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

The coolest paint

It’s the ‘est’ of it all. The coolest, the whitest, the blackest … Scientists and artists are both pursuing the ‘est’. (More about the pursuit later in this posting.)

In this case, scientists have developed the coolest, whitest paint yet. From an April 16, 2021 news item on Nanowerk,

In an effort to curb global warming, Purdue University engineers have created the whitest paint yet. Coating buildings with this paint may one day cool them off enough to reduce the need for air conditioning, the researchers say.

In October [2020], the team created an ultra-white paint that pushed limits on how white paint can be. Now they’ve outdone that. The newer paint not only is whiter but also can keep surfaces cooler than the formulation that the researchers had previously demonstrated.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” said Xiulin Ruan, a Purdue professor of mechanical engineering.

Caption: Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab’s sample of the whitest paint on record. Credit: Purdue University/Jared Pike

This is nicely done. Researcher Xiulin Ruan is standing close to a structure that could be said to resemble the sun while in shirtsleeves and sunglasses and holding up a sample of his whitest paint in April (not usually a warm month in Indiana).

An April 15, 2021 Purdue University news release (also on EurkeAlert), which originated the news item, provides more detail about the work and hints about its commercial applications both civilian and military,

The researchers believe that this white may be the closest equivalent of the blackest black, “Vantablack,” [emphasis mine; see comments later in this post] which absorbs up to 99.9% of visible light. The new whitest paint formulation reflects up to 98.1% of sunlight – compared with the 95.5% of sunlight reflected by the researchers’ previous ultra-white paint – and sends infrared heat away from a surface at the same time.

Typical commercial white paint gets warmer rather than cooler. Paints on the market that are designed to reject heat reflect only 80%-90% of sunlight and can’t make surfaces cooler than their surroundings.

The team’s research paper showing how the paint works publishes Thursday (April 15 [2021]) as the cover of the journal ACS Applied Materials & Interfaces.

What makes the whitest paint so white

Two features give the paint its extreme whiteness. One is the paint’s very high concentration of a chemical compound called barium sulfate [emphasis mine] which is also used to make photo paper and cosmetics white.

“We looked at various commercial products, basically anything that’s white,” said Xiangyu Li, a postdoctoral researcher at the Massachusetts Institute of Technology who worked on this project as a Purdue Ph.D. student in Ruan’s lab. “We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white.”

The second feature is that the barium sulfate particles are all different sizes in the paint. How much each particle scatters light depends on its size, so a wider range of particle sizes allows the paint to scatter more of the light spectrum from the sun.

“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” said Joseph Peoples, a Purdue Ph.D. student in mechanical engineering.

There is a little bit of room to make the paint whiter, but not much without compromising the paint.”Although a higher particle concentration is better for making something white, you can’t increase the concentration too much. The higher the concentration, the easier it is for the paint to break or peel off,” Li said.

How the whitest paint is also the coolest

The paint’s whiteness also means that the paint is the coolest on record. Using high-accuracy temperature reading equipment called thermocouples, the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.

The paint’s solar reflectance is so effective, it even worked in the middle of winter. During an outdoor test with an ambient temperature of 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.

This white paint is the result of six years of research building on attempts going back to the 1970s to develop radiative cooling paint as a feasible alternative to traditional air conditioners.

Ruan’s lab had considered over 100 different materials, narrowed them down to 10 and tested about 50 different formulations for each material. Their previous whitest paint was a formulation made of calcium carbonate, an earth-abundant compound commonly found in rocks and seashells.

The researchers showed in their study that like commercial paint, their barium sulfate-based paint can potentially handle outdoor conditions. The technique that the researchers used to create the paint also is compatible with the commercial paint fabrication process.

Patent applications for this paint formulation have been filed through the Purdue Research Foundation Office of Technology Commercialization. This research was supported by the Cooling Technologies Research Center at Purdue University and the Air Force Office of Scientific Research [emphasis mine] through the Defense University Research Instrumentation Program (Grant No.427 FA9550-17-1-0368). The research was performed at Purdue’s FLEX Lab and Ray W. Herrick Laboratories and the Birck Nanotechnology Center of Purdue’s Discovery Park.

