“Our digital technology operates through a series of electronic on-off switches that control the flow of current and voltage,” said Rajiv Giridharagopal, a research scientist at the University of Washington. “But our bodies operate on chemistry. In our brains, neurons propagate signals electrochemically, by moving ions — charged atoms or molecules — not electrons.”

Implantable devices from pacemakers to glucose monitors rely on components that can speak both languages and bridge that gap. Among those components are OECTs — or organic electrochemical transistors — which allow current to flow in devices like implantable biosensors. But scientists long knew about a quirk of OECTs that no one could explain: When an OECT is switched on, there is a lag before current reaches the desired operational level. When switched off, there is no lag. Current drops almost immediately.

A UW-led study has solved this lagging mystery, and in the process paved the way to custom-tailored OECTs for a growing list of applications in biosensing, brain-inspired computation and beyond.

“How fast you can switch a transistor is important for almost any application,” said project leader David Ginger, a UW professor of chemistry, chief scientist at the UW Clean Energy Institute and faculty member in the UW Molecular Engineering and Sciences Institute. “Scientists have recognized the unusual switching behavior of OECTs, but we never knew its cause — until now.”

In a paper published April 17 in Nature Materials, Ginger’s team at the UW — along with Professor Christine Luscombe at the Okinawa Institute of Science and Technology in Japan and Professor Chang-Zhi Li at Zhejiang University in China — report that OECTs turn on via a two-step process, which causes the lag. But they appear to turn off through a simpler one-step process.

In principle, OECTs operate like transistors in electronics: When switched on, they allow the flow of electrical current. When switched off, they block it. But OECTs operate by coupling the flow of ions with the flow of electrons, which makes them interesting routes for interfacing with chemistry and biology.

The new study illuminates the two steps OECTs go through when switched on. First, a wavefront of ions races across the transistor. Then, more charge-bearing particles invade the transistor’s flexible structure, causing it to swell slightly and bringing current up to operational levels. In contrast, the team discovered that deactivation is a one-step process: Levels of charged chemicals simply drop uniformly across the transistor, quickly interrupting the flow of current.

Knowing the lag’s cause should help scientists design new generations of OECTs for a wider set of applications.

“There’s always been this drive in technology development to make components faster, more reliable and more efficient,” Ginger said. “Yet, the ‘rules’ for how OECTs behave haven’t been well understood. A driving force in this work is to learn them and apply them to future research and development efforts.”

Whether they reside within devices to measure blood glucose or brain activity, OECTs are largely made up of flexible, organic semiconducting polymers — repeating units of complex, carbon-rich compounds — and operate immersed in liquids containing salts and other chemicals. For this project, the team studied OECTs that change color in response to electrical charge. The polymer materials were synthesized by Luscombe’s team at the Okinawa Institute of Science and Technology and Li’s at Zhejiang University, and then fabricated into transistors by UW doctoral students Jiajie Guo and Shinya “Emerson” Chen, who are co-lead authors on the paper.

“A challenge in the materials design for OECTs lies in creating a substance that facilitates effective ion transport and retains electronic conductivity,” said Luscombe, who is also a UW affiliate professor of chemistry and of materials science and engineering. “The ion transport requires a flexible material, whereas ensuring high electronic conductivity typically necessitates a more rigid structure, posing a dilemma in the development of such materials.”

Guo and Chen observed under a microscope — and recorded with a smartphone camera — precisely what happens when the custom-built OECTs are switched on and off. It showed clearly that a two-step chemical process lies at the heart of the OECT activation lag.

Past research, including by Ginger’s group at the UW, demonstrated that polymer structure, especially its flexibility, is important to how OECTs function. These devices operate in fluid-filled environments containing chemical salts and other biological compounds, which are more bulky compared to the electronic underpinnings of our digital devices.

The new study goes further by more directly linking OECT structure and performance. The team found that the degree of activation lag should vary based on what material the OECT is made of, such as whether its polymers are more ordered or more randomly arranged, according to Giridharagopal. Future research could explore how to reduce or lengthen the lag times, which for OECTs in the current study were fractions of a second.

“Depending on the type of device you’re trying to build, you could tailor composition, fluid, salts, charge carriers and other parameters to suit your needs,” said Giridharagopal.

