Tag Archives: University of Delaware

Ooblek (non-Newtonian goo) and bras from Reebok

I have taken a liberty in the title for this piece, strictly speaking the non-Newtonian goo in the bra isn’t the stuff (ooblek) made of cornstarch and water from your childhood science experiments but it has many of the same qualities. The material in the Reebok bra, PureMove, is called Shear Thickening Fluid and was developed at the University of Delaware in 2005 and subsequently employed by NASA (US National Aeronautics and Space Administration) for use in the suits used by astronauts as noted in an August 6, 2018 article by Elizabeth Secgran for Fast Company who explains how it came be used for the latest sports bra,

While the activewear industry floods the market with hundreds of different sports bras every season, research shows that most female consumers are unsatisfied with their sports bra options, and 1 in 5 women avoid exercise altogether because they don’t have a sports bra that fits them properly.

Reebok wants to make that experience a thing of the past. Today, it launches a new bra, the PureMove, that adapts to your movements, tightening up when you’re moving fast and relaxing when you’re not. …

When I visited Reebok’s Boston headquarters, Witek [Danielle Witek, Reebok designer who spearheaded the R&D making the bra possible] handed me a jar of the fluid with a stick in it. When I moved the stick quickly, it seemed to turn into a solid, and when I moved it slowly, it had the texture of honey. Witek and the scientists have incorporated this fluid into a fabric that Reebok dubs “Motion Sense Technology.” The fluid is woven into the textile, so that on the surface, it looks and feels like the synthetic material you might find in any sports bra. But what you can’t see is that the fabric adapts to the body’s shape, the velocity of the breast tissue in motion, and the type and force of movement. It stretches less with high-impact movements and then stretches more during rest and lower intensity activities.

I tested an early version of the PureMove bra a few months ago, before it had even gone into production. I did a high-intensity workout that involved doing jumping jacks and sprints, followed by a cool-down session. The best thing about the bra was that I didn’t notice it at all. I didn’t feel stifled when I was just strolling around the gym, and I didn’t feel like I was unsupported when I was running around. Ultimately, the best bras are the ones that you don’t have to think about so you can focus on getting on with your life.

Since this technology is so new, Reebok had to do a lot of testing to make sure the bra would actually do what it advertised. The company set up a breast biomechanics testing center with the help of the University of Delaware, with 54 separate motion sensors tracking and measuring various parts of a tester’s chest area. This is a far more rigorous approach than most testing facilities in the industry that typically only use between two to four sensors. Over the course of a year, the facility gathered the data required for the scientists and Reebok product designers to develop the PureMove bra.

… If it’s well-received, the logical next step would be to incorporate the Motion Sense Technology into other products, like running tights or swimsuits, since transitioning between compression and looseness is something that we want in all of our sportswear. ..

According to the Reebok PureMove bra webpage, it was available from August 16, 2018,

Credit: Reebok

It’s $60 (I imagine those are US dollars).

For anyone interested in the science of non-Newtonian goo, shear thickening fluid, and NASA, there’s a November 24, 2015 article by Lydia Chain for Popular Science (Note: Links have been removed),

There’s an experiment you may have done in high school: When you mix cornstarch with water—a concoction colloquially called oobleck—and give it a stir, it acts like a liquid. But scrape it quickly or hit it hard, and it stiffens up into a solid. If you set the right pace, you can even run on top of a pool of the stuff. This phenomenon is called shear force thickening, and scientists have been trying to understand how it happens for decades.

There are two main theories, and figuring out which is right could affect the way we make things like cement, body armor, concussion preventing helmets, and even spacesuits.

The prevailing theory is that it’s all about the fluid dynamics (the nature of how fluids move) of the liquid and the particles in a solution. As the particles are pushed closer and closer together, it becomes harder to squeeze the liquid out from between them. Eventually, it’s too hard to squeeze out any more fluid and the particles lock up into hydrodynamic clusters, still separated by a thin film of fluid. They then move together, thickening the mixture and forming a solid.

The other idea is that contact forces like friction keep the particles locked together. Under this theory, when force is applied, the particles actually touch. The shearing force and friction keep them pressed together, which makes the solution more solid.

“The debate has been raging, and we’ve been wracking our brains to think of a method to conclusively go one way or the other,” says Itai Cohen, a physicist at Cornell University. He and his team recently ran a new experiment that seems to point to friction as the driving cause of shear thickening.

