Liquid (Reversibly) Solidifies At Room Temperature, Gets Used For 3D Prints

August 9, 2024 by Donald Papp 8 Comments

Researchers demonstrate sustainable 3D printing by using poly(N-isopropylacrylamide) solutions (PNIPAM), which speedily and reliably turn solid by undergoing a rapid phase change when in a salt solution.

This property has been used to 3D print objects by using a syringe tip as if it were a nozzle in a filament-based printer. As long as the liquid is being printed into contact with a salt solution, the result is a polymer that solidifies upon leaving the syringe.

What’s also interesting is that the process by which the PNIPAM-based solutions solidify is entirely reversible. Researchers demonstrate printing, breaking down, then re-printing, which is an awfully neat trick. Finally, by mixing different additives in with PNIPAM, one can obtain different properties in the final product. For example, researchers demonstrate making conductive prints by adding carbon nanotubes.

While we’ve seen the concept of printing with liquids by extruding them into a gel bath or similar approach, we haven’t seen a process that prides itself on being so reversible before. The research paper with all the details is available here, so check it out for all the details.

On Carbon Fiber Types And Their Carcinogenic Risks

August 7, 2024 by Maya Posch 13 Comments

Initially only seeing brief popular use as the filament in incandescent lighting, carbon fibers (CF) experienced a resurgence during the 20th century as part of composite materials that are lighter and stronger than materials like steel and aluminium, for use in aircraft, boats and countless more applications. This rising popularity has also meant that the wider population is now exposed to fragments of CF, both from using CF-based products as well as from mechanically processing CF materials during (hobby) projects.

It is this popularity that has also led to the addition of short CF sections to FDM 3D printing filaments, where they improve the mechanical properties of the printed parts. However, during subsequent mechanical actions such as sanding, grinding, and cutting, CF dust is created and some fraction of these particles are small enough to be respirable. Of these, another fraction will bypass the respiratory system’s dust clearing mechanisms, to end up deep inside the lungs. This raises the question of whether CF fragments can be carcinogenic, much like the once very popular and very infamous example of asbestos mineral fibers.

Continue reading “On Carbon Fiber Types And Their Carcinogenic Risks” →

Illustrative models of collinear ferromagnetism, antiferromagnetism, and altermagnetism in crystal-structure real space and nonrelativistic electronic-structure momentum space. (Credit: Libor Šmejkal et al., Phys. Rev. X, 2022)

Altermagnetism In Manganese Telluride And Others: The Future Of Spintronics?

August 1, 2024 by Maya Posch 5 Comments

Magnetic materials are typically divided into ferromagnetic and antiferromagnetic types, depending on their magnetic moments (electron spins), resulting in either macroscopic (net) magnetism or not. Altermagnetism is however a recently experimentally confirmed third type that as the name suggests alternates effectively between these two states, demonstrating a splitting of the spin energy levels (spin-split band structure). Like antiferromagnets, altermagnets possess a net zero magnetic state due to alternating electron spin, but they differ in that the electronic band structure are not Kramers degenerate, which is the feature that can be tested to confirm altermagnetism. This is the crux of the February 2024 research paper in Nature by [J. Krempaský] and colleagues.

Specifically they were looking for the antiferromagnetic-like vanishing magnetization and ferromagnetic-like strong lifted Kramers spin degeneracy (LKSD) in manganese telluride (MnTe) samples, using photoemission spectroscopy in the UV and soft X-ray spectra. A similar confirmation in RuO2 samples was published in Science Advances by [Olena Fedchenko] and colleagues.

What this discovery and confirmation of altermagnetism means has been covered previously in a range of papers ever since altermagnetism was first proposed in 2019 by [Tomas Jungwirth] et al.. A 2022 paper published in Physical Review X by [Libor Šmejkal] and colleagues details a range of potential applications (section IV), which includes spintronics. Specific applications here include things like memory storage (e.g. GMR), where both ferromagnetic and antiferromagnetics have limitations that altermagnetism could overcome.

Naturally, as a fairly new discovery there is a lot of fundamental research and development left to be done, but there is a good chance that within the near future we will see altermagnetism begin to make a difference in daily life, simply due to how much of a fundamental shift this entails within our fundamental understanding of magnetics.

Heading image: Illustrative models of collinear ferromagnetism, antiferromagnetism, and altermagnetism in crystal-structure real space and nonrelativistic electronic-structure momentum space. (Credit: Libor Šmejkal et al., Phys. Rev. X, 2022)

A finger points at a diagram of a battery with two green bars. Above it is another battery with four smaller green bars with a similar area to the first battery's two. The bottom batter is next to a blue box with a blue wave emanating from it and the top battery has a red box with a red wave emanating from it. Below the red wave is written "2x wavelength" and below the top battery is "1/2 energy in a photon."

What Are Photons, Anyway?

August 1, 2024 by Navarre Bartz 33 Comments

Photons are particles of light, or waves, or something like that, right? [Mithuna Yoganathan] explains this conundrum in more detail than you probably got in your high school physics class.

