Category: 7. Science

August 1, 2025 by Marni Ellery

UC Berkeley professor Junqiao Wu has spent over a decade working with vanadium dioxide, a compound known for its ability to shift between insulating and metallic states. By harnessing this unusual property, he and his lab have developed innovative technologies ranging from “smart” roofing materials to ultra-precise thermography techniques.

Now, they have discovered a new application for this versatile material. In a study published today (August 1) in Nature Materials, Wu and his team demonstrated how vanadium dioxide can also be used to help electronic sensors more efficiently interface with wet, salty systems — a persistent problem for scientists and engineers.

Using this material, the researchers created a new in-memory sensor, or memsensor, that can both detect and remember its chemical environment, enabling it to adapt to challenging aqueous conditions. And, unlike conventional designs, it can do all of this without external power input or complex circuitry.

“This breakthrough could pave the way for simpler, more energy-efficient sensors and adaptive robots capable of operating in complex environments,” said Wu, the study’s principal investigator and the Chancellor’s Professor in the Department of Materials Science and Engineering. “It may also open exciting possibilities for next-generation computing systems that integrate memory and sensing in liquid settings, much like how biological neurons function in the brain’s wet, ionic environment.”

Based on what they knew about vanadium dioxide, the researchers wondered if the material could potentially be used to help electronic sensors efficiently operate under such conditions.

“While it was already known that vanadium dioxide can switch phases and ‘remember’ changes when doped with certain ions, we wanted to explore whether this could automatically happen in water with mobile ions, similar to how nerve cells in living organisms sense and store information with ion motion,” said Ruihan Guo, lead author of the study and a graduate student researcher in Wu’s lab.

To create their memsensor, the researchers attached a thin layer of vanadium dioxide to a small piece of indium, an extremely soft, silvery metal. When the device is placed in salt water, indium releases ions where the solution touches the vanadium dioxide. With the built-in electric fields at the solid-liquid interface, the ions are drawn to vanadium dioxide’s surface, causing part of the material to turn metallic — a resistance change that persists over time.

This shift in conductivity effectively “records” the history of salt exposure, and the rate of conductivity change correlates with the salt concentration. More importantly, the memsensor can sense and store this information without the need for any external voltage.

“Using vanadium dioxide’s ability to switch between insulating and metallic states, we were able to create a fast, energy-efficient, in-memory sensor capable of operating in salt solutions and retaining information about the salt concentration even when the sensor is taken out of the solutions,” said Guo.

While engineering their memsensor, the researchers took inspiration from the tiny nematode C. elegans. “This worm uses specialized neurons to remember salt exposure and guide its movement toward or away from certain environments when searching for food,” said Guo. “Mimicking this behavior, we used our sensor to direct a small robotic boat to navigate salt gradients — avoiding undesirable zones and seeking favorable ones — based on its prior salt exposure history.”

Wu explained that their memsensing technology may someday be useful in designing low-power aquatic robotics. Such robots could explore underwater or contaminated environments while adapting their movements like living organisms.

“In a broader sense, the underlying principles point toward the possibility of brain-inspired computing in wet environments — just like our own brain, which operates in a salty, aqueous medium,” he said. “In such systems, devices could sense, store and process chemical information spontaneously, all within a single, integrated platform.”

This work was supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. For additional details and a complete list of authors, view the study.

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Caltech scientists have developed a method to create metallic objects of a precisely specified shape and composition, giving them unprecedented control of the metallic mixtures, or alloys, they create and the enhanced properties those creations will display. Want a stent that is biocompatible and mechanically robust? How about strong but lightweight satellite components that can operate in space for decades? The new technique can tell scientists exactly which combination of metals will yield the best product. In addition, it offers a route to making alloys with beneficial properties determined by their underlying structure, such as surprisingly strong copper–nickel alloys.

“If you look at how metallurgy has been done for centuries, in broad strokes, you nearly always start with a raw ore, which is then thermally and/or chemically treated and refined, to produce the desired metal or alloy. And basically, the mechanical properties of the metals produced this way are limited,” says Julia R. Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering at Caltech and executive officer for applied physics and materials science at Caltech. “What we are showing is that you can actually fine-tune the chemical composition and the microstructure of metallic materials, substantially enhancing their mechanical resilience.”

