In paint form, the world's "whitest white" reflects so much light that surfaces become cooler than the surrounding air.
- Scientists at Purdue University announce the whitest white ever developed. It will be available as paint and a nanofilm.
- The new paint can actually cool surfaces on which it's applied, potentially reducing the need for climate-unfriendly air conditioners.
- This is the second whitest white to come from these researchers, and they believe this is about as white as any material could ever be.
A few years ago, researchers announced the development of the blackest black ever, a place where colors go to die. It was called Vantablack®, and it was so absorptive of visible light that only the tiniest amount escaped its surface to reflect back to our eyes. (All of that light energy is dissipated into the surrounding substrate, so Vantablack doesn't become hot.)
In a new paper published in the journal ACS Applied Materials & Interfaces, scientists at Purdue University announced BaSO4 (barium sulfate), the whitest white ever. BaSO4 is practically impervious to the colors of the visible spectrum. Even better, while it's a very cool invention in the colloquial sense, it's also cool in the thermal sense.
The coolest white
The infrared image on the right shows how a square of the super-white paint and the board on which it's painted — shown in a normal image on the left — are cooler than the surrounding materials.Credit: Purdue University/Joseph Peoples
Most outside paints actually warm the surfaces to which they're applied. While there are already some reflective paints on the market, they only reflect 80 to 90 percent of sunlight, not enough for a cooling effect.
By contrast, BaSO4 results in 98.1 percent of sunlight bouncing off. According to senior investigator Xuilin Ruan, "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."
Ruan and his colleagues tested BaSO4 using thermocouples, high-accuracy devices that measure voltage to determine temperature. They found that at night, BaSO4 surfaces are 19° F. cooler than surrounding air. Under strong sunlight the effect is not quite so extreme, but still dramatic: 8° of cooling.
The researchers even found the paint works in cold weather. Testing it on a 43° F. day, the surface on which BaSO4 was painted was a brisk 25° F. Their tests also indicate that BaSO4 is hardy enough for outdoor conditions.
How the new white was developed
Xuilin Ruan and a square of BaSO4Credit: Purdue University/Jared Pike
Research in the field of radiative paint for cooling goes back to the 1970s, though Ruan's team has been working toward BaSO4 for only six years. Along the way, they analyzed over 100 reflective materials, trying them out in about 50 experimental formulations.
Lead author, postdoc Xiangyu Li explains, "We looked at various commercial products, basically anything that's white. We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they're really, really white."
The whitest white paint before — developed by the same team just last autumn — depended on calcium carbonate, a compound commonly found in seashells, rocks, and blackboard chalk.
The team crammed as many tiny BaSO4 particles into the paint as possible. Says Li: "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."
Another factor that makes the team's BaSO4 formulation so reflective is that the researchers used barium sulfate particles of many different sizes. When it comes to reflecting light, size matters.
Co-author and PhD student Joseph Peoples said, "A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance."
The team's formulation method, they report, is compatible with commercial paint production.
Cool support for the planet
Purdue has applied for patents relating to BaSO4, though there are as yet no plans to make it commercially available.
However, the sooner they release it, the better. Air conditioning currently accounts for 12% of U.S. energy consumption. Also, many air conditioners use hydrofluorocarbons (HFCs). While HFCs constitute just a small percentage of greenhouse gases, they trap thousands of times the amount of heat as carbon dioxide.
Therefore, BaSO4 can play a role in combating global warming by reducing energy consumption and the emission of HFCs.
Measuring a person's movements and poses, smart clothes could be used for athletic training, rehabilitation, or health-monitoring.
In recent years there have been exciting breakthroughs in wearable technologies, like smartwatches that can monitor your breathing and blood oxygen levels.
But what about a wearable that can detect how you move as you do a physical activity or play a sport, and could potentially even offer feedback on how to improve your technique?
And, as a major bonus, what if the wearable were something you'd actually already be wearing, like a shirt of a pair of socks?
That's the idea behind a new set of MIT-designed clothing that use special fibers to sense a person's movement via touch. Among other things, the researchers showed that their clothes can actually determine things like if someone is sitting, walking, or doing particular poses.
The group from MIT's Computer Science and Artificial Intelligence Lab (CSAIL) says that their clothes could be used for athletic training and rehabilitation. With patients' permission, they could even help passively monitor the health of residents in assisted-care facilities and determine if, for example, someone has fallen or is unconscious.
The researchers have developed a range of prototypes, from socks and gloves to a full vest. The team's "tactile electronics" use a mix of more typical textile fibers alongside a small amount of custom-made functional fibers that sense pressure from the person wearing the garment.