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

Ultrawhite BaSO4 Paints and Films for Remarkable Daytime Subambient Radiative Cooling by Xiangyu Li, Joseph Peoples, Peiyan Yao, and Xiulin Ruan. ACS Appl. Mater. Interfaces 2021, XXXX, XXX, XXX-XXX DOI: https://doi.org/10.1021/acsami.1c02368 Publication Date:April 15, 2021 © 2021 American Chemical Society

This paper is behind a paywall.

Vantablack and the ongoing ‘est’ of blackest

Vantablack’s 99.9% light absorption no longer qualifies it for the ‘blackest black’. A newer standard for the ‘blackest black’ was set by the US National Institute of Standards and Technology at 99.99% light absorption with its N.I.S.T. ultra-black in 2019, although that too seems to have been bested.

I have three postings covering the Vantablack and blackest black story,

The third posting (December 2019) provides a brief summary of the story along with what was the latest from the US National Institute of Standards and Technology. There’s also a little bit about the ‘The Redemption of Vanity’ an art piece demonstrating the blackest black material from the Massachusetts Institute of Technology, which they state has 99.995% (at least) absorption of light.

From a science perspective, the blackest black would be useful for space exploration.

I am surprised there doesn’t seem to have been an artistic rush to work with the whitest white. That impression may be due to the fact that the feuds get more attention than quiet work.

Dark side to the whitest white?

Andrew Parnell, research fellow in physics and astronomy at the University of Sheffield (UK), mentions a downside to obtaining the material needed to produce this cooling white paint in a June 10, 2021 essay on The Conversation (h/t Fast Company), Note: Links have been removed,

… this whiter-than-white paint has a darker side. The energy required to dig up raw barite ore to produce and process the barium sulphite that makes up nearly 60% of the paint means it has a huge carbon footprint. And using the paint widely would mean a dramatic increase in the mining of barium.

Parnell ends his essay with this (Note: Links have been removed),

Barium sulphite-based paint is just one way to improve the reflectivity of buildings. I’ve spent the last few years researching the colour white in the natural world, from white surfaces to white animals. Animal hairs, feathers and butterfly wings provide different examples of how nature regulates temperature within a structure. Mimicking these natural techniques could help to keep our cities cooler with less cost to the environment.

The wings of one intensely white beetle species called Lepidiota stigma appear a strikingly bright white thanks to nanostructures in their scales, which are very good at scattering incoming light. This natural light-scattering property can be used to design even better paints: for example, by using recycled plastic to create white paint containing similar nanostructures with a far lower carbon footprint. When it comes to taking inspiration from nature, the sky’s the limit.

Moon dust at the nanoscale

Before getting to the moon dust, it seems the US National Institute of Standards and Technology (NIST) has undergone a communications strategy transformation. For example, there’s this whimsical video about the NIST’s latest on moon dust,

An April 28, 2021 news item on phys.org offers a little more whimsy and moon dust from the NIST,

Like a chameleon of the night sky, the moon often changes its appearance. It might look larger, brighter or redder, for example, due to its phases, its position in the solar system or smoke in Earth’s atmosphere. (It is not made of green cheese, however.)

Another factor in its appearance is the size and shape of moon dust particles, the small rock grains that cover the moon’s surface. Researchers at the National Institute of Standards and Technology (NIST) are now measuring tinier moon dust particles than ever before, a step toward more precisely explaining the moon’s apparent color and brightness. This in turn might help improve tracking of weather patterns and other phenomena by satellite cameras that use the moon as a calibration source.

An April 28, 2021US NIST news release (also on EurekAlert), which originated the news item, provides more technical detail,

NIST researchers and collaborators have developed a complex method of measuring the exact three-dimensional shape of 25 particles of moon dust collected during the Apollo 11 mission in 1969. The team includes researchers from the Air Force Research Laboratory, the Space Science Institute and the University of Missouri-Kansas City.

These researchers have been studying moon dust for several years. But as described in a new journal paper, they now have X-ray nano computed tomography (XCT), which allowed them to examine the shape of particles as small as 400 nanometers (billionths of a meter) in length.