Norman Wagner, a chemical engineer at the University of Delaware, says that research into frictional interactions like this is important, but notes that he isn’t completely convinced as Cohen’s team didn’t measure friction directly (they inferred it was friction from their modeling however they didn’t find the exact measurement of the friction between the particles). He also says that there’s a lot of data in the field already that strongly indicates hydrodynamic clusters as the cause for shear thickening.

Wagner and his team are working on a NASA funded project to improve space suits so that micrometeorites or other debris can’t puncture them. They have also bent their technology to make padding for helmets and shin guards that would do a better job protecting athletes from harmful impacts. They are even making puncture resistant gloves that would give healthcare workers the same dexterity as current ones but with extra protection against accidental needle sticks.

“It’s a very exciting area,” says Wagner. He’s very interested in designing materials that automatically protect someone, without robotics or power. …

I guess that in 2015 Wagner didn’t realize his work would also end up in a 2018 sports bra.

Art masterpieces are turning into soap

This piece of research has made a winding trek through the online science world. First it was featured in an April 20, 2017 American Chemical Society news release on EurekAlert,

A good art dealer can really clean up in today’s market, but not when some weird chemistry wreaks havoc on masterpieces. Art conservators started to notice microscopic pockmarks forming on the surfaces of treasured oil paintings that cause the images to look hazy. It turns out the marks are eruptions of paint caused, weirdly, by soap that forms via chemical reactions. Since you have no time to watch paint dry, we explain how paintings from Rembrandts to O’Keefes are threatened by their own compositions — and we don’t mean the imagery.

Here’s the video,

Interestingly, this seems to be based on a May 23, 2016 article by Sarah Everts for Chemical and Engineering News (an American Society publication) Note: Links have been removed,

When conservator Petria Noble first peered at Rembrandt’s “Anatomy Lesson of Dr. Nicolaes Tulp” under a microscope back in 1996, she was surprised to find pockmarks across the nearly 400-year-old painting’s surface.

Each tiny crater was just a few hundred micrometers in diameter, no wider than the period at the end of this sentence. The painting’s surface was entirely riddled with these curious structures, giving it “a dull, rather hazy, gritty surface,” Noble says.

A structure of lead nonanoate.

The crystal structures of metal soaps vary: Shown here is lead nonanoate, based on a structure solved by Cecil Dybowski at the University of Delaware and colleagues at the Metropolitan Museum of Art. Dashed lines are nearest oxygen neighbors.

This concerned Noble, who was tasked with cleaning the masterpiece with her then-colleague Jørgen Wadum at the Mauritshuis museum, the painting’s home in The Hague.

When Noble called physicist Jaap Boon, then at the Foundation for Fundamental Research on Matter in Amsterdam, to help figure out what was going on, the researchers unsuspectingly embarked on an investigation that would transform the art world’s understanding of aging paint.

More recently this ‘metal soaps in paintings’ story has made its way into a May 16, 2017 news item on phys.org,

An oil painting is not a permanent and unchangeable object, but undergoes a very slow change in the outer and inner structure. Metal soap formation is of great importance. Joen Hermans has managed to recreate the molecular structure of old oil paints: a big step towards better preservation of works of art. He graduated cum laude on Tuesday 9 May [2017] at the University of Amsterdam with NWO funding from the Science4Arts program.

A May 15, 2017 Netherlands Organization for Scientific Research (NWO) press release, which originated the phys.org news item, provides more information about Hermans’ work (albeit some of this is repetitive),

Johannes Vermeer, View of Delft, c. 1660 - 1661 (Mauritshuis, The Hague)Johannes Vermeer, View of Delft, c. 1660 – 1661 (Mauritshuis, The Hague)

Paint can fade, varnish can discolour and paintings can collect dust and dirt. Joen Hermans has examined the chemical processes behind ageing processes in paints. ‘While restorers do their best to repair any damages that have occurred, the fact remains that at present we do not know enough about the molecular structure of ageing oil paint and the chemical processes they undergo’, says Hermans. ‘This makes it difficult to predict with confidence how paints will react to restoration treatments or to changes in a painting’s environment.’

