Printing Human Tissue
Oxford University has demonstrated a proprietary 3D printer that can create materials with the properties of living tissue.

The materials consist of connected water droplets, which are encapsulated within lipid films. These “droplet networks” could form the building blocks of a new kind of drug delivery technology or someday replace damaged human tissue.

Each droplet is an aqueous compartment about 50 microns in diameter, according to Oxford, whose 3D printer has created networks of up to 35,000 droplets. The 3D printer itself consists of two droplet generators, each with a glass capillary nozzle, next to an oil well mounted on a motorized micromanipulator.

“We aren’t trying to make materials that faithfully resemble tissues but rather structures that can carry out the functions of tissues,” said Professor Hagan Bayley of Oxford’s Department of Chemistry, on the university’s Web Site. “We’ve shown that it is possible to create networks of tens of thousands of connected droplets. The droplets can be printed with protein pores to form pathways through the network that mimic nerves and are able to transmit electrical signals from one side of a network to the other.”

DNA Lithography
Harvard University and the Massachusetts Institute of Technology (MIT) have devised a metallized DNA nanolithography process for encoding and transferring spatial information for use in patterning graphene. This, in turn, could enable the production of novel devices based on graphene materials.

DNA sequences can be manipulated to form many different shapes. In fact, DNA origami and single-stranded tiles can be used to devise different shapes, but the ability to pattern these materials has been limited. And DNA degrades when exposed to sunlight or oxygen, according to researchers.

As a result, researchers have devised a new chemical process. First, DNA is put on a graphene surface using a molecule. The DNA is then coated with small clusters of silver along the surface. A layer of gold is deposited on top of the silver.

Then, the DNA can be used as a mask for a process called DNA nanolithography or plasma lithography. The metallized DNA mask allows for plasmonic enhanced Raman spectroscopy of the underlying graphene, providing information on defects, doping and lattice symmetry.

The process also leaves behind a graphene structure identical to the original DNA shape. This DNA nanolithography process could ultimately create diverse circuit elements, including nanorings, three- and four-membered nanojunctions, and extended nanoribbons, according to researchers.

Driving without GPS
DARPA researchers at the University of Michigan have devised a breakthrough timing and inertial measurement unit (TIMU). The technology aids in navigation when GPS is temporarily unavailable.

The single chip TIMU prototype contains of a six-axis IMU, which includes three gyroscopes and three accelerometers. It also integrates a master clock into a single miniature system, smaller than the size of a penny.

Each of the six micro-fabricated layers of the TIMU is only 50 microns thick. This design comes in a 10 cubic millimeter package. “Both the structural layer of the sensors and the integrated package are made of silica,” said Andrei Shkel, DARPA program manager, on the agency’s site. “The hardness and the high-performance material properties of silica make it the material of choice for integrating all of these devices into a miniature package. The resulting TIMU is small enough and should be robust enough for applications—when GPS is unavailable or limited for a short period of time—such as personnel tracking, handheld navigation, small diameter munitions and small airborne platforms.”

—Mark LaPedus

The Next Wonder Material
Graphene is generating a wave of interest in the semiconductor community. Supposedly, the next new and wonder material is molybdenite, a mineral of molybdenum disulfide (MoS2) that resembles graphene.

Some time ago, researchers from École Polytechnique Fédérale de Lausanne (EPFL) talked about building molybdenite chips. Now, EPFL has combined two materials, graphene and molybdenite, to enable a flash memory prototype.

Scientists have combined two materials with advantageous electronic properties – graphene and molybdenite – into a flash memory prototype that is very promising in terms of performance, size, flexibility and energy consumption. Source: EPFL

Graphene is a better conductor. It consists of one-atom-thick planar sheets, which are packed in honeycomb crystal lattice structures. But it doesn’t have a band gap, meaning it can’t be turned off in a system. Unlike graphene, MoS2 has an ideal band gap. MoS2 also has conducting properties.

The flash memory prototype from EPFL resembles a sandwich. On the bottom, there is a layer of graphene. The electrodes from this layer transmits electricity to the middle layer, which is based on MoS2. The MoS2 layer channels the electrons. On the top, there is an element made up of several layers of graphene, which captures electric charge.

On EPFL’s Web site, Andras Kis, director of EPFL’s Laboratory of Nanometer Electronics and Structures (LANES), said: “Combining these two materials enabled us to make great progress in miniaturization, and also using these transistors we can make flexible nanoelectronic devices.”

Mimicking The Brain
IBM has discovered a new way to operate chips using tiny ionic currents. These are streams of charged atoms that could mimic the event-driven way in which the human brain operates.

This means that nonvolatile chips using this novel phenomenon could be used to store and transport data in a more efficient manner.

Researchers from IBM have demonstrated the ability to reversibly transform metal oxides between insulating and conductive states. This is demonstrated by the insertion and removal of oxygen ions driven by electric fields at oxide-liquid interfaces.

Optical image of a typical ionic liquid (IL) gated device with a droplet of IL on top of the gate electrode and the oxide channel. The gold squares are pads used to make contact to the device via wire-bonding. On right is the magnified image of the device showing the channel (brownish yellow) and the gold electrical contacts (bright yellow). The contacts on the right and left of the channel are the source and drain contacts. The four other contact are used for 4-wire resistance & Hall measurements. (Credit: IBM)

Once the oxide materials, which are innately insulating, are transformed into a conducting state, IBM showed that the materials maintain a stable metallic state even when power to the device is removed.

To achieve this technology, IBM applied a positively charged ionic liquid electrolyte to an insulating oxide material, vanadium dioxide, and converted the material to a metallic state. The material held its metallic state until a negatively charged ionic liquid electrolyte was applied, to convert it back to its original, insulating state, according to IBM.

“Our ability to understand and control matter at atomic scale dimensions allows us to engineer new materials and devices that operate on entirely different principles than the silicon-based information technologies of today,” said Stuart Parkin, fellow at IBM Research, on the company’s Web site. “Going beyond today’s charge-based devices to those that use miniscule ionic currents to reversibly control the state of matter has the potential for new types of mobile devices. Using these devices and concepts in novel three-dimensional architectures could prevent the information technology industry from hitting a technology brick wall.”