Greer and her colleagues describe the new method in a paper published online by the journal Small. The lead author of the paper is Thomas T. Tran (PhD ’25), and the second author is Rebecca Gallivan (PhD ’23), a former member of the Greer lab who is now an assistant professor of engineering at Dartmouth College.

The new technique builds on previous work from the Greer lab in which the scientists showed how to use a form of 3D printing, or additive manufacturing, to make complex microscale metal structures. Previously, the technique, called hydrogel-infusion additive manufacturing (HIAM), had been used to carefully build structures from a single type of metal. In the new work, Tran has figured out a way to infuse more than one metal at a time, creating copper–nickel alloys containing custom percentages of copper and nickel—differences that matter when it comes to material properties.

The process begins with 3D printing of an organic hydrogel material, depositing the polymer resin precisely where it is wanted, layer by layer, to create a gel-like scaffold. That scaffold is then infused with metal ions by pouring a liquid solution of metallic salts over the structure. Next, in a process called calcination, the scientists burn the material, removing all the organic content and leaving behind the metals. Since this is done in the presence of oxygen, what is left is a mixture of metal oxides.

In an innovative next step, called reductive annealing, Tran raises the temperature in a hydrogen environment causing most of the oxygen to diffuse back out of the solid; it then reacts with hydrogen to form water vapor. This leaves behind a metallic structure of the desired shape that is an alloy of the two added metals.

“The composition can be varied in whatever manner you like, which has not been possible in traditional metallurgy processes,” Greer explains. “One of our colleagues described this work as bringing metallurgy into the 21st century.”

By analyzing the microstructure, which includes the orientation of the individual crystal grains and the boundaries among them within the alloys they produced, and by mechanically testing the materials, the scientists were able to reveal more about the special alloys made with the new technique.

“This lays the groundwork for thinking about 3D-printed alloy design in a unique way from other microscale additive manufacturing techniques,” says Gallivan. “We see that the processing environment leads to very different microstructures in comparison to other methods.”

Using a transmission electron microscope (TEM) at the UC Irvine Materials Research Institute, the Caltech researchers were able to show that alloys produced using their HIAM method form more homogenously, resulting in higher degrees of symmetry throughout their crystal structure, Tran explains. The shape, size, and orientation of metal grains are influenced by the transition between oxide and metal during reductive annealing. At elevated temperatures, pores form as water vapor escapes. Metal grain growth is slowed by these pores and oxides. The new work shows that this growth is modified by the types of oxides present in these 3D-printed metals.

As a result, the new paper shows that the strength of alloys created by HIAM is determined not only by the size of the grains within the metals—as was previously thought— but also by their composition. A Cu12Ni88 alloy with 12 atoms of copper for every 88 atoms of nickel, for example, is nearly four times as strong as a Cu59Ni41 alloy that has copper and nickel in a 59/41 ratio.

The TEM studies also revealed that the HIAM process leaves these alloys with tiny oxide inclusions that contribute to the materials’ exceptional strength. “Because of the complex ways in which metal is formed during this process, we find nanoscale structures rich with metal–oxide interfaces that contribute to the hardening of our alloys by up to a factor of four,” Tran says.

The paper is titled “Multiscale Microstructural and Mechanical Characterization of Cu–Ni Binary Alloys Reduced During Hydrogel Infusion-Based Additive Manufacturing (HIAM).” The work was supported by the US Department of Energy’s Basic Energy Sciences program and by a National Science Foundation graduate fellowship.

A beam of particles speeding away from the vicinity of a monstrous black hole has been found to be severely kinked, providing compelling evidence that the black hole is actually part of the most extreme binary system known.

The black hole and its crooked jet are found in a blazar known as OJ 287, located about four billion light-years away. A blazar is a quasar seen head-on, and a quasar is the active core of a galaxy where the resident supermassive black hole is pulling in huge amounts of matter. That matter spirals around the black hole, forming what’s called an accretion disk, and there’s so much matter that the accretion disk becomes a bottleneck.