The research team developed a method for both measuring and computationally analyzing how the dust particle shapes scatter light. Follow-up studies will include many more particles, and more clearly link their shape to light scattering. Researchers are especially interested in a feature called “albedo,” moonspeak for how much light or radiation it reflects.

The recipe for measuring the Moon’s nano dust is complicated. First you need to mix it with something, as if making an omelet, and then turn it on a stick for hours like a rotisserie chicken. Straws and dressmakers’ pins are involved too.

“The procedure is elaborate because it is hard to get a small particle by itself, but one needs to measure many particles for good statistics, since they are randomly distributed in size and shape,” NIST Fellow Ed Garboczi said.

“Since they are so tiny and because they only come in powders, a single particle needs to be separated from all the others,” Garboczi continued. “They are too small to do that by hand, at least not in any quantity, so they must be carefully dispersed in a medium. The medium must also freeze their mechanical motion, in order to be able to get good XCT images. If there is any movement of the particles during the several hours of the XCT scan, then the images will be badly blurred and generally not usable. The final form of the sample must also be compatible with getting the X-ray source and camera close to the sample while it rotates, so a narrow, straight cylinder is best.”

The procedure involved stirring the Apollo 11 material into epoxy, which was then dripped over the outside of a tiny straw to get a thin layer. Small pieces of this layer were then removed from the straw and mounted on dressmakers’ pins, which were inserted into the XCT instrument.

The XCT machine generated X-ray images of the samples that were reconstructed by software into slices. NIST software stacked the slices into a 3D image and then converted it into a format that classified units of volume, or voxels, as either inside or outside the particles. The 3D particle shapes were identified computationally from these segmented images. The voxels making up each particle were saved in separate files that were forwarded to software for solving electromagnetic scattering problems in the visible to the infrared frequency range.

The results indicated that the color of light absorbed by a moon dust particle is highly sensitive to its shape and can be significantly different from that of spherical or ellipsoidal particles of the same size. That doesn’t mean too much to the researchers — yet.

“This is our first look at the influence of actual shapes of lunar particles on light scattering and focuses on some fundamental particle properties,” co-author Jay Goguen of the Space Science Institute said. “The models developed here form the basis of future calculations that could model observations of the spectrum, brightness and polarization of the moon’s surface and how those observed quantities change during the moon’s phases.”

The authors are now studying a wider range of moon dust shapes and sizes, including particles collected during the Apollo 14 mission in 1971. The moon dust samples were loaned to NIST by NASA’s Curation and Analysis Planning Team for Extraterrestrial Materials program.

Here’s a (2nd) link to and a citation for the paper,

Optical Scattering Characteristics of 3-D Lunar Regolith Particles Measured Using X-Ray Nano Computed Tomography by Somen Baidya; Mikolas Melius; Ahmed M. Hassan; Andrew Sharits; Ann N. Chiaramonti; Thomas Lafarge; Jay D. Goguen; Edward J. Garboczi. IEEE Geoscience and Remote Sensing Letters DOI: 10.1109/LGRS.2021.3073344 Published online April 27, 2021

This paper is behind a paywall.

Beginner’s guide to folding DNA origami

I think this Aug. 6, 2010 post, Folding, origami, and shapeshifting and an article with over 50,000 authors is the first time I wrote about DNA (deoxyribonucleic acid) and origami (the Japanese art of paper folding).

Since then, the technique has become even more popular with the result that the US National Institute of Standards and Technology (NIST) has produced a beginner’s guide, according to a Jan. 8, 2021 news item on Nanowerk,

In a technique known as DNA origami, researchers fold long strands of DNA over and over again to construct a variety of tiny 3D structures, including miniature biosensors and drug-delivery containers. Pioneered at the California Institute of Technology in 2006, DNA origami has attracted hundreds of new researchers over the past decade, eager to build receptacles and sensors that could detect and treat disease in the human body, assess the environmental impact of pollutants, and assist in a host of other biological applications.