Quantum Dot Solar
By embedding quantum dots within a collection of nanowires, the Massachusetts Institute of Technology (MIT) has found a way to boost the efficiencies of solar cells.

Solar cells based on quantum dots are still in their infancy. Still, the technology can be made in a room-temperature process, thereby avoiding the complications associated with traditional solar cell production. Another advantage of quantum dot solar cells is that they can be tuned to absorb light over a wide range, said Joel Jean, a doctoral student in MIT’s Department of Electrical Engineering and Computer Science.

MIT’s quantum dot solar cell was devised by using a layer of gold at the top. A layer of indium-tin-oxide was used at the bottom to form the two electrodes of the solar cell.

Then, researchers devised vertical arrays of zinc-oxide (ZnO) nanowires. The nanowires can decouple light absorption from carrier collection in lead sulfide (PbS) quantum dot solar cells. This, in turn, can increase power conversion efficiencies by 35%, according to MIT. The resulting ordered bulk heterojunction devices achieve short-circuit current densities in excess of 20 mA cm−2 and efficiencies of up to 4.9%, according to researchers.

All told, MIT believes it can boost overall efficiency beyond 10%.

—Mark LaPedus

Thanks For The Memories
The Massachusetts Institute of Technology (MIT) has created genetic circuits that perform logic functions and can remember the results. The data, in turn, is encoded in DNA and passed on for dozens of generations. The technology could pave the way for therapeutic, diagnostic and basic science applications.

Logic and memory are functions of circuits that generate state-dependent responses. MIT devised a technology for assembling synthetic genetic circuits that use recombinases to implement Boolean logic functions with stable DNA-encoded memory of events.

Synthetic genetic circuits. Source: MIT.

Recombinases, which are genetic recombination enzymes, are used in multicellular organisms to manipulate the structure of genomes. In MIT’s research, recombinases can cut out stretches of DNA, flip them, or insert them. The activation of those enzymes allows the circuits to count events happening inside a cell, according to researchers.

Researchers have created 16 two-input Boolean logic functions in living Escherichia coli cells based on multiple logic gates. They demonstrated long-term maintenance of memory for at least 90 cell generations. MIT also demonstrated the ability to interrogate the states of these synthetic devices with fluorescent reporters.

Using this approach, MIT created two-bit digital-to-analog converters. The converters are used for encoding multiple stable gene expression outputs using transient inputs of inducers.

Used as environmental sensors, such circuits also could provide long-term memory. “You could have different digital signals you wanted to sense, and just have one analog output that summarizes everything that was happening inside,” said Timothy Lu, an MIT assistant professor of electrical engineering and computer science, on the university’s Web site.

“Almost all of the previous work in synthetic biology that we’re aware of has either focused on logic components or on memory modules that just encode memory. We think complex computation will involve combining both logic and memory, and that’s why we built this particular framework to do so,” he added.

Superionic Materials
SLAC National Accelerator Laboratory and Stanford have devised a new class of superionic materials to enable faster memories and more efficient batteries. The material, copper sulfide, can switch between high and low ionic conductivity states much faster than previously thought.

Superionic materials are multi-component solids with characteristics of both solids and liquids. When heated above a temperature associated with a structural phase transition, the materials exhibit liquid-like ionic conductivities and dynamic disorder within a rigid crystalline structure.

Researchers used X-ray spectroscopy and scattering techniques to obtain an atomic-level, real-time view of the transition state in copper sulphide nanocrystals. They observed the transformation to occur on a 20 picosecond timescale, according to researchers.

Researchers found that 10nm nanodisks of copper sulfide, switched at about 70 degrees C, can be controlled by light to switch in only 20 trillionths of a second, a million times faster than previously observed.

Artist's rendering of copper sulfide above the critical temperature at which it becomes "superionic." (Credit: Greg Stewart/SLAC National Accelerator Laboratory)

On SLAC’s Web site, Aaron Lindenberg of the Stanford Institute for Materials and Energy Sciences and the Stanford PULSE Institute, said: “For the first time, we’ve seen the atomic-scale details of exactly how these nanoscale materials transform, or switch, from a state that is poorly conducting to one that is highly conducting. And what we’ve learned gives us confidence about our ability to tune its structure and properties to be useful in new technologies.”

A Dual Damascene Replacement?
Dual damascene is the workhorse process flow for manufacturing the copper interconnects in chips. But some believe the dual damascene flow may extend to 10nm—and then could promptly run out of steam.

The next possible candidates to replace dual damascene are single damascene and subtractive etch. “As minimum pattern sizes drop below 14nm, it is unclear whether the damascene process will meet IC device requirements,” said Dennis Hess, a professor for the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology. “Renewed interest has therefore arisen in developing a process for subtractive etching/patterning of copper.”

For some time, Georgia Tech has been working on subtractive etch. Researchers have developed a hydrogen plasma-based approach to copper etching and patterning that can be performed at low temperatures. “Although subtractive patterning of copper with excellent selectivity to barrier layers at reasonable temperatures is feasible, this approach will require integration into the overall interconnect fabrication sequence,” Hess said.

Georgia Tech has made recent progress with the technology. “Initial investigations focused on removal of 100–300nm thick blanket copper layers. Preliminary patterning studies with pure hydrogen plasmas indicate that for pattern sizes of 600nm and above, sidewall angles are about 82 degrees; for 60 nm lines, the slope is about 73 degrees,” he said. “Etch studies have been performed at temperatures between -100 degrees and +100 degrees C. These results suggest that copper hydrides are the primary etch products, and gas phase copper emission has been observed by optical emission spectroscopy.”

