Each year, roughly 2.47 billion gallons of lubricating oil are consumed in the United States alone for engines and industrial machinery, according to DOE, with about half eventually finding its way into the environment.

While environmentally acceptable lubricants are available, they are not optimized with additives that can greatly improve performance while posing minimal environmental impact if accidentally released. To create nontoxic, biodegradable and high-performing lubricant additives for water power turbines, researchers turned to ionic liquids, or ILs: organic liquid salts that mix well with oil, reduce friction between bearings and gears, and are stable in a range of temperatures.

A team of materials and environmental scientists at ORNL worked together to design, synthesize and test top-candidate ILs of ammonium phosphate and phosphonium phosphate that provide a good mix of properties.

When added to base oils, the ILs demonstrated 50% less friction and a tenfold decrease in equipment wear compared to a commercially available gear oil, while meeting federal standards for environmental toxicity and biodegradability, as described in ACS Sustainable Chemistry & Engineering

The project builds on more than 20 years of IL research at ORNL, including the development of lubricant additives designed to reduce engine wear and boost fuel economy in vehicles.

“Our previous work showed us that you could dramatically increase the performance of lubricants with the addition of just 1% or even a half-percent of ILs,” said ORNL’s Jun Qu, who leads the project and the Surface Engineering and Tribology group at ORNL.

This time around, scientists sought to create a nontoxic additive for use in turbines installed in aquatic environments, generating electricity using waves, tides, ocean and river currents. Although ILs are generally considered less toxic than conventional lubricant ingredients, their impact on the environment has not been closely studied.

“On the environmental side, there are three main factors we care about with these lubricants,” said Teresa Mathews, lead for the Biodiversity and Ecosystem Health group at ORNL. “They have to be highly performing, we don’t want them to be toxic to any aquatic organisms, and if there’s a spill, we don’t want the lubricants to be compounds that last in the environment. We want them to degrade very rapidly.”

Pursuing a cleaner formula

The team first sought to eliminate potential toxic elements such as fluorine and chlorine and metals such as zinc and iron from the candidate ILs. They also focused on creating ILs made up of shorter hydrocarbon chains — chains containing fewer than six carbon atoms — which are generally considered to be less toxic.

“We found a four-carbon chain to be the sweet spot,” Qu said. Going shorter than four carbons resulted in an IL that didn’t mix well with oil and was less thermally stable, he added.

Friction testing was accomplished with metal pieces simulating turbine gears and bearings coated with a lubricant containing the IL. Resulting surface wear of the pieces was characterized using electron microscopy at the Center for Nanophase Materials Sciences, a DOE Office of Science user facility at ORNL.

These particular ILs are fairly straightforward to produce and can be easily scaled up for commercialization, said Huimin Luo, a chemist in ORNL’s Manufacturing Science Division who led the chemical synthesis work.

To determine the additives’ environmental impact, ORNL ecotoxicologist Louise Stevenson conducted toxicity and biodegradability tests in ORNL’s Environmental Toxicology Laboratory, where assessments are routinely conducted for DOE, the Department of Defense and other agencies. Following Environmental Protection Agency protocols, the toxicity tests used Ceriodaphnia, tiny planktonic crustaceans commonly known as water fleas that sit at the bottom of the food chain, have a short life cycle and rapid reproduction rate, and are highly sensitive to environmental conditions.

Tiny plankton provide big insights

The organisms “are like canaries in a coal mine for aquatic toxicity because they are filter feeders and interact with a lot of water,” Stevenson said. “In a seven-day test, we’ll get three to four rounds of reproduction with daily hatching, so we can look for both lethal effects and sublethal effects such as reproductive and growth impacts that have an effect on population survival.”

While the environmentally acceptable lubricant base oils had no effect on the crustaceans, the commercial lubricant additives and two early IL compounds were found to be extremely toxic to the organisms, resulting in 100% mortality within one to three days after exposure. The team’s ultimate designs for short-chain ammonium phosphate and phosphonium phosphate IL additives resulted in 90-100% survival rates after seven days.

The final, top-performing IL-enhanced lubricants were also found to be highly biodegradable compared to standard lubricant additives. Testing involved exposing the compounds to aquatic microbes and then measuring the rate of carbon dioxide production as the microbes broke down the materials.

High-performing, environmentally friendly lubricants designed specifically for marine energy turbines are important for other reasons, including equipment durability. Lubricant technology currently in use for marine turbines was borrowed from wind turbines, which are serviced every six to 18 months, Qu said. But tidal turbines installed in the ocean or rivers are typically designed for service every six years and operate under much harsher conditions.

The project is expected to next focus on further development of IL lubricant additives specifically for use in tidal turbines operating in the ocean and exposed to potential seawater contamination and pressure and temperature extremes.

