Purdue engineers develop “cool” MEMS device

WEST LAFAYETTE, Ind. - Engineers at Purdue University have developed a “micro-pump” cooling device small enough to fit on a computer chip that circulates coolant through channels etched into the chip. The new MEMS device has been integrated onto a silicon chip that is about one centimeter square.

Innovative cooling systems will be needed for future computer chips that will generate more heat than current technology, and this extra heating could damage electronic devices or hinder performance, said Suresh Garimella, a professor of mechanical engineering.

Brian Iverson, a mechanical engineering doctoral student at Purdue, holds up a disk containing several “micro-pump” cooling devices small enough to fit on a computer chip. The tiny pumps circulate coolant through channels etched into the chip. Photo courtesy of David Umberger/Purdue University
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Chips in today’s computers are cooled primarily with an assembly containing conventional fans and “heat sinks,” or metal plates containing fins to dissipate heat. But because chips a decade from now will likely contain upwards of 100 times more transistors and other devices, they will generate far more heat than chips currently in use, Garimella said.

The prototype chip contains numerous water-filled micro-channels, grooves about 100 microns wide. The channels are covered with a series of electrodes, electronic devices that receive varying voltage pulses in such a way that a traveling electric field is created in each channel. A pumping action is created by electrohydrodynamics, which uses the interactions of ions and electric fields to cause fluid to flow.

Nanostars could shine light on chemical sensing

HOUSTON - Optics research from Rice University’s Laboratory for Nanophotonics (LANP) suggests that tiny gold particles called nanostars could become powerful chemical sensors.

Nanostars, named for their spiky surface, incorporate some of the properties of often-studied photonic particles like nanorods and quantum dots. For example, they deliver strong spectral peaks that are easy to distinguish with relatively low-cost detectors. But Jason Hafner, associate director of LANP, and his team found unique properties too.

Nanostars, named for reasons that are obvious by looking at the image above, could open up new possibilities for sensing applications. Image courtesy of Rice University
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An analysis revealed that each spike on a nanostar has a unique spectral signature. Preliminary tests show that these signatures can be used to discern the three-dimensional orientation of the nanostar, which could open up new possibilities for 3-D molecular sensing. Their findings appeared in the journal Nano Letters.

Nanoparticles found to improve ultrasound images

COLUMBUS, Ohio - Nanotechnology may one day help physicians detect the very earliest stages of diseases like cancer, a study in the journal Physics in Medicine and Biology suggests. It would do so by improving the quality of images produced by one of the most common diagnostic tools used in doctors’ offices, the ultrasound machine.

In laboratory experiments on mice, scientists found that nanoparticles injected into the animals improved the resulting images. This study is one of the first reports showing that ultrasound can detect these tiny particles when they are inside the body, said Thomas Rosol, a study co-author and dean of the college of veterinary medicine at Ohio State University. The particles also can brighten the resulting image.

Clemson group develops “carbon dots”

CLEMSON, S.C. - Chemists at Clemson University say they have developed a new type of quantum dot that is the first to be made from carbon. Like their metal-based counterparts, these nano-sized “carbon dots” glow brightly when exposed to light and show promise for a broad range of applications, including improved biological sensors, medical imaging devices and tiny light-emitting diodes, the researchers say.

The carbon-based quantum dots show less possibility for toxicity and environmental harm and have the potential to be less expensive than metal-based quantum dots. Cheap, disposable sensors that can detect hidden explosives and biological warfare agents such as anthrax are among the possibilities envisioned by the researchers.

A microscope image of bacterial spores (Bacillus subtilis) labeled with luminescent carbon nanoparticles. B. subtilis serves as a common model for anthrax research. These carbon nanoparticles, or carbon dots, could lead to safer, disposable biosensors to detect biological warfare agents. Image courtesy of Ya-Ping Sun/Clemson University
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“Carbon is hardly considered to be a semiconductor, so luminescent carbon nanoparticles are very interesting both fundamentally and practically,” said study leader Ya-Ping Sun. “It represents a new platform for the development of luminescent nanomaterials for a wide range of applications.” The research was published in the Journal of the American Chemical Society.

