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News Article | April 25, 2017
Site: www.materialstoday.com

This is a schematic of an interpocket paired state, one of two topological superconducting states proposed in the latest work from the lab of Eun-Ah Kim, associate professor of physics at Cornell University. The material used is a monolayer transition metal dichalcogenide. Image: Eun-Ah Kim, Cornell University.The experimental realization of ultrathin graphene has ushered in a new age in materials research. What started with graphene has now evolved to encompass numerous related single-atom-thick materials, which have unusual properties due to their ultra-thinness. Among these materials are transition metal dichalcogenides (TMDs), which offer several key features not available in graphene and are emerging as next-generation semiconductors. Now, new research shows that TMDs could even realize topological superconductivity and thus provide a platform for quantum computing – the ultimate goal of a research group at Cornell University led by Eun-Ah Kim, associate professor of physics. "Our proposal is very realistic – that's why it's exciting," Kim said of her group's research. "We have a theoretical strategy to materialize a topological superconductor ... and that will be a step toward building a quantum computer. The history of superconductivity over the last 100 years has been led by accidental discoveries. We have a proposal that's sitting on firm principles. "Instead of hoping for a new material that has the properties you want, let's go after it with insight and design principle." Yi-Ting Hsu, a doctoral student in Kim’s group, is lead author of a new paper on this research in Nature Communications. Other team members include Kim group alumni Mark Fischer, now at ETH Zurich in Switzerland, and Abolhassan Vaezi, now at Stanford University. The group propose that TMDs' unusual properties favor two topological superconducting states, which if experimentally confirmed will open up possibilities for manipulating topological superconductors at temperatures near absolute zero. Kim identified hole-doped (positive charge-enhanced) single-layer TMDs as a promising candidate for topological superconductivity. She did this based on the known special locking between spin state and the kinetic energy of electrons (spin-valley locking) of single-layer TMDs, as well as the recent observations of superconductivity in electron-doped (negative charge-enhanced) single-layer TMDs. The group's goal is a superconductor that operates at around 1K (approximately -457°F), which could be sufficiently cooled with liquid helium to maintain quantum computing potential in a superconducting state. Theoretically, housing a quantum computer powerful enough to justify the power needed to keep the superconductor at 1K is not out of the question, Kim said. In fact, IBM already has a 7-qubit (quantum bit) computer that operates at less than 1K, which is available to the public through its IBM Quantum Experience. A quantum computer with approximately six times more qubits would fundamentally change computing, Kim said. "If you get to 40 qubits, that computing power will exceed any classical computers out there," she said. "And to house a 40-qubit quantum computer in cryogenic temperature is not that big a deal. It will be a revolution." Kim and her group are working with Debdeep Jena and Grace Xing of electrical and computer engineering, and Katja Nowack of physics, through an interdisciplinary research group seed grant from the Cornell Center for Materials Research (CCMR). Each group brings researchers from different departments together, with support from both the university and the US National Science Foundation's Materials Research Science and Engineering Centers program. "We're combining the engineering expertise of DJ and Grace, and expertise Katja has in mesoscopic systems and superconductors," Kim said. "It requires different expertise to come together to pursue this, and CCMR allows that." This story is adapted from material from Cornell University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


