News Archive 2018
Chen Named Arkansas Research Alliance Fellow
Reference: University of Arkansas Newswire December 14, 2018
Jingyi Chen, associate professor of physical chemistry, has been named an Arkansas Research Alliance Fellow. The ARA Fellows program supports distinguished researchers currently working at one of the five research universities in the state with a $75,000 grant paid over three years. The program recognizes research leaders with an established history of impact.
Chen's research focuses on how the physical properties of macroscopic objects arise out of the component atoms as the aggregate into larger and larger particles. She is developing novel multi-metal-based nanostructures and new methods for functionalizing their surface with soft materials. The ultimate goal of her research is to establish the structure-property relationship and further explore their applications in energy conversion, tribology, and nanomedicine.
Chen joined the U of A in 2010. She received her doctorate from the University of Washington-Seattle, completed a postdoctoral fellowship at the Brookhaven National Laboratory in Upton, New York, and served as a research assistant professor at Washington University in St. Louis.
Past University of Arkansas ARA Fellows include Laurent Belliache, Distinguished Professor of physics; Min Zou, professor of mechanical engineering; and Alan Mantooth, Distinguished Professor of electrical engineering.
U of A Partners With DoE, National Labs in New Field of Topological Materials
Reference: University of Arkansas Newswire December 12, 2018
FAYETTEVILLE, Ark. – University of Arkansas physicists are exploring the new field of “topological quantum materials,” which are unusual in that they have a robustness of electrical properties regardless of temperature shifts or changes in structural form.
The research could lead to advancements in the fields of electronics, optoelectronics, quantum information and spintronics, or the use of a property of electrons called “spin” to record and store data. The researchers recently received a $750,000 grant from the U.S. Department of Energy to support this project.
Theories related to topological quantum materials were recognized with the Nobel Prize for Physics in 2016. These crystalline solids show evidence of unusual quantum particles. Previously, these particles could only be studied in high-energy particle accelerators. Their presence in these materials provide a new way for researchers to study them, and more easily investigate a number of fundamental concepts from high energy physics.
Topological quantum materials also display novel electronic properties. For instance, some of these materials, known as topological insulators, conduct electricity over their surface, but act as insulators everywhere else. A more thorough understanding of topological quantum materials could lead to a wide range of technological breakthroughs.
The U of A physics team is led by assistant professor Jin Hu and includes assistant professor Hugh Churchill and associate professor Salvador Barraza-Lopez. They are working with researchers from Argonne National Laboratory, Lawrence Berkeley National Laboratory, Los Alamos National Laboratory and Oak Ridge National Laboratory.
“We could not be more excited for this very talented young team of colleagues led by Dr. Jin Hu,” said Lin Oliver, chair of the Department of Physics. “They worked extremely hard on this proposal, both in a tough internal competition as well as in producing their winning grant proposal to the DOE. Solid support during this process from the Vice Chancellor for Research and Innovation and the Dean of the J. William Fulbright College of Arts and Sciences is also most appreciated.”
Research Uncovers the Spontaneous Polarization of Novel Ultrathin Materials
Reference: University of Arkansas Newswire November 15, 2018
Many materials exhibit new properties when in the form of thin films composed of just a few atomic layers. Most people are familiar with graphene, the two-dimensional form of graphite, but thin film versions of other materials also have the potential to facilitate technological breakthroughs.
For example, a class of three-dimensional materials called Group-IV monochalcogenides are semiconductors that perform in applications such as thermoelectrics and optoelectronics among others. Researchers are now creating two-dimensional versions of these materials, in the hope that they will offer improved performance or even new applications.
Recently, a research team that includes Salvador Barraza-Lopez, associate professor of physics at the U of A and Taneshwor Kaloni, a former post-doctoral researcher in Barraza-Lopez's lab, has shed light on the behavior of one of these ultrathin materials known as tin telluride (SnTe). Barraza-Lopez and his colleagues at the Max-Planck Institute of Microstructure Physics in Germany, the Key Laboratory of Low-Dimensional Quantum Physics and the Collaborative Innovation Center of Quantum Matter in China and the RIKEN Center for Emergent Matter Science in Japan recently published a paper on their findings in the journal Advanced Materials.
