research
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Visualizing Chemical Reaction on Bimetal Surfaces
Catalysts are the result of many chemists searching to unravel the beauty of molecules and the mystery of chemical reactions. Professor Jeong Young Park from the Department of Chemistry, whose research focuses on catalytic chemical reactions, is no exception. His research team recently made breakthroughs in addressing long-standing questions for understanding reaction mechanisms on bimetal catalysts.
During the studies reported in Science Advances, following a publication in Nature Communications this month, Professor Park’s research team identified that the formation of metal–oxide interfaces is the key factor responsible for the synergistic catalytic effect in bimetal catalysts. The team confirmed this fundamental reaction mechanism through in situ imaging of reaction conditions. This is the first visualization of bimetal surfaces under reaction conditions, signifying the role of metal–oxide interfaces in heterogeneous catalysis.
Bimetallic materials have outstanding catalytic performance, which opens a new pathway for controlling electronic structures and binding energy in catalysts. Despite considerable research on various catalytic reaction efficiencies, there are yet unanswered questions on the underlying principles behind the improved performance. Even more, it was very hard to figure out what led to the efficiency because the structure, chemical composition, and oxidation state of bimetallic materials change according to reaction conditions.
Recently, some research groups suggested that oxide–metal interfacial sites formed by the surface segregation of bimetallic nanoparticles might be responsible for the increased catalytic performance. However, they failed to present any definitive evidence illustrating the physical nature or the fundamental role of the oxide–metal interfaces leading to the improved performance.
To specifically address this challenge, the research team carried out in situ observations of structural modulation on platinum–nickel bimetal catalysts under carbon monoxide oxidation conditions with ambient pressure scanning tunneling microscopy and ambient pressure X-ray photoelectron spectroscopy.
The team observed that platinum–nickel bimetal catalysts exhibited a variety of different structures depending on the gas conditions. Under ultrahigh vacuum conditions, the surface exhibited a platinum skin layer on the platinum–nickel alloyed surface, selective nickel segregation followed by the formation of nickel oxide clusters using oxygen gas, and finally the coexistence of nickel oxide clusters on the platinum skin during carbon monoxide oxidation. The research team found that the formation of interfacial platinum–nickel oxide nanostructures is responsible for a highly efficient step in the carbon monoxide oxidation reaction.
These findings illustrate that the enhancement of the catalytic activity on the bimetallic catalyst surface originates from the thermodynamically efficient reaction pathways at the metal–metal oxide interface, which demonstrates a straightforward process for the strong metal–support interaction effect. The formation of these interfacial metal–metal oxide nanostructures increases catalytic activity while providing a thermodynamically efficient reaction pathway by lowering the heat of the reactions on the surface. [J. Kim et al. Adsorbate-driven reactive interfacial Pt-NiO1-x nanostructure formation on the Pt3Ni(111) alloy surface, Science Advances (DOI: 10.1126/sciadv.aat3151 ]
Professor Park said that one way to monitor catalysts is to detect hot electrons associated with energy dissipation and conversion processes during surface reactions. His team led the real-time detection of hot electrons generated on bimetallic PtCo nanoparticles during exothermic hydrogen oxidation. The team successfully clarified the origin of the synergistic catalytic activity of PtCo nanoparticles with corresponding chemicurrent values.
By estimating the chemicurrent yield, the research team conclude that the catalytic properties of the bimetallic nanoparticles are strongly governed by the oxide–metal interface, which facilitates hot electron transfer. [H. Lee et al. Boosting hot electron flux and catalytic activity at metal–oxide interfaces of PtCo bimetallic nanoparticles, Nature Comm, 9, 2235 (2018)].
Professor Park explained, “We feel that the precise measurement of hot electrons on catalysts gives insight into the mechanism for heterogeneous catalysis, which can help with the smart design of highly reactive materials. The control of catalytic activity via electronic engineering of catalysts is a promising prospect that may open the door to the new field of combining catalysis with electronics, called “catalytronics.” He added that the study also establishes a strategy for improving catalytic activity for catalytic reactions in industrial chemical reactors.
Professors Park and Yousung Jung from the Department of Chemical and Biomolecular Engineering and the Graduate School of EEWS conducted this research in collaboration with Professor Bongjin Mun from the Department of Physics at GIST.
Figure 1. Evolution of surface structures of PtNi bimetal surfaces under various ambient conditions.