‘Sand grains’ In the red tiles of 'View of Delft' by Johannes Vermeer shows 'lead soap spheres' (Annelies van Loon, UvA/Mauritshuis)‘Sand grains’ In the red tiles of ‘View of Delft’ by Johannes Vermeer shows ‘lead soap spheres’ (Annelies van Loon, UvA/Mauritshuis)

Visible to the naked eye

Hermans explains that in its simplest form, oil paint is a mixture of pigment and drying oil, which forms the binding element. Colour pigments are often metal salts. ‘When the pigment and the drying oil are combined, an incredibly complicated chemical process begins’, says Hermans, ‘which continues for centuries’. The fatty acids in the oil form a polymer network when exposed to oxygen in the air. Meanwhile, metal ions react with the oil on the surface of the grains of pigment.

‘A common problem when conserving oil paintings is the formation of what are known as metal soaps’, Hermans continues. These are compounds of metal ions and fatty acids. The formation of metal soaps is linked to various ways in which paint deteriorates, as when it becomes increasingly brittle, transparent or forms a crust on the paint surface. Hermans: ‘You can see clumps of metal soap with the naked eye on some paintings, like Rembrandt’s Anatomy Lesson of Dr Nicolaes Tulp or Vermeer’s View of Delft’. Around 70 per cent of all oil paintings show signs of metal soap formation.’

Conserving valuable paintings

Hermans has studied in detail how metal soaps form. He began by defining the structure of metal soaps. One of the things he discovered was that the process that causes metal ions to move in the painting is crucial to the speed at which the painting ages. Hermans also managed to recreate the molecular structure of old oil paints, making it possible to simulate and study the behaviour of old paints without actually having to remove samples from Rembrandt’s Night Watch. Hermans hopes this knowledge will contribute towards a solid foundation for the conservation of valuable works of art.

I imagine this will make anyone who owns an oil painting or appreciates paintings in general pause for thought and the inclination to utter a short prayer for conservators to find a solution.

Sea sapphires: now you see them, now you don’t and more about structural colour/color

The structural colour of the sea sapphire

 Scientists are studying the disappearing act of this ocean-dwelling copepod. Credit: Kaj Maney, www.liquidguru.com Courtesy: American Chemical Society


Scientists are studying the disappearing act of this ocean-dwelling copepod.
Credit: Kaj Maney, www.liquidguru.com Courtesy: American Chemical Society

Now, you’ve seen a sea sapphire. Here’s more about them and the interest they hold for experts in photonics, from a July 15, 2015 news item on ScienceDaily,

Sapphirina, or sea sapphire, has been called “the most beautiful animal you’ve never seen,” and it could be one of the most magical. Some of the tiny, little-known copepods appear to flash in and out of brilliantly colored blue, violet or red existence. Now scientists are figuring out the trick to their hues and their invisibility. The findings appear in the Journal of the American Chemical Society and could inspire the next generation of optical technologies.

A July 15, 2015 American Chemical Society (ACS) news release, which originated the news item, provides more detail,

Copepods are tiny aquatic crustaceans that live in both fresh and salt water. Some males of the ocean-dwelling Sapphirina genus display striking, iridescent colors that scientists think play a role in communication and mate recognition. The shimmering animals’ colors result when light bounces off of the thin, hexagonal crystal plates that cover their backs. These plates also help them vanish, if only fleetingly. Scientists didn’t know specifically what factors contributed to creating different shades. Scientists at the Weizmann Institute [Israel] and the Interuniversity Institute for Marine Sciences in Eilat [Israel] wanted to investigate the matter.

The researchers measured the light reflectance — which determines color — of live Sapphirina males and the spacing between crystal layers. They found that changes of reflectance depended on the thickness of the spacing. And for at least one particular species, when light hits an animal at a 45-degree angle, reflectance shifts out of the visible light range and into the ultraviolet, and it practically disappears. Their results could help inform the design of artificial photonic crystal structures, which have many potential uses in reflective coatings, optical mirrors and optical displays.

To sum this up, the colour and the invisibility properties are due to thin, hexagonal crystal plates and the spacing of these plates, in other words, structural colour, which is usually achieved at the nanoscale.

