TechBlog

Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

 The far-ranging potential applications of this technology include DOE’s hydrogen fuel cell-powered “Freedom CAR,” and personal power-jackets that could use heat from the human body to recharge cell-phones and other electronic devices.

Continue reading ‘Researchers Make Thermoelectric Breakthrough In Silicon Nanowires’ »

Hailed as the world’s most powerful transmission electron microscope, TEAM 0.5 is living up to expectations. Using TEAM 0.5 (TEAM stands for Transmission Electron Aberration-corrected Microscope), researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have produced stunning images of individual carbon atoms in graphene, the two-dimensional crystalline form of carbon that is highly prized by the electronics industry. These first time ever images were recorded at Berkeley Lab’s National Center for Electron Microscopy (NCEM), a DOE national user facility that is a premier center for electron microscopy and microcharacterization. TEAM 0.5, its newest instrument, is capable of producing images with half-angstrom resolution, which is less than the diameter of a single hydrogen atom. “Simply put, TEAM 0.5 is the best transmission electron microscope in the world, representing a quantum leap forward in instrumentation,” said physicist Alex Zettl who led this research. “Having the ability to see, basically in real time, each and every individual atom in a sample is unbelievably useful and the images we can now see have been jaw-dropping for even the most seasoned electron microscopists. TEAM 0.5 is pushing transmission electron microscopy to a new level.” Zettl holds joint appointments with Berkeley Lab’s Materials Sciences Division (MSD) and the Physics Department at the University of California’s Berkeley campus, where he is the director of the Center of Integrated Nanomechanical Systems. Collaborating with him on this graphene imaging project were Jannik Meyer, also with Berkeley Lab’s Materials Sciences Division, and Christian Kisielowski, Rolf Erni and Marta Rossell of NCEM. Their results were published in the journal Nanoletters, in a paper entitled: “Direct imaging of lattice atoms and topological defects in graphene membranes.” The properties of solid materials stem from the arrangement of their constituent atoms in the solid’s crystal structure. While technologies such as electron and x-ray crystallography can reveal the atomic geometry of a crystal, they do not identify the precise location and position of each individual atom. When the dimensions of a material shrink to the nanoscale, the location and position of each individual atom becomes critically important, as Zettl explains. “Think of the steel re-bars on a three-dimensional structure, like a jungle gym,” he said. “If a small piece of re-bar is rusted out somewhere in the center of the gym, it won’t likely have much affect on the overall properties of the structure. In a two-dimensional structure, however, a rusted out segment becomes a much bigger problem, and in a one-dimensional structure, i.e., a single re-bar, a rusted out segment can be catastrophic, causing the entire structure to fail.

On a nanoscale crystal, one missing atom or some other defect in the arrangement can result in catastrophic failure.” Graphene is especially sensitive to defects in its atomic structure. Consisting of a single-layered sheet of carbon atoms arranged in hexagons, like a sheet of chicken wire with an atom at each nexus, graphene features extraordinary electrical, mechanical and thermal properties that could enable it to serve in a broad array of carbon-based electronic devices. For the enormous promises of graphene to be fulfilled, however, scientists need a much better understanding of how specific types of defects in the crystal structure, including those that change location over time, affect its properties.

Continue reading ‘Closest Look Ever At Graphene’ »

SiC MEMS Pressure Sensors: Technology, Applications and Markets

Silicon Carbide: Material Platform for Harsh Environment Solutions Silicon carbide (SiC) has been used for many conventional applications that require mechanical and chemical stability at high temperatures. Mechanical stability is defined as the ability of a particular material to preserve its mechanical properties – elasticity, fracture toughness, hardness – at temperatures below and above room temperature.

Chemical stability is similarly defined as the ability of a particular material to preserve its composition at temperatures below and above room temperature. For high temperature applications, mechanical properties tend to deteriorate and chemical stability is compromised as corrosion processes occur.

Any material that can overcome these mechanical and chemical limitations becomes a candidate for what are called “harsh environment” applications. Harsh environment means a combination of media properties that can interact with the exposed material and alter its originally intended behavior. Harsh environments can be classified in three broad categories: 1) mechanically aggressive: high loads, vibration, shock; 2) thermally aggressive: high temperature; and 3) chemically aggressive: corrosive media.