News Article | April 26, 2017
Site: www.eurekalert.org

ITHACA, N.Y. - Lithium-oxygen fuel cells boast energy density levels comparable to fossil fuels and are thus seen as a promising candidate for future transportation-related energy needs. Several roadblocks stand in the way of realizing that vision, however. They include poor rechargeability, reduced efficiency due to high overpotentials (more charge energy than discharge energy) and low specific energy. Two instabilities contribute to these roadblocks. Much of the previous work done in the lab of Lynden Archer, the James A. Friend Family Distinguished Professor of Engineering in the Robert F. Smith School of Chemical and Biomolecular Engineering (CBE) at Cornell University, has centered on one: the nucleation and growth of dendrites from one electrode to the other, which causes short-circuiting, a source of premature cell failure that invariably ends in fires. It's the other instability - the loss of battery power, also known as capacity fade - that is the focus of the lab's most recent work. Snehashis Choudhury, a doctoral student in the Archer Research Group, has come up with what Archer terms an "ingenious" answer to the problem of capacity fade. Their work is detailed in "Designer interphases for the lithium-oxygen electrochemical cell," published this month in Science Advances. Choudhury is co-first author along with Charles Wan, a chemical engineering major. Capacity fade occurs when the electrolyte, which transports charged ions from the negative electrode (anode) to the positive (cathode), reacts with the electrodes. "It starts to consume the electrodes," Choudhury said. "It forms many insulating products that impede ion transport. Over time, these build up to produce such prohibitive internal cell resistance that finally the battery fades." The problem: How do you stop one electrolyte-electrode reaction, when it's another necessary reaction between the two - the transfer of ions - that produces power? Choudhury's solution is called an artificial solid-electrolyte interphase (SEI), a material that protects the electrodes while promoting the flow of electrons from one end of the cell to the other. "Such interphases form naturally in all electrochemical cells ... and their chemo-mechanical stability is critical to the success of the graphite anode in lithium-ion batteries," Archer said. " Choudhury's approach for creating a functional designer interphase is based on bromide-containing ionic polymers (ionomers) that selectively tether to the lithium anode to form a few-nanometers-thick conductive coating that protects the electrode from degradation and fade. The SEI ionomers display three attributes that allow for increased stability during electrodeposition: protection of the anode against growth of dendrites; reduction-oxidation (redox) mediation, which reduces charge overpotentials; and the formation of a stable interphase with lithium, protecting the metal while promoting ion transport. One challenge still exists: All research-grade lithium-oxygen electrochemical cells are evaluated using pure oxygen as the active cathode material. For a commercially viable lithium-oxygen (or lithium-air, as it's also known) cell, it would need to pull oxygen out of the air, and that oxygen also contains other reactive components, such as moisture and carbon dioxide. If the inefficiencies that limit performance of lithium-oxygen fuel cells can be resolved, the exceptional energy storage options offered by the cell chemistry would be a giant step forward for electrified transportation and a revolutionary advance for autonomous robotics, Archer said. "It is telling from observations of the most advanced humanoid robots that they are always either tethered to an ultra-long electrical cable or are using something like a loud lawnmower engine to generate energy," Archer said. "Either energy source compares poorly to those found in nature. Energy storage technologies such as Li-air cells, which harness materials from the surroundings, promise to close this gap." Other contributors were Lena Kourkoutis, assistant professor and the Rebecca Q. and James C. Morgan Sesquicentennial Faculty Fellow in applied and engineering physics; CBE doctoral student Wajdi Al Sadat; Sampson Lau, Ph.D. '16; Zhengyuan Tu, doctoral student in materials science and engineering; and Michael Zachman, doctoral student in applied and engineering physics. Support for this work came from the Advanced Research Projects Agency-Energy. In addition, electron microscopy was done at the Cornell Center for Materials Research, a National Science Foundation-supported Materials Research Science and Engineering Center.


