Manufacturing Bits: Jan. 16

Coherent X-ray imaging; cheaper MRI; geometry mystery.


Coherent X-ray imaging
Russia’s National University of Science and Technology MISIS has developed a non-destructive way to observe the inner structures of photonic crystals.

The technology, called ptychographic coherent X-ray imaging, obtains the electron density of colloidal crystals. Ptychography is a lensless, X-ray coherent imaging technique.

Others are also working on the technology, including the Paul Scherrer Institute (PSI). Last year, PSI made detailed non-destructive, three-dimensional images of a tiny chip.

3-D representation of the internal structure of a microchip (Photo: Paul Scherrer Institute/Mirko Holler)

Researchers from the National University of Science and Technology MISIS, meanwhile, used an incident X-ray wavefield technique. This, in turn, enables a high-resolution image of a colloidal crystal structure. The image reveals a structure with an average domain size of about 2µm. It also showed the presence of random hexagonal close-packed layers, according to researchers.

The technology solves a major problem. Traditional electronic microcopy can observe the defects on two-dimensional photonic crystals. But microcopy has an issue in terms of resolving bulk photonic crystals.

“A photonic crystal is like a waveguide for the light, only better. The waveguide is almost impossible to bend, and it’s impossible to create photonic microchips on waveguides. A photonic crystal is most suitable for the creation of integral optical microchips where the light can spread where the developers need it to,” said Ilya Besedin, an engineer from the NUST MISIS Laboratory of Superconducting Metamaterials, on the university’s Web site.

“We have shown that now, with the help of X-rays, we can observe defects in periodic mesoscopic structures. The next stage of specification is to expose these structures to radiation with an X-ray laser. This can give a more accurate picture of the internal structure, but there are also some difficulties. The laser beam is, by definition, more powerful than just an outgoing one from synchrotron. While increasing the power, the probability of destroying the investigated structure increases significantly, which is not (good). Ptychography also allows researchers to study the inner structure of a crystal without destroying it. That is why such a method will definitely find its application,”Besedin said.

Cheaper MRI
Magnetic resonance imaging (MRI) is used for the diagnosis of cancer and other diseases, but the cost of the technology is relatively high.

In response, NUST MISIS has developed a low-field MRI prototype. The prototype is based on magnetic materials and components produced in Russia.

The system does not incorporate rare-earth permanent magnets from China. China is the world’s main producer of rare earth metals and rare-earth permanent magnets. In some cases, the magnets from China are expensive.

The use of domestic magnetic components allows Russia to develop a less expensive system. “We have developed an innovative technology for the production of low cost hard-magnetic materials and permanent magnets manufactured from alloys of rare, domestic earth metals and their compounds, including the ones obtained in the processing of industrial waste magnetic production,” said Evgeny Gorelikov, the project head and deputy director of the NUST MISIS Engineering Center for Industrial Technologies, on the university’s Web site.

“During the production of raw materials for permanent magnets we have managed to reduce their cost by 1.5 times through the use of industrial waste magnetic production and cheap alloys of rare earth metals. The use of new soft magnetic materials has allowed us to develop magnetic conductors for a magnetic system of the scanner with low loss while maintaining high values of magnetization saturation (more than 2 T). All this allowed us to design and reduce the weight of permanent magnets used in the design of magnetic systems by almost 30%, and thus to reduce the cost of the devices,” Gorelikov said.

Geometry mystery
Mathematicians from the Israel Institute of Technology and the Moscow Institute of Physics and Technology (MIPT) have proved László Fejes Tóth’s zone conjecture.

The math formula says that if a unit sphere is completely covered by several zones, their combined width is at least π. This is important for discrete geometry, according to MIPT. A larger description of the zone conjecture can be found here.

László Fejes Tóth’s conjecture. A sphere with a radius of one is covered by zones of equal width. The least possible combined width of all zones is π. Each zone is uniquely colored. (Source: Moscow Institute of Physics and Technology)

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