Figure 2. Formation of Pt-CoO interface leads to the catalytic enhancement of PtCo bimetal catalysts.
2018.07.25 View 10044 -
It's Time to 3D Sketch with Air Scaffolding
People often use their hands when describing an object, while pens are great tools for describing objects in detail. Taking this idea, a KAIST team introduced a new 3D sketching workflow, combining the strengths of hand and pen input. This technique will ease the way for ideation in three dimensions, leading to efficient product design in terms of time and cost.
For a designer's drawing to become a product in reality, one has to transform a designer's 2D drawing into a 3D shape; however, it is difficult to infer accurate 3D shapes that match the original intention from an inaccurate 2D drawing made by hand. When creating a 3D shape from a planar 2D drawing, unobtainable information is required. On the other hand, loss of depth information occurs when a 3D shape is expressed as a 2D drawing using perspective drawing techniques.
To fill in these “missing links” during the conversion, "3D sketching" techniques have been actively studied. Their main purpose is to help designers naturally provide missing 3D shape information in a 2D drawing. For example, if a designer draws two symmetric curves from a single point of view or draws the same curves from different points of view, the geometric clues that are left in this process are collected and mathematically interpreted to define the proper 3D curve. As a result, designers can use 3D sketching to directly draw a 3D shape as if using pen and paper.
Among 3D sketching tools, sketching with hand motions, in VR environments in particular, has drawn attention because it is easy and quick. But the biggest limitation is that they cannot articulate the design solely using rough hand motions, hence they are difficult to be applied to product designs. Moreover, users may feel tired after raising their hands in the air during the entire drawing process.
Using hand motions but to elaborate designs, Professor Seok-Hyung Bae and his team from the Department of Industrial Design integrated hand motions and pen-based sketching, allocating roles according to their strengths. This new technique is called Agile 3D Sketching with Air Scaffolding. Designers use their hand motions in the air to create rough 3D shapes which will be used as scaffolds, and then they can add details with pen-based 3D sketching on a tablet (Figure 1).
Figure 1. In the agile 3D sketching workflow with air scaffolding, the user (a) makes unconstrained hand movements in the air to quickly generate rough shapes to be used as scaffolds, (b) uses the scaffolds as references and draws finer details with them, (c) produces a high-fidelity 3D concept sketch of a steering wheel in an iterative and progressive manner.
The team came up with an algorithm to identify descriptive hand motions from transitory hand motions and extract only the intended shapes from unconstrained hand motions, based on air scaffolds from the identified motions.
Through user tests, the team identified that this technique is easy to learn and use, and demonstrates good applicability. Most importantly, the users can reduce time, yet enhance the accuracy of defining the proportion and scale of products.
Eventually, this tool will be able to be applied to various fields including the automobile industry, home appliances, animations and the movie making industry, and robotics. It also can be linked to smart production technology, such as 3D printing, to make manufacturing process faster and more flexible.
PhD candidate Yongkwan Kim, who led the research project, said, “I believe the system will enhance product quality and work efficiency because designers can express their 3D ideas quickly yet accurately without using complex 3D CAD modeling software. I will make it into a product that every designer wants to use in various fields.”
“There have been many attempts to encourage creative activities in various fields by using advanced computer technology. Based on in-depth understanding of designers, we will take the lead in innovating the design process by applying cutting-edge technology,” Professor Bae added.
Professor Bae and his team from the Department of Industrial Design has been delving into developing better 3D sketching tools. They started with a 3D curve sketching system for professional designers called ILoveSketch and moved on to SketchingWithHands for designing a handheld product with first-person hand postures captured by a hand-tracking sensor. They then took their project to the next level and introduced Agile 3D Sketching with Air Scaffolding, a new 3D sketching workflow combining hand motion and pen drawing which was chosen as one of the CHI (Conference on Human Factors in Computing Systems) 2018 Best Papers by the Association for Computing Machinery.
- Click the link to watch video clip of SketchingWithHands
2018.07.25 View 9741 -
A New Efficient Oxide Coating Technology to Improve Fuel Cells
A new efficient oxide coating technology that can be applied in less than five minutes could lead to dramatic improvements in the lifetime and performance of fuel cells. The fundamental principle behind this approach is maximizing the oxygen reduction reaction site of a platinum thin-film electrode, preventing the electrodes from aggregating at high temperatures.
Fuel cells have emerged as a clean electricity generation system that does not pollute the air. In particular, solid oxide fuel cells (SOFCs) are beginning to gain a great deal of attention due to their higher power generation efficiency compared to other fuel cells. It is also advantageous to use other power sources than expensive hydrogen fuel.