According to CSAIL graduate student Yiyue Luo, a key advantage of the team's design is that, unlike many existing wearable electronics, theirs can be incorporated into traditional large-scale clothing production. The machine-knitted tactile textiles are soft, stretchable, breathable, and can take a wide range of forms.
"Traditionally it's been hard to develop a mass-production wearable that provides high-accuracy data across a large number of sensors," says Luo, lead author on a new paper about the project that is appearing in this month's edition of Nature Electronics. "When you manufacture lots of sensor arrays, some of them will not work and some of them will work worse than others, so we developed a self-correcting mechanism that uses a self-supervised machine learning algorithm to recognize and adjust when certain sensors in the design are off-base."
The team's clothes have a range of capabilities. Their socks predict motion by looking at how different sequences of tactile footprints correlate to different poses as the user transitions from one pose to another. The full-sized vest can also detect the wearers' pose, activity, and the texture of the contacted surfaces.
The authors imagine a coach using the sensor to analyze people's postures and give suggestions on improvement. It could also be used by an experienced athlete to record their posture so that beginners can learn from them. In the long term, they even imagine that robots could be trained to learn how to do different activities using data from the wearables.
"Imagine robots that are no longer tactilely blind, and that have 'skins' that can provide tactile sensing just like we have as humans," says corresponding author Wan Shou, a postdoc at CSAIL. "Clothing with high-resolution tactile sensing opens up a lot of exciting new application areas for researchers to explore in the years to come."
The paper was co-written by MIT professors Antonio Torralba, Wojciech Matusik, and Tomás Palacios, alongside PhD students Yunzhu Li, Pratyusha Sharma, and Beichen Li; postdoc Kui Wu; and research engineer Michael Foshey.
The work was partially funded by Toyota Research Institute.
The bird demonstrates cutting-edge technology for devising self-folding nanoscale robots.
Cornell University has just announced what may be the smallest origami bird ever folded. While a typical origami animal is the product of an artist's dexterous hands, the Cornell bird was folded by the strategic application of small electrical voltages. It had to be: The material of which the bird is comprised is just 30 atoms thick.
Creative expression isn't the point of the university's little avian — its construction previews principles and techniques that will lead to new generations of moving, nano-scaled robots that "can enable smart material design and interaction with the molecular biological world," says Dean Culver of the U.S. Army Combat Capabilities Development Command's Army Research Laboratory, which supported the research.
According to Cornell's Paul McEuen, "We humans, our defining characteristic is we've learned how to build complex systems and machines at human scales, and at enormous scales as well. But what we haven't learned how to do is build machines at tiny scales. And this is a step in that basic, fundamental evolution in what humans can do, of learning how to construct machines that are as small as cells."
The lead author of the paper describing the tiny bird is postdoctoral researcher Qingkun Liu. The paper, "Micrometer-Sized Electrically Programmable Shape Memory Actuators for Low-Power Microrobotics," is the cover story of the March 17 issue of the journal Science Robotics.
A minuscule swarm of helpers
The project is the result of a collaboration between physical scientist McEeuen and physicist Itai Cohen, both of Cornell's College of Arts and Sciences. It's already resulted in a (very) small herd of nanoscale machines and devices.
Cohen explains, "We want to have robots that are microscopic but have brains on board. So that means you need to have appendages that are driven by complementary metal-oxide-semiconductor (CMOS) transistors, basically a computer chip on a robot that's 100 microns on a side."
The idea is that these minuscule workhorses—a metaphor, no nanoscale origami horses yet exist—are released from a wafer, fold themselves into the desired form factor, and then go on about their business. Additional folding would endow them with motion as they work, change shapes to move their limbs and manipulate microscopic objects. The researchers anticipate that these nanobots will eventually be able to achieve similar functionality to their larger brethren.
Credit: nobeastsofierce/Adobe Stock
How a tiny robot is made and works
The project combines materials science with chemistry, since the folding is achieved with the strategic deployment of electrochemical reactions. Liu explains, "At this small scale, it's not like traditional mechanical engineering, but rather chemistry, material science, and mechanical engineering all mixed together."
"The hard part," says Cohen, "is making the materials that respond to the CMOS circuits. And this is what Qingkun and his colleagues have done with this shape memory actuator that you can drive with voltage and make it hold a bent shape."
The bots are constructed from a nanometer-thick platinum layer that's coated with a titanium oxide film. Rigid panels of silicon oxide glass are affixed to the platinum. A positive voltage creates oxidation, forcing oxygen atoms into the platinum seams between the glass panels, and forcing platinum atoms out. This causes the platinum to expand, which bends the entire glass-platinum structure to a desired angle.
