(Press-News.org) Researchers from North Carolina State University and Brown University have found that nanoscale wires (nanowires) made of common semiconductor materials have a pronounced anelasticity - meaning that the wires, when bent, return slowly to their original shape rather than snapping back quickly.
"All materials have some degree of anelasticity, but it is usually negligible at the macroscopic scale," says Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and corresponding author of a paper describing the work. "Because nanowires are so small, the anelasticity is significant and easily observed -- although it was a total surprise when we first discovered the anelasticity in nanowires." The anelasticity was discovered when Zhu and his students were studying the buckling behavior of nanowires.
"Anelasticity is a fundamental mechanical property of nanowires, and we need to understand these sort of mechanical behaviors if we want to incorporate nanowires into electronics or other devices," says Elizabeth Dickey, a professor of materials science and engineering at NC State and co-author of the paper. Nanowires hold promise for use in a variety of applications, including flexible, stretchable and wearable electronic devices.
The researchers worked with both zinc oxide and silicon nanowires, and found that - when bent - the nanowires would return more than 80 percent of the way to their original shape instantaneously, but return the rest of the way (up to 20 percent) slowly.
"In nanowires that are approximately 50 nanometers in diameter, it can take 20 or 30 minutes for them to recover that last 20 percent of their original shape," says Guangming Cheng, a Ph.D. student in Zhu's lab and the first author for the paper.
The work was done using tools developed in Zhu's group that enabled the team to conduct experiments on nanowires while they were in a scanning electron microscope. Additional analysis was done using a Titan aberration-corrected scanning transmission electron microscope in NC State's Analytical Instrumentation Facility.
When any material is bent, the bonds between atoms are stretched or compressed to accommodate the bending, but in nanoscale materials there is time for the atoms to also move, or diffuse, from the compressed area to the stretched area in the material. If you think of the bent nanowire as an arch, the atoms are moving from the inside of the arch to the outside. When the tension in the bent wire is released, the atoms that simply moved closer or further apart snap back immediately; this is what we call elasticity. But the atoms that moved out of position altogether take time to return to their original sites. That time lag is a characteristic of anelasticity.
"This phenomenon is pronounced in nanowires. For instance, zinc oxide nanowires exhibited anelastic behavior that is up to four orders of magnitude larger than the largest anelasticity observed in bulk materials, with a recovery time-scale in the order of minutes," says Huajian Gao, a professor at Brown University and co-corresponding author of the paper. Detailed modeling by Gao's group indicates that the pronounced anelasticity in nanowires is because it is much easier for atoms to move through nanoscale materials than through bulk materials. And the atoms don't have to travel as far. In addition, nanowires can be bent much further than thicker wires without becoming permanently deformed or breaking.
"A reviewer commented that this is a new important page in the book on mechanics of nanostructures, which was very flattering to hear," Zhu says. The team plans to explore whether this pronounced anelasticity is common across nanoscale materials and structures. They also want to evaluate how this characteristic may affect other properties, such as electrical conductivity and thermal transport.
INFORMATION:
The paper, "Large Anelasticity and Associated Energy Dissipation in Single-Crystalline Nanowires," is published online in the journal Nature Nanotechnology. Lead authors of the paper are Guangming Cheng, a Ph.D. student at NC State, and Chunyang Miao of Brown and Nanjing University of Aeronautics and Astronautics. Co-authors include Qingquan Qin, Jing Li and Feng Xu of NC State; and Hamed Haftbaradaran and Huajian Gao of Brown. Gao is a co-corresponding author with Zhu.
The work was done with funding from the National Science Foundation.
New research from the Johns Hopkins Bloomberg School of Public Health suggests that the protein keratin 17 - the presence of which is used in the lab to detect and stage various types of cancers - is not just a biomarker for the disease, but may play a critical role in tumor growth.
This new understanding of how keratin 17 works, the researchers say, could lead to the development of better ways to detect and prevent cancer, and identify new targets for therapeutic treatment. A report on the findings is published July 13 in Nature Genetics.
"Keratin 17 is a sensitive ...