Aug. 1 (UPI) — The SpaceX transport of Crew-11 to the International Space Station is ready to launch Friday after Thursday’s scrub.

NASA astronauts Zena Cardman and Mike Fincke, Japan Aerospace Exploration Agency astronaut Kimiya Yui, and Roscosmos cosmonaut Oleg Platonov, arrived at the launch complex, where SpaceX’s Dragon spacecraft is ready for liftoff at 11:43 a.m. EDT Friday. Cardman is the commander, Fincke is the pilot, and Yui and Platonov are mission specialists.

The launch was scrubbed on Thursday just before liftoff due to inclement weather at Kennedy Space Center in Florida. The mission was scheduled for 12:09 p.m. EDT from Launch Complex 39A at Kennedy Space Center aboard a Falcon 9 Rocket.

It will be the first spaceflight for Cardman and Platonov, the second for Yui and the fourth for Fincke. It will be the sixth mission for Endeavour, SpaceX’s most-flown Crew Dragon capsule.

Crew-11 will relieve astronauts who have been at the ISS since March. Crew-11 is 11th operational astronaut mission SpaceX takes to and from the ISS under its contract with NASA’s Commercial Crew Program.

Some science testing on the trip includes:

• Bionutrients 3. How to grow vitamins in space so astronauts can stay healthy on long flights. They’ll be testing yogurt, kefir and a yeast-based drink.
• Stem cell X IP1. Stem cells could one day help fight cancer. Growing them in micro-gravity could help grow more volumes of cells, more cells and better ones than we can make on earth.
• Genes in space 12. This is testing phage therapy, which uses viruses that could target and kill bacteria. It could be a powerful alternative to antibiotics, especially in space, where infections can become harder to treat.

Members of Crew-11 will participate in a series of experiments to address health challenges astronauts may face on deep space missions during NASA’s Artemis campaign and future human expeditions to Mars, as well as other experiments led by NASA’s Human Research Program.

One study will investigate fluid pressure on the brain and another will examine how the body processes B vitamins and whether supplements can affect how astronauts respond to bodily fluid shifts. Some crew members also will wear thigh cuffs to keep bodily fluids from traveling toward their heads. Possible goals of these studies include ways to treat or prevent a group of eye and brain changes that can happen during long-duration space travel.

Another experiment will measure how multiple systems within the human body change in space, using vision assessments, MRI scans, and other medical exams to give a complete overview of the body’s response to long-duration spaceflight.

How do astronauts get a good night’s sleep in space? Erin Flynn-Evans, director of the Fatigue Countermeasures Laboratory at NASA Ames Research Center, joined this week’s Planetary Radio to explore how her team studies sleep, fatigue, and circadian rhythms to keep astronauts healthy and mission-ready. Pictured: Astronaut Marsha Ivins taking a nap on the Space Shuttle Atlantis. Image credit: NASA.

When you wish on a shooting star, you don’t usually wish for it to land on you. But there have been several documented cases of meteorites falling right onto people or their property. In some cases, these space rocks were gifts from above. But in others, they wrought terrible destruction. Read our review of some of the most noteworthy eyewitness accounts of meteorite encounters.

We’re organizing a special Day of Action to oppose the proposed NASA cuts. In response to the unprecedented attack on NASA’s science activities in the FY 2026 budget proposal, The Planetary Society and nearly a dozen partner organizations are holding a joint Day of Action on Oct. 5 and 6 in Washington, D.C. Sign up today, and we’ll train you and set up your meetings with elected officials to push back against the drastic cuts proposed to NASA science.

Dava Sobel has a wonderful talent for writing about the people of science. That’s one of the reasons why The Planetary Society honored her with our 2025 Cosmos Award for the Outstanding Public Presentation of Science. Sobel will join the next meeting of the Society’s virtual, members-only book club on Aug. 5 to talk about her life’s work and answer members’ questions. Not yet a Planetary Society member? Join today.