The process demonstrated excellent selectivity to barrier layers such as Ta and Ti. “Pure hydrogen gives a copper etch rate of ~13nm/min at 10 degrees C; at this time, no optimization has been performed to determine the maximum etch rate possible, although with additives to the H2 plasma, an increase in etch rate is observed. Etching of a blanket 100nm copper layer on a 10 mm wafer leaves no detectable by XPS copper residue on the wafer,” he added.

—Mark LaPedus

Spintronics Are No Longer Spinning Its Wheels
Göttingen University and others have found a way to store up to 1 petabyte of data per square inch. One petabyte is equivalent to 1,000 terabytes or 1 million gigabytes. The Indian Institute of Science Education and Research, the Massachusetts Institute of Technology (MIT) and the Jülich Research Centre were also involved in the research.

Using a technology called spintronics, researchers have stored information in an organic molecule and read it at or close to room temperatures. Electronic coupling between the spin center of molecules are generally weak. But researchers have fused non-magnetic carbon atoms linked to one another in three benzene rings. Using spin injection, they chemically added an unpaired electron that carries a net spin.

Organic molecule with spin: The molecule is magnetic, allowing data to be read as "0" and "1" through the spin filter effect. Source: Göttingen University

Researchers constructed a molecular device using such molecules as templates. Using this technique, a device demonstrated an interfacial magnetoresistance of more than 20 per cent near room temperature. They also demonstrated the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. All told, the use of chemically amenable phenalenyl-based molecules enabled molecular-scale quantum spin memory and processors.

“Spin storage on an organic material and the successful reading at room temperature represent a breakthrough in organic spin electronics,” said Markus Münzenberg, a physicists from Göttingen University, on the entity’s Web site. “Spintronics integrated into flexible plastic components are already a familiar part of the organic LEDs employed in today’s displays, TV screens and smartphones. Our recently developed molecular units have a similar potential.”

Imprinting Photonic Devices
Using nanoimprint lithography, the Department of Energy, aBeam Technologies and others have demonstrated printable photonic devices at sub-10nm feature sizes, according to the Nanowerk Web site.

Researchers devised sub-10nm titanium dioxide (TiO2) nanostructures using nanoimprint and organic–inorganic resist materials. The process enables TiO2 films with feature sizes down to 5nm.

The resist material also permits fabrication of crack-free films over large areas. A post-imprint thermal annealing process allows a wide range of optical values. For instance, a refractive index higher than 2.0 and an extinction coefficient close to zero can be achieved in the visible wavelength range.

Applications for the technology include photonics, planar holograms, solar cells and LEDs. On Nanowerk’s site, Christophe Peroz, director of nanofabrication and optical devices at aBeam Technologies, said: “The core of our development is a process for patterning films with high refractive and high optical transparency which is suitable for fabricating printable photonic devices.

Natural Solar Cells
The University of Texas is using nanoimprint lithography to enable more efficient organic photovoltaic cells based on polymers.

Organic solar cells, which are flexible and semi-transparent, can be made using a screen-printing, inkjet or roll-to-roll process. But the best polymer solar cells have an efficiency of only 6% to 7%.

There are three acceptor deposition methods to make polymer solar cells: spin-coating, physical vapor deposition, and double nanoimprint or lamination.

Nanoimprint has emerged as a promising method, according to the Nanowerk Web site. The progress in the bulk heterojunction structures has improved the efficiency of polymer solar cells. But active layer morphology within this structure still remains disordered, according to researchers.

Nanoimprint is said to define the morphologies at higher resolutions. The carrier transport in conjugated polymers can be enhanced using nanoimprint-induced polymer chain alignment, according to researchers.

—Mark LaPedus

Seeing In The Dark
The University of Wisconsin-Madison, the U.S. Air Force and the U.S. Department of Defense have developed curved night-vision goggles using germanium nanomembranes.

Using flexible semiconductors, the goggles supposedly will make night vision more accurate and easier for soldiers and pilots to use.

There are several major challenges with the technology. “Because of their higher dark current, the image often comes up much noisier on germanium-based imagers,” said Zhenqiang Ma, a professor of electrical and computer engineering at the University of Wisconsin-Madison, on the university’s Web site. “We solved that problem.”

In a separate project, the U.S. Department of Defense also has provided Ma with $750,000 in support of development of imagers for military surveillance. The imagers span multiple spectra, combining infrared (IR) and visible light into a single image.

The current approach involves a sensor for IR images and a sensor for visible light. This combines the two images in post-processing. This, however, requires greater computing power and hardware complexity.

To enable the next-generation imager, researchers will implement a heterogeneous semiconductor nanomembrane technology. They will stack two incompatible materials on each pixel of the new imager in order to create a single image. The result will be imagers that can seamlessly shift between IR and visible images. The DoD is interested in IR, “because visible light can be blocked by clouds, dust, smoke,” Ma said.

It’s A Material World
Researchers led by the CSIRO and RMIT University have devised the layers of crystal known as molybdenum oxide, a new 2D material that enables the free flow of electrons at high speeds.

Researchers adapted graphene to create this new material. Monash University, the University of California at Los Angeles (UCLA) and the Massachusetts Institute of Technology (MIT) also participated in the work. The Commonwealth Scientific and Industrial Research Organization (CSIRO) is Australia’s national science agency.

Artist impression of high carrier mobility through layered molybdenum oxide crystal lattice. Credit: Dr Daniel J White, ScienceFX

Graphene itself consists of one-atom-thick planar sheets, which are packed in honeycomb crystal lattice structures. The technology is expensive and difficult to put into manufacturing. And it doesn’t have a band gap, meaning it can’t be turned off in a system.

Researchers were able to overcome graphene’s apparent limitations. They demonstrate that the energy bandgap of layered, high-dielectric α-MoO3 can be reduced to values viable for the fabrication of 2D electronic devices.

This is achieved through embedding Coulomb charges within the high dielectric media, thereby limiting charge scattering. Devices with α-MoO3 of ∼11 nm thickness were obtained. It also resulted in electron mobility values of >1,100 cm2/Vs, according to researchers.

