E waste problem is that electronic devices are difficult to recycle. While pieces of copper, aluminum and steel can be recycled, the silicon chips at the heart of the devices cannot. A team led by Aaron Franklin, Professor of Electrical and Computer Engineering at Duke, now has demonstrated a completely recyclable, fully functional transistor made out of three carbonbased inks that can be easily printed onto paper or other flexible, environmentally friendly surfaces. The trick is in the use of a wood-derived nanocellulose ink. The researchers developed a method for suspending crystals of nanocellulose that were extracted from wood fibers that yields an ink that performs admirably as an insulator in their printed transistors. Using the three inks in an aerosol jet printer at room temperature, the team shows that their all-carbon transistors perform well enough for use in a wide variety of applications. The team then demonstrates just how recyclable their design is. By submerging their devices in a series of baths, gently vibrating them with sound waves and centrifuging the resulting solution, the carbon nanotubes and graphene are sequentially recovered with an average yield of nearly 100 %. Both materials can then be reused in the same printing process while losing very little of their performance viability. And because the nanocellulose is made from wood, it can simply be recycled along with the paper it was printed on. According to Franklin, the research is primarily intended as a source of inspiration. He thinks recyclable electronics like this aren’t going replace an entire half-trillion-dollar industry, but hopefully demonstrate these types of new materials and their functionality as a stepping stone in the direction for a new type of electronics lifecycle.
