Wednesday, January 15, 2025

New research helps eliminate dead zones in desalination technology and beyond

University of Illinois at Urbana-Champaign, News Bureau

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Researchers from the University of Illinois Urbana-Champaign are leading the charge toward wide-scale implementation of water desalination by developing an efficient new electrode for use in battery-based desalination.
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Credit: Photo by Fred Zwicky

CHAMPAIGN, Ill. — Engineers have found a way to eliminate the fluid flow “dead zones” that plague the types of electrodes used for battery-based seawater desalination. The new technique uses a physics-based tapered flow channel design within electrodes that moves fluids quickly and efficiently, potentially requiring less energy than reverse osmosis techniques currently require.

Technical hurdles have prevented the wide-scale implementation of desalination technology. The most-used method, reverse osmosis, pushes water through a membrane that filters out the salt and is costly and energy-intensive. By contrast, the battery method uses electricity to draw charged salt ions out of the water. Still, it also requires energy to help push the water through electrodes that contain tiny, nonuniform pore spaces.

“Traditional electrodes still require energy to pump fluids through because they do not contain any inherently structured flow channels,” said University of Illinois Urbana-Champaign mechanical science and engineering professor Kyle Smith, who led the study. “However, by creating channels within the electrodes, the technique could require less energy to push the water through and eventually become more efficient than what is commonly used in the reverse-osmosis process.”

Smith’s battery-based desalination technique builds from years of modeling and experiments by his research group at Illinois, culminating in a recent study demonstrating the first use of electrodes containing tiny microchannels called interdigitated flow fields.

The group’s new study also incorporates IDFFs in electrodes, but this time the channel shape is tapered, not straight. Using electrodes with tapered channels improved fluid flow — or permeability —two to three times over straight channels. The findings are published in the journal Electrochimica Acta.

“Our initial work on straight channels in electrodes led us to discover dead zones within the electrodes where we saw pressure drops and nonuniform flow distribution,” said Illinois graduate student Habib Rahman. “To overcome this challenge, we created a library of 28 different straight channels to experiment with and understand conductance and flow variation, and eventually implemented this channel-tapering technique.”

While performing the experiments, Smith and Rahman said they faced some manufacturing challenges, particularly with the time it takes to mill the channels into the electrodes, which would be problematic in any scaled-up production scenario. However, Smith said they are confident this challenge can be overcome.

Click here to view a video about this research.

“Beyond its impact toward electrochemical desalination, our channel-tapering theory and associated design principles can be applied directly to any other electrochemical device that uses flowing fluids, including those for energy storage conversion and environmental sustainability like fuel cells, electrolysis cells, flow batteries, carbon capture devices and lithium recovery devices,” Smith said. “Unlike prior channel-tapering strategies that used impromptu designs, our approach here provides physics-based design guidelines to create uniform flow and minimize pressure drops simultaneously.”

The Office of Naval Research supported this study. Smith, Rahman and study coauthors Irwin Loud IV, Vu Do and Abdul Hamid have patents pending under the U.S. patent applications 17/980,017, 17/980,023, and 63/743,995.

Smith is also affiliated with material science and engineering and the Beckman Institute for Advanced Science and Technology.

Editor’s note:

To reach Kyle Smith, email kcsmith@illinois.edu.

The paper “Tapered, interdigitated channels for uniform, low-pressure flow through porous electrodes for desalination and beyond” is available online. DOI: 10.1016/j.electacta.2024.145632.

Mechanical science and engineering and material science and engineering are part of The Grainger College of Engineering at Illinois.

Journal

Electrochimica Acta

DOI

10.1016/j.electacta.2024.145632

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Tapered, interdigitated channels for uniform, low-pressure flow through porous electrodes for desalination and beyond

Article Publication Date

15-Jan-2025

COI Statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kyle C. Smith reports that financial support was provided by Office of Naval Research. Kyle C. Smith, Irwin C. Loud IV, and Vu Q. Do have patent #US Patent App. 17/980,017 pending. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Mosquitoes can be extra-bitey in droughts

Findings explain why rates of mosquito-borne disease don't always fall in dry periods

University of Cincinnati

Mosquitoes can survive prolonged droughts by drinking blood, which helps to explain how their populations quickly rebound when it finally rains, biologists at the University of Cincinnati said.

UC postdoctoral researcher Christopher Holmes led a study examining how two species of mosquito known for infecting people with diseases such as malaria were able to survive nearly three weeks without rain.

The findings could help explain why the incidence of infection from mosquito-borne illness does not always decline during droughts. While there may be fewer mosquitoes, those that survive bite more often.

“We’re finding that mosquitoes bite people more than we imagined, unfortunately,” Holmes said.

And mosquitoes appear to be benefiting from climate change as winters get warmer, Holmes said.

The study was published in the journal iScience.

Holmes said under favorable conditions, female mosquitoes draw blood from a host to fuel egg production. About four days later, the mosquitoes lay their eggs and seek another blood meal to repeat the process.

But during droughts, mosquitoes will supplement their initial blood meal by feeding again and again to stay hydrated in the days before laying eggs. And this could give mosquitoes more opportunity to spread diseases like dengue fever, Zika or malaria, he said.

“Everyone is under the assumption that during drought there are fewer mosquitoes and less opportunity to spread mosquito-borne illness. But the modeling doesn’t necessarily show that,” co-author and UC Professor Joshua Benoit said.

The study examined mosquitoes that were genetically altered to impair particular senses such as the ability to detect carbon dioxide, key to finding people or animals to bite. They also impaired some mosquitoes’ ability to sense changing humidity levels.

They found that carbon dioxide-impaired mosquitoes did not survive dry periods because they could not find hosts to bite.

Co-author and UC doctoral student Souvik Chakraborty said even the eggs of mosquitoes have impressive abilities to withstand long periods of drought.

“The Aedes aegypti mosquito is resistant to drying out. Its eggs can survive sometimes for as long as a year,” he said. “You’ll get rainfall and the water level rises and as soon as it touches the eggs, they hatch like magic.”

Likewise, UC postdoctoral researcher and study coauthor Oluwaseun Ajayi said mosquitoes in the genus Culex, which are found around the world, can tolerate cold temperatures, too.

“They’re often called a house mosquito,” Holmes added. “They’ll hide out in cellars or culverts. Before winter, they’ll drink nectar and get really fat, building up these huge lipid deposits. And then when it gets warm enough, they’ll quickly seek a blood meal, lay eggs and die.”

Lead researcher Holmes said the team’s latest findings give him a greater appreciation for the improbably long history of mosquitoes on Earth. The oldest mosquitoes date back to the early Cretaceous 125 million years ago. They are an integral part of the food chain, feeding everything from fish to birds to bats and other insects.

Today, the diseases they spread are responsible for killing more than 700,000 people each year.

Benoit said the study demonstrates the resilience of these insects that predate dinosaurs.

“They live almost everywhere except Antarctica. They tolerate a wide range of habitats,” he said. “Knowing more about theri biology is critical to understanding how they survive and reproduce.”

University of Cincinnati researcher Christopher Holmes works with mosquitoes in a biology lab.

University of Cincinnati postdoctoral researcher Oluwaseun Ajayi works with mosquitoes in a biology lab.

Credit

Andrew Higley