Matching gift challenge — one week only! Did you know that you can help advance the search for near-Earth objects? With a gift of any amount, you can help power the asteroid hunters who protect our planet. Plus, for one week only, your gift will be matched up to $6,000 thanks to a group of generous Society members who have come together to issue a matching gift challenge!

GA, UNITED STATES, August 1, 2025 /EINPresswire.com/ — A team of researchers has developed a new biosensor that turns the invisible signals into visible color changes to detect urea levels in a simple way. The sensor works by combining gold nanoparticles and a pH-controlled reaction, with a special chemical reaction that changes color depending on the amount of urea. As more urea is present, the reaction slows down, and the gold nanoparticles keep their shape, resulting in a visible color shift. This enables a clear, multicolor visual cue across a wide concentration range. The sensor can detect urea down to 0.098 µM in solution and 0.2 µM in solid form. It significantly outperforms traditional methods and performed well in real urine samples, opening new possibilities for easy, accurate urea monitoring at the point of care.

Urea is a vital indicator of human health, particularly for diagnosing kidney and liver function. It is also widely used in agriculture, where overuse can lead to environmental contamination. While colorimetric tests are popular for their simplicity, most existing tools rely on single-color changes that are difficult to interpret by the naked eye, especially at low concentrations. More advanced methods, like fluorometry or electrochemical sensing, require complex equipment or training, limiting their accessibility. Improving the clarity and sensitivity of urea detection, especially through a visual and low-tech method—could bridge this gap. Due to these challenges, there is a growing need to develop multicolor sensors capable of intuitive, high-resolution readouts for both clinical and environmental use.

Scientists at Sungkyunkwan University, South Korea, have unveiled a multicolor biosensing platform for urea detection, published (DOI: 10.1038/s41378-025-00931-5) on June 5, 2025, in Microsystems & Nanoengineering. The new sensor uses an enzyme called urease to break down urea to produce ammonia and raise the pH. This rise in pH prevents the chemical reaction that would normally change the gold nanoparticles. As a result, the particles keep their shape. Unlike conventional tests, this biosensor offers five visually distinct colors: blue, violet, purple, pink, and red, depending on the urea level. that can be read by the naked eye. The team validated the sensor’s performance in both liquid and solid formats, paving the way for convenient, ultra-sensitive urea testing in clinical and field settings.

To make the sensor more practical and easier to handle, the team also developed a solid version using a gel by embedding the sensing chemistry into a hydrogel. This makes it easier to store and use. Both the liquid and solid versions worked well and were not affected by other substances in urine. The sensor’s performance rivaled that of commercial urea kits, while offering the unique advantage of real-time, multicolor visual feedback. A built-in self-validation feature further ensures reliability by showing a clear color change only when all components function properly, making the sensor both powerful and foolproof.

“This sensor is not only technically advanced but also user-centric,” said Professor Dong-Hwan Kim, senior author of the study. “Its multicolor output allows anyone—even without lab training—to interpret results clearly and quickly. By controlling the Fenton etching through a simple pH shift, we’ve unlocked a highly tunable visual signal that outperforms many current diagnostic tools. We believe this is a significant step forward for point-of-care diagnostics, especially in resource-limited settings.”

This visually intuitive biosensor holds enormous potential for healthcare and environmental monitoring. Its solid-state format simplifies storage and usage, making it ideal for portable diagnostic kits, home testing, and rural clinics. In medical settings, the sensor can offer early warnings of kidney dysfunction or metabolic imbalance through simple urine analysis. In agriculture, it could be adapted for on-site detection of urea-based fertilizer runoff. Moreover, the underlying principle—pH-modulated nanoparticle etching—could be expanded to detect other analytes using similar strategies. With its combination of accuracy, ease of use, and multicolor feedback, this biosensor represents a meaningful leap toward accessible, next-generation diagnostics.

DOI
10.1038/s41378-025-00931-5

Original Source URL
https://doi.org/10.1038/s41378-025-00931-5

Funding information
This work was supported by the Institute for Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (RS-2023-00228994), RS-2024-00346003, and the National Research Foundation of Korea (2020R1A5A1018052) and (RS-2024-00410209).

Lucy Wang
BioDesign Research
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