OECTs aren’t just used in biosensing. They are also used to study nerve impulses in muscles, as well as forms of computing to create artificial neural networks and understand how our brains store and retrieve information. These widely divergent applications necessitate building new generations of OECTs with specialized features, including ramp-up and ramp-down times, according to Ginger.

“Now that we’re learning the steps needed to realize those applications, development can really accelerate,” said Ginger.

Guo is now a postdoctoral researcher at the Lawrence Berkeley National Laboratory and Chen is now a scientist at Analog Devices. Other co-authors on the paper are Connor Bischak, a former UW postdoctoral researcher in chemistry who is now an assistant professor at the University of Utah; Jonathan Onorato, a UW doctoral alum and scientist at Exponent; and Kangrong Yan and Ziqui Shen of Zhejiang University. The research was funded by the U.S. National Science Foundation, and polymers developed at Zhejiang University were funded by the National Science Foundation of China.

Land users rely on subsidies, but money is not everything

The researchers focused on the motivation and challenges driving decision-making among all land users engaged in low-intensity grazing practices. This was despite economic considerations becoming increasingly important as land users’ revenue-generating activities are no longer sufficient to cover the rising cost of equipment, rent, and taxes.

“Money is not everything. Many of the land users we interviewed practice this type of grazing management because they think it is good, not out of economic motivation,” says first author Dr Julia Rouet-Leduc. Rouet-Leduc led the project as a former doctoral researcher at iDiv and UL and is now a postdoctoral researcher at the Stockholm Resilience Centre. Caring for nature and, in some cases, also the desire to maintain traditional agricultural practices were important aspects of the land users’ motivation. For example, a land user working with wild ponies in Galicia (Spain) shared: “The main reason for the maintenance of this system is that people … love the ponies; they ‘have a fever’, and this tradition runs very deeply in their hearts.”

The researchers found that many land users struggle with rules and regulations that are incompatible with low-intensity grazing management. For example, rules to mark or tag livestock — an extremely challenging task when animals are allowed to graze freely in large areas — were perceived as limiting. Land users also felt that the policies in place, especially the Common Agricultural Policy of the European Commission (CAP), were holding back nature-friendly and sustainable practices. For example, a land user in Romania noted that farmers were required to remove scrubs from their pastures or they would otherwise not be eligible for subsidies or even have to pay penalties. However, scrubs have important ecosystem functions, such as providing shade in the summer and as an additional food resource in the winter. In general, the CAP was perceived as too restrictive, and many land users chose not to apply for subsidies at all. “By not applying for CAP support, we have the freedom to really see what suits the local ecosystem,” a Belgian land user stated.

Rural exodus is putting traditional labour at risk

The interviews also showed that many land users struggle with socio-economic changes in the countryside. The so-called ‘Rural Exodus’ is leading to a lack of workforce, while physical work is still very much needed, especially for work with cattle or horses. “The next generation does not want to farm because it is too hard, too much work,” a land user from Lithuania said. “They usually move abroad and choose easier career options’.’

“The CAP could support farmers in High Nature Value farming regions and put incentives in place to preserve or restore extensive grazing systems,” senior author Dr Guy Pe’er, a senior researcher at UFZ and iDiv, suggests. “It’s not a lack of budgets but rather the lack of ambition to support sustainable farming.”

More flexibility and improved market access needed

The researchers used the interviews to derive and suggest interventions to encourage better grazing practices. “What is needed is more flexibility for land users,” Rouet-Leduc says. “Current policies are, for the most part, not encouraging such practices, and particularly not offering a level playing field for land users.” While the EU’s CAP offers important economic support, it also drives counter-productive management due to problematic requirements, she adds. Additional financial incentives could improve the support for more sustainable grazing management, according to the study’s authors. Especially in areas where land has been abandoned, there can be opportunities for rewilding large herbivores, which ultimately provide multiple ecosystem services. However, such systems require flexibility since they differ from management approaches with domestic animals.

The researchers also call for better labelling and certification for environmentally friendly grazing practices to increase public support and to help develop markets for such products. Some of the interviewed land users felt that market access could be improved by supporting direct marketing, for example, via farm shops.

