Your favorite stretchy workout clothes may be much easier to recycle one day, thanks to a new type of elastic yarn that is as strong and stretchy as today's spandex-containing fabrics.

The yarn, described in a July 25 study in the journal ACS Materials Letters, is built entirely from polyethylene, the plastic used in milk jugs and single-use grocery bags. By contrast, most of today's stretchy fabrics blend spandex, a bouncy-but-weak polyurethane fiber, with a tougher fiber like polyester or nylon.

That combination gives clothes their stretch and durability. But because the fibers are chemically different, it's difficult and costly to separate them for recycling, and chemicals used to break down the fabrics are toxic. The result is that almost none of this material is recycled. An estimated 80% of textiles sold in the U.S. contain spandex, and most end up incinerated or in a landfill, study co-author Svetlana Boriskina, a research scientist in the Department of Mechanical Engineering at MIT, said in a statement.

To solve that problem, the MIT team turned to polyethylene, one of the world's most widely recycled plastics. For the yarn's stretchy core, the researchers created a soft, springy version of polyethylene akin to a rubber band. Around that core, they wound a second, stiffer polyethylene fiber, more like a fishing line, coiling it tightly the way a spring or a twisted phone cord is coiled. Because both materials come from the same plastic family, they don't need to be separated before they're recycled.

In laboratory tests, the researchers melted a spool of the yarn and respun it into new yarn 10 separate times. Each time, they tested its strength, and the recycled yarn performed just as well as the original in every case. In head-to-head tests, the new yarn even outperformed commercial spandex-polyester yarn in maximum load, meaning it could bear more force before breaking, according to the study.

The team has already shown that these lightweight polyethylene fibers can be engineered for other perks, too ‪—‬ like cooling, moisture wicking and stain resistance ‪—‬ building on their earlier work spinning polyethylene into wearable fabric. Even buttons, zippers and buckles could eventually be made from compatible plastics, so a whole garment could be melted down and remade without being taken apart first.

New images captured by the world's most powerful solar telescope have revealed something that was hiding in plain sight on the sun for 150 years: thousands of tiny whirlpools twisting across our star's surface. The ultra-detailed observations could help to explain some of the sun's most violent behavior as well as hint at the answer to a long-standing solar mystery.

The new time-lapse footage offers the first direct proof of a long-predicted phenomenon called Kelvin-Helmholtz instability. The effect itself isn't new to science; it's named for physicists Lord Kelvin and Hermann von Helmholtz, who described it in the 19th century. The physicists found that whenever two fluids slide past each other at different speeds, the friction between them, or shear, rolls into spiraling patterns. However, this is the first time this effect has been seen on the sun, where that shear plays out between neighboring streams of solar plasma.

Researchers captured the swirls using the U.S. National Science Foundation's Daniel K. Inouye Solar Telescope in Hawaii and then compared the images against computer simulations of the sun's visible surface, called the photosphere. The findings were published Aug. 5 in the journal Nature.

The resulting time-lapse footage from the telescope is unlike anything solar physicists have captured before. It shows dozens of tiny vortices clustering along the edges of magnetic regions, some accompanied by delicate, dark stripes known as striations, according to a statement from the National Science Foundation. The telescope's resolution is sharp enough to pick out structures just tens of miles across — a scale so fine that the vortices had gone completely undetected until now.

When the researchers lined the images up against their simulations, the match was close enough ‪—‬ down to the average spacing between vortices ‪—‬ to confirm that they'd finally caught the instability in action.

Beyond the impressive visuals, researchers think these swirls may serve an important function. By constantly twisting and mixing the sun's magnetic-field lines, these vortices may play a part in building up the energy behind solar flares and coronal mass ejections.

The effect also might help to explain the long-standing mystery of why the sun's outer atmosphere, or corona, reaches temperatures of around 2 million degrees Fahrenheit (around 1 million degrees Celsius) while its surface remains hundreds of thousands of degrees cooler, Thomas Rimmele, chief technologist at the National Solar Observatory, said in the statement.

The team now plans to use computer programs to automatically track these vortices across future observations. This will help them measure exactly how much these swirls contribute to heating the corona and driving the explosive space weather that can disrupt satellites, communications and power grids on Earth.

See how much you know about the sun with our sun quiz!

Researchers have designed a material that can "program" the way it releases heat, paving the way for more efficient energy systems and, potentially, devices that store information using heat instead of electricity.

The design, described in a June 25 study in the journal Laser & Photonics Reviews, sidesteps a nearly 160-year-old rule of physics linking how materials absorb and emit heat. Under ordinary conditions, a material that's good at absorbing heat from one direction is equally good at emitting heat in that direction. This rule of reciprocity, first described by physicist Gustav Kirchhoff in the 19th century, has limited engineers' ability to control incoming heat independently from and outgoing heat.

In the new study, the researchers designed a theoretical device that could direct heat radiation in different directions and remember that setting even after the power was switched off.

The new device pairs two materials that don't normally work together. Using a magnetic field, the team broke the natural symmetry in a layer of indium arsenide ‪—‬ a material that absorbs and emits infrared light ‪—‬ so that radiation traveling in one direction behaves differently than radiation traveling the other way.

On top of that layer sits a grating made of germanium-antimony-tellurium (GST) — a phase-changing substance that can switch between two distinct physical structures and stay in whichever structure it's set to until it's deliberately switched again. Once the GST is set into position, it locks the directional difference of radiation in place and holds it there without needing continuous power, which is what lets the device's heat-directing behavior be "programmed."

"I was impressed by the elegant combination of magneto-optical nonreciprocity with a nonvolatile phase-change material," Juejun Hu, a professor of materials science and engineering at MIT who wasn't involved in the study, told Live Science in an email.

That's significant because earlier attempts at this kind of directional control typically worked only at steep angles, which made them impractical. It's "particularly noteworthy" that this device functions when radiation arrives just 3 degrees off an otherwise-straight line, making it far easier to fit into real-world optical systems, Hu said.

The researchers compared their design to computer memory, since it holds onto its programmed state after the power is cut. However, the device stores a material state rather than heat itself, Hu told Live Science. GST simply keeps its amorphous or crystalline structure without power, which preserves the programmed response.

For now, the device exists only on paper; it hasn't been built or tested. Still, Hu thinks it's realistic, since it relies on well-established materials and manufacturing methods. However, the GST layer is thick enough that switching it back and forth repeatedly would be difficult, though other materials could fix this problem. Once that hurdle is surpassed, Hu expects the first real-world use to be infrared sensing, where compact, direction-selective heat absorption is most directly useful.