However, the high costs and insufficient lifetimes caused by high temperatures needed to operate the solid oxide fuel cells have remained significant challenges to commercialization.
Recently, attempts to lower the operating temperature (< 600°C) of these devices by introducing thin-film processes have drew attention of researchers, with the resulting products known as thin-film-based solid oxide fuel cells.
In order to create enhanced device performance at lower temperatures, the research team, led by Professor WooChul Jung in the Department of Materials Science and Engineering, applied and developed oxide coating technology to maximize the oxygen reduction reaction sites of a platinum thin-film electrode and to prevent platinum electrodes from thermal aggregating.
The team succeeded in over-coating a platinum electrode with a new coating material called praseodymium-doped ceria (Pr,Ce)O2-, which has high conductivity for both electrons and oxygen ions and excellent catalytic properties for oxygen reduction reactions. As a result, electrode resistance was reduced by more than 1000 times, creating the potential for these electrodes to be used in high-temperature electrochemical cells.
In addition, they proposed that the high performance of thin-film-based oxide fuel cells’ oxygen electrodes could be realized through the nano-structuring of (Pr,Ce)O2-δ without any platinum.
Professor Jung said, “The electrode coating technology used in this study is of great technical value because of the utilization of affordable and mass-produced electrochemical deposition.” He added, “In the future, this technology will be feasible for replacing platinum electrodes in thin-film-based oxide fuel cells, and we expect that the affordable prices of this fuel cell will eventually boost market competitiveness.”
This research was described in Advanced Energy Materials in July and was featured as the Inside Front Cover and video abstract. It was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Korea Electric Power Corporation (KEPCO) Research Institute.
Figure 1. The change of electrode activity with and without overcoated (Pr,Ce)O2-δ nanostructures.
2018.07.18 View 8523 -
Enhanced PDT to Cure Cancer with Fewer Side Effects
(From left: PhD candidate Ilkoo Noh and Professor Yeu-Chun Kim)
A KAIST research team developed near-infrared fluorophores-based photodynamic therapy (PDT) that reduced the downside of existing PDTs.
PDT is a way to cure wounds with lasers instead of drug treatment. When a laser irradiates a targeted site, a photosensitizer (PS) absorbs light energy and then converts oxygen to singlet oxygen or free radicals, leading to programmed cell death. This treatment has been used widely in clinical fields, especially for skin disease because it allows noninvasive treatment.
However, the existing PDTs have limitations for first-line therapy because PDT agents can cause genetic variations when they have low efficiency, hence reducing treatment effects.
The key to enhancing the efficiency of PDTs is how much PS can be concentrated to a wanted site, which laser wavelength the PS is reacted to, and how fast the PS clears organelle after treatment.
Professor Yeu-Chun Kim and his team from the Department of Chemical and Biomolecular Engineering, in collaboration with Professor Ji-Ho Park from the Department of Bio and Brain Engineering, developed a new PS called mitochondria targeting photodynamic therapeutic agent (MitDt) to maximize PDT effects while reducing unwanted side effects.
Mitochondria has emerged as target sites to maximize the effects of PS since they play essential roles in metabolism and have high transmembrane potential.
According to the team, when mitochondria is photodamaged by reactive oxygen species (ROS) generated after laser irradiation, they immediately lose their mitochondrial membrane potential and initiate apoptosis. Therefore, combining the PDT agent with the mitochondrial targeting agent can result in rapid damage to cancer cells, improving therapeutic efficacy and reducing unwanted side effects.
To successfully apply mitochondria-targeting PS, the team developed near-infrared (NIR) region PDT agents, which can be used to treat deep-tissue level cancer due to the permeability of the NIR laser. Light scattering is also decreased, thus obtaining higher therapeutic efficacy.
However, there is a problem of generating singlet oxygen when irradiating with an NIR laser. To address this issue, the team developed a novel PS that combines a functionalized NIR dye and a mitochondria-targeting agent to gain the benefit of rapid organelle clearance after treatment and also remain in cancer mitochondria for a long time, amplifying the amount of ROS to the target sites irradiated by the laser.
To verify the efficacy, the team injected MitDt into tumor-bearing mice. They were irradiated with an NIR laser at 662 nm to induce cancer treatment and their cancer size was reduced up to three-fold.