“Within these layers, electrons are able to zip through at high speeds with minimal scattering,” said Serge Zhuiykov, a scientist from CSIRO on the research organization’s Web site. “The importance of our breakthrough is how quickly and fluently electrons–which conduct electricity – are able to flow through the new material.”

RMIT’s Professor Kourosh Kalantar-zadeh added: “Quite simply, if electrons can pass through a structure quicker, we can build devices that are smaller and transfer data at much higher speeds. While more work needs to be done before we can develop actual gadgets using this new 2D nano-material, this breakthrough lays the foundation for a new electronics revolution and we look forward to exploring its potential.”

Sensing A Breakthrough
The A*STAR Institute of Microelectronics in Singapore and others have devised a MEMS-based miniaturized pressure sensor that combines a stable diaphragm with sensitive silicon nanowires. With the technology, researchers are looking to develop tiny and implantable medical devices.

The idea was to create a pressure-deformable diaphragm and then embed a piezoresistor made from a material in which pressure causes a change in electrical resistance, such as a silicon nanowire.

Researchers devised a pressure sensor with a 200µm diaphragm using silicon nanowires. The silicon nanowires are embedded in a multilayered diaphragm structure comprising silicon nitride (SiNx) and silicon oxide (SiO2).

Optimizations were performed on both silicon nanowires and the diaphragm structure. The diaphragm with a 1.2µm SiNx layer is considered to be an optimized design in terms of small initial central deflection (0.1µm), relatively high sensitivity (0.6% psi−1) and good linearity within a given measurement range.

SiO2 was used because of its pressure sensitivity. But the material tended to buckle and twist even without pressure. Researchers, in turn, used a double layer of SiO2, with piezoresistive silicon nanowires embedded in between, topped by a stabilizing layer of SiNx.

By etching down the silicon nitride and varying the thickness and treatment of the silicon nanowires, the team found an optimum combination. “The high internal stress of silicon nitride improves the diaphragm structure with good flatness, a large measurement range and waterproof properties,” said Liang Lou, a researcher at the A*STAR Institute of Microelectronics, on the research organization’s Web site. “Our work provides a pioneering demonstration that integrating silicon nanowires into a multi-layer diaphragm allows us to scale down the sensor without losing high sensitivity.”

—Mark LaPedus

By Mark LaPedus
In October, Draper Laboratory and the University of South Florida (USF) disclosed an ambitious plan to develop a brain-on-a-chip.

The idea is to devise a “micro-environment’’ that mimics the human brain. Researchers hope to study neurodegenerative conditions such as Alzheimer’s disease, strokes and concussions. The eventual goal is to study the effects of drugs and vaccines on the brain.

Draper, a spinoff from the Massachusetts Institute of Technology (MIT), and USF are using embryonic cells from rats, but researchers plan to use human cells in the future. The brain-on-a-chip combines several technologies, including an emerging field called microfluidics.

Microfluidics deals with the control of fluids in devices. Tiny chip-like devices using microfluidics are used in many applications, such as cell sorting and detection, gene analysis, inkjet print heads, lab-on-a-chip units and point-of-care diagnostic tools. Meanwhile, lab-on-a-chip, and a related field, organ-on-a-chip (i.e. brain-on-a-chip), are systems that integrate various functions in a chip-like format. Some, but not all, lab-on-a-chip systems use microfluidics.

In these areas, OEMs and researchers use many of the same tools and processes borrowed from the semiconductor and MEMS industries. “The tools that are used to manufacture semiconductor devices can also be applied to make an organ-on-a-chip,” said Jeffrey Borenstein, distinguished member of the technical staff at Draper Labs. “The reason for that is you may need a lot of precision to structure these materials. The common tools are photolithography, etching, and other familiar processes in the semiconductor industry.”

Draper is not using leading-edge process technology, but it still faces some major challenges. “There is a need in the microfluidics field for process technologies that will enable things to be made at a higher volume and a lower cost,” said Borenstein, who is also the technical director for a separate project that is developing a human-on-a-chip. “There are some broader research goals in terms of understanding how organs work and understanding disease processes.”

Microfluidics emerges
Driven by the progress in the identification of genes and proteins, sales of microfluidic devices reached $1.3 billion in 2011, up 19% from 2010, according to Yole Développement. Yole also predicts that sales of fab-level microfluidics devices will average 23% annual growth through 2016, pushing the sector to almost $4 billion.

Microfluidics first emerged in the 1980s, but it has only recently begun to ramp up. The technology is being pursued by a plethora of device makers, OEMs and research entities. Affymetrix, Fluidigm, HP, IBM, Philips, Roche, Samsung, Siemens, Sony, STMicroelectronics are just a few of the names in the field.

In microfluidics, the products tend to be customized and the development cycles are long, but manufacturing costs are not an overriding issue. “A lot of people have set up fabrication capabilities for microfluidics that are relatively inexpensive,” said Draper’s Borenstein.

The tiny microfluidic devices themselves are generally comprised of complex pumps and external plumbing to transport a given fluid. The ability to pump the fluids at the micro-scale level is just one of the challenges. This has fueled the need for a new class of micro-pumps based on active and passive schemes.

“Microfluidics still suffers from the lack of a small, cheap and easy to integrate micro-pump,” said Alexander Govyadinov, an R&D engineer at Hewlett-Packard. “Generally, for a breakthrough to occur in microfluidic system development, essential microfluidic elements, pumps, valves, mixers and sensors, need to be integrated via low-cost fabrication technologies. There is also a lack of a killer application. A lot of progress happened, but even more development is required.”

There are other manufacturing challenges as well. “Most structures are 25 or 50 microns,” said Donald Johnson, chief executive of DJ DevCorp, a supplier of specialty dry film resist materials. “Now, there is a drive to get smaller dimensions. If you are looking at the channels, you want to get them down to a few microns. If you look at surface structures, you may be putting nano-structures on the surface.”