Although the principles of DNA origami are straightforward, the technique’s tools and methods for designing new structures are not always easy to grasp and have not been well documented. In addition, scientists new to the method have had no single reference they could turn to for the most efficient way of building DNA structures and how to avoid pitfalls that could waste months or even years of research.

That’s why Jacob Majikes and Alex Liddle, researchers at the National Institute of Standards and Technology (NIST) who have studied DNA origami for years, have compiled the first detailed tutorial on the technique. Their comprehensive report provides a step-by-step guide to designing DNA origami nanostructures, using state-of-the-art tools.

Here’s an image illustrating some of the techniques for DNA origami,

Caption: Collage shows some of the techniques and designs employed in DNA origami. Credit: K. Dill/NIST

A Jan. 8, 2021 US NIST news release (also on EurekAlert), which originated the news item, provide more detail as to the authors’ motivations, objectives, and future plans for their beginner’s guide,

“We wanted to take all the tools that people have developed and put them all in one place, and to explain things that you can’t say in a traditional journal article,” said Majikes. “Review papers might tell you everything that everyone’s done, but they don’t tell you how the people did it. “

DNA origami relies on the ability of complementary base pairs of the DNA molecule to bind to each other. Among DNA’s four bases — adenine (A), cytosine (C), guanine (G) and thymine (T) — A binds with T and G with C. This means that a specific sequence of As, Ts, Cs and Gs will find and bind to its complement.

The binding enables short strands of DNA to act as “staples,” keeping sections of long strands folded or joining separate strands. A typical origami design may require 250 staples. In this way, the DNA can self-assemble into a variety of shapes, forming a nanoscale framework to which an assortment of nanoparticles — many useful in medical treatment, biological research and environmental monitoring — can attach.

The challenges in using DNA origami are twofold, said Majikes. First, researchers are fabricating 3D structures using a foreign language — the base pairs A, G, T and C. In addition, they’re using those base-pair staples to twist and untwist the familiar double helix of DNA molecules so that the strands bend into specific shapes. That can be difficult to design and visualize. Majikes and Liddle urge researchers to strengthen their design intuition by building 3D mock-ups, such as sculptures made with bar magnets, before they start fabrication. These models, which can reveal which aspects of the folding process are critical and which ones are less important, should then be “flattened” into 2D to be compatible with computer-aided design tools for DNA origami, which typically use two-dimensional representations.

DNA folding can be accomplished in a variety of ways, some less efficient than others, noted Majikes. Some strategies, in fact, may be doomed to failure.

“Pointing out things like ‘You could do this, but it’s not a good idea’ — that type of perspective isn’t in a traditional journal article, but because NIST is focused on driving the state of technology in the nation, we’re able to publish this work in the NIST journal,” Majikes said. “I don’t think there’s anywhere else that would have given us the leeway and the time and the person hours to put all this together.”

Liddle and Majikes plan to follow up their work with several additional manuscripts detailing how to successfully fabricate nanoscale devices with DNA.

Here’s a link to and a citation for the beginner’s guide,

DNA Origami Design: A How-To Tutorial by Majikes, Jacob M. and Liddle, J. Alexander. Journal of Research of the National Institute of Standards and Technology Volume 126, Article No. 126001 (2021) Published online Jan. 8, 2021. DOI: 10.6028/jres.126.001

This is open access and it include such gems as this,

1.2 Education or Skill Level

Readers of this tutorial should be familiar with the physical properties of B-DNA, single-stranded DNA (ssDNA), and crossover junctions. In addition, once ready to create a structure for a specific application, the designer should determine the full list of functional requirements. This list includes answers to the following questions: What should the structure do? What specific properties are critical to the system’s performance?

1.3 Prerequisites

The designer should have either sufficient paper for manual design (not recommended) or a design program such as cadnano [1] (all versions sufficient), nanoengineer®, ParaboninSēquio®, or equivalent.1 A registered account with three-dimensional (3D) structure prediction servers such as CanDo [2, 3] is also recommended.

1.4Tools or Equipment

Equipment includes desktop or laptop computer equipment, craft supplies for macroscale models, and DNA nanotechnology computer-aided design (CAD) software.

Feel free to go forth and fold!