The researchers used a variable temperature scanning tunneling microscope to study the structure and polarization of SnTe thin films grown on graphene substrates. They studied the material at a range of temperatures, from 4.7 Kelvin to over 400 Kelvin. They discovered that when SnTe is only a few atomic layers thick, it forms a layered structure that is different from the bulk, rhombic-shaped version of the material. The Arkansas team contributed to this research by providing calculations that account for the quantum mechanical nature of these atomic structures, using a method known as density functional theory.
The atoms in ultrathin SnTe create electric dipoles oriented along opposite directions in every other atomic layer, which makes the material anti-polar, as opposed to the bulk sample in which all layers point along the same direction. Moreover, the transition temperature, which is the temperature at which the material loses this spontaneous polarization, is much higher than that of the bulk material.
"[These findings] underline the potential of atomically thin g-SnTe films for the development of novel spontaneous polarization-based devices," said the researchers in the paper.
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)-Project number PA 1812/2-1, the National Natural Science Foundation of China (Grant No. 51561145005) and the Ministry of Science and Technology of China (Grant No. 2016YFA0301002). Work performed at Arkansas was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under the Early Career Award DE-SC0016139. Calculations were carried out at Trestles (funded by multiple grants from the National Science Foundation, a grant from the Arkansas Economic Development Commission, and the U of A Office of the Vice Provost for Research and Innovation.)
Stanford, U of A Engineers Look to Future of Electronics Research Workshop
Reference: University of Arkansas Newswire November 1, 2018
Researchers and industry partners gathered in Fayetteville last month to chart a course for the next generation of batteries, microprocessors and power electronics — including changes that could revolutionize how automobiles, aircraft and spacecraft are designed in a growing electrified fleet.
The workshop was hosted by the Center for Power Optimization of Electro-Thermal Systems, also known as POETS.
Participants included researchers from the University of Arkansas, Stanford University, University of Illinois-Urbana Champaign and Howard University.
The workshop was led by Debbie Senesky, assistant professor of aeronautics and astronautics at Stanford University, and David Huitink, assistant professor of mechanical engineering at the University of Arkansas.
The workshop introduced the questions, "What could be accomplished if the power electronics, microprocessors, and batteries of the future ran hotter (perhaps as high as 500 degrees Celsius, or more)? How would this new operating point revolutionize the design of automobiles, aircraft, and spacecraft?"
The Center for Power Optimization of Electro-Thermal Systems is working to design and develop vehicle electrical systems that are more powerful, efficient and heat-resistant.
The long-term goal is to increase the power density of current mobile electrified systems by 10-100 times over current state-of-the-art systems. Results from the study could save highway vehicles between 100-300 million liters of fuel per year.
A great challenge in today's semiconductor industry, Huitink said, is the thermal limit of electronic devices — the maximum temperature at which devices can operate.
Increasing that limit would give engineers more options when designing electronics, which could make the final products smaller, cheaper and more efficient at delivering power.
The limit is approximately 250 degrees Celsius (482 Fahrenheit) for commonly used silicon for semiconductors, and often less than 150 Celsius (302 Fahrenheit) for their associated packaging.
That limit prevents the engineering of safe electronic systems with power densities exceeding about 1 kilowatt per centimeter-squared, Huitink said.
To overcome these significant environmental challenges, engineers integrate active cooling systems or complex packaging into the design of electronic modules to make them more durable, but those fixes can significantly increase cost and payload requirements. The workshop was designed to help researchers and businesses address those issues.
"Building on the current successes in POETS and standing upon the shoulders of the 'giants' in power electronics research was the fundamental premise in this workshop," Huitink said. "We have a spectacular team in POETS, through whom we expect to revolutionize the capabilities in mobile power electronic systems. Bringing the key minds in device, packaging, sensing and reliability of these systems together with the major industrial partnerships, ranging from electric vehicles to aircraft and heavy machinery helps us to pinpoint technical challenges, which we can then work together to solve."