While quantum physics has been around for over a century, it can still be a bit tricky to wrap one’s head around since some of the behaviors of energy and matter at such a small scale aren’t what we’d expect based on our day-to-day experiences. In classical optics, for instance, a brighter light has more energy, and a greater amplitude of its electromagnetic wave. But, when it comes to ejecting an electron from a material via the photoelectric effect, if your wavelength of light is above a certain threshold (bigger wavelengths are less energetic), then nothing happens no matter how bright the light is.

Scientists pondered this for some time until the early 20th Century when Max Planck and Albert Einstein theorized that electromagnetic waves could only release energy in packets of energy, or photons. These quanta can be approximated as particles, but as [Yoganathan] explains, that’s not exactly what’s happening. Despite taking a few classes in quantum mechanics, I still learned something from this video myself. I definitely appreciate her including a failed experiment as anyone who has worked in a lab knows happens all the time. Science is never as tidy as it’s portrayed on TV.

If you want to do some quantum mechanics experiments at home (hopefully with more luck than [Yoganathan]), then how about trying to measure Planck’s Constant with a multimeter or LEGO? If you’re wondering how you might better explain electromagnetism to others, maybe this museum exhibit will be inspiring.

Continue reading “What Are Photons, Anyway?” →

Secret Messages On Plastic, Just Add Tesla Coil

August 1, 2024 by Donald Papp 15 Comments

Here’s a short research paper from 2013 that explains how to create “hydroglyphics”, or writing with selecting surface wetting. In it, an apparently normal-looking petri dish is treated so as to reveal a message when wetted with water vapor. The contrast between hydrophobic and hydrophilic surfaces, which is not visible to the naked eye, becomes visible when misted with water. All it took was a mask, and a little treatment with a modified Tesla coil.

Plastics tend to be hydrophobic, meaning their surface repels water. These plastics also tend to be non-receptive to things like inks and adhesives. However, there is an industrial process called corona treatment (invented by Verner Eisby in 1951) that changes the surface energy of materials like plastics, rendering them more receptive to inks, coatings, and adhesives. Eisby’s company Vetaphone still exists today, and has a page describing the process.

What’s this got to do with the petri dishes and their secret messages? The process is essentially the same. By using a Tesla coil modified with a metal wire mesh, the surface of the petri dish is exposed to the coil’s discharge, altering its surface energy and rendering it hydrophilic. By selectively blocking the discharge with a nonconductive mask made from a foam sticker, the masked area remains hydrophobic. Mist the surface with water, and the design becomes visible.

The effects of corona treatment decay over time, but we think this is exactly the sort of thing that is worth keeping in mind just in case it ever comes in useful. Compact Tesla coils are fairly easy to get a hold of nowadays, but it’s also possible to make your own.

Climate Change May Make Days Longer

July 31, 2024 by Navarre Bartz 31 Comments

For those who say there’s never enough time in a day, your wish for more time is getting granted, if ever so slightly. Scientists have now found a new source of our days getting longer — climate change.

You may have already been aware that the length of the day on Earth has been getting longer over time due to the drag exerted on our planet by our friendly neighborhood Moon. Many other factors come into play though, including the Earth’s own mass distribution. As the Earth warms and polar caps melt, the water redistributes to the Earth’s equator causing it to slow more rapidly.

In the worst-case scenario, RCP8.5, it would result in climate-related effects to planetary rotational velocity even larger than those caused by lunar tides. Under that scenario, the earth would probably be a less pleasant place to live in many other ways, but at least you’d have a little more time in your day.

While we’re talking about time, we wonder what ever happened to getting rid of Daylight Savings in the US? If you long for a simpler time, perhaps you should take up repairing mechanical watches and clocks?

A bright orange sailboat with solar panels on the wing sail and the hull of the craft. A number of protuberances from the wing are visible containing instruments and radio equipment.

Saildrones Searching The Sea For Clues To Hurricane Behavior

July 29, 2024 by Navarre Bartz 26 Comments

Hurricanes can cause widespread destruction, so early forecasting of their strength is important to protect people and their homes. The US National Oceanic and Atmospheric Administration (NOAA) is using saildrones to get better data from inside these monster storms.

Rising ocean temperatures due to climate change are causing hurricanes to intensify more rapidly than in the past, although modeling these changes is still a difficult task. People on shore need to know if they’re in store for a tropical storm or a high strength hurricane to know what precautions to take. Evacuating an area is expensive and disruptive, so it’s understandable that people want to know if it’s necessary.

Starting with five units in 2021, the fleet has gradually increased in size to twelve last summer. These 23ft (7m), 33ft (10m), or 65ft (20m) long vessels are propelled by wing sails and power their radio and telemetry systems with a combination of solar and battery power. No fossil fueled vessel can match the up to 370 days at sea without refueling that these drones can achieve, and the ability to withstand hurricane winds and sea conditions allow scientists an up-close-and-personal look at a hurricane without risking human lives.

We’ve covered how the data gets from a saildrone to shore before, and if you want to know how robots learn to sail, there’s a Supercon talk for that.

Thanks to [CrLz] for the tip!