North Carolina State University researchers have developed an effective and environmentally benign method to combat bacteria by engineering nanoscale particles that add the antimicrobial potency of silver to a core of lignin, a ubiquitous substance found in all plant cells. The findings introduce ideas for better, greener and safer nanotechnology and could lead to enhanced efficiency of antimicrobial products used in agriculture and personal care.
In a study being published in Nature Nanotechnology July 13, NC State engineer Orlin Velev and colleagues show that silver-ion ...
A follow-up to a 2005 study of industry relationships among members of Institutional Review Boards (IRBs) at academic health centers finds both improvements in the management of such relationships, with increased levels of disclosure and fewer problematic relationships, and the persistence of problems such as IRB members' voting on protocols with which they may have conflicts of interest, a violation of federal regulations. The new study from the Mongan Institute for Health Policy at Massachusetts General Hospital appears in the July 13 issue of JAMA Internal Medicine. ...
Contact with another player was the most common way boys and girls sustained concussions in a study of U.S. high school soccer players, while heading the ball was the most common soccer-specific activity during which about one-third of boys and one-quarter of girls sustained concussions, according to an article published online by JAMA Pediatrics.
Soccer has increased in popularity in the United States over the past three decades. In 1969-1970, there were 2,217 schools that fielded 49,593 boys' soccer players and no girls' soccer players compared to 2013-2014 when 11,718 ...
While the percentage of institutional review board (IRB) members with an industry relationship has not changed significantly since 2005, the percentage of members who felt other members had not properly disclosed a financial relationship has decreased as did the percentage of IRB members who felt pressure from their institution or department to approve a protocol, according to an article published online by JAMA Internal Medicine.
Academic-industry relationships are defined as academics who provide life science companies (for example biotechnology, drug and device companies) ...
A small imaging study suggests cortical cerebral microbleeds in the brain, which are the remnant of red blood cell leakage from small vessels, were associated with reduced brain blood flow in a group of cognitively normal older patients, according to an article published online by JAMA Neurology.
Cerebral microbleeds (CMBs) are a common finding in magnetic resonance imaging of elderly patients. Some previous research has suggested an association between CMBs and cognitive deficits, although the mechanism is not clear. Some studies also have suggested CMBs may be related ...
Global air travel contributes around 3.5 percent of the greenhouse gas emissions behind/driving anthropogenic climate change, according to the International Panel on Climate Change (IPCC). But what impact does a warming planet have on air travel and how might that, in turn, affect the rate of warming itself?
A new study by researchers at the Woods Hole Oceanographic Institution and University of Wisconsin Madison found a connection between climate and airline flight times, suggesting a feedback loop could exist between the carbon emissions of airplanes and our changing ...
The remarkable ease and accuracy with which scientists can alter genomes using the CRISPR-Cas9 system has led to promising advances toward improving human health and the environment through genetic engineering. Cas9, a protein found naturally in certain bacteria, functions like a pair of molecular scissors to precisely cut sections of DNA and is extremely effective as a gene-editing tool. It can be directed to a specific gene through the use of a matching guide RNA sequence to perform gene mutations, putting programmable control of gene editing in the hands of scientists.
Even ...
Scientists from the University of Leeds have uncovered the most comprehensive list yet of genes implicated in a group of common inherited diseases.
The research, published in Nature Cell Biology today, means that these disorders, known as ciliopathies, can be diagnosed more quickly and could lead to new treatments for patients.
Ciliopathies are caused by defects in cilia, finger-like projections from cells that act as microscopic "antenna" to detect and respond to chemical changes or fluid flow outside the cell.
Kidney disease, which often leads to kidney failure, ...
UNSW Australia scientists have discovered a link between autism and genetic changes in some segments of DNA that are responsible for switching on genes in the brain.
The finding is the result of a world-first study of the human brain that identified more than 100 of these DNA segments, known as enhancers, which are thought to play a vital role in normal development by controlling gene activity in the brain.
"Our study provides a unique resource of information on gene function in the human brain which could help reveal the basis of autism and related neurological disorders," ...