Taking a Close Look at Bacteria
Reference: University of Arkansas Newswire October 23, 2018
Yong Wang, assistant professor of physics, and graduate student Asmaa Sadoon have been studying how molecules travel through bacterial cytoplasm in order to understand more about how these tiny organisms function. Using new high-tech tools, they have been able to observe certain processes inside live bacteria for the first time. They published their results in the journal Physical Review E.
The researchers used a combination of super-resolution fluorescence microscopy and a technique called single-particle tracking to study how a type of protein called H-NS moves through the cytoplasm of E. coli cells. The researchers chose this protein because it interacts with both proteins and DNA, and it helps regulate gene expression in the bacteria. Understanding bacterial gene expression could lead to new techniques to mitigate bacterial resistance to antibiotics.
In this study, the researchers learned new information about this protein, and about the properties of bacterial cytoplasm. Wang describes cytoplasm as "a thick soup of proteins, DNA, and various other molecules." Because bacteria don't have transport systems, such as digestive or circulatory systems, they depend on the diffusion of molecules through this soup for the processes that keep them alive.
By tracking the movement of H-NS through the cytoplasm of the E. coli, the researchers were able to calculate the viscoelasticity of the cytoplasm. They found that the bacterial "soup" doesn't behave the same way a homogenous protein solution does.
Previous research, which used homogenous solutions studied in vitro, observed that in these solutions, both elasticity and viscosity decreased over time. In other words, the solutions became both thinner and softer. In actual bacteria, however, Wang and Sadoon observed that, after a certain time-scale, the viscosity, or thickness, of the cytoplasm flattens out, so the bacterial cytoplasm gets softer without getting thinner.
"Our findings are expected to fundamentally change the way bacterial cytoplasm is viewed," the researchers explained in the paper. "Unlike a simple viscous or viscoelastic fluid that current models of bacterial processes typically consider, the bacterial cytoplasm behaves differently at different time scales in terms of mechanical properties, which is expected to impact various interactions among small molecules, proteins and DNA/RNA molecules inside bacteria, as well as bacterial interactions with other species, such as bacteriophages."
This work was supported by the University of Arkansas, the Arkansas Biosciences Institute (Grants No. ABI-0189, No. ABI-0226, and No. ABI-0277), and the National Science Foundation (Grant No. 1826642).
U of A Graduate Students Receive Awards and Grants at International Optics Conference
Reference: University of Arkansas Newswire August 28, 2018
SAN DIEGO — Two graduate students from the University of Arkansas were honored at the annual Optics and Photonics conference, one of the two largest meetings organized by SPIE, the international society for optics and photonics.
Oluwatobi ''Tobi'' Olorunsola received the MKS Instruments Research Excellence Travel Awards, which enabled him to present his research at the conference, held Aug. 17-23 in San Diego. Abayomi Omolewu, the current president of the SPIE Arkansas Laserbacks Student Chapter was also awarded the student leadership travel grant to represent the University of Arkansas at the conference.
Tobi Olorunsola received a B.S. in engineering physics from Obafemi Awolowo University and dual M.S. degrees in physics and geophysics from Western Illinois University and the University of Oklahoma respectively. He is a first-year doctoral student in the U of A's microelectronics-photonics graduate program. The work he presented at the conference was advised by professor Joseph B. Herzog in collaboration with other members of the Plasmonic Nano-Optics group, and now Tobi is a member of professor Shui-Quing "Fisher" Yu's Applied Nanophotonics group. His current research interests include developing and characterizing plasmonic nanostructures, semiconductor materials growth and optoelectronic device development. He is also a doctoral academy fellowship recipient.
Abayomi is a doctoral student in the U of A's microelectronics-photonics graduate program. The two students are officers of the University of Arkansas student chapter of SPIE. SPIE, founded in 1955 as the Society of Photographic Instrumentation Engineers, is an international professional society that advances emerging light-based technologies through interdisciplinary information exchange, continuing education, publications, career development, and advocacy.
