Tag Archives: #biodegradable

The Biodegradable Battery (Chemistry)

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. And it works reliably.

The fabrication device for the battery revolution looks quite unconspicuous: It is a modified, commercially available 3D printer, located in a room in the Empa laboratory building. But the real innovation lies within the recipe for the gelatinous inks this printer can dispense onto a surface. The mixture in question 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 and two different types of alcohol. Plus a pinch of table salt for ionic conductivity.

A sandwich of four layers

The biodegradable battery consists of four layers, all flowing out of a 3D printer one after the other. The whole thing is then folded up like a sandwich, with the electrolyte in the center. Image: Gian Vaitl / Empa

To build a functioning supercapacitor from these ingredients, four layers are needed, all flowing out of the 3D printer one after the other: a flexible substrate, a conductive layer, the electrode and finally the electrolyte. The whole thing is then folded up like a sandwich, with the electrolyte in the center.

What emerges is an ecological miracle. The mini-capacitor from the lab can store electricity for hours and can already power 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.

Biodegradable power supply

Best of all, though, when you no longer need it, you could toss it in the compost or simply leave it in nature. After two months, the capacitor will have disintegrated, leaving only a few visible carbon particles. The researchers have already tried this, too.

“It sounds quite simple, but it wasn’t at all,” says Xavier Aeby of Empa’s Cellulose & Wood Materials lab. It took an extended series of tests until all the parameters were right, until all the components flowed reliably from the printer and the capacitor worked. Says Aeby: “As researchers, we don’t want to just fiddle about, we also want to understand what’s happening inside our materials.”

Together with his supervisor, Gustav Nyström, Aeby developed and implemented the concept of a biodegradable electricity storage device. Aeby studied microsystems engineering at EPFL and came to Empa for his doctorate. Nyström and his team have been investigating functional gels based on nanocellulose for some time. The material is not only an environmentally friendly, renewable raw material, but its internal chemistry makes it extremely versatile.

“The project of a biodegradable electricity storage system has been close to my heart for a long time,” Nyström says. “We applied for Empa internal funding with our project, Printed Paper Batteries, and were able to start our activities with this funding. Now we have achieved our first goal.”

Application in the Internet of Things

The supercapacitor could soon become a key component for the Internet of Things, Nyström and Aeby expect. “In the future, 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.

After two months buried in the soil, the capacitor has disintegrated, leaving only a few visible carbon particles. Image: Gian Vaitl/ Empa.

The number of electronic microdevices will also be increasing due to a much more widespread use of near-patient laboratory diagnostics (“point of care testing”), which is currently booming. Small test devices for use at the bedside or self-testing devices for diabetics are among them. “A disposable cellulose capacitor could also be well suited for these applications”, says Gustav Nyström.

Featured image: Xavier Aeby and Gustav Nyström invented a fully printed biodegradable battery made from cellulose and other non-toxic components. Image: Gian Vaitl / Empa


X Aeby, A Poulin, G Siqueira, MK Hausmann, G Nyström; Fully 3D Printed and Disposable Paper Supercapacitors; Advanced Materials (2021); doi.org/10.1002/adma.202101328

Provided by EMPA

New Process Breaks Down Biodegradable Plastics Faster (Chemistry)

Invention could solve waste management challenges on the battlefield

With Army funding, scientists invented a way to make compostable plastics break down within a few weeks with just heat and water. This advance will potentially solve waste management challenges at forward operating bases and offer additional technological advances for American Soldiers.

The new process, developed by researchers at University of California, Berkeley and the University of Massachusetts Amherst, involves embedding polyester-eating enzymes in the plastic as it’s made.

When exposed to heat and water, an enzyme shrugs off its polymer shroud and starts chomping the plastic polymer into its building blocks — in the case of biodegradable plastics, which are made primarily of the polyester known as polylactic acid, or PLA, it reduces it to lactic acid that can feed the soil microbes in compost. The polymer wrapping also degrades.

The process, published in Nature, eliminates microplastics, a byproduct of many chemical degradation processes and a pollutant in its own right. Up to 98% of the plastic made using this technique degrades into small molecules.

“These results provide a foundation for the rational design of polymeric materials that could degrade over relatively short timescales, which could provide significant advantages for Army logistics related to waste management,” said Dr. Stephanie McElhinny, program manager, Army Research Office, an element of the U.S. Army Combat Capabilities Development Command, known as DEVCOM, Army Research Laboratory. “More broadly, these results provide insight into strategies for the incorporation of active biomolecules into solid-state materials, which could have implications for a variety of future Army capabilities including sensing, decontamination, and self-healing materials.”