The initial, and many of the current, microfluidic devices are composed of silicon or glass and are made using etch and other processes taken from the semiconductor industry. “In many cases, the devices were manufactured using a single material, such as a microfluidic channel etched into a glass plate and sealed with a glass plate, yielding a monolithic microfluidic glass chip,” Johnson said during a recent presentation at an event sponsored by the Microelectronics Packaging and Test Engineering Council (MEPTEC).

The high cost involved in processing glass and silicon has prompted many vendors and research labs to use cheaper and transparent polymer materials like polydimethylsiloxane (PDMS). The polymer does not self-assemble, but rather the material is used to create the patterns or channels in a microfluidic device.

There are several ways to make a microfluidic device. In one common method, a vendor first makes a “master pattern” or “mold” of a microfluidic device. To make a mold, a resist, photomask and an absorber pattern are first applied on a substrate. Then, the “master mold” is patterned using laser ablation, micromilling or lithography.

Once the “master pattern” is created, the device is then replicated. There are several methods to replicate a device, such as casting, injection molding, thermoforming and hot embossing. A more advanced hot embossing technique is called nanoimprint lithography, which could shrink the channels down to the nano-scale. “You will probably see more embossing than imprint today,” Johnson said. “Nanoimprint is mainly in R&D at this point.”

Some are also using a technology called multi-layer soft lithography. In this process, a liquid polymer is poured over the mold. After a curing process, the polymer is peeled off the mold, leaving an imprint of the topography. Several layers of elastomer, which have different patterns, can be stacked and bonded. A microfluidic device usually has two elastomer layers for the flow and control functions.

New and emerging apps
The manufacturing processes and material choices depend on the application. For example, U.S.-based Micronics, which was recently acquired by Sony, last month launched a single-use, disposable card system that makes it possible to quickly determine a blood type.

Developed in part under funding from the U.S. Army, the company’s so-called ABORhCard is designed for a field-deployable test of potential blood donors in austere settings. “We were the first microfluidics company to move away from PDMS and glass to laminates. Final products are hybrid structures-laminates and injection mold,” said Karen Hedine, president of Micronics.

Another application is for a cell detection and sorting system. Cell sorting separates cells according to their properties. The microfluidics device in such a system can be done using micro-contact printing. “A well-known technique is done by contact printing, which can generate monolayers on the surface,” said Tohid Fatanat Didar, a visiting scholar within the Wyss Institute for Biologically Inspired Engineering at Harvard Medical School.

Microfluidics also plays a role in the emerging organ-on-a-chip field. Last year, the National Institutes of Health (NIH), the Defense Advanced Research Projects Agency (DARPA), and the U.S. Food and Drug Administration (FDA) announced plans to develop a chip technology that could screen drugs and vaccines more rapidly and efficiently than current methods. The chip is based on specific cell types that reflect human biology. NIH will commit up to $70 million and DARPA will commit a comparable amount.

DARPA recently awarded a contract to Draper through MIT. Draper is working on various projects such as a human-on-a-chip, brain-on-a-chip, liver-on-a-chip, and a kidney-on-a-chip.

The brain-on-a-chip project itself combines cellular neuroscience, tissue engineering and microfluidics. The chip aggregates cultured neurons, astrocytes, microglia and brain endothelial cells from rats on two micro-fabricated layers. A microfluidic pump was used to circulate nutrients or therapeutics across the vascular channels simulating blood flow. “What we’re trying to do is take the most important features of an organ and scale them down to the micro-scale. Then, you put them on some kind of a platform, where you can evaluate them,” said Draper’s Borenstein.

The fabrication process is straightforward. “You start with a silicon wafer process. And then you transfer that into a polymer using some kind of a molding or embossing technique,” he said. “The bigger challenge is to transition this from a silicon to a non-silicon base. We do not use the latest and greatest photolithography. In fact, most of the photolithographic work that’s done in our lab is done with structures that may have a minimum dimension of 10 microns.”

Still, Draper and other entities will need new manufacturing breakthroughs. “Hot embossing is a good example. Hot embossing is a great process, but it’s a little bit slow,” he said. “The material that has carried the microfluidic field for many years is called PDMS. It’s very inexpensive and easy to process, but it’s not particularly stable chemically.”

Researchers are looking at new and advanced bio-degradable materials for future work. And, of course, the field of organ-on-a-chip technology is still in its infancy. “It’s still in the very early stages,” said Anil Achyuta, principal investigator for the brain-on-a-chip project at Draper. “We have the potential to revolutionize how scientists study the effects of drugs, vaccines, and specialized therapies like stem cells on the brain.”

Baking A (Chip) Cake
In a process that is like baking a cake, the University of Manchester has assembled individual atomic layers on top of each other.

Researchers used individual one-atom-thick crystals to construct a multilayer cake that works as a nanoscale electric transformer. The researchers devised individual atomic planes from bulk graphite and boron nitride. Then, they assembled the crystallites one by one, in a Lego style, into a crystal with the desired sequence of planes.

Source: University of Manchester.

In its nanoscale transformer, the electrons moving in one metallic layer pull electrons in the second metallic layer by using their local electric fields. On the university’s Web Site, Professor Andre Geim said: “The work proves that complex devices with various functionalities can be constructed plane by plane with atomic precision. There is a whole library of atomically-thin materials. By combining them, it is possible to create principally new materials that don’t exist in nature.”

Butterflies Are Free
The University of Pennsylvania has devised a manufacturing technology based on the structural color and superhydrophobicity found in butterfly wings.

Based on holographic lithography and directed self-assembly (DSA), the technique could enable new materials for semiconductors, coatings for solar panels and other products.

“A lot of research over the last 10 years has gone into trying to create structural colors like those found in nature, in things like butterfly wings and opals,” said Shu Yang, associate professor in the Department of Materials Science and Engineering at the university’s School of Engineering and Applied Science, on the school’s Web site. “People have also been interested in creating superhydrophobic surfaces, which are found in things like lotus leaves, and in butterfly wings, too, since they couldn’t stay in air with raindrops clinging to them.”