News Article | November 24, 2016
Site: www.medicalnewstoday.com

Interactions between an animal cell and its environment, a fibrous network called the extracellular matrix, play a critical role in cell function, including growth and migration. But less understood is the mechanical force that governs those interactions. A multidisciplinary team of Cornell engineers and colleagues from the University of Pennsylvania have devised a method for measuring the force a cell - in this case, a breast cancer cell - exerts on its fibrous surroundings. Understanding those forces has implications in many disciplines, including immunology and cancer biology, and could help scientists better design biomaterial scaffolds for tissue engineering. The group, led by Mingming Wu, associate professor in the Department of Biological and Environmental Engineering, developed 3-D traction-force microscopy to measure the displacement of fluorescent marker beads distributed in a collagen matrix. The beads are displaced by the pulling of migrating breast cancer cells embedded in the matrix. An important part of the puzzle was to calculate the force exerted by the cells using the displacement of the beads. That calculation was carried out by the team led by Vivek Shenoy, professor of materials science and engineering at the University of Pennsylvania. The group's paper, "Fibrous nonlinear elasticity enables positive mechanical feedback between cells and extracellular matrices," published online in Proceedings of the National Academy of Sciences. Matthew Hall, Ph.D. '16, now a postdoctoral researcher at the University of Michigan, is lead author and engineered the collagen matrices used in the study. Wu - who also was affiliated with the Cornell Center on the Microenvironment and Metastasis at Weill Cornell Medicine, which existed from 2009 through 2015 - said her group's work centered on a basic question: How much force do cells exert on their extracellular matrix when they migrate? "The matrix is like a rope, and in order for the cell to move, they have to exert force on this rope," she said. "The question arose from cancer metastasis, because if the cells don't move around, it's a benign tumor and generally not life-threatening." It's when the cancerous cell migrates that serious problems can arise. That migration occurs through "cross-talk" between the cell and the matrix, the group found. As the cell pulls on the matrix, the fibrous matrix stiffens; in turn, the stiffening of the matrix causes the cell to pull harder, which stiffens the matrix even more. This increased stiffening also increases cell force transmission distance, which can potentially promote metastasis of cancer cells. "We've shown that the cells are able to align the fibers in their vicinity by exerting force," Hall said. "We've also shown that when the matrix is more fibrous - less like a continuous material and more like a mesh of fibers - they're able to align the fibers through the production of force. And once the fiber is aligned and taut, it's easier for cells to pull on them and migrate." "I'm a strong believer that every new science discovery goes hand-in-hand with new technology development," she said. "And with every new tool, you discover something new." This research was supported by grants from the National Institutes of Health, the National Cancer Institute and the National Science Foundation, and made use of the Cornell NanoScale Science and Technology Facility, the Cornell Biotechnology Resource Center Imaging Facility, the Cornell Center for Materials Research and the Cornell Nanobiotechnology Center. Article: Fibrous nonlinear elasticity enables positive mechanical feedback between cells and ECMs, Matthew S. Hall, Farid Alisafaei, Ehsan Ban, Xinzeng Feng, Chung-Yuen Hui, Vivek B. Shenoy, and Mingming Wu, PNAS, doi: 10.1073/pnas.1613058113, published online 21 November 2016.


News Article | November 22, 2016
Site: www.eurekalert.org

Interactions between an animal cell and its environment, a fibrous network called the extracellular matrix, play a critical role in cell function, including growth and migration. But less understood is the mechanical force that governs those interactions. A multidisciplinary team of Cornell engineers and colleagues from the University of Pennsylvania have devised a method for measuring the force a cell -- in this case, a breast cancer cell -- exerts on its fibrous surroundings. Understanding those forces has implications in many disciplines, including immunology and cancer biology, and could help scientists better design biomaterial scaffolds for tissue engineering. The group, led by Mingming Wu, associate professor in the Department of Biological and Environmental Engineering, developed 3-D traction-force microscopy to measure the displacement of fluorescent marker beads distributed in a collagen matrix. The beads are displaced by the pulling of migrating breast cancer cells embedded in the matrix. An important part of the puzzle was to calculate the force exerted by the cells using the displacement of the beads. That calculation was carried out by the team led by Vivek Shenoy, professor of materials science and engineering at the University of Pennsylvania. The group's paper, "Fibrous nonlinear elasticity enables positive mechanical feedback between cells and extracellular matrices," published online Nov. 21 in Proceedings of the National Academy of Sciences. Matthew Hall, Ph.D. '16, now a postdoctoral researcher at the University of Michigan, is lead author and engineered the collagen matrices used in the study. Wu -- who also was affiliated with the Cornell Center on the Microenvironment and Metastasis at Weill Cornell Medicine, which existed from 2009 through 2015 -- said her group's work centered on a basic question: How much force do cells exert on their extracellular matrix when they migrate? "The matrix is like a rope, and in order for the cell to move, they have to exert force on this rope," she said. "The question arose from cancer metastasis, because if the cells don't move around, it's a benign tumor and generally not life-threatening." It's when the cancerous cell migrates that serious problems can arise. That migration occurs through "cross-talk" between the cell and the matrix, the group found. As the cell pulls on the matrix, the fibrous matrix stiffens; in turn, the stiffening of the matrix causes the cell to pull harder, which stiffens the matrix even more. This increased stiffening also increases cell force transmission distance, which can potentially promote metastasis of cancer cells. "We've shown that the cells are able to align the fibers in their vicinity by exerting force," Hall said. "We've also shown that when the matrix is more fibrous - less like a continuous material and more like a mesh of fibers - they're able to align the fibers through the production of force. And once the fiber is aligned and taut, it's easier for cells to pull on them and migrate." "I'm a strong believer that every new science discovery goes hand-in-hand with new technology development," she said. "And with every new tool, you discover something new." This research was supported by grants from the National Institutes of Health, the National Cancer Institute and the National Science Foundation, and made use of the Cornell NanoScale Science and Technology Facility, the Cornell Biotechnology Resource Center Imaging Facility, the Cornell Center for Materials Research and the Cornell Nanobiotechnology Center.