Because the oxygen atoms collect to form a barrier, a bend is retained even after the charge is switched off. To undo a fold, a negative charge can be applied that removes the oxygen atoms from the seam, allowing it to relax and unbend.
This all happens very quickly — a machine can fold itself within just 100 milliseconds. The process is also repeatable. The team reports that a bot can flatten and refold itself thousands of times, and all it takes is a single volt of electricity.
Artistry after all
None of this really removes what one might consider the artistry. Working out how and where to apply voltages to effect the desired shape is not a simple thing to do. McEuen says, "One thing that's quite remarkable is that these little tiny layers are only about 30 atoms thick, compared to a sheet of paper, which might be 100,000 atoms thick. So it's an enormous engineering challenge to figure out how to make something like that have the kind of functionalities we want."
Still, the group is getting quite good at microscopic robotics, and has already been awarded the Guinness World Record for assembling the smallest-ever walking robot. The little 4-legged dude is 40 microns wide and between 40 and 70 microns long. They're angling for a new record with their 60-micron-wide origami bird.
Says Cohen, "These are major advances over current state-of-the-art devices. We're really in a class of our own."
Researchers find a way to distort laser light to survive a trip through disordered obstacles.
- Lasers are great for measuring—if they can get a clear view of their target.
- In biomedical applications, there's often disordered stuff in the way of objects needing measurement.
- A new technique leverages that disorder to formulate a custom-made, optimal laser light beam.
Lasers can make amazingly precise measurements. Invaluable for precision construction and manufacturing, they also allow biomedical researchers and doctors to accurately detect the position and movement of microscopic objects, from cells to tissues to tiny biological structures. That is, when the laser can get a direct shot at the target, which is often not possible. In the human body, for example, these objects may be partially obscured by, situated in, or even behind complicated, obfuscating stuff.
Now scientists from Utrecht University (Netherlands) and TU Wien in Austria have devised a cool way to alter lasers so that they can bounce right through such distortion fields, arriving on the other side as an "optimal wave" intact enough to get to work.
Their new system is described in the journal Nature Physics.
Understanding the problem
Credit: gavran333/Adobe Stock
When working with lasers or any other measurement tool, "You always want to achieve the best possible measurement accuracy — that's a central element of all natural sciences," says paper co-author Stefan Rotter of TU Wien in a press release. A highly focused laser beam is an ideal tool for this. However, getting it through a disordered barrier without destroying the integrity of the beam is a challenge.
The researchers describe the problem using the example of the type of frosted glass one might encounter in a bathroom window. Explains Utrecht University's Allan Mosk, another co-author, "Let's imagine a panel of glass that is not perfectly transparent, but rough and unpolished like a bathroom window." To keep people from seeing into the bathroom, "Light can pass through, but not in a straight line. The light waves are altered and scattered, so we can't accurately see an object on the other side of the window with the naked eye."
This is not very different from what happens when a scientist tries to examine some tiny object inside biological tissue. The disordered stuff between the scientist and the object turns the concentrated laser beam into a complex wave pattern that scatters on its way through the visual barrier.
The new solution
Credit: TU Wien
The researchers have found that they can modify a laser's light in anticipation of the way it will travel through the disordered environment so that it hits its target on the other side with sufficient coherence for making accurate measurements.
While that optimal wave may not be a pure, pristine laser light, it's nonetheless just the light wave needed to successfully make its way through that particular barrier. The researchers were able to develop a mathematical procedure that gives them the distortion required to produce such a wave. Says first author Dorian Bouchet, also of Utrecht University, "You can show that for various measurements there are certain waves that deliver a maximum of information as, e.g., on the spatial coordinates at which a certain object is located."
Bouchet adds, "To achieve this, you don't even need to know exactly what the disturbances are. It's enough to first send a set of trial waves through the system to study how they are changed by [it]."
Returning to the glazed bathroom window example, the system would identify an optimal light wave that could travel through the disordered glass and still accurately measure movement of a person behind the glass.
Testing the system
The researchers confirmed that their formula worked in experiments at Utrecht in which they were able to make nano-scale measurements using a laser that successfully transited a turbid plate playing the role of a disordered medium. They also tried simpler and simpler laser beams—reducing the number of photons being used—to see how far they could push their system. They found that it even with the simplest laser possible, it still performed satisfactorily.