The new process to break down compostable plastics involves embedding polyester-eating enzymes in the plastic as it’s made. When exposed to heat and water, the enzyme shrugs off its polymer shroud and starts chomping the plastic polymer into its building blocks — in the case of PLA, reducing it to lactic acid, which can feed the soil microbes in compost. (Courtesy University of California, Berkeley)

Plastics are designed not to break down during normal use, but that also means they don’t break down after they’re discarded. Compostable plastics can take years to break down, often lasting as long as traditional plastics.

The research teams embedded nanoscale polymer-eating enzymes directly in a plastic or other material in a way that sequesters and protected them until the right conditions to unleash them. In 2018, they showed how this works in practice. The team embedded in a fiber mat an enzyme that degrades toxic organophosphate chemicals, like those in insecticides and chemical warfare agents. When the mat was immersed in the chemical, the embedded enzyme broke down the organophosphate.

The researchers said protecting the enzyme from falling apart, which proteins typically do outside of their normal environment, such as a living cell, resulted in the key innovation.

For the Nature paper, the researchers showcased a similar technique by enshrouding the enzyme in molecules they designed called random heteropolymers or RHPs, and embedding billions of these nanoparticles throughout plastic resin beads that are the starting point for all plastic manufacturing. The process is similar to embedding pigments in plastic to color them.

“This work, combined with the 2018 discovery, reveals these RHPs as highly effective enzyme stabilizers, enabling the retention of enzyme structure and activity in non-biological environments,” said Dr. Dawanne Poree, program manager, ARO. “This research really opens the door to a new class of biotic-abiotic hybrid materials with functions only currently found in living systems.”

Much of the planet is swimming in discarded plastic, which is harming animal and possibly human health. Can it be cleaned up? (Shutterstock)

The results showed that the RHP-shrouded enzymes did not change the character of the plastic, which could be melted and extruded into fibers like normal polyester plastic at temperatures around 170 degrees Celsius (338 degrees Fahrenheit).

To trigger degradation, it was necessary only to add water and a little heat. At room temperature, 80% of the modified PLA fibers degraded entirely within about one week. Degradation was faster at higher temperatures. Under industrial composting conditions, the modified PLA degraded within six days at 50 degrees Celsius (122 degrees Fahrenheit).

Another polyester plastic, PCL (polycaprolactone), degraded in two days under industrial composting conditions at 40 degrees Celsius (104 degrees Fahrenheit). For PLA, the team embedded an enzyme called proteinase K that chews PLA up into molecules of lactic acid; for PCL, they used lipase. Both are inexpensive and readily available enzymes.

“If you have the enzyme only on the surface of the plastic, it would just etch down very slowly,” said Ting Xu, UC Berkeley professor of materials science and engineering and of chemistry. “You want it distributed nanoscopically everywhere so that, essentially, each of them just needs to eat away their polymer neighbors, and then the whole material disintegrates.”

Xu suspects that higher temperatures make the enshrouded enzyme move around more, allowing it to more quickly find the end of a polymer chain and chew it up and then move on to the next chain. The RHP-wrapped enzymes also tend to bind near the ends of polymer chains, keeping the enzymes near their targets.

The modified polyesters do not degrade at lower temperatures or during brief periods of dampness. For instance, a polyester shirt made with this process would withstand sweat and washing at moderate temperatures.

Soaking the biodegradable plastic in water for three months at room temperature did not cause it to degrade, but soaking for that time period in lukewarm water did.

Xu is developing RHP-wrapped enzymes that can degrade other types of polyester plastic, but she also is modifying the RHPs so that the degradation can be programmed to stop at a specified point and not completely destroy the material. This might be useful if the plastic were to be re-melted and turned into new plastic.

“Imagine, using biodegradable glue to assemble computer circuits or even entire phones or electronics, then, when you’re done with them, dissolving the glue so that the devices fall apart and all the pieces can be reused,” Xu said.

This technology could be very useful for generating new materials in forward operating environments, Poree said.

“Think of having a damaged equipment or vehicle parts that can be degraded and then re-made in the field, or even repurposed for a totally different use,” Poree said. “It also has potential impacts for expeditionary manufacturing.”

