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Warning on fracture of the alumina-bearing couple delta ceramic liner in hip implants

Although the fracture rate of third-generation alumina-bearing couples is low, we believe that it may not be possible to eliminate the actual risk of alumina head fracture. Patients should be informed about the potential for this complication before receiving an alumina-bearing couple.

Polymer nanocomposites drive opportunities in the automotive sector

Polymer nanocomposites represent a new class of multiphase materials containing dispersion of nano-sized filler materials such as nanoparticles, nanoclays, nanotubes, nanofibers etc. within the polymer matrices. These multifunctional nanocomposites exhibit excellent mechanical properties, but also display an outstanding combination of optical, electrical, thermal, magnetic and other physico-chemical properties. It is believed that the molecular level interactions between the nanoparticles and polymer matrices along with the presence of very high nanoparticle-polymer interfacial area play a major role in influencing the physical and mechanical properties of nanocomposites.

Magnetic memory miniaturized to just 12 atoms

The smallest magnetic-memory bit ever made-an aggregation of just 12 iron atoms created by researchers at IBM-shows the ultimate limits of future data-storage systems. The magnetic memory elements don’t work in the same way that today’s hard drives work, and, in theory, they can be much smaller without becoming unstable. As the semiconductor industry bumps up against the limits of scaling by making memory and computation devices ever smaller, the IBM Almaden research group, led by Andreas Heinrich, is working from the other end, building computing elements atom-by-atom in the lab. Data-storage arrays made from these atomic bits would be about 100 times denser than anything that can be built today.

The solar shakeout, and what to expect in 2012

With bankruptcies an unwanted but increasingly common feature of the photovoltaic landscape, questions abound as to what to expect from 2012. Lux Research’s Matt Feinstein investigates and picks a list of winners from the up and downstream markets. Innovation it seems, and not just when it comes to technology, is the key

New thermal diodes: Jumping droplets take a lot of heat, as long as it comes in a cool way

Microscopic water droplets jumping between surfaces that repel and attract moisture could hold the key to a wide array of more energy efficient products, ranging from large solar panels to compact laptop computers. Duke University engineers have developed a new way of producing thermal diodes, devices which regulate heat to preferentially flow in a certain direction, effectively creating a thermal conductor in the forward direction and an insulator in the reverse direction.

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A fully automated robot arm pours molten glass into the sample mold. Credit: Knud Dobberke; Fraunhofer ISC.

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Instant-on computers may be possible with modified materials

Researchers from three NSF-supported Materials Research Science and Engineering Centers at Penn State and Cornell recently added ferroelectric capability to materials used in common computer transistors–a feat that scientists have tried to achieve for more than half a century. Ferroelectric materials—found in subway, ATM, fuel and other “smart cards”—may eliminate time-consuming booting and rebooting of computer operating systems by providing an “instant-on” capability. Besides reducing the waiting time for everyday computer users, the discovery could pave the way for memory devices that are lower power, higher speed, and more convenient to use. The materials may also help prevent losses from power outages.

A super-absorbent solar material

A new nanostructured material that absorbs a broad spectrum of light from any angle could lead to the most efficient thin-film solar cells ever. Researchers at Caltech are applying the design to semiconductor materials to make solar cells that they hope will save money on materials costs while still offering high power-conversion efficiency. Initial tests with silicon suggest that this kind of patterning can lead to a fivefold enhancement in absorbance.

Robot speeds up glass development

Model by model, the electronics in a car are being moved closer to the engine block. This is why the materials used for the electronics must resist increasing heat—so the glass solder being used as glue must be continually optimized. For the first time ever, a robot takes on the task of developing new types of glass and examining their characteristics. Researchers will introduce this robot at the “productronica” trade fair to be held in Munich, Germany, from November 15 - 18, 2011

Better batteries

A team of engineers at Northwestern University has created an electrode for lithium-ion batteries—rechargeable batteries such as those found in cellphones and iPods —that allows the batteries to hold a charge up to 10 times greater than current technology. Batteries with the new electrode also can charge 10 times faster than current batteries. The researchers combined two chemical engineering approaches to address two major battery limitations—energy capacity and charge rate—in one fell swoop. In addition to better batteries for cellphones and iPods, the technology could pave the way for more efficient, smaller batteries for electric cars.