Says Mosk, "We see that the precision of our method is only limited by the so-called quantum noise. This noise results from the fact that light consists of photons—nothing can be done about that." Still, he says, "within the limits of what quantum physics allows us to do for a coherent laser beam, we can actually calculate the optimal waves to measure different things. Not only the position, but also the movement or the direction of rotation of objects."
A fairly old idea, but a really good one, is about to hit the store shelves.
- The idea of growing food from CO2 dates back to NASA 50 years ago.
- Two companies are bringing high-quality, CO2-derived protein to market.
- CO2-based foods provide an environmentally benign way of producing the protein we need to live.
The idea of making food from little more than thin air— carbon dioxide, actually—is not a new one. NASA was tinkering with the idea in the 1960s as a means of growing food on future long missions. In recent years, as we've come to understand that Earth's resources—land and rainforests chief among them—are limited, interest in the concept has been renewed, with NASA doing new research and two companies racing to market with CO2-derived food products.
The basic idea
Credit: Big Think
The basic mechanism for deriving food from CO2 involves a fairly simple closed-loop system that executes a process over and over in a cyclical manner, producing edible matter along the way. In space, astronauts produce carbon dioxide when they breathe, which is then captured by microbes, which then convert it into a carbon-rich material. The astronauts eat the material, breathe out more CO2, and on and on. On Earth, the CO2 is captured from the atmosphere.
Drawing first breath
NASA's investigation into using CO2 for food production began with a 1966 report written by R. B. Jagow and R. S. Thomas and published by Ames Research Center. The nine-chapter report was called "The Closed Life-Support System." Each chapter contained a proposal for growing food on long missions.
Chapter 8, written by J. F. Foster and J. H. Litchfield of the Battelle Memorial Institute in Columbus, Ohio, proposed a system that utilized a hydrogen-fixing bacteria, Hydrogenomonas—NASA had been experimenting with the bacteria for several years at that point—and recycled CO2 in a compact, low-power, closed-loop system. The system would be able to produce edible cell matter in way that "should then be possible to maintain continuous cultures at high efficiencies for very long periods of time."
At the time, extended missions that would benefit from such a system were off in the future.
In 2019, and with its eye toward upcoming Mars missions, NASA returned to the idea, sponsoring the CO2 Conversion Challenge, "seeking novel ways to convert carbon dioxide into useful compounds." Phase 1 of the contest invited proposals for processes that could "convert carbon dioxide into glucose in order to eventually create sugar-based fuel, food, medicines, adhesives and other products."
Approaching the Finnish line
Credit: Solar Foods
We've written previously about Solar Foods, a company backed by the Finnish government who recently invested €4.3 million to help complete the company's €8.6 million commercialization of their nutrient-rich CO2-based protein powder, Solein. The company anticipates Solein will provide protein to some 400 million meals by 2025, and has so far developed 20 different food products from it.
In the air tonight
Another player, Air Protein, is based in California's Bay Area and is also bringing to market their own CO2 protein named after the company. The company describes it as a "nutrient-rich protein with the same amino acid profile as an animal protein and packed with crucial B vitamins, which are often deficient in a vegan diet."
The company recently secured $32 million in venture-capital funding.
Although Air Protein is actually flour—like Solein—the company is positioning Air Protein as offering "the first air-based meat," while Solein was announced first, and there's no public timetable yet for the arrival of Air Protein products on store shelves. In any event, non-animal "meats" are a hot market these days with the success of Beyond Burger and Impossible Foods cruelty-free meat substitutes.
Deforestation for palm oil
Credit: whitcomberd/Adobe Stock
Though Air Protein's promotional materials emphasize meat substitutes that will be derived from their flour, a TED Talk by company co-founder Lisa Dyson reveals another Air Protein product that could arguably have an even greater impact by potentially eliminating the need for palm oil and the deforestation it requires — their CO2 process can produce oils.
The company has already created a citrus-like oil that can be used for fragrances, flavoring, as a biodegradable cleaner, and "even as a jet fuel." Perhaps more excitingly, the company has made another oil that's similar to palm oil. Since palm trees are the crop most responsible for the decimation of the world's rain forests, an environmentally benign replacement for it would be a very big deal. Dyson also notes that their oils could substitute morally problematic coconut oil, whose harvesting has lately been reported to often involve the abuse of macaque monkeys.
Putting carbon dioxide to work
We know we have too much of the stuff, so finding a way of utilizing at least some CO2 to create foods and other products that reduce the need for destructive commercial practices is a solid win for humankind. Harkening back to its NASA origins, Dyson notes in her talk that Earth, too, is sort of a self-contained spaceship, albeit a big one. Finding new ways to productively reuse what it has to offer clearly benefits us all.