In addition to the Army, the U.S. Department of Energy with assistance from the UC Berkeley’s Bakar Fellowship program also funded the research.

Featured image: With Army funding, scientists invent a way to make compostable plastics break down within a few weeks with just heat and water, potentially solving waste management challenges at forward operating bases and offering additional technological advances for Soldiers. (Courtesy University of California, Berkeley)

Reference: DelRe, C., Jiang, Y., Kang, P. et al. Near-complete depolymerization of polyesters with nano-dispersed enzymes. Nature 592, 558–563 (2021). https://doi.org/10.1038/s41586-021-03408-3

Provided by US Army

Researchers Turn Wood Into Plastic (Engineering)

Plastics are one of the world’s largest polluters, taking hundreds of years to degrade in nature. A research team, led by YSE professor Yuan Yao and Liangbing Hu from the University of Maryland, has created a high-quality bioplastic from wood byproducts that they hope can solve one of the world’s most pressing environmental issues.

Efforts to shift from petrochemical plastics to renewable and biodegradable plastics have proven tricky — the production process can require toxic chemicals and is expensive, and the mechanical strength and water stability is often insufficient. But researchers have made a breakthrough, using wood byproducts, that shows promise for producing more durable and sustainable bioplastics. 

A study published in Nature Sustainability, co-authored by Yuan Yao, assistant professor of industrial ecology and sustainable systems at Yale School of the Environment (YSE), outlines the process of deconstructing the porous matrix of natural wood into a slurry. The researchers say the resulting material shows a high mechanical strength, stability when holding liquids, and UV-light resistance. It can also be recycled or safely biodegraded in the natural environment, and has a lower life-cycle environmental impact when compared with petroleum-based plastics and other biodegradable plastics. 

“There are many people who have tried to develop these kinds of polymers in plastic, but the mechanical strands are not good enough to replace the plastics we currently use, which are made mostly from fossil fuels,” says Yao. “We’ve developed a straightforward and simple manufacturing process that generates biomass-based plastics from wood, but also plastic that delivers good mechanical properties as well.”

To create the slurry mixture, the researchers used a wood powder — a processing residue usually discarded as waste in lumber mills — and deconstructed the loose, porous structure of the powder with a biodegradable and recyclable deep eutectic solvent (DES). The resulting mixture, which features nanoscale entanglement and hydrogen bonding between the regenerated lignin and cellulose micro/nanofibrils, has a high solid content and high viscosity, which can be casted and rolled without breaking.

“We’ve developed a straightforward and simple manufacturing process that generates biomass-based plastics from wood, but also plastic that delivers good mechanical properties as well.”

— Yuan Yao, assistant professor of industrial ecology and sustainable systems.

Yao then led a comprehensive life cycle assessment to test the environmental impacts of the bioplastic against commons plastics. Sheets of the bioplastic were buried in soil, fracturing after two weeks and completely degrading after three months; additionally, researchers say the bioplastic can be broken back down into the slurry by mechanical stirring, which also allows for the DES to be recovered and reused. 

“That, to me, is what really makes this plastic good: It can all be recycled or biodegraded,” says Yao. “We’ve minimized all of the materials and the waste going into nature.”

The bioplastic has numerous applications, says Liangbing Hu, a professor at the Center for Materials Innovation at the University of Maryland and co-author of the paper. It can be molded into a film that can be used in plastic bags and packaging — one of the major uses of plastic and causes of waste production. Hu also says that because the bioplastic can be molded into different shapes, it has potential for use in automobile manufacturing, as well.

One area the research team continues to investigate is the potential impact on forests if the manufacturing of this bioplastic is scaled up. While the process currently uses wood byproducts in manufacturing, the researchers say they are keenly aware that large-scale production could require usage of massive amounts of wood, which could have far-reaching implications on forests, land management, ecosystems and climate change, to name a few.

Yao says the research team has already begun working with a forest ecologist to create forest simulation models, linking the growth cycle of forests with the manufacturing process. She also sees an opportunity to collaborate with people who work in forest-related fields at YSE — an uncommon convenience.

“It’s not often an engineer can walk down the hall and talk to a forester,” says Yao.

Yao, an emerging scholar in the field of industrial ecology, joined the YSE faculty last year. Her research examines the environmental and economic impacts of emerging technologies and industrial processes., integrating interdisciplinary approaches from the fields of industrial ecology, sustainable engineering, and systems modeling to develop techniques that promote more sustainable engineering approaches and policies.

