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EVs that go 1,000 km on a single charge: Gel makes it possible

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EVs that go 1,000 km on a single charge: Gel makes it possible


Futuristic advancements in AI and healthcare stole the limelight at the tech extravaganza Consumer Electronics Show (CES) 2024. However, battery technology is the game-changer at the heart of these innovations, enabling greater power efficiency. Importantly, electric vehicles are where this technology is being applied most intensely. Today’s EVs can travel around 700km on a single charge, while researchers are aiming for a 1,000km battery range. Researchers are fervently exploring the use of silicon, known for its high storage capacity, as the anode material in lithium-ion batteries for EVs. However, despite its potential, bringing silicon into practical use remains a puzzle that researchers are still working hard to piece together.

Enter Professor Soojin Park, PhD candidate Minjun Je, and Dr. Hye Bin Son from the Department of Chemistry at Pohang University of Science and Technology (POSTECH). They have cracked the code, developing a pocket-friendly and rock-solid next-generation high-energy-density Li-ion battery system using micro silicon particles and gel polymer electrolytes. This work was published on the online pages of Advanced Science on the 17th of January.

Employing silicon as a battery material presents challenges: It expands by more than three times during charging and then contracts back to its original size while discharging, significantly impacting battery efficiency. Utilizing nano-sized silicon (10-9m) partially addresses the issue, but the sophisticated production process is complex and astronomically expensive, making it a challenging budget proposition. By contrast, micro-sized silicon (10-6m) is superbly practical in terms of cost and energy density. Yet, the expansion issue of the larger silicon particles becomes more pronounced during battery operation, posing limitations for its use as an anode material.

The research team applied gel polymer electrolytes to develop an economical yet stable silicon-based battery system. The electrolyte within a lithium-ion battery is a crucial component, facilitating the movement of ions between the cathode and anode. Unlike conventional liquid electrolytes, gel electrolytes exist in a solid or gel state, characterized by an elastic polymer structure that has better stability than their liquid counterparts do.

The research team employed an electron beam to form covalent linkages between micro-silicon particles and gel electrolytes. These covalent linkages serve to disperse internal stress caused by volume expansion during lithium-ion battery operation, alleviating the changes in micro silicon volume and enhancing structural stability.

The outcome was remarkable: The battery exhibited stable performance even with micro silicon particles (5μm), which were a hundred times larger than those used in traditional nano-silicon anodes. Additionally, the silicon-gel electrolyte system developed by the research team exhibited ion conductivity similar to conventional batteries using liquid electrolytes, with an approximate 40% improvement in energy density. Moreover, the team’s system holds significant value due to its straightforward manufacturing process that is ready for immediate application.

Professor Soojin Park stressed: “We used a micro-silicon anode, yet, we have a stable battery. This research brings us closer to a real high-energy-density lithium-ion battery system.”

This study was conducted with the support from the Independent Researcher Program of the National Research Foundation of Korea.



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The unintended consequences of success against malaria

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EVs that go 1,000 km on a single charge: Gel makes it possible


For decades, insecticide-treated bed nets and indoor insecticide spraying regimens have been important — and widely successful — treatments against mosquitoes that transmit malaria, a dangerous global disease. Yet these treatments also — for a time — suppressed undesirable household insects like bed bugs, cockroaches and flies.

Now, a new North Carolina State University study reviewing the academic literature on indoor pest control shows that as the household insects developed resistance to the insecticides targeting mosquitoes, the return of these bed bugs, cockroaches and flies into homes has led to community distrust and often abandonment of these treatments — and to rising rates of malaria.

In short, the bed nets and insecticide treatments that were so effective in preventing mosquito bites — and therefore malaria — are increasingly viewed as the causes of household pest resurgence.

“These insecticide-treated bed nets were not intended to kill household pests like bed bugs, but they were really good at it,” said Chris Hayes, an NC State Ph.D. student and co-corresponding author of a paper describing the work. “It’s what people really liked, but the insecticides are not working as effectively on household pests anymore.”

“Non-target effects are usually harmful, but in this case they were beneficial,” said Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State and co-corresponding author of the paper.