Continue reading ‘SiC MEMS Pressure Sensors: Technology, Applications and Markets’ »

Researchers at Children’s Hospital Boston have developed a new “nanobiotechnology” that enables magnetic control of events at the cellular level. They describe the technology, which could lead to finely-tuned but noninvasive treatments for disease, in the January issue of Nature Nanotechnology.

Don Ingber, MD, PhD, and Robert Mannix, PhD, of Children’s program in Vascular Biology, in collaboration with Mara Prentiss, PhD, a physicist at Harvard University, devised a way to get tiny beads — 30 nanometers (billionths of a meter) in diameter — to bind to receptor molecules on the cell surface. When exposed to a magnetic field, the beads themselves become magnets, and pull together through magnetic attraction. This pull drags the cell’s receptors into large clusters, mimicking what happens when drugs or other molecules bind to them. This clustering, in turn, activates the receptors, triggering a cascade of biochemical signals that influence different cell functions.

The technology could lead to non-invasive ways of controlling drug release or physiologic processes such as heart rhythms and muscle contractions, says Ingber, the study’s senior investigator. More importantly, it represents the first time magnetism has been used to harness specific cellular signaling systems normally used by hormones or other natural molecules.

Continue reading ‘An “Attractive” Man-Machine Interface: Researchers Use Magnetic Fields, Rather Than Drugs, To Control Cellular Signaling’ »

Berkeley, CA — As structures made of metal get smaller — as their dimensions approach the micrometer scale (millionths of a meter) or less — they get stronger. Scientists discovered this phenomenon 50 years ago while measuring the strength of tin “whiskers” a few micrometers in diameter and a few millimeters in length. Many theories have been proposed to explain why smaller is stronger, but only recently has it become possible to see and record what’s actually happening in tiny structures under stress.Andrew Minor, of the Materials Sciences Division in the Department of Energy’s Lawrence Berkeley National Laboratory, with colleagues from Hysitron Incorporated and the General Motors Research and Development Center, used the In Situ Microscope at the National Center for Electron Microscopy (NCEM) to record what happens when pillars of nickel with diameters between 150 and 400 nanometers (billionths of a meter) are compressed under a flat punch made of diamond. The transmission electron microscope is equipped so that samples can be stressed, measured, and videotaped while being observed under the electron beam.

“What controls the deformation of a metal object is the way that defects, called dislocations, move along planes in its crystal structure,” Minor says. “The result of dislocation slip is plastic deformation. For example, bending a paper clip causes its trillions of dislocations per square centimeter to tangle up and multiply as they run into one another and slide along numerous slip planes.”

In general, mechanical deformation tends to increase the number of dislocations in a material. But for small-scale structures, with a much greater proportion of surface area to volume, the process can be very different. The videotaped images from the electron microscope helped the researchers understand why nanoscale nickel pillars are so strong by allowing them to observe changes in the microstructure of the pillars during deformation — including a never-before-seen process the researchers dubbed “mechanical annealing.” (In bulk materials, annealing, a treatment that reduces the density of defects, is usually accomplished by heating.)

Continue reading ‘Smaller Is Stronger — Now Scientists Know Why’ »

Berkeley, CA — Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley. The far-ranging potential applications of this technology include DOE’s hydrogen fuel cell-powered “Freedom CAR,” and personal power-jackets that could use heat from the human body to recharge cell-phones and other electronic devices.

“This is the first demonstration of high performance thermoelectric capability in silicon, an abundant semiconductor for which there already exists a multibillion dollar infrastructure for low-cost and high-yield processing and packaging,” said Arun Majumdar, a mechanical engineer and materials scientist with joint appointments at Berkeley Lab and UC Berkeley, who was one of the principal investigators behind this research.

“We’ve shown that it’s possible to achieve a large enhancement of thermoelectric energy efficiency at room temperature in rough silicon nanowires that have been processed by wafer-scale electrochemical synthesis,” said chemist Peidong Yang, the other principal investigator behind this research, who also holds a joint Berkeley Lab and UC Berkeley appointment.

Continue reading ‘Feeling The Heat: Berkeley Researchers Make Thermoelectric Breakthrough In Silicon Nanowires’ »