News Article | August 8, 2016
Site: www.techtimes.com

Researchers from Cornell University have developed a new carbon capture method that not only converts carbon dioxide into useful components but also creates electricity with the help of oxygen. In a study published in the journal Science Advances, Lynden Archer and Wajdi Al Sadat detailed the development of an aluminum-carbon dioxide power cell assisted by oxygen that utilizes electrochemical reactions in sequestering and converting carbon dioxide and creating electricity. The power cell uses aluminum as the anode while carbon dioxide and oxygen were mixed to become the cathode. Aluminum was the perfect choice for the anode because it is abundant in supply, safer to use than other metals and lower in cost than sodium and lithium while still offering energy density comparable to lithium. Most carbon-capture systems in place today typically capture carbon in solids or fluids, which are then depressurized or heated to release carbon dioxide. The gas is then compressed before being transported either for reuse in industries or to be sequestered below the ground. According to Archer, their study presents a possible shift in the usual practice of capturing carbon, adding that simply devising a carbon-capture method that generates electricity as well is in itself important. A lot of people understand the benefits of carbon-capture technology but there are roadblocks to adopting it. In electrical power plants, for instance, regenerating the fluids needed to capture carbon can consume up to 25 percent of the facility's energy output. Additionally, there's the cost associated with transporting the captured gas. The researchers reported that the power cell they came up with is capable of generating 13 ampere hours for every gram of porous carbon in the cathode, with a 1.4-volt discharge potential. This kind of energy production is comparable to what battery systems with the highest energy density levels are capable of. Alongside electricity, the power cell generates superoxide intermediates when carbon dioxide reduction occurs at the cathode. When the superoxide is combined with inert carbon dioxide, a carbon-carbon oxalate is formed, which is commonly used in various industries, like metal smelting and pharmaceuticals. However, there is a drawback: the electrolyte connecting the anode and cathode. The liquid is highly sensitive to water so the researchers are working on developing electrochemical systems that use electrolytes that are less water-sensitive. The study was carried out with assistance from the Cornell Center for Materials Research. It received funding support from the King Abdullah University of Science and Technology Global Research Partnership Program. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | December 12, 2016
Site: www.eurekalert.org