In a study published recently in Cell Reports Physical Science, Fleeman showed that an antimicrobial peptide from cows has potential for treating incurable infections from the bacterium Klebsiella pneumoniae. The bacteria, commonly found in the intestines, is usually harmless. It becomes a health hazard when it enters other parts of the body and can cause pneumonia, urinary tract and wound infections. Those at highest risk include seniors and patients with other health problems such as diabetes, cancer, kidney failure and liver disease. However, younger adults and people without additional health problems can acquire urinary tract and wound infections from the bacteria that cannot be treated by antibiotics available today.

The CDC reports that antibiotic resistant bacteria are a growing global health threat. A 2019 study found that nearly 5 million people died worldwide that year from drug-resistant infections. A large portion of those deaths are attributable to K. pneumoniae because it has a 50% death rate without antibiotic therapy.

These bacteria are more resistant to drugs when they live in a biofilm — microorganisms that stick together and are embedded in a protective slime. Recent studies have shown that 60-80% of infections are associated with bacteria biofilms, which increase their drug resistance.

“It’s Iike a coat that bacteria put around itself,” Fleeman says.

Her research is examining ways to remove the protective coat and expose the bacteria so it can be killed by the body’s immune system or antibiotics that currently cannot pass through the biofilm. Through that research, Fleeman discovered how the peptides made by cows can quickly kill K. pneumoniae.

She determined that the peptides interact with sugar connections that keep the slime intact. She likened the process to cutting into a chain-linked fence. Once multiple chains are cut, the integrity of the slime structure is damaged, and the peptide can enter and destroy the bacteria that are no longer protected.

“Our research has shown polyproline peptide can penetrate and begin to break the slime barrier down in as little as an hour after treatment,” says Fleeman.

The peptide has another advantage — once it breaks through the protective slime barrier, tests showed it killed the bacteria better than antibiotics used as a last resort to treat incurable infections. Peptides kill the bacteria by punching holes in their cell membrane, causing death quickly compared to other antibiotics that inhibit growth from inside the cell.

The peptide could also be used as a topical treatment for a wide range of uses, especially for the military, to treat open wounds in the field. “Bacteria divide every 30 minutes, so you have to act fast,” Fleeman says.

The next phase of her research will seek to understand the biology behind the peptide’s efficacy and if combinations of other drugs would aid in its application.

Her research is funded through a three-year National Institutes of Health funding Pathway to Independence R00 grant and is in its second year. Her study initially started as a K99 award at University of Texas at Austin, where she worked before joining UCF in September of 2022.

Fleeman says research into resistant infections must continue because they pose such a threat to health.

“It is estimated that by 2050, antibiotic resistant bacterial infections will be the number one cause of human deaths,” she says. “Our work is focused on preparing for this post-antibiotic era battle, where common antibiotics that we take for granted will no longer be effective, jeopardizing cancer therapy, organ transplants, and any modern medical advancement that relies on effective antibiotic therapies.”

Archaea are a distinct group of microbes, similar to bacteria*. The team of NIOZ microbiologists studies the so-called DPANN-archaea, that have particularly tiny cells and relatively little genetic material. The DPANN archaea are about half of all known archaea and are dependent on other microbes for their livelihood: they attach to their host and take lipids from them as building material for their membrane, their own outer layer.

Picky eaters

So far, it was thought that these parasitic archaea just eat any kind of lipids from their host to construct their membrane. But for the first time, Ding and Hamm were able to show that the parasitic archaeon Candidatus Nanohaloarchaeum antarcticus does not contain all the lipids that his host Halorubrum lacusprofundi contains, but only a selection of them. “In other words: Ca. N. antarcticus is a picky eater,” Hamm concludes.

Host responds to parasite

By analyzing the lipids in the host with or without their parasites, Ding and Hamm were also able to show that the host responds to the presence of their parasites. The hosts change their membrane, not only which types of lipids and the amounts of each type that are used, but also modifying the lipids to change how they behave. The result is an increased metabolism and a more flexible membrane that is also harder for the parasite to get through. That could have some consequences for the host, explains Hamm. ‘If the membrane of the host changes, this could have an impact on how these hosts can respond to environmental changes, in for example temperature or acidity.”

Game-changing new technique

The game-changer in this microbiological research was the design of a new analytical technique by Su Ding at NIOZ. Thus far, to analyze lipids you needed to know what lipid groups you were looking for and target them in the analysis. Ding designed a new technique in which he can look at all lipids simultaneously, also the ones you don’t know yet. “We probably wouldn’t have been able to see the changes in the lipids if we had used a classical approach, but the new approach made it straightforward,” says Hamm.

New insight

The microbiologists are very excited about these new findings. “Not only does it shed a first light on the interactions between different archaea; it gives a totally new insight in the fundamentals of microbial ecology,” Hamm says. “Especially that we’ve now demonstrated that these parasitic microbes can affect the metabolism of other microbes, which in turn could alter how they can respond to their environment. Future work is needed to determine to what extent this may impact the stability of the microbial community in changing conditions.”