PhD candidate Ilkoo Noh, who led this research said, “This enhanced photodynamic cancer treatment has the advantage of treating a wanted site without any side effects because this PS stays longer in a mitochondrial cancer cell. We also confirmed that the PS did not cause cytotoxicity.”
Professor Kim added, “This research outcome will reduce the danger of side effects and can be applied for treating various diseases”.
This research was chosen as the cover page of Advanced Science on March 25.
Figure 1. The cover of Advanced Science
Figure 2. a) Chemical structure of MitDt compounds (above) b) mitochondria localization of designed PS (left) and ROS generation after 662nm laser irradiation (right)
2018.07.16 View 6831 -
Photonic Capsules for Injectable Laser Resonators
A KAIST research group presented photonic capsules for injectable laser resonators using microfluidic technology. The capsule’s diameter is comparable to a human hair and stable in gas and liquid media, so it is injectable into any target volume.
The research group headed by Professor Shin-Hyun Kim in the Department of Chemical and Biomolecular Engineering applied an interesting optical property from nature. Professor Kim, who has dived deep into photonic materials research inspired from nature such as the Morpho butterfly, used a trait of beetles this time.
Chrysina gloriosa, commonly known as the glorious beetle, shows a green color similar to leaves when illuminated by left-handed, circularly-polarized light while showing no color with right-handed, circularly-polarized light. This unique optical feature helps the beetles communicate with each other and protects them from predators.
The principle behind this interesting optical property of the beetles relies on helical nanostructures with left-handedness that are present on the shell of the beetles. The helical structures reflect a circularly-polarized light with the same handedness of the helix at the wavelength selected by the helical pitch through optical interference.
Such helical nanostructures can be artificially created using liquid crystals (LCs). LCs with a helical arrangement are referred to as cholesteric LCs (CLCs). The CLCs exhibit the polarization-dependent reflection of light in the same manner as the beetles and have been used for various photonic applications.
In particular, CLCs have been cast to a film format that serves as mirrorless laser resonators, unlike conventional lasing systems. However, the film-type CLCs are large in size and show unidirectional emission, which restricts the use of CLC resonators in microenvironments.
To overcome these limitations, Professor Kim’s group has encapsulated the CLCs with dual shells using microfluidic technology. The inner shell is a water layer that promotes the alignment of LC molecules and the outer shell is an elastic polymer layer that secures capsule stability and enables reversible mechanical deformation. The spherical symmetry of the capsules enables omnidirectional laser emissions. Moreover, laser intensity and lasing direction can be further controlled by deforming the capsules, while its wavelength remains tunable. This new type of CLC laser resonator is promising for laser treatments in various biomedical applications.
Professor Kim said, “The helical nanostructure used in the laser resonator resembles that of the shell of chrysina gloriosa. Humans learn from nature and engineer materials to create something unprecedented.”
This research was led by graduate student Sang Seok Lee and an article entitled “Wavelength-tunable and shape-reconfigurable photonic capsule resonators containing cholesteric liquid crystals” was published online on June 22, in Science Advances.
Figure 1. Chrysina gloriosa illuminated by left-handed (left panel) and right-handed (right panel) circularly-polarized lights.
(Image source: https://doi.org/10.1016/j.cub.2010.05.036 , permitted for reuse in news media)
Figure 2. Composition (left panel) and optical microscopy image (right panel) of the capsule-type laser resonator
2018.07.05 View 9459 -
Mechanism Leading to Cortical Malformation from Brain-Only Mutations Identified
Focal malformations of cortical development (FMCDs) are a heterogeneous group of brain cortical abnormalities. These conditions are the most common causes of medically refractory epilepsy in children and are highly associated with intellectual disability, developmental delay, and autism-spectrum disorders. Despite a broad spectrum of cortical abnormalities in FMCDs, the defective migration of neuronal cells is considered a key pathological hallmark.
A research team led by Professor Jeong Ho Lee in the Graduate School of Medical Science and Engineering at KAIST has recently investigated the molecular mechanism of defective neuronal migration in FMCDs. Their research results were published online in Neuron on June 21, 2018.
The research team previously demonstrated that brain-only mutations in the mechanistic target of rapamycin (MTOR) gene causes focal cortical dysplasia, one major form of FMCDs leading to intractable epilepsy in children. However, the molecular mechanisms by which brain-only mutations in MTOR lead to cortical dyslamination and defective neuronal migration in FMCDs remain unclear.