New journal on disruptive science and technology launching in 2012

Mary Ann Liebert, Inc., publishers is launching a new journal, the Journal of Disruptive Science and Technology, a highly innovative, bimonthly peer-reviewed journal that seeks to publish game-changing research that has the potential to significantly improve human health, well-being, and productivity. The Journal will present new and innovative results, essential data, cutting-edge discoveries, thorough syntheses and analyses, and publish out-of-the-box concepts that will improve the way we live.

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Optical vortex generated using a radial polarization converter. Credit: Altechna; Kazansky et al., University of Southampton.

Back in May, University of Southampton researchers published a short paper in Applied Physics Letters regarding how they used novel microscopy-based optical polarization techniques to turn nanostructured silica glass into a new type of relatively inexpensive, data-dense, stable computer memory. Now, the group says it has extended five-dimensional memory capabilities to their system, adding even more data storage possibilities, and the potential applications seem to be mounting.

Let’s back up a little bit. The research group, led by Peter Kazansky at the university’s Optoelectronics Research Center, describes in the initial paper how they are able—if I understand this correctly—to use a femtosecond laser combined with a space variant polarization converter to “write” self-assembled nanostructures in silica glass. The vortices can either be “left handed” or “right handed” depending on whether the converter is used to induce radial or azimuthal polarization. In other words, on a nanoscale, information can be stored by switching from radial to azimuthal polarization (or vice versa) by controlling the “handedness” of the incident circular polarization.

Put even more simply, this approach uses microscopy tools and ultra-short laser pulses to create tiny voxels (volumetric pixels) in glass.

The authors acknowledge that somewhat similar techniques have been used with liquid crystals and photolithography/subwavelength gratings. However, they point out that a problem with the former is that the liquid crystals have a low damage threshhold, and a problem with the latter is that there are limits to the resolution.

Besides resilience and resolution, several other immediate advantages to nanostructured glass approach jump out, particularly in regard to costs and permanence.

For example, the investigators claim the use of microscopy tools makes the approach 20-times cheaper and it is more compact. In a university news release, Kazansky says, “Before this we had to use a spatial light modulator based on liquid crystal which cost about £20,000. Instead we have just put a tiny device into the optical beam and we get the same result.”

However, since publication of the paper, the researchers have developed this technology even further and adapted it for a five-dimensional optical recording. “We have improved the quality and fabrication time and we have developed this five-dimensional memory, which means that data can be stored on the glass and last forever,” said Martynas Beresna, lead researcher for the project. “No one has ever done this before.”

When Beresna says, “No one has ever done this before,” I think he is mainly referring to the use of glass plus the combination of five-dimensional memory. Five-dimensional memory (think of this as two polarization orientation options, plus three wavelength options) isn’t novel by itself. In 2009, for example, Nature carried a widely covered paper about a team led by Min Gu, which was doing 5D memory work with gold nanorods in a polymer on a glass substrate.

In an interview with the London Telegraph, Beresna says their rewritable approach can, “currently store the equivalent of a whole Blu-ray Disc – up to 50GB of data – on a piece of glass no bigger than a mobile phone screen.”

The researchers say the stability of the glass they studied, its resistance to temperature, moisture, etc., gives it an obvious edge compared to existing archival media. On this issue, Beresna also says in the Telegraph piece, “Data can be stored on the glass and last forever. It could become a very stable and safe form of portable memory. It could be very useful for organizations with big archives. At the moment companies have to back up their archives every five to ten years because hard-drive memory has a relatively short lifespan. Museums who want to preserve information or places like the National Archives where they have huge numbers of documents, would really benefit.”