ITHACA, N.Y. - Most robots achieve grasping and tactile sensing through motorized means, which can be excessively bulky and rigid. A Cornell University group has devised a way for a soft robot to feel its surroundings internally, in much the same way humans do. A group led by Robert Shepherd, assistant professor of mechanical and aerospace engineering and principal investigator of Organic Robotics Lab, has published a paper describing how stretchable optical waveguides act as curvature, elongation and force sensors in a soft robotic hand. Doctoral student Huichan Zhao is lead author of "Optoelectronically Innervated Soft Prosthetic Hand via Stretchable Optical Waveguides," which is featured in the debut edition of Science Robotics. "Most robots today have sensors on the outside of the body that detect things from the surface," Zhao said. "Our sensors are integrated within the body, so they can actually detect forces being transmitted through the thickness of the robot, a lot like we and all organisms do when we feel pain, for example." Optical waveguides have been in use since the early 1970s for numerous sensing functions, including tactile, position and acoustic. Fabrication was originally a complicated process, but the advent over the last 20 years of soft lithography and 3-D printing has led to development of elastomeric sensors that are easily produced and incorporated into a soft robotic application. Shepherd's group employed a four-step soft lithography process to produce the core (through which light propagates), and the cladding (outer surface of the waveguide), which also houses the LED (light-emitting diode) and the photodiode. The more the prosthetic hand deforms, the more light is lost through the core. That variable loss of light, as detected by the photodiode, is what allows the prosthesis to "sense" its surroundings. "If no light was lost when we bend the prosthesis, we wouldn't get any information about the state of the sensor," Shepherd said. "The amount of loss is dependent on how it's bent." The group used its optoelectronic prosthesis to perform a variety of tasks, including grasping and probing for both shape and texture. Most notably, the hand was able to scan three tomatoes and determine, by softness, which was the ripest. This work was supported by a grant from Air Force Office of Scientific Research, and made use of the Cornell NanoScale Science and Technology Facility and the Cornell Center for Materials Research, both of which are supported by the National Science Foundation. Cornell University has television, ISDN and dedicated Skype/Google+ Hangout studios available for media interviews. For additional information, see this Cornell Chronicle story.


News Article | December 13, 2016
Site: www.chromatographytechniques.com

Most robots achieve grasping and tactile sensing through motorized means, which can be excessively bulky and rigid. A Cornell University group has devised a way for a soft robot to feel its surroundings internally, in much the same way humans do. A group led by Robert Shepherd, assistant professor of mechanical and aerospace engineering and principal investigator of Organic Robotics Lab, has published a paper describing how stretchable optical waveguides act as curvature, elongation and force sensors in a soft robotic hand. Doctoral student Huichan Zhao is lead author of “Optoelectronically Innervated Soft Prosthetic Hand via Stretchable Optical Waveguides,” which is featured in the debut edition of Science Robotics. “Most robots today have sensors on the outside of the body that detect things from the surface,” Zhao said. “Our sensors are integrated within the body, so they can actually detect forces being transmitted through the thickness of the robot, a lot like we and all organisms do when we feel pain, for example.” Optical waveguides have been in use since the early 1970s for numerous sensing functions, including tactile, position and acoustic. Fabrication was originally a complicated process, but the advent over the last 20 years of soft lithography and 3-D printing has led to development of elastomeric sensors that are easily produced and incorporated into a soft robotic application. Shepherd’s group employed a four-step soft lithography process to produce the core (through which light propagates), and the cladding (outer surface of the waveguide), which also houses the LED (light-emitting diode) and the photodiode. The more the prosthetic hand deforms, the more light is lost through the core. That variable loss of light, as detected by the photodiode, is what allows the prosthesis to “sense” its surroundings. “If no light was lost when we bend the prosthesis, we wouldn’t get any information about the state of the sensor,” Shepherd said. “The amount of loss is dependent on how it’s bent.” The group used its optoelectronic prosthesis to perform a variety of tasks, including grasping and probing for both shape and texture. Most notably, the hand was able to scan three tomatoes and determine, by softness, which was the ripest. This work was supported by a grant from Air Force Office of Scientific Research, and made use of the Cornell NanoScale Science and Technology Facility and the Cornell Center for Materials Research, both of which are supported by the National Science Foundation.