Source: University of Pennsylvania

In an experiment, researchers fabricated 3D diamond photonic crystals with a controllable roughness of ≤120nm on the surface of a structure. Researchers used a block co-polymer derived from an epoxy-functionalized cyclohexyl polyhedral oligomeric silsesquioxanes (POSS) material.

The crystals were generated during the phase separation and rinsing step in the holographic lithography process, according to researchers. The degree of roughness can be tuned by the crosslinking density of the polymer network, which is dependent on the loading of photoacid generators, the exposure dosage, and the choice of developer and rinsing solvent, researchers said.

“Specifically, we’re interested in putting this kind of material on the outside of buildings,” Yang said. “The structural color we can produce is bright and highly decorative, and it won’t fade away like conventional pigmentation color dies. The introduction of nano-roughness will offer additional benefits, such as energy efficiency and environmental friendliness. It could be a high-end facade for the aesthetics alone, in addition to the appeal of its self-cleaning properties. We are also developing energy-efficient building skins that will integrate such materials in optical sensors.”

Playing The HARPES
Spintronics is a promising technology in which data is processed on the basis of electron “spin” rather than charge. Dilute magnetic semiconductors are the key materials that could enable spintronics. But understanding the source of ferromagnetism in dilute magnetic semiconductors has been a major challenge.

Researchers led by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have devised a new technique called HARPES, or Hard X-ray Angle-Resolved PhotoEmission Spectroscopy. Using this technology, researchers have investigated the bulk electronic structure of a dilute magnetic semiconductor gallium manganese arsenide.

With the HARPES technique, a beam of hard x-rays flashed on a sample causes photoelectrons from within the bulk to be emitted. Measuring the kinetic energy of these photoelectrons and the angles at which they are ejected reveals much about the sample’s electronic structure. Here the Mn atoms in GaMnAs are shown to be aligned ferromagnetically, with all their atomic magnets pointing the same way. (Source: Alex Gray/Berkeley Labs)

“This study represents the first application of HARPES to a forefront problem in materials science, uncovering the origin of the ferromagnetism in the so-called dilute magnetic semiconductors,” said Charles Fadley, a physicist, on the lab’s Web site. “Our results also suggest that the HARPES technique should be broadly applicable to many new classes of materials in the future.”

HARPES is based on the photoelectric effect described by Albert Einstein in 1905. It enables scientists to study bulk electronic effects with minimum interference from surface reactions or contamination. “We now have a better fundamental understanding of electronic interactions in dilute magnetic semiconductors that can suggest future materials with different parent semiconductors and different magnetic dopants. HARPES should provide an important tool for characterizing these future materials,” he added.

By Mark LaPedus
Gartner says by 2014, 10% to 15% of reviews on social media sites are expected to be fake and paid for by companies.

The 2012 IEEE International Electron Devices Meeting (IEDM) is near. At the event, slated for Dec. 10 to 12 in San Francisco, GlobalFoundries CEO Ajit Manocha will give a keynote, entitled: “Is the Fabless/Foundry Model Dead? We Don’t Think So. Long Live Foundry 2.0!” Here are some of the major papers at the event:

• IBM will demonstrate high-performance state-of-the-art CMOS circuits—including SRAM memory and ring oscillators—on a flexible plastic substrate. The extremely-thin silicon-on-insulator (ETSOI) devices have a body thickness of just 60 angstroms.

• A team led by IBM will separately report on the world’s first high-performance hybrid-channel ETSOI CMOS device. Researchers have integrated a PFET having a thin, uniform strained SiGe channel, with an NFET having a Si channel, at 22nm geometries.

• Intel will talk about its 22nm Tri-Gate technology for SoC applications.

• TSMC will describe a heterogeneous epitaxial growth process for finFETs.

• MIT will describe how they achieved the highest nanowire hole mobilities ever reported, in trigate nanowire PFETs. Separately, MIT has begun to investigate a new 2D material, molybdenum sulfide (MoS), which has similar characteristics but offers something graphene doesn’t: a wide energy bandgap.

• Everspin will talk about a highest-density ST-MRAM.

• Macronix has built flash memories that could heal themselves by means of tiny onboard heaters that provide thermal annealing just at the spots where it is needed.

• Gwangju Institute of Science and Technology will detail a high-speed pattern-recognition system comprising of CMOS “neurons” and an array of resistive-RAM (ReRAM)-based “synapses.”

GlobalFoundries took the covers off its new finFET architecture, which it will introduce for the 14nm node next year.

Extreme ultraviolet (EUV) lithography is late for the 10nm node and could possibly miss the window for that insertion point.

Piper Jaffray says Intel is working on a foundry partnership with Cisco, according to reports.

Japan’s Sharp is renegotiating a stake sale to Foxconn. Sharp is also in talks with Intel for a possible capital tie-up, according to reports.

North America-based manufacturers of semiconductor equipment posted $1.12 billion in orders worldwide in August 2012 and a book-to-bill ratio of 0.84, according to SEMI. This compares to an 0.86 ratio in July.

SEMI reported worldwide PV manufacturing equipment billings and bookings for the second quarter of 2012. At 0.33, the book-to-bill ratio stayed below parity for the fifth consecutive quarter.

Solar installations are growing at a fast pace, according to Applied Materials. Applied Materials will highlight its latest products in solar technology at the upcoming 27th European Solar Energy Conference and Exhibition.

Cypress and Ramtron have entered into a definitive merger agreement under which Cypress will acquire all the outstanding stock of FRAM maker Ramtron at a price of $3.10 per share in cash.

Mixed-signal foundry vendor LFoundry plans to invest a total of 25 million euros in R&D in its fabs and other projects.

The soaring demand for voice and data traffic is choking the network. Here are some current and futuristic solutions to solve the problems.

The explosion of mobile devices, virtualization and cloud computing is putting a strain on the network, thereby fueling the need for a new technology called software-defined networking (SDN).

For the first time since it entered the industry seven years ago, U.S.-based Micron managed to cross the 20% market share threshold in the NAND flash memory business during the second quarter.

The market for integrated circuits is forecast to post much stronger average annual growth through 2021 compared to the average market growth over the past 15 years, according to an analysis recently completed by IC Insights.

