Manufacturing Bits: August 25

South Pole neutrinos; microwaved quantum dots; multi-material 3D printers.


South Pole neutrinos
A group of researchers using an instrument buried deep in the ice at the South Pole have announced a new observation of high-energy neutrinos from beyond our solar system and the galaxy.

The IceCube Neutrino Observatory, a cubic-kilometer-sized detector sunk into the ice sheet at the South Pole, allows researchers to see the byproducts of neutrino interactions with the ice. The instrument’s array, IceTop, and its denser inner sub-detector, DeepCore, enhance its detection capabilities.

The IceCube Neutrino Observatory produced a recording of a neutrino event. (Source: National Science Foundation)

The IceCube Neutrino Observatory produced a recording of a neutrino event. (Source: National Science Foundation)

The observatory records 100,000 neutrinos each year, most of which are a type called “muon neutrinos” generated when cosmic rays interact with the Earth’s atmosphere. In contrast, researchers are attempting to find just a few dozen neutrinos generated elsewhere.

The muon is also an elementary particle, which is similar to the electron. They live for two millionths of a second before decaying. A neutrino is a sub-atomic particle that is nearly massless. They interact rarely with other matter. Trillions of them pass through our bodies each second without leaving a trace.

Neutrinos travel throughout the universe almost undisturbed by matter. The highest energy neutrinos are expected to emanate from the most extreme environments in the universe: powerful cosmic generators, such as black holes or massive exploding stars.

“Cosmic neutrinos are the key to yet unexplored parts of our universe and might be able to finally reveal the origins of the highest energy cosmic rays, including the rare ‘Oh-My-God’ particles,” said IceCube Collaboration spokesperson Olga Botner of Uppsala University.

Microwaved quantum dots
Quantum dots are inorganic semiconductor nano-crystals. The technology can be used to boost the color gamut in LCD TVs. It can also be used in LEDs and other products.

The problem? One drawback is that the dots are made of binary compounds such as cadmium. Many nations have voiced their concerns over the use of cadmium in quantum dots due to environmental issues.

Some TV makers are using quantum dots that don’t use cadmium, but the performance is not as robust.

In response, Oregon State University (OSU) has developed synthesized cadmium-free, visible light-emitting quantum dots using a simple technique: microwave heating.

Using a microwave-assisted continuous flow reactor, researchers produced LEDs with less toxic materials and chemistries.

In the lab, quantum dots were synthesized. Then, the quantum dot cores underwent a zinc-based cation exchange reaction in a reactor, according to researchers. This was followed by the growth of a zinc sulfide shell.
The process enabled quantum dots with a composition of about 98% zinc sulfide. The compound improved the stability of the photoluminescence (PL). And the synthesized dots have a PL down conversion efficiency of about 65% when using a blue LED source, according to OSU.

“There are a variety of products and technologies that quantum dots can be applied to, but for mass consumer use, possibly the most important is improved LED lighting,” said Greg Herman, an associate professor and chemical engineer in OSU’s College of Engineering, on the university’s Web site.

“We may finally be able to produce low cost, energy efficient LED lighting with the soft quality of white light that people really want,” Herman said. “At the same time, this technology will use nontoxic materials and dramatically reduce the waste of the materials that are used, which translates to lower cost and environmental protection.”

Multi-material 3D printers
3D printers are gaining steam. The latest 3D printers involve so-called multi-material capabilities. In multi-material 3D printing, the system allows users to combine several base resins at once.

The problem? Multi-material 3D printers are expensive, according to the Massachusetts Institute of Technology (MIT).

In response, researchers from MIT have developed a simple and cheaper 3D printer that can print 10 different materials at once with 40-micron resolutions.

MIT’s 3D printer, dubbed MultiFab, was built using off-the-shelf components that cost about $7,000. MultiFab enables users to embed circuits and sensors into an object. The system has demonstrated the ability to print smartphone cases, LED lenses and other products.

Next-generation 3D printer (Source: MIT)

Next-generation 3D printer (Source: MIT)

MultiFab makes use of machine vision technology, enabling the system to print objects in a more accurate fashion. In addition, the printer is also self-calibrating and self-correcting, according to MIT.

“The platform opens up new possibilities for manufacturing, giving researchers and hobbyists alike the power to create objects that have previously been difficult or even impossible to print,” says Javier Ramos, a research engineer at MIT.

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