News Article | August 26, 2016
Site: phys.org

A research group—consisting of Masahiro Goto, distinguished chief researcher, Center for Green Research on Energy and Environmental Materials, NIMS; Michiko Sasaki, postdoctoral researcher, Center for Materials Research by Information Integration, NIMS; Masahiro Tosa, group leader, Research Center for Structural Materials, NIMS; Kazue Kurihara, professor, and Motohiro Kasuya, assistant professor, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University—developed a coating technique using a zinc oxide (ZnO) material, an environment-friendly, low-friction material developed exclusively by NIMS. When bearing balls were coated with the ZnO material, the material's low frictional characteristics were maintained and the friction coefficient of the bearing was reduced by approximately one-third. Moreover, the research group and Fox Corporation jointly developed a small jet engine generator for emergency use. By integrating the ZnO-coated bearings into the generator, its fuel consumption was reduced by 1%. In consideration of worsening global environment/energy issues, it is important to reduce friction occurring in drive mechanisms including engines in terms of energy saving. However, because the mechanically driven part in an engine becomes extremely hot, friction reduction technology applied in such an environment must be heat resistant. We focused on ZnO, capable of both reducing friction and resisting heat, and identified its friction reduction mechanism at the nano level. Then, we developed a basic technique to apply a low-friction ZnO coating by controlling the crystal orientation of ZnO. In efforts to put the developed basic technique to practical use, we applied the technique to reduce the friction level of commercially-available, high-performance bearings to an even further extent. We developed the technique for applying ZnO coating to bearing balls while controlling the crystal orientation of the ZnO material by rotating bearing balls in cage-shaped sample holders. As a result, we succeeded in reducing the friction coefficient of the bearings by approximately one-third. In addition, we integrated the resulting bearings into a small jet engine, evaluated its performance, and observed a 1% reduction in fuel consumption. Furthermore, we worked to miniaturize generators to be used in times of emergency when procurement of fuel is difficult. In this effort, we succeeded in developing a small jet engine generator equipped with ZnO-coated bearings. It weighs only about 40 kg, and can be carried by two adults. This compact generator, however, can produce 8,000 W of power, which can approximately cover the amount of power consumed by two households, and will be made available for emergency use. The newly developed low-friction ZnO coating is expected to be applicable not only to bearings but also to any mechanically driven parts that require friction reduction, given that the coating is usable in a wide range of conditions: from room temperature to high temperature, in oil, in vacuum and in atmosphere. By applying this coating technology to different types of mechanically driven parts in systems such as automobiles, it may be possible to save energy in these systems. This study was conducted in line with the university-led green innovation project "Green Network of Excellence (GRENE)" sponsored by the Ministry of Education, Culture, Sports, Science and Technology. More specifically, this study was carried out in accordance with the "Green Tribology Innovation Network" project (Principal investigator: Professor Kazue Kurihara, Tohoku University) within a GRENE category, the "Advanced Environmental Materials." We will give a presentation on this study on August 5, 2016, during the PRICM9 meetings to be held in Kyoto.