Booming tablet shipments—including the iPad with its 9-inch screen, as well as smaller 7.x-inch models from various brands—will drive a robust 56% annual increase in shipments for the tablet display market in 2012, according to the IHS iSuppli.

By Mark LaPedus
Directed self-assembly (DSA) is making progress for potential use in semiconductor production, but the industry must make some major advances in a sometimes forgotten and unsung segment—materials.

DSA is a complementary patterning technology that makes use of block copolymer materials to enable fine pitches in chip designs. But today’s block copolymers based on poly (MMA-co-styrene), or better known as PS-b-PMMA materials, do not scale beyond 11nm.

To bring DSA from the lab to the fab, Arkema, AZ, Dow, IBM, JSR, SEH, TOK and others are separately developing next-generation DSA copolymers that promise to scale beyond 11nm. But for the most part, the commercial vendors are keeping their R&D work close to the vest.

To date, most of the research in the public domain has originated at universities. Given that the universities provide a clue of what’s coming down the pike, there are several DSA materials candidates on the table, including high chi copolymers, blended compounds, and even one based on simple sugar.

Each approach, which is still in R&D, consists of complex chemical compounds that resemble a mix of letters in a bowl of alphabet soup. The candidates have various trade-offs, but there is no clear leader in the next-generation copolymer race right now.

“The field is much more wide open than it was for the first generation PS-b-PMMA materials,” said Ralph Dammel, chief technology officer for AZ Electronic Materials, a supplier of materials for DSA and other applications. “There certainly are a number of possible high chi materials. It may be that one single high chi polymer technology will evolve, or several ones may co-exist, possibly for different applications. It is too early to say.”

DSA to the rescue?
DSA is one of several lithographic options for chip production. In the current lithography landscape, chipmakers are expected to use 193nm immersion and double patterning at 20nm. Then, at 14nm and 10nm, the industry would like to insert extreme ultraviolet (EUV) lithography. If EUV misses those windows, the industry will extend 193nm immersion and move to a more complex multi-patterning scheme.

The wild card is DSA, which is still in R&D. Technically, DSA is a complementary scheme. When used in conjunction with a pre-pattern that directs the orientation for patterning, DSA is said to reduce the pitch of the final printed structure. Used in conjunction with 193nm immersion, DSA could extend 193nm lithography beyond 10nm, eliminate expensive multi-patterning steps and push out EUV.

In the lab, DSA has demonstrated the ability to devise features down to 5nm. The likely insertion point for DSA is the 10nm node, said Moshe Preil, manager of emerging lithography and tools at GlobalFoundries. “If it was only about the chemistry, we would know how to implement DSA at 14nm,” Preil said. “We still don’t know how to design a chip using DSA.”

Design enablement and defectivity are among the challenges with DSA. And to put DSA in a production fab, chipmakers must make some complex choices. First, there are two main types of DSA methods: graphoepitaxy and chemical epitaxy. In chemical epitaxy, self-assembly is guided by a sparse chemical pre-pattern. Graphoepitaxy is based on a topographical pre-pattern.

Chipmakers must come up with the right DSA materials, which is also a challenge. “The design of high chi block copolymers has a number of pitfalls. It is not easy, but there has already been a lot of progress, enough that we can say there will not be a technical issue with availability of high chi materials for <10nm patterning,” said AZ’s Dammel.

A polymer is a molecule that consists of repeating structural units. A copolymer is a polymer compound derived from two or more structural units. Block copolymers consist of dissimilar structural units or chains linked by covalent bonds.

In DSA, the dissimilar units are able to phase separate into distinct domains and then self-assemble into controllable dimensions. The trouble is today’s block copolymers based on PS-b-PMMA materials have a chi factor of about 0.04. If the chi N factor is less than 10.5 in certain mixes, the blocks will not phase separate. N denotes the degree of polymerization, while chi represents the interaction parameter.

So, the industry must find a suitable material that scales. In this area, there are two basic approaches: organic-organic versus organic-inorganic. Academia has focused on organic-organic compounds, while commercial vendors are narrowing their options down to organic-inorganic materials, said Mark Slezak, vice president of sales and technology at JSR Micro, the U.S. sales arm for JSR.

IBM and JSR have been co-developing a technology that blends a copolymer and organosilicate material. This blended approach can scale and consists of fewer process steps using sidewall image transfer technology, according to JSR and IBM. “This has opened Pandora’s Box,” said Yoshi Hishiro, director of R&D at JSR Micro. “The blended approach enables several possibilities. The chi for the blended system can be defined.”

IBM also is working on other solutions, including non-blended copolymers with AZ Electronic Materials. “Both polymer blends and block copolymers phase separate on annealing. Polymer blends are very easy to make, and they also are easier to process. Usually, they require lower annealing temperatures and it is easier to achieve short annealing times,” AZ’s Dammel said. “But the blended approaches are restricted to 2x frequency duplication. For 3x or more, one has to use the longer range self-assembly capability of block copolymers.”

Frequency duplication is key for DSA. “Let’s say we have 20nm lines with 160nm pitch. Let’s say we also use a copolymer with a natural period L0 of 40nm. After the process, we have 20nm equal lines and spaces, or 4x the lines that were there before. That’s what is called 4x frequency multiplication,” Dammel explained.

Today’s block copolymers have scaling limitations. “So, one needs to make block copolymers with higher chi factors. One problem is that some types of block copolymers with high chis are difficult to phase separate by thermal annealing. The blocks repel each other so strongly that they have a hard time moving past each other. One has to use solvent vapor to soften them enough to get them to phase separate.” Dammel explained.

The problem is that solvent annealing may not be the right solution, because the technology is incompatible with today’s semiconductor manufacturing processes, he added.

The contenders
At present, there are several promising next-generation, high chi copolymer candidates on the table. “All of them have their strong attributes. They also have their shortcomings,” said Christopher Ober, professor in the Department of Materials Science and Engineering at Cornell University.