“There are clearly real challenges for farmers, and they are not easy to overcome,” Pe’er explains in light of ongoing farmers’ demonstrations in countries like Germany, Poland, and Italy. “But removing environmental standards will not help land users. They need a package that includes an ambitious CAP reform, providing real support for farmers who need it to be more sustainable; the Nature Restoration Law to improve the standards of good management; and a framework for sustainable food systems to improve the market options for sustainable farming.”

Methane is a far more potent greenhouse gas than carbon dioxide (CO₂). According to the International Energy Agency, the concentration of methane in the atmosphere is currently around two-and-a-half times greater than pre-industrial levels and is increasing steadily, with waste emissions and the burning of fossil fuels accounting for a significant proportion.

The research was published in the Journal of the American Chemical Society.

Australia recently joined the international methane mitigation agreement with the United States, the European Union, Japan and the Republic of Korea.

Lead author, Professor PJ Cullen from the University of Sydney’s School of Chemical and Biomolecular Engineering and Net Zero Initiative said: “Globally, landfills are a major emitter of greenhouse gases, mainly a mixture of CO₂ and methane. We have developed a process that would take these gases and convert them into fuels, targeting sectors that are difficult to electrify, like aviation.”

“Modern landfill facilities already capture, upgrade and combust their gas emissions for electricity generation, however, our process creates a much more environmentally impactful and commercially valuable product,” he said.

Global landfill emissions are estimated at 10-20 million tonnes of greenhouse gases per year, a value comparable to the emissions of the global energy sector.

Aviation currently accounts for approximately three percent of the world’s emissions. Creating a “closed loop” fuel based on existing emissions would eliminate the need for traditional and sustainable jet fuels, which add further emissions into the atmosphere.

How plasma makes the process work

The process would work by extracting methane from a landfill site, known as a methane well, which uses a shaft-like mechanism to extract gases.

“The beauty of this is that this simple process captures almost the exact composition that we need for our process,” said Professor Cullen.

“Non-thermal plasma is an electricity-driven technology which can excite gas at both a low temperature and atmospheric pressure. Essentially, what this means is this approach facilitates the conversion of the gas into value-added products by inducing plasma discharge within forming gas bubbles. The process doesn’t require heat or pressure, meaning it requires less energy, making it highly compatible with renewable energy power sources.”

DISCLOSURE

Authors PJ Cullen, Emma Lovell and Tianqi Zhang are associated with PlasmaLeap Technologies, the supplier of the plasma technology employed to generate plasma bubbles in this study.

The authors acknowledge the MagRes node at Sydney Analytical Core Research Facility for access to the NMR infrastructure, Michelle Wood at Sydney Analytical for additional assistance in ATR-FTIR and Aditya Rawal at the University of New South Wales Mark Wainwright Analytical Centre for solid-state NMR measurements.

The fundamental research sheds light on the biomechanics of the unique hunting behavior (known as mousing), advances our understanding of animal adaptations and offers insights into snow injuries people experience during snowboarding or skiing.

The study published April 29 in the Proceedings of the National Academy of Sciences.

While there have been many studies of water birds and animals such as porpoises and dolphins diving from air into water, interactions between animals and the air-snow interface have not been well-researched. Snow has fluid-like properties when light and fluffy, and solid-like properties when compacted, such as when people make snowballs.

“The fox’s sharp snout doesn’t significantly compress the snow, it penetrates it without much resistance,” said Sunghwan Jung, the paper’s corresponding author and professor of biological and environmental engineering. Jisoo Yuk, a doctoral student in Jung’s lab, is the paper’s first author.

In the study, the authors scanned skulls of red and arctic foxes (from the Canidae family) and lynx and puma skulls (from the Felidae family) at the American Museum of Natural History in Manhattan. They 3D-printed the skulls and attached each to a sensor that measured impact force. The skulls were then dropped into both snow and water, and the researchers entered data into computer models to compare impacts of both.

Jung and colleagues found that the foxes’ sharp snouts penetrated the snow with little resistance, minimizing potential tissue damage during a headfirst dive. “Without much compression, in spite of the high-speed impact, the snow behaves like water,” Jung said. But the flat Felidae snouts compressed the snow upon impact, creating a large and potentially damaging resistance.