Reference: Xia, Q., Chen, C., Yao, Y. et al. A strong, biodegradable and recyclable lignocellulosic bioplastic. Nat Sustain (2021). https://www.nature.com/articles/s41893-021-00702-w https://doi.org/10.1038/s41893-021-00702-w

Provided by Yale School of Environment

Biodegradable Inorganic Upconversion Nanocrystals Developed for In Vivo Applications (Chemistry)

Lanthanide-doped inorganic upconversion nanocrystals (UCNCs) are attracting more and more attentions as they are potential fluorescent diagnostic and therapeutic agents for in vivo applications including biological imaging and disease theragnostics.

Schematic illustration by Peng et al.

However, all currently available lanthanide-doped inorganic UCNCs, as exemplified by the most presentative b-NaYF4:Yb/Er, are not biodegradable and thus cannot be harmlessly eliminated from the body of living organism during a reasonable period of time, making their clinical translations nearly impossible.

In a study published in ACS Nano, the research group led by Prof. HONG Maochun from Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences reported a new class of red-emitting biodegradable UCNCs based on Yb3+/Er3+-doped inorganic potassium heptafluozirconate (K3ZrF7:Yb/Er) that features dynamically “soft” crystal lattice containing water-soluble [ZrF7]3- cluster and K+ cation.

The researchers found that this arrangement of K3ZrF7 crystal lattice enables the preparation of a family of red-emitting biodegradable inorganic UCNCs after substituted Yb3+/Er3+ doping into the high-symmetry host matrix.

In particular, the red-emitting K3ZrF7:Yb/Er UCNCs exhibit a pH-dependent biodegradation capability upon exposure to water both in vitro and in vivo, and of which the rapid biodegradation rate, monitored by using the intrinsic red upconversion luminescence (UCL), can be tuned by changing the pH value during degradation process.

Through histopathological and elemental analyses, the researchers also found that the final biodegradation products of K3ZrF7:Yb/Er UCNCs can rapidly excrete from the bodies of mice in a short period of time without evident toxicity to their muscles and main organs, in stark contrast to the non-degradable b-NaYF4:Yb/Er UCNCs that primarily accumulate in the main organs of mice.

This study unambiguously offers an opportunity to produce a family of UCL diagnostic and therapeutic agents that are biodegradable in vivo during a reasonable period of time after carrying out their biological applications, which also stimulate an upsurge of research interest on biodegradable Ln3+-doped inorganic UCNCs for various biomedical applications and benefit their future clinical translations.

Reference: Pengfei Peng, Na Wu, Lixiang Ye, Feilong Jiang, Wei Feng, Fuyou Li, Yongsheng Liu, and Maochun Hong, “Biodegradable Inorganic Upconversion Nanocrystals for In Vivo Applications”, ACS Nano 2020, 14, 12, 16672–16680. https://pubs.acs.org/doi/10.1021/acsnano.0c02601

Provided by Chinese Academy of Sciences

Researchers Develop New Combined Process For 3D Printing (Chemistry)

Chemists at Martin Luther University Halle-Wittenberg (MLU) have developed a way to integrate liquids directly into materials during the 3D printing process. This allows, for example, active medical agents to be incorporated into pharmaceutical products or luminous liquids to be integrated into materials, which allow monitoring of damage. The study was published in “Advanced Materials Technologies”.

Inside the 3-D-printed material (right) a lattice structure (left) contains the added liquids. © Harald Rupp / Uni Halle

3D printing is now widely used for a range of applications. Generally, however, the method is limited to materials which are liquefied through heat and become solid after printing. If the finished product is to contain liquid components, these are usually added afterwards. This is time-consuming and costly. “The future lies in more complex methods that combine several production steps,” says Professor Wolfgang Binder from the Institute of Chemistry at MLU. “That is why we were looking for a way to integrate liquids directly into the material during the printing process.”

To this endeavour, Binder and his colleague Harald Rupp combined common 3D printing processes with traditional printing methods such as those used in inkjet or laser printers. Liquids are added drop by drop at the desired location during the extrusion of the basic material. This allows them to be integrated directly and into the material in a targeted manner.

The chemists have been able to show that their method works through two examples. First, they integrated an active liquid substance into a biodegradable material. “We were able to prove that the active ingredient was not affected by the printing process and remained active,” explains Binder. In the pharmaceutical industry, such materials are used as drug depots which can be slowly broken down by the body. They can be used after operations, for example, to prevent inflammation. This new process could facilitate their production.