Regarding the mention of table-top particle accelerators in the headline—something I’ve always wanted for my coffee table at home—the authors don’t directly mention this, but the university’s press release does speak of particle accelerators as another possible application for the radial polarization converters, along with high-resolution medical imaging and laser processing of materials.

The university and the researchers have already partnered with a Lithuanian company, Altechna, to transfer the technology to various markets. The Altechna website does not specifically discuss a memory device, but does suggest uses related to laser machining, optical tweezers and Raman spectroscopy systems.

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IBM Research chart compares memory technologies. Credit: IBM Research

Two new studies serve as bookend demonstrations of the near-term potential for phase-change memory materials for use as nonvolatile data storage devices, and the long-term potential for these materials to change fundamentally what a computer memory is. A third study just out considers the efficiency of the crystalline to amorphous transformation on the lattice scale.

In an important step toward near-term adoption of PCMM technology for nonvolatile data storage, IBM Research, Zurich, Switzerland has demonstrated a device capable of stable multibit storage over an extended time.

Longer term, a research group at the University of Exeter in the United Kingdom has shown that PCMMs can store and process data simultaneously. That is, PCMM has the potential to mimic the human brain’s neurons and synapses and have ability to learn and process information.

A press release from IBM describes work that breaks down two barriers to using PCMM: the ability to store multiple data bits and the ability of the material to reliably store data for extended time periods.

The advantages of PCMM over flash memory are volume, speed and durability. The IBM press release says that PCMMs can write and retrieve data 100 times faster than flash and can endure 10 million or more write cycles.

By comparison, today’s consumer-grade flash memories last about 3,000 write cycles (which tend to be more than enough) and enterprise-grade flash memories are good for upwards of 30,000 write cycles. The real promise of PCMM materials is for the enterprise-grade (nonconsumer applications like business or research IT). Durable for over 300 times more write cycles, combined with the ability to hold data when the power is off, PCMM would allow servers and computers to boot instantly and to handle very large volumes of data quickly. An earlier post described a prototype device that was demonstrated at the Device Automation Conference in June and summarized the computing advantages of PCMM memories.

Applying a voltage, current or optical pulse causes the phase change to occur, and the extent of the phase change is proportional to the applied stimulus, and this, in turn, is a way to control the resistance of the cell. Taking advantage of the proportionality of the resistance, the IBM team was able to store multiple bits—four in this case—in a single cell by manipulating the applied voltage.

Getting the data in is only valuable if the data can be gotten out later. PCMMs have a tendency to “resistance drift” caused by structural relaxation of the amorphous material, which increases resistance and, therefore, errors during read-out of the data. The press release explains that “…on average, the relative order of programmed cells with different resistance levels does not change due to drift,” which allowed the IBM team to solve the problem with an “advanced modulation coding technique that is inherently drift tolerant.”

An IBM test device is storing bits in a subarray of 200,000 cells in a PCMM test chip. The retention test has been running for over five months, thus demonstrating a volume and stability that are of practical use.

On a smaller scale but with potentially bigger implications, David Wright’s group at the University of Exeter in the UK used a single cell of PCMM to demonstrate that the material could store and process information simultaneously, similar to the way neurons and synapses do in the human brain. They also showed the ability perform the simple arithmetic operations of addition, subtraction, multiplication and division. Results are published in Advanced Materials, “Arithmetic and Biologically-Inspired Computing Using Phase-Change Materials” (doi: 10.1002/adma.201101060)

As explained in a press release from the Exeter, the processing and memory functions for current technology are separate, “resulting in a speed and power ‘bottleneck’ caused by the need to continually move data around.” Multicore processors are an effort to get around the power and speed lost to the bottleneck. The human brain, however, composed of neurons and synapses, does not distinguish between processing (i.e., computation) and memory.

In an interview published by The Engineer, Wright, a professor at Exeter, said “We’ve shown that phase-change materials have a natural accumulation and threshold property, which makes them a good candidate for simple implementation of a hardware neuron.” Thus, PCMM components may be able to be connected in “networks via structures akin to synapses, potentially opening up an entirely novel way of computing.”