When mousing in snow, the fox’s long snout also allows it to reach its prey earlier, as mice are very sensitive to movements in their environment and can quickly escape. Other behavioral studies have shown that prior to pouncing, foxes shake their heads to listen to the rustling sounds of mice or other animals beneath the snow’s surface, thereby gauging the depth of the sound source.

“This is a very dangerous process, but we haven’t had reports of foxes getting injured,” Jung said.

The study was funded by the National Science Foundation.

“For the first time, the new enzyme cocktails not only remove the well-described A and B antigens, but also extended variants previously not recognized as problematic for transfusion safety. We are close to being able to produce universal blood from group B donors, while there is still work to be done to convert the more complex group A blood. Our focus is now to investigate in detail if there are additional obstacles and how we can improve our enzymes to reach the ultimate goal of universal blood production,” says Professor Maher Abou Hachem, who is the study leader at DTU and one of the senior scientists behind the discovery.

He states that the discovery is the result of combining the expertise of DTU researchers in enzymes from the human gut microbiota and Lund University researchers in carbohydrate-based blood groups and transfusion medicine.

High demand for donor blood

Human red blood cells carry specific complex sugars structures (antigens) that define the four ABO blood groups A, B, AB and O. These antigens control compatibility between donors and recipients for safe blood transfusion and organ transplantation. Donor blood is screened for disease markers and the main blood groups. It can then be stored refrigerated for up to 42 days.

The need for donor blood is high due to the elderly making up a larger proportion of the population and more patients undergoing blood-intensive medical procedures. Successfully converting A or B blood types into ABO universal donor blood can markedly reduce the logistics and costs currently associated with storing four different blood types. In addition, the development of universal donor blood will lead to an increased supply of donor blood by reducing the waste of blood approaching its expiry date.

The reason why it is necessary to remove the A and B antigens to create universal donor blood is because they can trigger life-threatening immune reactions when transfused into non-matched recipients.

The concept of using enzymes to generate universal donor blood was introduced more than 40 years ago. Since then, higher efficiency enzymes to remove the A and B antigens were discovered, but researchers are still not able to explain or abolish all immune reactions related to the blood, and therefore these enzymes are still not used in clinical practice.

Enzymes from the gut

The research groups from DTU and Lund University have gone new ways to find enzymes that can remove both the A and B blood antigens and the sugars that block them. The research teams discovered new mixtures of enzymes from the human gut bacterium Akkermansia muciniphila that feeds by breaking down the mucus, which covers the surface of the gut. It turns out that these enzymes are exceptionally efficient, as the complex sugars at the surface of the intestinal mucosa share chemical resemblance with those found at the surface of blood cells.

“What is special about the mucosa is that bacteria, which are able to live on this material, often have tailor-made enzymes to break down mucosal sugar structures, which include blood group ABO antigens. This hypothesis turned out to be correct,” says Maher Abou Hachem.

The researchers in this study tested 24 enzymes, which they used to process hundreds of blood samples.

“Universal blood will create a more efficient utilization of donor blood, and also avoid giving ABO-mismatched transfusions by mistake, which can otherwise lead to potentially fatal consequences in the recipient. When we can create ABO-universal donor blood, we will simplify the logistics of transporting and administering safe blood products, while at the same time minimizing blood waste” says Professor Martin L. Olsson, the leader of the study at Lund University.

The researchers from DTU and Lund University have applied for a patent on the new enzymes and the method for enzyme treatment and expect to make further progress on this in their new joint project over the next three and a half years. If successful, the concept needs to be tested in controlled patient trials before this can be considered for commercial production and clinical use.

The initial research project is funded by the Independent Research Fund Denmark (Technology and Production Sciences, FTP), the Swedish Research Council, ALF grants from the Swedish government and county councils as well as the Knut and Alice Wallenberg Foundation and Research Fund Denmark, Natural Sciences, FNU), while the new continued project is funded by the Novo Nordisk Foundation, Interdisciplinary Synergy Programme.

FACTS:

Donorblood

In Scandinavia, the four main blood types are distributed with approximately 40-45 percent blood type A, the majority of whom are so-called RhD positive and 10-15 percent RhD negative, followed by blood type O with about 40 percent, B with about 10 percent and AB with about 5 percent. Red blood cells from blood group O are the only type that can be used by all receiving patients regardless of ABO type.