Researchers explore nanotubes as minuscule metalworking tools

TROY, N.Y. - Bombarding a carbon nanotube with electrons causes it to collapse with such incredible force that it can squeeze out even the hardest of materials, much like a tube of toothpaste, according to an international team of scientists. The researchers suggest that carbon nanotubes can act as minuscule metalworking tools, offering the ability to process materials as in a nanoscale jig or extruder.

Engineers use a variety of tools to manipulate and process metals. For example, handy “jigs” control the motion of tools, and extruders push or draw materials through molds to create long objects of a fixed diameter. The new findings suggest that nanotubes could perform similar functions at the scale of atoms and molecules, the researchers say. The results also demonstrate the impressive strength of carbon nanotubes against internal pressure, which could make them ideal structures for nanoscale hydraulics and cylinders.

A multi-walled carbon nanotube is partly filled with an iron carbide nanowire. The work is the result of an international collaboration. Photo courtesy of Johannes Gutenberg University/Banhart
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“Researchers will need a wide range of tools to manipulate structures at the nanoscale, and this could be one of them,” says Pulickel Ajayan, professor of materials science and engineering at Rensselaer Polytechnic Institute and an author of the paper. “For the time being our work is focused at the level of basic research, but certainly this could be part of the nanotechnology tool set in the future.”

The paper is the latest result of Ajayan’s longtime collaboration with researchers at Johannes Gutenberg University in Mainz, Germany; the Institute for Scientific and Technological Research of San Luis Potosi, Mexico; and the University of Helsinki in Finland. The paper appeared in Science.

UCLA engineers announce spin wave breakthrough

LOS ANGELES - Engineers at the University of California at Los Angeles Henry Samueli School of Engineering and Applied Science announced new semiconductor spin wave research. Adjunct professor Mary Mehrnoosh Eshaghian-Wilner, researcher Alexander Khitun and professor Kang Wang created three novel nanoscale computational architectures using technology they pioneered, called “spin-wave buses,” as the mechanism for interconnection. The three nanoscale architectures are power efficient and possess a high degree of interconnectivity.

“Progress in the miniaturization of semiconductor electronic devices has meant chip features have become nanoscale. Today’s current devices, which are based on complementary metal oxide semiconductor standards, or CMOS, can’t get much smaller and still function properly and effectively. CMOS continues to face increasing power and cost challenges,” Wang said.

In contrast to traditional information processing technology devices that simply move electric charges around while ignoring the extra spin that tags along for the ride, spin-wave buses put the extra motion to work transferring data or power between computer components. Information is encoded directly into the phase of the spin waves. Unlike a point-to-point connection, a “bus” can logically connect several peripherals. The result is a reduction in power consumption and less heat.

Nanotube membranes open possibilities for cheaper desalinization

LIVERMORE, Calif. - A nanotube membrane on a silicon chip the size of a quarter may offer a cheaper way to remove salt from water. Researchers at the Lawrence Livermore National Laboratory have created a membrane made of carbon nanotubes and silicon that may offer, among many possible applications, a less expensive method for desalinization.

Billions of nanotubes act as the pores in the membrane. The super smooth inside of the nanotubes allows liquids and gases to rapidly flow through, while the tiny pore size can block larger molecules.

The team was able to measure the flow of liquids and gases by making a membrane on a silicon chip with carbon nanotube pores as the holes of the membrane. The membrane is created by filling the gaps between aligned carbon nanotubes with a ceramic matrix material. The pores are so small that only six water molecules could fit across their diameter.

The research resulted from collaboration between Olgica Bakajin and Aleksandr Noy, both recruited to Lawrence Livermore Lab as “Lawrence Fellows” - the laboratory’s initiative to bring in young, talented scientists. The principal contributors to the work are postdoctoral researcher Jason Holt and Hyung Gyu Park, a UC Berkeley mechanical engineering graduate student and student employee at Livermore. The research appeared in the journal Science.