Archaea, bacteria and higher organisms

Archaea are single celled organisms that were long believed to be a specific group of bacteria. Similar to bacteria, they do not have a nucleus with dna, or other organelles within their cells. As of the 1970’s, however, microbiologists no longer consider archaea bacteria, but classify them as a separate domain in all life forms. So, now we have archaea, bacteria, and eukaryotes, the latter including all animals and plants, that have a nucleus with genetic material in their cells. 

The researchers combined 2019 satellite observations with an atmospheric transport model to generate a high-resolution map of methane emissions, which was then compared to EPA estimates from the same year. The researchers found:

• Methane emissions from landfills are 51% higher compared to EPA estimates
• Methane emissions from 95 urban areas are 39% higher than EPA estimates
• Methane emissions from the 10 states with the highest methane emissions are 27% higher than EPA estimates

“Methane is the second largest contributor to climate change behind carbon dioxide so it’s really important that we quantify methane emissions at the highest possible resolution to pinpoint what sources it is coming from,” said Hannah Nesser, a former PhD student at SEAS and first author of the paper. Nesser is currently a NASA Postdoctoral Program (NPP) Fellow in the Carbon Cycle & Ecosystems Group at the Jet Propulsion Laboratory.

The research, published in Atmospheric Chemistry and Physics, was a collaboration between scientists at Harvard and an interdisciplinary team of researchers from across the U.S. and around the world, including universities in China and the Netherlands.

The EPA estimates that landfills are the third-largest source of human-caused methane emissions in the U.S., but the EPA uses a bottom-up accounting method that often doesn’t match observations of atmospheric methane.

The EPA methane estimate for landfills uses the Greenhouse Gas Reporting Program, which requires high-emitting facilities to self-report their emissions annually. For landfills without methane capture, the emissions are simply calculated by looking at the amount of trash that comes in and estimating how much methane trash produces over time. That figure is then scaled up to include landfill operations that don’t report to the Greenhouse Gas Reporting Program.

Nesser and her colleagues’ top-down approach uses observations of atmospheric methane from the Tropospheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor satellite together with an atmospheric transport model to trace the path of emissions from the atmosphere back to the ground.

Using this method, the team zoomed in on 70 individual landfills across the U.S. In these facilities, the researchers found emissions that were on median 77% higher than the estimates from the Greenhouse Gas Reporting Program.

The disparity is wider for landfills that collect methane as part of their operations.

Landfills don’t measure the exact amounts of methane they are losing but rather estimate how efficient their collection systems are. The EPA assumes the default efficacy rate for methane collection is 75%.

But Nesser and her colleagues found that, in fact, landfills are much less effective at collecting methane than previously thought.

Of the 70 landfills the team studied, 38 recover gas. Among those facilities, the researchers found that methane levels were on median more than 200% higher than the estimates from the Greenhouse Gas Reporting Program.

“Our research shows that these facilities are losing more methane than they think,” said Nesser. “The EPA uses 75% efficacy as the default for methane collection, but we find that it’s actually much closer to 50%.”

The EPA estimates also do not capture one-off events, such as construction projects or temporary leaks, which could lead to a massive increase in methane emissions and contribute to the discrepancy between EPA estimates and observed atmospheric methane.

The research team also compared their analysis to the EPA’s new state-level greenhouse gas inventories.

The researchers found 27% higher methane emissions from the 10 top methane-producing states, with the largest increases in Texas, Louisiana, Florida, and Oklahoma. The team found that those 10 states are responsible for 55% of U.S. human-caused methane emissions. Perhaps unsurprisingly, Texas is responsible for 21% of anthropogenic methane emissions in the U.S., 69% of which is from the oil and gas industry.

At the city level, the researchers found that, on average, the 10 cities with the highest urban methane emissions actually have 58% higher emissions than previously estimated. Those cities include New York, Detroit, Atlanta, Dallas, Houston, Chicago, Los Angeles, Cincinnati, Miami and Philadelphia.

“All of these places have a different profile of emission sources, so there’s no one thing driving the methane underestimate across the board,” said Nesser.

The researchers hope that future work will provide more clarity on exactly where these emissions are coming from and how they are changing.

“This research highlights the importance of understanding these emissions,” said Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS and senior author of the paper. “We plan to continue to monitor U.S. emissions of methane using new high-resolution satellite observations, and to work with the EPA to improve emission inventories.”

The research was co-authored by Joannes D. Maasakkers, Alba Lorente, Zichong Chen, Xiao Lu, Lu Shen, Zhen Qu, Melissa P. Sulprizio, Margaux Winter, Shuang Ma, A. Anthony Bloom, John R. Worden, Robert N. Stavins and Cynthia A. Randles.

It was supported by the NASA Carbon Monitoring System (CMS) and the Harvard Climate Change Solutions Fund.

“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.