Tag Archives: (US) National Institute of Standards and Technology (NIST)

Uniting oil and water for a manufacturing-friendly approach to gel production

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This is a newish type of gel for which a new manufacturing has been developed jointly by the US National Institute of Standards and Technology (NIST) and the University of Delaware as described in a February 11, 2021 news item on phys.org (Note: A link has been removed),

Oil and water may not mix, but adding the right nanoparticles to the recipe can convert these two immiscible fluids into an exotic gel with uses ranging from batteries to water filters to tint-changing smart windows. A new approach to creating this unusual class of soft materials could carry them out of the laboratory and into the marketplace.

Scientists at the National Institute of Standards and Technology (NIST) and the University of Delaware have found what appears to be a better way to create these gels, which have been an area of intense research focus for more than a decade. Part of their potentially broad utility is the complex set of interconnected microscopic channels that form within them, creating a spongelike structure. These channels not only offer passageways for other materials to travel through, making them useful for filtration, but also give the gel a high amount of internal surface area, a characteristic valuable for speeding up chemical reactions or as scaffolding on which living tissue can grow.

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It seems they have great hopes for what they’ve called ‘SeedGel’, if this image is anything to go by,

Unlike other gel-creation approaches, where nanoparticles remain at the interface between the gel’s two constituent solvents (top left), the new approach concentrates nanoparticles in the interior of one of the solvents (top right), giving the resulting “SeedGel” unusual mechanical strength. The method could lead to gels that could be manufactured at industrial scales for a wide variety of potential applications. Credit: N. Hanacek / NIST

A February 10, 2021 NIST news release (also on EurekAlert), which originated the news item, delves further into the topic,

While these and other advantages make it sound like gel innovators have struck oil, their creations have not yet mixed well with the marketplace. The gels are commonly formed of two liquid solvents mingled together. As with oil and water, these solvents do not mix well, but to prevent them from completely separating, researchers add custom-designed nanoparticles that can stay at the interface between them. Carefully cooking these ingredients allows a cohesive gel to form. However, the process is demanding because custom-designing nanoparticles for each application has been difficult, and forming the gels has required carefully controlled rapid temperature change. These constraints have made it hard to create this type of gel in any more than small quantities suitable for lab experiments rather than on an industrial scale.

As described in a new Nature Communications paper, the NIST/Delaware team has found ways to sidestep many of these problems. Its novel approach forms what the researchers refer to as a “SeedGel,” an abbreviation for “solvent segregation driven gel.” Instead of designing nanoparticles to remain at the interface between the two solvents, their chosen particles concentrate within one of them. While these particles tend to repel one another, the particles’ affinity toward one of the solvents is stronger and keeps them together in the channel. Using neutron scattering tools at the NIST Center for Neutron Research (NCNR), the team unambiguously proved that it had succeeded at concentrating the nanoparticles where it wanted. 

The resulting gel could be far easier to create, as its two solvents are essentially oil and water, and its nanoparticles are silicon dioxide — essentially tiny spheres of common quartz. It also could have a variety of industrial uses. 

“Our SeedGel has great mechanical strength, it’s much easier to make, and the process is scalable to what manufacturers would need,” said Yun Liu, who is both an NCNR scientist and an affiliated full professor at the University of Delaware. “Plus it’s thermo-reversible.”

This reversibility refers to an optical property that the finished SeedGel possesses: It can switch from transparent to opaque and back again, just by changing its temperature. This property could be harnessed in smart windows that sandwich a thin layer of the gel between two panes of glass.

“This optical property could make the SeedGel useful in other light-sensitive applications as well,” said Yuyin Xi, a researcher from the University of Delaware also working at the NCNR. “They could be useful in sensors.”

Because the team’s gel-creation approach could be used with other solvent-and-nanoparticle combinations, it could become useful in filters for water purification and possibly other filtration processes depending on what type of nanoparticles are used.

Liu also said that the creation approach allows for the size of the channels within the gel to be tuned by changing the rate at which the temperature changes during the formation process, offering application designers another degree of freedom to explore.