MicroEP Students Clean Frisco Trail
July 21, 2018
FAYETTEVILLE, Ark. – A group of MicroEP graduate students, along with MicroEP REU participants, carried out the cleaning of the Frisco Trail on Saturday, July 21. The Frisco Trail is a portion of the Razorback Greenway that runs from Fayetteville to Bentonville.
The Frisco Trail was adopted by the MicroEP Graduate Program in October 2017. This trail adoption was due to the rigorous cleaning of the trail that the MicroEP Program has continued to do for a number of years.
The trail is cleaned at least once a semester by MicroEP graduate students and their families.
Quantum Dots Enable Faster, Easier Photon Detection, More Secure Data
Reference: University of Arkansas Newswire April 25, 2018
FAYETTEVILLE, Ark. – A team of researchers including U of A engineering and physics faculty has developed a new method of detecting single photons, or light particles, using quantum dots.
Single photon detection is a key element to enable use of quantum information, a method of transferring information that is much faster and more secure than current methods. This technology has other applications as well, including biological and medical imaging, spectroscopy, and astronomical observation.
Shui-Qing “Fisher” Yu, associate professor of electrical engineering; Greg Salamo, distinguished professor of physics; and Yang Zhang, a post-doctoral fellow in electrical engineering at the time, worked with colleagues from Dartmouth and the University of Wisconsin on this research, which was recently published by ACS Photonics.
Quantum information uses different quantum states of particles, such as polarization or phase, to encode information. Because quantum information is not limited to the ones and zeroes used to encode digital information, this technology can transfer a large amount of information very securely.
Since quantum information can be transmitted using an infinite variety of quantum states, the sender and receiver must both agree on which state they are using to encode and interpret the data. An outsider intercepting the signal would have little way of reading it without this knowledge.
A photon is a quantum of light. When a photon enters a detector in a quantum information system, its energy is transferred to an electron and this results in a current or a voltage. This effect is so small, though, that it is difficult to detect. Other designs for photon detectors solve this problem by using a device called an avalanche photodiode to amplify the current or voltage, but this approach tends to add delays to the detection and increases background noise.
The new approach created and modeled by these researchers uses a quantum dot, which is a semiconductor nanoscale particle, to detect single photons. Compared to other methods, the change in voltage caused by a single photon in this detector is large, with a low background noise level.
Yu compared this to adding a drop of water to a container. “If you put one drop of water in a large tank, that change is hard to see,” he said. “But if you put a drop of water into a very small container, you can see the change more easily.” In the researchers’ design, the electron is in a small container – the quantum dot.
The researchers have used computer models to demonstrate that their design can detect single photons more accurately than existing technologies.
Malshe Elected to National Academy of Engineering
Reference: University of Arkansas Newswire Feb. 09, 2018
Distinguished Professor Ajay Malshe of the Department of Mechanical Engineering has been elected to the National Academy of Engineering, one of the most prestigious professional distinctions awarded to an engineer.
Malshe holds the Twenty-First Century Endowed Chair in Materials, Manufacturing and Integrated Systems in the College of Engineering. He specializes in nanomanufacturing, bio-inspired systems, high-density electronic packaging and entrepreneurship in the University of Arkansas' Institute for Nano Science and Engineering.
Membership in the National Academy of Engineering honors those who have made outstanding contributions to "engineering research, practice, or education, including, where appropriate, significant contributions to the engineering literature" and to "the pioneering of new and developing fields of technology, making major advancements in traditional fields of engineering, or developing/implementing innovative approaches to engineering education," according to the NAE.
Malshe was recognized for his innovations in nanomanufacturing, which have impacts in multiple industry sectors, as well as for his role as founder, executive vice president and chief technology officer of NanoMech Inc. in Springdale. NanoMech is the world's leading company in nanomanufacturing products for Fortune 500 global corporations in energy, transportation, racing, aerospace, industrial, defense and other key sectors.
John English, dean of the College of Engineering, praised Malshe's achievement.