For years, Cornell has been developing block copolymers. The other pioneers in the DSA materials field include the University of Massachusetts Amherst (UMASS) and the University of Wisconsin.

In a more recent effort, Intel and the University of Queensland in Australia described a diblock copolymer, based on poly(styrene)-b-poly(DL-lactide) or PS-b-PDLA materials. Using a graphoepitaxy process flow with 4x frequency multiplication, the entities demonstrated 8nm lines and spaces with PS-b-PDLA materials.

“The new high chi systems such as p(S-b-DLA) have even better selectivity than p(S-b-MMA),” Dammel said. “The p(S-b-DLA) system also has much lower annealing temperatures than the p(S-b-MMA) system.”

In another effort, the Massachusetts Institute of Technology (MIT) recently disclosed that self-assembly can form 3D structures. MIT used a poly (styreneb-dimethylsiloxane) or PS-b-PDMS block copolymer. PS-b-PDMS has a chi factor of 0.27. MIT also HAS devised higher chi materials based on poly(2-vinylpyridine-b-dimethylsiloxane) or P2VP-PDMS.

“I would not treat the chi parameter as the only figure of merit,” said Caroline Ross, professor in the Department of Materials Science and Engineering at MIT. “Chi is one consideration, but there are others that are relevant to microphase separation, such as the molecular weight, volume fraction, surface energy of the blocks and relative etch resistance.”

Hitachi and CNRS-CEA/LETI also are pursuing PS-b-PDMS. In a separate effort, CNRS and the University of Texas at Austin have recently described the synthesis and self-assembly of block copolymers “composed of naturally derived oligosaccharides” or sugar.

These block copolymers enable 5nm feature sizes. “However, that system can never be annealed thermally,” said C. Grant Willson, professor of chemical engineering at the University of Texas at Austin. “It has to be annealed with a solvent. I personally do not think that long solvent annealing processes are compatible with semiconductor manufacturing.”

Willson and his associates are working on other materials. “We have designed a new block copolymer that has all of the attributes of the sugar polymer, but can be annealed thermally with a top coat. This new material looks very promising,” he added.

Meanwhile, UMASS and others are developing copolymers based on polystyrene-block-poly(ethylene oxide) or PS-b-PEO materials. UMASS is also exploring tri-block copolymers based on poly(ethylene oxide) or PEO-b-PPO-b-PEO materials.

In another effort, Pohang University of Science and Technology, Tokyo Institute of Technology, and the University of Wisconsin-Madison, Wisconsin recently described an organic-inorganic diblock copolymer, dubbed poly(styrene-b-methacrylate) or PS-b-PMAPOSS.

Cornell has been developing the concept of orthogonal processing of block copolymers. By using a semi-flourinated photoresist/solvent system, researchers are able to selectively pattern or lift-off and then recover the block copolymer film intact. This relates to “orthogonal lithography,” a new patterning process for organic semiconductors. The process is based on a novel photoresist that is compatible with sensitive organic systems. The specially designed photoresist is composed of polymeric or molecular glass that enables the use of fluorous solvents, thus not damaging the organic material while enabling pattern formation.

New materials to herd photons
Used in communication systems, optical networks employ isolators to keep light from reflecting backwards. Isolators also absorb photons, thereby reducing a signal in a system.

All of that may be unnecessary in the future, however. MIT, Zhejiang University in China, and the University of Texas at Austin have devised a new “metamaterial” that keeps photons moving in only one direction. This, in turn, could pave the way toward chips that move data with light.

To prevent microwaves passing through it from reflecting backward, a new 'metamaterial' uses antennas of alternating orientations (top) that are connected by amplifier circuits (bottom). Source: MIT

Electromagnetic materials that lack so-called local time-reversal symmetry could enable these types of chips. Gyrotropic materials, for one, are the most promising.

Using such materials, researchers have devised a “metamaterial.” They also have made use of antennas of alternating orientations, which are connected by amplifier circuits. The antennas are embedded in a pair of circuit boards. The direction of current flow through the circuits determines the direction of the electromagnetic waves.

Electron interactions spotted in graphene
Graphene, a promising material for future transistors, consists of one-atom-thick planar sheets that are packed in honeycomb crystal lattice structures. But graphene is complex and doesn’t have a band gap, meaning it can’t be turned off in a system.

Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the University of California at Berkeley are claiming a new breakthrough in this arena— they have demonstrated the electron interactions in graphene.

Using a scanning tunneling microscope (STM), researchers observed gated devices consisting of a graphene layer deposited atop boron nitride flakes. The flakes were placed on a silicon dioxide substrate.

The response of ultrarelativistic electrons in graphene to Coulomb potentials created by cobalt trimers was observed to be signficantly different the response of non-relativistic electrons in traditional atomic and impurity systems. Source: Lawrence Berkeley National Laboratory.

Researchers observed how electrons and holes respond to a charged impurity placed on a gated graphene device. The charged impurities were cobalt trimers constructed on graphene.

“Theorists have predicted that compared with other materials, electrons in graphene are pulled into a positively-charged impurity either too weakly, the subcritical regime; or too strongly, the supercritical regime,” said Michael Crommie, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department.

“In our study, we verified the predictions for the subcritical regime and found the value for the dielectric to be small enough to indicate that electron–electron interactions contribute significantly to graphene properties. This information is fundamental to our understanding of how electrons move through graphene,” he added.

SWAN dives into study of molecules
Researchers from Iowa State University and Ames Laboratory have developed a new microscope technology that enables the study of single biological molecules.

Called standing wave axial nanometry (SWAN), the technology combines atomic force and optical microscope technologies. SWAN is able to image the axial location of a single nanoscale fluorescent object down to 3.7nm.

A standing wave, generated by positioning an atomic force microscope tip over a focused laser beam, is used to excite the fluorescence of an object. The axial position is determined from the phase of the emission intensity.

Researchers used SWAN to measure the orientation of single DNA molecules of different lengths. The technology can be used in the medical and other fields.

—Mark LaPedus