Secondly, the scientists integrated a luminous liquid into a plastic material. When the material becomes damaged, the liquid leaks out and indicates where the damage has occurred. “You could imprint something like this into a small part of a product that is exposed to particularly high levels of stress,” says Binder. For example, in parts of cars or aircraft that are under a lot of strain. According to Binder, damage to plastic materials has so far been difficult to detect – unlike damage to metals, where X-rays can expose micro-cracks. The new approach could therefore increase safety.

The combined process is also conceivable for many other areas of application, says the chemist. The team soon plans to use the method to print parts of batteries. “Larger quantities cannot be produced in the laboratory with our setup,” Binder explains. In order to produce industrial quantities, the process must be further developed outside the university.

The research was supported by the Leistungszentrum “System- und Biotechnologie”, the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and by the EU as part of the “Horizon 2020” programme.

References: Rupp, H., Binder, W.H. 3D Printing of Core-Shell Capsule Composites for Post-Reactive and Damage Sensing Applications. Advanced Materials Technologies (2020). doi: 10.1002/admt.202000509 https://onlinelibrary.wiley.com/doi/10.1002/admt.202000509

Provided by Martin-Luther-Universität Halle-Wittenberg

Leaf-cutter Bees As Plastic Recyclers? Not A Good Idea, Say Scientists (Biology)

In observational paper, team of scientists report evidence of bees in the genus Megachile using plastic in nest construction.

Plastic has become ubiquitous in modern life and its accumulation as waste in the environment is sounding warning bells for the health of humans and wildlife. In a recent study, Utah State University scientist Janice Brahney cited alarming amounts of microplastics in the nation’s national parks and wilderness areas.

Joseph Wilson, associate professor of biology at Utah State University-Tooele, handles pieces of plastic sheeting with tell-tale circular cut-outs made by leaf-cutter bees. Wilson says the solitary bees use the plastic in nest construction, which could harm their offspring. ©USU.

Bioengineers around the world are working to develop plastic-eating “super” enzymes that can break down the man-made material’s molecular structure faster to aid recycling efforts. In another research effort published in 2019, entomologists noted leaf-cutter bees were using plastic waste to construct their nests. The researchers suggested such behavior could be an “ecologically adaptive trait” and a beneficial recycling effort.

Not so fast, says USU evolutionary ecologist Joseph Wilson. Just because bees can use plastic, doesn’t mean they should.

Wilson and undergraduate researcher Sussy Jones, along with colleagues Scott McCleve, a naturalist and retired math teacher in Douglas, Arizona, and USU alum and New Mexico-based independent scientist Olivia Carril ’00, MS’06, jointly authored an observational paper in the Oct. 9, 2020 issue of ‘Science Matters’, exploring the nest building behavior of bees in the genus Megachile.

“Leaf-cutter bees are among the most recognizable of solitary bees, because of their habit of cutting circles out of leaves to build their cylindrical nests,” says Wilson, associate professor of biology at USU-Tooele. “We’ve heard reports of these bees using plastic, especially plastic flagging primarily in construction and agriculture, and we decided to investigate.”

A leaf-cutter bee carries a piece of a leaf it’s cut to build a nest cell for its offspring. Utah State University scientist Joseph Wilson says the bees may be using plastic waste in place of natural materials. ©Joseph Wilson.

The researchers don’t yet know how widespread the use of plastic by leaf-cutter bees is and they also know little about plastic’s effects on the insects.

“Building from plastic could change the dynamics and environment of the bee’s nest cells, because plastic doesn’t breathe like natural materials,” says Wilson, who produced a video about the phenomenon. “In the 1970s, some researcher let leaf-cutter bees nest in plastic straws and found ninety percent of the bees’ offspring died because of fungal growth. The plastic sealed in the moisture and didn’t allow gas exchange.”

Examples of leaf-cutter bee use of a sumac leave and two pieces of plastic flagging.

To deter bees’ use of flagging, Wilson suggests use of fabric ribbons made from natural fibers.

“These materials are biodegradable and, if used by bees, will likely avoid the harmful moisture-capturing effects of plastic,” he says.

References: Joseph Wilson, Sussy Jones, Scott McCleve, Olivia M Carril, “Evidence of leaf-cutter bees using plastic flagging as nesting material”, Matters, 2020. https://sciencematters.io/articles/202010000003

Provided by Utah State University