The Exeter group studied GeSbTe and AgInSbTe compounds. The IBM press release did not specify the material, but a chalcogenide composition is assumed.

Finally, a just-published paper in Nature Nanotechnology also addresses PCMM technology by considering the nature of the amorphous state (see Simpson, et al, “Interfacial phase-change memory,” doi: 10.1038/nnano.2011.96). In an earlier post we reported on work that confines the PCMM in a mesoporous SiO₂ scaffold to reduce the power needed for the phase change. Similarly, this paper aims to reduce the energy needed to “switch” the material by limiting the movement of atoms to a single dimension, which greatly reduces losses to entropy. By aligning the c-axis of a hexagonal Sb₂Te₃ layer in the <111> direction of a cubic GeTe layer in a superlattice structure, germanium atoms can switch sites at the interface of the layers. The abstract says they have demonstrated “interfacial phase-change memory data storage devices with reduced switching energies, improved write–erase cycle lifetimes and faster switching speeds.”

The IBM press release says PCMM nonvolatile memories could start replacing flash in the next five years. The basic research coming out of labs like Wright’s, Simpson’s and Chen’s will be the foundation of second and third generation PCMM devices.

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Volkov & Kaplan credit: Will Kirk/JHU

Two Johns Hopkins researchers believe they have developed a new method to use lasers to manipulate electrons in a crystal array, and if the discovery holds up to testing, it could lead to new forms of computer memory, biohazard alarms and cancer cell detectors. Alexander Kaplan, a professor in the Department of Electrical and Computer Engineering in Johns Hopkins’ Whiting School of Engineering and Sergei Volkov, a postdoctoral fellow in his lab, published their theory recently in the journal Physical Review Letters. Kaplan and Volkov’s ideas run slightly counter to the assumption that when lasers interact with atoms in a crystal, the light forces the electrons to move in a uniform fashion with their neighbors. The duo says that under the right conditions, electrons can abandon their lock-step motion and temporarily part ways with nearby electrons and then bump together. Kaplan and Volkov liken the action to swing dancing where partners push away and then pull back together.

“[W]e’ve concluded that under certain circumstances, the nearest atoms will behave much differently. Their electrons will move violently apart and come back together again, staging a sort of ‘nano-riot. By choosing particular atoms in the proper configuration and directing the right laser light at them, we could control the behavior of these ‘nano-dancers,’” said Kaplan.

According to a Johns Hopkins news release, at least three conditions are necessary for electrons to behave the way Kaplan and Volkov describe:

1. the system must be very small, typically involving no more than a few hundred atoms, and the atoms must be arranged in a one-dimensional or two-dimensional configuration.
2. the atoms must be grouped in a sufficiently close concentration; interestingly, though, this arrangement may allow more space between atoms than exists in a typical crystal
3. the frequency of the laser driving the atoms must be closely tuned to one of the specific frequencies of the atomic electrons - the so-called atomic resonance - in the way that a radio receiver might be tuned to a particular station.

When these conditions are met, electrons can get “coupled” instead of behaving uniformly as predicted under the prevailing Lorentz-Lorenz theory. The practical implications are intriguing:

“The essential thing is, these are completely designable atomic structures. Fortunately, once this atomic structure is built, the ‘dancing style’ of the atoms can be controlled by the laser tuning,” Kaplan said. “Furthermore, if the laser intensity is sufficient, we believe the atoms in this lattice will engage in so-called nonlinear behavior. That means they can be made to behave like switches in a computer. They will act like a computer’s memory or logic components, assuming the positions of either 1 or 0, depending on the initial conditions.”

Such a logic component would generate little heat and allow further miniaturization of electronic components. The JHU news release also reports that Kaplan and Volkov believe that groups of atoms in the right lattice could be “designed so that when a specific foreign bio-molecule enters a system, the atomic electron ‘dancing’ would stop. Because of this characteristic. . . the system could be designed to trigger an alarm signal whenever a bio-hazard or perhaps a cancer cell was detected.”

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