Bacterium from the gut

Akkermansia muciniphila is a bacterium found abundantly in the guts of most healthy humans. This bacterium can break down mucus in the gut and produces beneficial compounds such as the short-chain fatty acid propionate, in addition to exerting beneficial effects on body weight and metabolic markers.

It is estimated that up to 85% of stars exist in binary star systems, some even in systems with three or more stars. These stellar pairs are born together out of the same molecular cloud from a shared abundance of chemical building blocks, so astronomers would expect to find that they have nearly identical compositions and planetary systems. However, for many binaries that isn’t the case. While some proposed explanations attribute these dissimilarities to events occurring after the stars evolved, a team of astronomers have confirmed for the first time that they can actually originate from before the stars even began to form.

Led by Carlos Saffe of the Institute of Astronomical, Earth and Space Sciences (ICATE-CONICET) in Argentina, the team used the Gemini South telescope in Chile, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab. With the new, precise Gemini High Resolution Optical SpecTrograph (GHOST) the team studied the different wavelengths of light, or spectra, given off by a pair of giant stars, which revealed significant differences in their chemical make-up. “GHOST’s extremely high-quality spectra offered unprecedented resolution,” said Saffe, “allowing us to measure the stars’ stellar parameters and chemical abundances with the highest possible precision.” These measurements revealed that one star had higher abundances of heavy elements than the other. To disentangle the origin of this discrepancy, the team used a unique approach.

Previous studies have proposed three possible explanations for observed chemical differences between binary stars. Two of them involve processes that would occur well into the stars’ evolution: atomic diffusion, or the settling of chemical elements into gradient layers depending on each star’s temperature and surface gravity; and the engulfment of a small, rocky planet, which would introduce chemical variations in a star’s composition.

The third possible explanation looks back at the beginning of the stars’ formation, suggesting that the differences originate from primordial, or pre-existing, areas of nonuniformity within the molecular cloud. In simpler terms, if the molecular cloud has an uneven distribution of chemical elements, then stars born within that cloud will have different compositions depending on which elements were available at the location where each formed.

So far, studies have concluded that all three explanations are probable; however, these studies focused solely on main-sequence binaries. The ‘main-sequence’ is the stage where a star spends most of its existence, and the majority of stars in the Universe are main-sequence stars, including our Sun. Instead, Saffe and his team observed a binary consisting of two giant stars. These stars possess extremely deep and strongly turbulent external layers, or convective zones. Owing to the properties of these thick convective zones, the team was able to rule out two of the three possible explanations.

The continuous swirling of fluid within the convective zone would make it difficult for material to settle into layers, meaning giant stars are less sensitive to the effects of atomic diffusion — ruling out the first explanation. The thick external layer also means that a planetary engulfment would not change a star’s composition much since the ingested material would rapidly be diluted — ruling out the second explanation. This leaves primordial inhomogeneities within the molecular cloud as the confirmed explanation. “This is the first time astronomers have been able to confirm that differences between binary stars begin at the earliest stages of their formation,” said Saffe.

“Using the precision-measurement capabilities provided by the GHOST instrument, Gemini South is now collecting observations of stars at the end of their lives to reveal the environment in which they were born,” says Martin Still, NSF program director for the International Gemini Observatory. “This gives us the ability to explore how the conditions in which stars form can influence their entire existence over millions or billions of years.”

Three consequences of this study are of particular significance. First, these results offer an explanation for why astronomers see binary stars with such different planetary systems. “Different planetary systems could mean very different planets — rocky, Earth-like, ice giants, gas giants — that orbit their host stars at different distances and where the potential to support life might be very different,” said Saffe.

Second, these results pose a crucial challenge to the concept of chemical tagging — using chemical composition to identify stars that came from the same environment or stellar nursery — by showing that stars with different chemical compositions can still have the same origin.

Finally, observed differences previously attributed to planetary impacts on a star’s surface will need to be reviewed, as they might now be seen as having been there from the very beginning of the star’s life.

“By showing for the first time that primordial differences really are present and responsible for differences between twin stars, we show that star and planet formation could be more complex than initially thought,” said Saffe. “The Universe loves diversity!”