To study the molecular mechanism of brain cortical dyslamination, the research team utilized patients’ brain tissues and modeled the MTOR mutation-carrying cell and animal models recapitulating the pathogenesis and symptoms of FMCD patients. By performing comprehensive molecular genetic experiments, they found that the formation of primary cilia, one of cellular organelles, was disrupted in MTOR mutation-carrying neurons and demonstrated that this ciliary disruption was a cause of cortical dyslamination in FMCDs.
MTOR mutations prevented degradation of the OFD1 protein, one of the negative regulators of ciliary formation. As a result, the OFD1 protein was abnormally accumulated in MTOR mutation-carrying neurons, causing focal cortical dyslamination. By suppressing the expression of the OFD1 protein, the research team was able to rescue the defective formation of primary cilia, leading to the restoration of cortical dyslamination and defective neuronal migration considerably.
Based on these results, the research team is carrying out further research to develop novel therapeutics for patients with FMCDs caused by brain-only mutations.
This work was supported by grants from the Suh Kyungbae Foundation and Citizens United for Research in Epilepsy.
The research paper is titled “Brain Somatic Mutations in MTOR Disrupt Neuronal Ciliogenesis, Leading to Focal Cortical Dyslamination.” (Digital Object Identifier #: 10.1016/j.neuron.2018.05.039)
Picture 1: The disrupted formation of primary cilia in brain tissues of FMCD mouse models and patients with FMCDs caused by brain somatic mutations in MTOR.
Picture 2: The rescue of defective ciliary formation in FMCD mouse models leading to the restoration of cortical dyslamination and defective neuronal migration.
2018.07.02 View 8585 -
KAIST Team Develops Flexible Blue Vertical Micro LEDs
A KAIST research team developed a crucial source technology that will advance the commercialization of micro LEDs.
Professor Keon Jae Lee from the Department of Materials Science and Engineering and his team have developed a low cost production technology for thin-film blue flexible vertical micro LEDs (f-VLEDs).
In CES 2018, micro LED TV was spotlighted as a strong candidate for replacing the active-matrix organic light-emitting diode (AMOLED) display. Micro LED is a sub-100 um light source for red, green and blue light, which has advantages of outstanding optical output, ultra-low power consumption, fast response speed, and excellent flexibility.
However, the current display industry has utilized the individual chip transfer of millions of LED pixels, causing high production cost. Therefore, the initial market of micro LED TV will be estimated to ~ a hundred thousand dollars for global premium market.
To widely commercialize micro LEDs for mobile and TV displays, the transfer method of thin film micro LEDs requires a one-time transfer of one million LEDs. In addition, highly efficient thin-film blue micro LED is crucial for a full-color display.
The team developed thin-film red f-VLED in previous projects, and now has realized thousands of thin-film blue vertical micro LEDs (thickness < 2 μm) on plastics using a one-time transfer.
The blue GaN f-VLEDs achieved optical power density (~30 mW/mm2) three times higher than that of lateral micro LEDs, and a device lifetime of 100,000 hours by reducing heat generation. These blue f-VLEDs could be conformally attached to the curved skin and brains for wearable devices, and stably operated by wirelessly transferred electrical energy.
Professor Lee said, “For future micro LEDs, the innovative technology of thin-film transfer, efficient devices, and interconnection is necessary. We plan to demonstrate a full-color micro LED display in smart watch sizes by the end of this year. ”
This research “ Monolithic Flexible Vertical GaN Light‐Emitting Diodes for a Transparent Wireless Brain Optical Stimulator ” led by a PhD candidate Han Eol Lee was published in the June 2018 issue of Advanced Materials.
Figure 1. Schematic image of wireless thin-film blue f-VLED arrays on the brain surface
Figure 2. Photo of high-performance and high-density blue f-VLED arrays
2018.06.18 View 8863 -
Lead-free, Efficient Perovskite for Photovoltaic Cells
(Clockwise from left: Post-doc Researcher Lamjed Debbichi, Master’s Candidate Songju Lee, Professor Min Seok Jang and Professor Hyungjun Kim)
A KAIST research team has proposed a perovskite material, Cs2Au2I6 that serves as a potential active material for highly efficient lead-free thin-film photovoltaic devices. This material is expected to lay the foundation to overcome previously known limitations of perovskite including its stability and toxicity issues.