“The value to people wasn’t necessarily in reducing malaria, but was in killing other pests,” Hayes added. “There’s probably a link between use of these nets and widespread insecticide resistance in these house pests, at least in Africa.”

The researchers add that other factors — famine, war, the rural/city divide, and population displacement, for example — also could contribute to rising rates of malaria.

To produce the review, Hayes combed through the academic literature to find research on indoor pests like bed bugs, cockroaches and fleas, as well as papers on malaria, bed nets, pesticides and indoor pest control. The search yielded more than 1,200 papers, which, after an exhaustive review process, was whittled down to a final count of 28 peer-reviewed papers fulfilling the necessary criteria.

One paper — a 2022 survey of 1,000 households in Botswana — found that while 58% were most concerned with mosquitoes in homes, more than 40% were most concerned with cockroaches and flies.

Hayes said a recent paper — published after this NC State review was concluded — showed that people blamed the presence of bed bugs on bed nets.

“There is some evidence that people stop using bed nets when they don’t control pests,” Hayes said.

The researchers say that all hope is not lost, though.

“There are, ideally, two routes,” Schal said. “One would be a two-pronged approach with both mosquito treatment and a separate urban pest management treatment that targets pests. The other would be the discovery of new malaria-control tools that also target these household pests at the same time. For example, the bottom portion of a bed net could be a different chemistry that targets cockroaches and bed bugs.

“If you offer something in bed nets that suppresses pests, you might reduce the vilification of bed nets.”

The study appears in Proceedings of the Royal Society B. The review was supported in part by the Blanton J. Whitmire Endowment at NC State, and grants from the U.S. Department of Housing and Urban Development Healthy Homes program (NCHHU0053-19), the Department of the Army, U.S. Army Contracting Command, Aberdeen Proving Ground, Natick Contracting Division, Ft. Detrick, Maryland (W911QY1910011), and the Triangle Center for Evolutionary Medicine (257367).



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Drawing water from dry air

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EVs that go 1,000 km on a single charge: Gel makes it possible


Earth’s atmosphere holds an ocean of water, enough liquid to fill Utah’s Great Salt Lake 800 times.

Extracting some of that moisture is seen as a potential way to provide clean drinking water to billions of people globally who face chronic shortages.

Existing technologies for atmospheric water harvesting (AWH) are saddled with numerous downsides associated with size, cost and efficiency. But new research from University of Utah engineering researchers has yielded insights that could improve efficiencies and bring the world one step closer to tapping the air as a culinary water source in arid places.

The study unveils the first-of-its-kind compact rapid cycling fuel-fired AWH device. This two-step prototype relies on adsorbent materials that draw water molecules out of non-humid air, then applies heat to release those molecules into liquid form, according to Sameer Rao, senior author of the study published Monday and an assistant professor of mechanical engineering.

“Hygroscopic materials intrinsically have affinity to water. They soak up water wherever you go. One of the best examples is the stuff inside diapers,” said Rao, who happens to be the father of an infant son. “We work with a specific type of hygroscopic material called a metal organic framework.”

Rao likened metal organic frameworks to Lego blocks, which can be rearranged to build all sorts of structures. It this case they are arranged to create a molecule ideal for gas separation.

“They can make it specific to adsorb water vapor from the air and nothing else. They’re really selective,” Rao said. Developed with graduate student Nathan Ortiz, the study’s lead author, this prototype uses aluminum fumarate that was fashioned into panels that collect the water as air is drawn through.

“The water molecules themselves get trapped on the surfaces of our material, and that’s a reversible process. And so instead of becoming ingrained into the material itself, it sits on the walls,” Ortiz said. “What’s special about these absorbent materials is they have just an immense amount of internal surface area. There’s so many sites for water molecules to get stuck.”

Just a gram of this material holds as much surface area as two football fields, according to Rao. So just a little material can capture a lot of water.

“All of this surface area is at the molecular scale,” Rao said. “And that’s awesome for us because we want to trap water vapor onto that surface area within the pores of this material.”

Funding for the research came from the DEVCOM Soldier Center, a program run by the Department of Defense to facilitate technology transfer that supports Army modernization. The Army’s interest in the project stems from the need to keep soldiers hydrated while operating in remote areas with few water sources.