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

Structural Basis for the Brilliant Colors of the Sapphirinid Copepods by Dvir Gur, Ben Leshem, Maria Pierantoni, Viviana Farstey, Dan Oron, Steve Weiner, and Lia Addadi. J. Am. Chem. Soc., 2015, 137 (26), pp 8408–8411 DOI: 10.1021/jacs.5b05289 Publication Date (Web): June 22, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

For anyone who’s interested, Lynn Kimlicka has a nice explanation of structural colour in a July 22, 2015 posting on the Something About Science blog where she discusses some recent research iridescence in bird feathers and synthetic melanin. She also shares a picture of her budgie and its iridescent feathers. The ‘melanin’ research was mentioned here in a May 19, 2015 posting where I also provide a link to a great 2013 piece on structural throughout the animal and plant kingdoms by Cristina Luiggi for The Scientist.

Understanding how nanostructures can affect optical properties could be leading to new ways of managing light. A July 23, 2015 news item on ScienceDaily describes a project at the University of Delaware dedicated to “changing the color of light,”

Researchers at the University of Delaware have received a $1 million grant from the W.M. Keck Foundation to explore a new idea that could improve solar cells, medical imaging and even cancer treatments. Simply put, they want to change the color of light.

A July 23, 2015 University of Delaware (UD) news release, which originated the news item, provides more information about the proposed research,

“A ray of light contains millions and millions of individual units of light called photons,” says project leader Matthew Doty. “The energy of each photon is directly related to the color of the light — a photon of red light has less energy than a photon of blue light. You can’t simply turn a red photon into a blue one, but you can combine the energy from two or more red photons to make one blue photon.”

This process, called “photon upconversion,” isn’t new, Doty says. However, the UD team’s approach to it is.

They want to design a new kind of semiconductor nanostructure that will act like a ratchet. It will absorb two red photons, one after the other, to push an electron into an excited state when it can emit a single high-energy (blue) photon.

These nanostructures will be so teeny they can only be viewed when magnified a million times under a high-powered electron microscope.

“Think of the electrons in this structure as if they were at a water park,” Doty says. “The first red photon has only enough energy to push an electron half-way up the ladder of the water slide. The second red photon pushes it the rest of the way up. Then the electron goes down the slide, releasing all of that energy in a single process, with the emission of the blue photon. The trick is to make sure the electron doesn’t slip down the ladder before the second photon arrives. The semiconductor ratchet structure is how we trap the electron in the middle of the ladder until the second photon arrives to push it the rest of the way up.”

The UD team will develop new semiconductor structures containing multiple layers of different materials, such as aluminum arsenide and gallium bismuth arsenide, each only a few nanometers thick. This “tailored landscape” will control the flow of electrons into states with varying potential energy, turning once-wasted photons into useful energy.

The UD team has shown theoretically that their semiconductors could reach an upconversion efficiency of 86 percent, which would be a vast improvement over the 36 percent efficiency demonstrated by today’s best materials. What’s more, Doty says, the amount of light absorbed and energy emitted by the structures could be customized for a variety of applications, from lightbulbs to laser-guided surgery.

How do you even begin to make structures so tiny they can only be seen with an electron microscope? In one technique the UD team will use, called molecular beam epitaxy, nanostructures will be built by depositing layers of atoms one at a time. Each structure will be tested to see how well it absorbs and emits light, and the results will be used to tailor the structure to improve performance.

The researchers also will develop a milk-like solution filled with millions of identical individual nanoparticles, each one containing multiple layers of different materials. The multiple layers of this structure, like multiple candy shells in an M&M, will implement the photon ratchet idea. Through such work, the team envisions a future upconversion “paint” that could be easily applied to solar cells, windows and other commercial products.

Improving medical tests and treatments

While the initial focus of the three-year project will be on improving solar energy harvesting, the team also will explore biomedical applications.

A number of diagnostic tests and medical treatments, ranging from CT [computed tomography] and PET [positron emission tomography] scans to chemotherapy, rely on the release of fluorescent dyes and pharmaceutical drugs. Ideally, such payloads are delivered both at specific disease sites and at specific times, but this is hard to control in practice.

The UD team aims to develop an upconversion nanoparticle that can be triggered by light to release its payload. The goal is to achieve the controlled release of drug therapies even deep within diseased human tissue while reducing the peripheral damage to normal tissue by minimizing the laser power required.

“This is high-risk, high-reward research,” Doty says. “High-risk because we don’t yet have proof-of-concept data. High-reward because it has such a huge potential impact in renewable energy to medicine. It’s amazing to think that this same technology could be used to harvest more solar energy and to treat cancer. We’re excited to get started!”

That’s it for structural colour/color today.