“Ours is a generic approach working for many different nanoparticles and solvents,” he said. “It greatly extends the applications of these sorts of gels.”

Here’s a link to and a citation for the paper,

Tunable thermo-reversible bicontinuous nanoparticle gel driven by the binary solvent segregation by Yuyin Xi, Ronald S. Lankone, Li-Piin Sung & Yun Liu. Nature Communications volume 12, Article number: 910 (2021) DOI: https://doi.org/10.1038/s41467-020-20701-3 Published: 10 February 2021

This is paper is open access.

Two-dimensional material stacks into multiple layers to build a memory cell for longer lasting batteries

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This research comes from Purdue University (US) and the December announcement seemed particularly timely since battery-powered gifts are popular at Christmas but since it could be many years before this work is commercialized, you may want to tuck it away for future reference.  Also, readers familiar with memristors might see a resemblance to the memory cells mentioned in the following excerpt. From a December 13, 2018 news item on Nanowerk,

The more objects we make “smart,” from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved functionality in a material called molybdenum ditelluride.

The two-dimensional material stacks into multiple layers to build a memory cell. Researchers at Purdue University engineered this device in collaboration with the National Institute of Standards and Technology (NIST) and Theiss Research Inc.

A December 13, 2018 Purdue University news release by Kayla Wiles, which originated the news item,  describes the work in more detail,

Chip-maker companies have long called for better memory technologies to enable a growing network of smart devices. One of these next-generation possibilities is resistive random access memory, or RRAM for short.

In RRAM, an electrical current is typically driven through a memory cell made up of stacked materials, creating a change in resistance that records data as 0s and 1s in memory. The sequence of 0s and 1s among memory cells identifies pieces of information that a computer reads to perform a function and then store into memory again.

A material would need to be robust enough for storing and retrieving data at least trillions of times, but materials currently used have been too unreliable. So RRAM hasn’t been available yet for widescale use on computer chips.

Molybdenum ditelluride could potentially last through all those cycles.
“We haven’t yet explored system fatigue using this new material, but our hope is that it is both faster and more reliable than other approaches due to the unique switching mechanism we’ve observed,” Joerg Appenzeller, Purdue University’s Barry M. and Patricia L. Epstein Professor of Electrical and Computer Engineering and the scientific director of nanoelectronics at the Birck Nanotechnology Center.

Molybdenum ditelluride allows a system to switch more quickly between 0 and 1, potentially increasing the rate of storing and retrieving information. This is because when an electric field is applied to the cell, atoms are displaced by a tiny distance, resulting in a state of high resistance, noted as 0, or a state of low resistance, noted as 1, which can occur much faster than switching in conventional RRAM devices.

“Because less power is needed for these resistive states to change, a battery could last longer,” Appenzeller said.

In a computer chip, each memory cell would be located at the intersection of wires, forming a memory array called cross-point RRAM.

Appenzeller’s lab wants to explore building a stacked memory cell that also incorporates the other main components of a computer chip: “logic,” which processes data, and “interconnects,” wires that transfer electrical signals, by utilizing a library of novel electronic materials fabricated at NIST.

“Logic and interconnects drain battery too, so the advantage of an entirely two-dimensional architecture is more functionality within a small space and better communication between memory and logic,” Appenzeller said.

Two U.S. patent applications have been filed for this technology through the Purdue Office of Technology Commercialization.

The work received financial support from the Semiconductor Research Corporation through the NEW LIMITS Center (led by Purdue University), NIST, the U.S. Department of Commerce and the Material Genome Initiative.

Here’s a link to and a citation for the paper,

Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories by Feng Zhang, Huairuo Zhang, Sergiy Krylyuk, Cory A. Milligan, Yuqi Zhu, Dmitry Y. Zemlyanov, Leonid A. Bendersky, Benjamin P. Burton, Albert V. Davydov, & Joerg Appenzeller. Nature Materials volume 18, pages 55–61 (2019) Published: 10 December 2018 DOI: https://doi.org/10.1038/s41563-018-0234-y

This paper is behind a paywall.