“We specifically looked at this for defense applications so that soldiers have a small compact water generation unit and don’t need to lug around a large canteen filled with water,” Rao said. “This would literally produce water on demand.”

Rao and Ortiz have filed for a preliminary patent based on the technology, which addresses non-military needs as well.

“As we were designing the system, I think we also had perspective of the broader water problem. It’s not just a defense issue, it’s very much a civilian issue,” Rao said. “We think in terms water consumption of a household for drinking water per day. That’s about 15 to 20 liters per day.”

In this proof of concept, the prototype achieved its target of producing 5 liters of water per day per kilogram of adsorbent material. In a matter of three days in the field, this devise would outperform packing water, according to Ortiz.

In the device’s second step, the water is precipitated into liquid by applying heat using a standard-issue Army camping stove. This works because of the exothermic nature of its water collecting process.

“As it collects water, it’s releasing little bits of heat. And then to reverse that, we add heat,” Ortiz said. “We just put a flame right under here, anything to get this temperature up. And then as we increase the temperature, we rapidly release the water molecules. Once we have a really humid airstream, that makes condensation at ambient temperature much easier.”

Nascent technologies abound for atmospheric water harvesting, which is more easily accomplished when the air is humid, but none has resulted in equipment that can be put to practical use in arid environments. Ortiz believes his device can be the first, mainly because it is powered with energy-dense fuel like the white gasoline used in camping stoves.

The team decided against using photovoltaics.

“If you’re reliant on solar panels, you’re limited to daytime operation or you need batteries, which is just more weight. You keep stacking challenges. It just takes up so much space,” Ortiz said. “This technology is superior in arid conditions, while refrigeration is best in high humidity.”



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3D-printed microstructure forest facilitates solar steam generator desalination

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Faced with the world’s impending freshwater scarcity, a team of researchers in Singapore turned to solar steam generators (SSGs), which are emerging as a promising device for seawater desalination. Desalination can be a costly, energy-intensive solution to water scarcity. This renewable-powered approach mimics the natural water cycle by using the sun’s energy to evaporate and isolate water. However, the technology is limited by the need to fabricate complex topologies to increase the surface area necessary to achieve high water evaporation efficiency.

To overcome this barrier, the team sought design inspiration from trees and harnessed the potential of 3D printing. In Applied Physics Reviews, the team presents a state-of-the-art technology for producing efficient SSGs for desalination and introduces a novel method for printing functional nanocomposites for multi-jet fusion (MJF).

“We created SSGs with exceptional photothermal performance and self-cleaning properties,” said Kun Zhou, a professor of mechanical engineering at Nanyang Technological University. “Using a treelike porous structure significantly enhances water evaporation rates and ensures continuous operation by preventing salt accumulation — its performance remains relatively stable even after prolonged testing.”

The physics behind their approach involves light-to-thermal energy conversion, where the SSGs absorb solar energy, convert it to heat, and evaporate the water/seawater. The SSG’s porous structure helps improve self-cleaning by removing accumulated salt to ensure sustained desalination performance.

“By using an effective photothermal fusing agent, MJF printing technology can rapidly create parts with intricate designs,” he said. “To improve the photothermal conversion efficiency of fusing agents and printed parts, we developed a novel type of fusing agent derived from metal-organic frameworks.”

Their SSGs were inspired by plant transpiration and are composed of miniature tree-shaped microstructures, forming an efficient, heat-distributing forest.

“Our bioinspired design increases the surface area of the SSG,” said Zhou. “Using a treelike design increases the surface area of the SSG, which enhances the water transport and boosts evaporation efficiency.”

One big surprise was the high rate of water evaporation observed in both simulated environments and field trials. The desalinated water consistently met standards for drinking water — even after a long-time test.

“This demonstrates the practicality and efficiency of our approach,” Zhou said. “And it can be quickly and easily mass-produced via MJF commercial printers.”

The team’s work shows significant potential for addressing freshwater scarcity.

“Our SSGs can be used in regions with limited access to freshwater to provide a sustainable and efficient desalination solution,” said Zhou. “Beyond desalination, it can be adapted for other applications that require efficient solar energy conversion and water purification.”



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