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Category: materials

The semiconductor shortage has curtailed the choices available to designers and caused some inventive solutions to be found, but the one used by [djzc] is probably the most inventive we’ve yet seen. The footprint trap, when a board is designed for one footprint but shortages mean the part is only available in another, has caught out many an engineer this year. In this case an FTDI chip had been designed with a PCB footprint for a QFN package when the only chip to be found was a QFP from a breakout board.

For those unfamiliar with semiconductor packaging, a QFN and QFP share a very similar epoxy package, but the QFN has its pins on the underside flush with the epoxy and the QFP has them splayed out sideways. A QFP is relatively straightforward to hand-solder so it’s likely we’ll have seen more of them than QFNs on these pages.

There is no chance for a QFP to be soldered directly to a QFN footprint, so what’s to be done? The solution is an extremely inventive one, a two-PCB sandwich bridging the two. A lower PCB is made of thick material and mirrors the QFN footprint above the level of the surrounding components, while the upper one has the QFN on its lower side and a QFP on its upper. When they are joined together they form an inverted top-hat structure with a QFN footprint below and a QFP footprint on top. Difficult to solder in place, but the result is a QFP footprint to which the chip can be attached. We like it, it’s much more elegant than elite dead-bug soldering!

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It is a well-known fact that pure, distilled water is an almost perfect insulator and does not conduct electricity. It consists of H2O molecules that are loosely linked to one another via hydrogen bonds. However, any impurities, like salts, in the water enable it to conduct electricity. To create a conduction band with freely moving electrons, water would have to be pressurized to such an extent that the orbitals of the outer electrons overlap, something that only exists deep inside of large planets such as Jupiter.

Now, a team of researchers from 11 institutions around the world have used a completely different approach to create metallic water for the first time. They have achieved that feat by forming a thin layer of gold-colored metallic water on the outside of a droplet of liquid metal and documented this phase transition at the BESSY II facility in Berlin.

The key to the breakthrough was to pair the water with alkali metals, which release their outer electron very easily.

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“The twisted coils are the most expensive and complicated part of the stellarator and have to be manufactured to very great precision in a very complicated form,” physicist Per Helander, head of the Stellarator Theory Division at Max Planck and lead author of the new paper, told Princeton Plasma Physics Laboratory News.

The new design offers a simpler approach by instead using permanent magnets, whose magnetic field is generated by the internal structure of the material itself. As described in an article published by Nature, Zarnstorff realized that neodymium–boron permanent magnets—which behave like refrigerator magnets, only stronger—had become powerful enough to potentially help control the plasma in stellarators.

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Scientists managed to arrange the electrons into a honeycomb-like lattice by sandwiching them in an electric field between two atom-thin layers of tungsten compounds, according to research published in the journal Nature last week. The ability to tame them — which scientists accomplished by exploiting the tiniest differences in the atomic structures of the two tungsten layers — marks an incredible experimental achievement that has, until now, eluded the most accomplished labs in physics.

Other researchers have claimed that they created Wigner crystals in the past, and Nature News notes that they had some convincing evidence. But no one’s actually presented imaged evidence of their crystal before, study coauthor and University of California, Berkeley physicist Feng Wang told Nature News in the physicist’s version of a microphone drop.

“If you say you have an electron crystal, show me the crystal,” he said.

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Unplanned discovery could lead to future pivotal discoveries in batteries, fuel cells, devices for converting heat to electricity and more.

Scientists normally conduct their research by carefully selecting a research problem, devising an appropriate plan to solve it and executing that plan. But unplanned discoveries can happen along the way.

Mercouri Kanatzidis, professor at Northwestern University with a joint appointment in the U.S. Department of Energy’s (DOE) Argonne National Laboratory, was searching for a new superconductor with unconventional behavior when he made an unexpected discovery. It was a material that is only four atoms thick and allows for studying the motion of charged particles in only two dimensions. Such studies could spur the invention of new materials for a variety of energy conversion devices.

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Researchers at McGill University have developed the strongest and toughest glass ever known. Inspired, in part, by the inner layer of mollusk shells, this glass does not shatter when hit, and acts more like plastic.

The material, once commercially viable, could be used to improve cell phone screens, among other applications in the future.

Interestingly, this may be an example of modern science rediscovering an old technology, now long lost.

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Electrons in two-dimensional hexagonal materials have an extra degree of freedom, the valley pseudospin, that can be used to encode and process quantum information. Valley-selective excitations, governed by the circularly polarized light resonant with the material’s bandgap, are the foundation of valleytronics. It is often assumed that achieving valley selective excitation in pristine graphene with all-optical means is not possible due to the inversion symmetry of the system. Here, we demonstrate that both valley-selective excitation and valley-selective high-harmonic generation can be achieved in pristine graphene by using a combination of two counter-rotating circularly polarized fields, the fundamental and its second harmonic. Controlling the relative phase between the two colors allows us to select the valleys where the electron–hole pairs and higher-order harmonics are generated. We also describe an all-optical method for measuring valley polarization in graphene with a weak probe pulse. This work offers a robust recipe to write and read valley-selective electron excitations in materials with zero bandgap and zero Berry curvature.

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Go to http://brilliant.org/Undecided to sign up for free. And also, the first 200 people will get 20% off their annual premium membership. As revolutionary as plastics were for changing the course of manufacturing forever, 91% of plastics aren’t recycled. There has to be a better solution. In a previous video I covered how mycelium fungus may be a viable plastic replacement, but there’s another solution starting to bloom… Algae. And it’s showing up in a place you might not expect… your feet. What if I told you we could wear plastic-free flip flops made from algae?Watch Is Mycelium Fungus the Plastic of the Future? https://youtu.be/cApVVuuqLFY?list=PLnTSM-ORSgi4dFnLD9622FK77atWtQVv7Video script and citations:
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