"Induction into the National Academy of Engineering is one of the highest honors in our profession and it represents a major career milestone," English said. "I congratulate Dr. Malshe, because his achievements in nanoscience are a point of immense pride for the entire College of Engineering and reflect very well on the spirit of innovation we work to foster at the University of Arkansas."
Darin Nutter, head of the department of mechanical engineering, lauded Malshe's dedication to the profession.
"We in the Department of Mechanical Engineering are so proud Dr. Malshe is being recognized
for his hard work," Nutter said. "This exceptionally high honor represents many years
of significant engineering and entrepreneurial accomplishments made during his time
at the University of Arkansas."
Malshe thanked his team, and said he was honored by the recognition.
"This is a truly an extraordinary and humbling honor to me and my world-class team," Malshe said. "It brings great recognition to the College of Engineering and the University of Arkansas, NanoMech Industries and the state of Arkansas. This is a special tribute to the rich entrepreneurial culture in the state of Arkansas, which is home to Walmart, Tyson Foods, NanoMech Industries, J.B. Hunt, Stevens, Murphy Oil and others. Also, this honor establishes the foundation for a new model for a 'Professor-of-Practice' in engineering."
John White, chancellor emeritus and distinguished professor of industrial engineering, said he believed Malshe is the first person elected to the National Academy of Engineering based on his work at the U of A. Jack E. Buffington, retired research professor of civil engineering, and Michael R. Johnson, associate vice chancellor for facilities management, were elected while at the university, but their elections were the result of their accomplishments while serving in the U.S. Navy.
"Ajay's nomination cited his individual accomplishments in manufacturing engineering, including numerous national and international awards he and NanoMech have received," White said. "The impressive list of companies using NanoMech's products to achieve remarkable improvements in productivity includes Indy 500 winners (Penske and Andretti Racing), J.B. Hunt, GE Aviation, Cameron-Schlumberger, Tesla, and Pace Industries, among many others. Undoubtedly, his election was due to Ajay's ability to keep one foot firmly planted in academe and the other foot firmly planted in industry. The coupling of his research and its commercialization paid off for him, for his company and for the University of Arkansas."
Malshe will be formally inducted during a ceremony at the National Academy of Engineering's annual meeting in Washington, D.C., on Sept. 30.
Malshe joins 98 engineers from around the world in this year's class, including Amazon founder Jeff Bezos and Google principal scientist Martin Abadi.
Research Reveals Unique Optical Properties in Nanoscale Materials
Reference: University of Arkansas Newswire Jan. 11, 2018
Recently published research on plasmonic metasurfaces — surfaces with nanoscale features that often exhibit new and unique optical properties — could lead to advances in microscale lenses and other optical components. Miniaturizing these lenses is a step toward improved super-resolution imaging and high-density photonic circuit integration.
The work is a collaboration between Joseph B. Herzog, an assistant professor in the Department of Physics at the J. William Fulbright College of Arts and Sciences, and scientists at the Naval Research Laboratory in Washington, D.C.
The project, led by Jake Fontana at the NRL and published in the journal ACS Photonics, created large area optical metasurfaces with gold nanoparticles. Gold nanoparticles support plasmons, which are oscillating electrons on the gold surface. The vibrating electrons and their collective interactions give rise to the unique optical properties of the metasurface. Dennis Doyle, an undergraduate at the University of Pittsburgh and first author of the paper, fabricated the surfaces with millions of gold nanospheres, precisely controlling subnanometer spacings between each sphere. Accurately controlling gap spacing allowed researchers to show that experimental results agree well with classical (local) electromagnetic models, revealing that the classical model can predict plasmonic and optical properties in subnanometer dimensions down to at least half of a nanometer, which is one-billionth of a meter.
The paper, titled Tunable Subnanometer Gap Plasmonic Metasurfaces, also shows that these metasurfaces exhibit unique optical properties beyond those found in nature. Typically, the real part of the refractive index, an important optical material property, is limited to less than 3 for naturally occurring materials. The research team was able to fabricate metasurfaces with values as high as 5, opening the door to new photonic and optical applications.