News Article | December 12, 2016
Site: www.cemag.us

Most robots achieve grasping and tactile sensing through motorized means, which can be excessively bulky and rigid. A Cornell University group has devised a way for a soft robot to feel its surroundings internally, in much the same way humans do. A group led by Robert Shepherd, assistant professor of mechanical and aerospace engineering and principal investigator of Organic Robotics Lab, has published a paper describing how stretchable optical waveguides act as curvature, elongation, and force sensors in a soft robotic hand. Doctoral student Huichan Zhao is lead author of “Optoelectronically Innervated Soft Prosthetic Hand via Stretchable Optical Waveguides,” which is featured in the debut edition of Science Robotics. The paper was published on Dec. 6; also contributing were doctoral students Kevin O’Brien and Shuo Li, both of Shepherd’s lab. “Most robots today have sensors on the outside of the body that detect things from the surface,” Zhao says. “Our sensors are integrated within the body, so they can actually detect forces being transmitted through the thickness of the robot, a lot like we and all organisms do when we feel pain, for example.” Optical waveguides have been in use since the early 1970s for numerous sensing functions, including tactile, position and acoustic. Fabrication was originally a complicated process, but the advent over the last 20 years of soft lithography and 3D printing has led to development of elastomeric sensors that are easily produced and incorporated into a soft robotic application. Shepherd’s group employed a four-step soft lithography process to produce the core (through which light propagates), and the cladding (outer surface of the waveguide), which also houses the LED (light-emitting diode) and the photodiode. The more the prosthetic hand deforms, the more light is lost through the core. That variable loss of light, as detected by the photodiode, is what allows the prosthesis to “sense” its surroundings. “If no light was lost when we bend the prosthesis, we wouldn’t get any information about the state of the sensor,” Shepherd says. “The amount of loss is dependent on how it’s bent.” The group used its optoelectronic prosthesis to perform a variety of tasks, including grasping and probing for both shape and texture. Most notably, the hand was able to scan three tomatoes and determine, by softness, which was the ripest. Zhao says this technology has many potential uses beyond prostheses, including bio-inspired robots, which Shepherd has explored along with Mason Peck, associate professor of mechanical and aerospace engineering, for use in space exploration. “That project has no sensory feedback,” Shepherd says, referring to the collaboration with Peck, “but if we did have sensors, we could monitor in real time the shape change during combustion [through water electrolysis] and develop better actuation sequences to make it move faster.” Future work on optical waveguides in soft robotics will focus on increased sensory capabilities, in part by 3D printing more complex sensor shapes, and by incorporating machine learning as a way of decoupling signals from an increased number of sensors. “Right now,” Shepherd says, “it’s hard to localize where a touch is coming from.” This work was supported by a grant from Air Force Office of Scientific Research, and made use of the Cornell NanoScale Science and Technology Facility and the Cornell Center for Materials Research, both of which are supported by the National Science Foundation.


News Article | February 20, 2017
Site: phys.org

A NIMS research group led by Masahiro Goto, Distinguished Chief Researcher, Center for Green Research on Energy and Environmental Materials, and Michiko Sasaki, postdoctoral researcher, Center for Materials Research by Information Integration (currently a postdoctoral fellow at the University of Tokyo) discovered that the amount of friction force between organic molecules and a sapphire substrate in a vacuum can be changed repeatedly by starting and stopping laser light irradiation. This discovery could potentially lead to the development of technology enabling the movement of micromachines and other small driving parts to be controlled. The performance of micromachines—used as moving components in small devices such as acceleration sensors and gyroscopes—is greatly affected by adhesion force (the attractive force between two or more materials that stick to each other). Adhesion force in a micromachine increases the friction force. Since increased friction force seriously impedes the movement of moving components, it is necessary to maintain a low level of adhesion force. In addition, if the level of friction force can be controlled, it may be feasible to control the movement of micromachines, leading to expansion of their use and enhancement of their functions. A great deal of attention was previously drawn to techniques enabling silicon-based materials, a major micromachine material, to be coated with diamond-like carbon, self-assembled monolayers, or fluorine-containing organic films in order to reduce friction force and thereby improve the movement of micromachines. However, it was difficult to control friction coefficients of two adjacent parts by coating them because the coefficients are determined predominantly by the materials used in these parts. The research group invented a completely novel method of controlling friction force between materials using light irradiation. Specifically, the group irradiated a localized area of a cantilever coated with organic molecules with laser light and observed that the friction force between the coated cantilever and a sapphire substrate increased by 15% using a scanning probe microscopic technique known as friction force mode. Moreover, the group was able to increase and decrease the friction force repeatedly by switching the laser light on and off. These findings may lead to the development of techniques to control the movement of micromachines and contribute to the identification of basic friction mechanism. While control of friction force by light at the nano level was achieved in this study, the technique also may be applicable to control of friction phenomena at the macro level. More information: Michiko Sasaki et al. Control of friction force by light observed by friction force microscopy in a vacuum, Applied Physics Express (2017). DOI: 10.7567/APEX.10.015201

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