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Category Archives: materialsscience

Electrons may be the glue in cuprate superconductors

Copper oxide-based superconductors were discovered in 1986. Known as cuprate or high-Tc (for "high critical temperature") superconductors, these materials have a much higher temperature for the transition to zero resistance. But they have proven challenging to explain, since they don't behave as conventional superconductors do. While cuprate superconductors seem to conduct current via paired electrons like conventional superconductors, 26 years later, we still don't know how those pairs are formed.

A new optical examination of a bismuth-based cuprate superconductor has demonstrated that electronic excitations may be the primary driver of the superconducting transition. As described by S. Dal Conte et al. in a new Science paper, the complex interactions between electrons give rise to special quasiparticles. These are states that act as a kind of "glue" between electrons, allowing them to form the pairs that carry the superconducting current. The quasiparticle excitations are sufficient to explain the relatively high temperature of transition between the insulating state and the superconducting state.

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Researchers mimic relativity and the Higgs field in graphene-like material

The behavior of electrons and other particles depends on their environment. In particular, the interactions inside materials can alter the collective properties of the material's electrons, producing what are effectively new "particles"—known as quasiparticles—with correspondingly new behaviors. The surfaces of solids are fertile ground for quasiparticles, since they are two-dimensional; as we've seen in a number of other experiments, the loss of the third dimension can lead to exciting new physics.

A new experiment involving a graphene-like material has shown that it's possible to perform some spectacular manipulations of the properties of these quasiparticles. The work is described in a Nature letter by Kenjiro Gomes, Warren Mar, Wonhee Ko, Francisco Guinea, and Hari C. Manoharan. The team arranged carbon monoxide molecules to form the same hexagonal pattern found in graphene, except that they could change the spacing slightly. 

This produced an environment where the material's electrons behave remarkably like relativistic particles, with a "speed of light" that they can adjust. Additionally, the researchers could change the spacing between molecules in a way that the masses of the quasiparticles changed, or cause them to behave as though they are interacting with electric and magnetic fields—without actually applying those fields to the material. This setup will potentially help us explore new physics that may arise in these environments. 

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NMR imaging used to catch performance-killing flaws inside batteries

Batteries based on lithium now power everything from our watches to our cars, and we've made major strides towards stuffing more energy into them more quickly over the last several years. But there are limits to how quickly a battery can charge, and pushing past them can cause the lithium to form metallic microstructures within the battery. These can do ugly things like creating a short between the electrodes or puncturing the membranes that contain the battery's electrolyte.

Most techniques that could image these miscrostructures involved taking the battery apart, meaning that we could only take static images of the impact of charge/discharge cycles on the battery. One of the best techniques for non-invasive imaging, NMR, relies on radiofrequency signals that simply don't penetrate beyond the surface of a battery. Now, some researchers have figured out that there are conditions that enable the use of NMR to peek inside a battery—and they happen to be the formation of the microstructures we care about.

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Researchers hack silkworm genome to get spidery silk

By a number of measures, spider silk is one of the toughest materials around. It's also light weight and (obviously) biocompatible. Unfortunately, it's also extremely hard to produce in any sort of usable quantity. Now, researchers have figured out a way that might help us make a lot more of something almost as good: they've engineered some DNA that encodes a hybrid of silkworm and spider proteins, and gotten silkworms to produce it.

We've cloned a number of spider silk proteins now, and managed to express them in everything from bacteria to goats. None of these methods end up making much in the way of protein, however, and the material that is made is difficult to purify and form into fibers. Spiders would seem like an obvious choice for making silk but they create a number of issues that we don't normally associate with manufacturing; as the authors put it, "territorialism and cannibalism preclude spider farming as a viable manufacturing approach."

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Researchers hack silkworm genome to get spidery silk

By a number of measures, spider silk is one of the toughest materials around. It's also light weight and (obviously) biocompatible. Unfortunately, it's also extremely hard to produce in any sort of usable quantity. Now, researchers have figured out a way that might help us make a lot more of something almost as good: they've engineered some DNA that encodes a hybrid of silkworm and spider proteins, and gotten silkworms to produce it.

We've cloned a number of spider silk proteins now, and managed to express them in everything from bacteria to goats. None of these methods end up making much in the way of protein, however, and the material that is made is difficult to purify and form into fibers. Spiders would seem like an obvious choice for making silk but they create a number of issues that we don't normally associate with manufacturing; as the authors put it, "territorialism and cannibalism preclude spider farming as a viable manufacturing approach."

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Robot without a skeleton inspired by squid, crawls on land

The design of many robots has been inspired by living creatures, from the humanoid machines that have appeared in science fiction for decades to the mechanical cockroaches that scurry around some research labs. There has even been a robotic tuna used to explore the ocean. But our reliance on the mechanical has left a very large area of the animal kingdom left out: soft bodied creatures with neither skeletons nor shells. In a paper that will be released by PNAS, researchers describe a soft-bodied robot that can crawl around lab, powered by compressed air.

The limits in robot design have been very practical. We don't yet have something that will mimic muscles well, which leaves our creations articulating their joints with things like gears and engines, which require a fairly rigid support structure. But the creators of this new robot were inspired by squid, which perform impressive feats of flexibility using a soft body that's supported by the ocean's buoyancy.

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Robot without a skeleton inspired by squid, crawls on land

The design of many robots has been inspired by living creatures, from the humanoid machines that have appeared in science fiction for decades to the mechanical cockroaches that scurry around some research labs. There has even been a robotic tuna used to explore the ocean. But our reliance on the mechanical has left a very large area of the animal kingdom left out: soft bodied creatures with neither skeletons nor shells. In a paper that will be released by PNAS, researchers describe a soft-bodied robot that can crawl around lab, powered by compressed air.

The limits in robot design have been very practical. We don't yet have something that will mimic muscles well, which leaves our creations articulating their joints with things like gears and engines, which require a fairly rigid support structure. But the creators of this new robot were inspired by squid, which perform impressive feats of flexibility using a soft body that's supported by the ocean's buoyancy.

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New, recyclable plastic lets you weld pieces together with a hairdryer

Organic polymers can be used to create materials with very distinct properties (both good and bad). For example, thermoset materials resist heat and solvents, making them extremely durable and allowing them to be used in the oven. The downside is that, once they're made, that's it—no recycling. Thermoplastics are stable below a set temperature, but they can be melted, allowing them to be remade into new materials. Unfortunately, they don't hold up very well to solvents.

Now, researchers are saying they've created a third option, one that acts like a thermoplastic at high temperatures but can hold up to most solvents. The material's secret? An embedded catalyst that allows chemical bonds to constantly rearrange. The material's desired properties can be tuned based on the polymer it's made from and how much catalyst remains.

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