As strong candidates for next-generation high-efficiency photovoltaic cells, perovskite photovoltaic cells have a maximum photoconversion efficiency of 22%, comparable to high-performance crystalline silicon photovoltaic cells. In addition, perovskite-based cells can be fabricated at low temperatures, thereby bringing about dramatic cost reductions.
However, it has been noted that conventional organic-inorganic hybrid perovskite materials exhibit low stability, eventually degrading their performance and making them unfit for continued use. Moreover, their inclusion of lead has undermined their environmental friendliness.
In light of this, a joint team led by Professor Hyungjun Kim from the KAIST Department of Chemistry and Professor Min Seok Jang from the School of Electrical Engineering has analyzed a previously discovered perovskite material, Cs2Au2I6, consisting of only inorganic substances and investigated its suitability for application in thin-film photovoltaic devices. Theoretical investigations suggests that this new perovskite material is not only as efficient but also more stable and environment friendly compared to the conventional perovskite materials. For this analysis, the team developed multiscale multiphysics simulation frameworks. Atomic-scale first-principle quantum calculations were carried out to study the optical properties of the proposed material, and device-scale electromagnetic simulations were conducted to suggest that the material could indeed serve as a promising photovoltaic substance at the device level.
From this point onward, the research team plans to extend the study in two directions: an empirical study to apply the perovskite material in real-world photovoltaic cells and a theoretical analysis to find the optimal and highly stable material for photovoltaic cells. The team said, “Perovskite materials are highly efficient, but in order to completely replace the conventional solar cells, their stability and toxicity issues must first be resolved.” They added that this research is expected to accelerate related studies in pursuit of high-efficiency, environment-friendly perovskite materials.
This research, led by post-doc researcher Lamjed Debbichi and master’s candidate Songju Lee, was selected as the front cover article of Advanced Materials on March 22.
Figure 1. Cover of Advanced Materials
Figure 2. Schematic of full solar cell device structure
2018.06.08 View 9249 -
Fast-Charging Lithium-Oxygen Batteries
(Professor Hye Ryung Byon)
KAIST researchers have paved the way for fast-charging lithium-oxygen batteries.
Professor Hye Ryung Byon from the Department of Chemistry and Professor Yousung Jung from the Graduate School of EEWS led a joint research team to develop lithium-oxygen batteries exhibiting 80% round-trip efficiency even at high charging rates, solving the problem of existing lithium-oxygen batteries which generally showed drastically lower efficiencies when the charge current rate was increased.
This study exploits the size and shape lithium peroxide, a discharge product, which is known to cause the very problems mentioned above. In doing so, the researchers have lowered the overpotential, which is the difference between the thermodynamic reversible potential and the measured potential, and simultaneously improved battery efficiency. Of particular interest is the fact that these high-performance lithium-oxygen batteries can be realized without costly catalysts.
One remarkable property of lithium-oxygen batteries is that they can accommodate three to five times the energy density of lithium-ion batteries commonly used today. Therefore, lithium-oxygen batteries would render longer driving distance to electric vehicles or drones, which operate on the continued use of electrical power.
However, their weakness lies in that, during charge, the lithium peroxide remains undecomposed at low overpotential, resulting in eventually compromising the battery’s overall performance. This is due to the poor ionic and electrical conductivity of lithium peroxide.
To tackle this issue, the researchers could form one-dimensional amorphous lithium peroxide nanostructures through the use of a mesoporous carbon electrode, CMK-3. When compared against non-mesoporous electrodes, CMK-3 showed exceptionally lower overpotential, thereby enhancing the round-trip efficiency of lithium-oxygen batteries.
The amorphous lithium peroxide produced along the electrode has a small volume and a large surface area contacting electrolyte solution, which is presumably endowed with high conductivity to speed up the charging of the lithium-oxygen batteries.
This research underpins the feasibility of overcoming the fundamental limitations of lithium-oxygen batteries even without the addition of expensive catalytic materials, but rather by the re-configuration of the size and shape of the lithium peroxide.
The findings of this research were published in Nature Communications on February 14.
Figure 1. Transmission electron microscopy (TEM) images
Figure 2. Galvanostatic rate capability
Figure 3. Density functional calculation and Bader charge analysis
2018.05.30 View 9954 -
KAIST-Developed LPV to Launch in LNG-Fueled Port Cleaning Ship in Ulsan
(From left:CEO of LATTICE Technology Kun-Oh Park, research fellow Hwa-Ryong Yu, and Professor Chang )
A KAIST-developed Lattice Pressure Vessel (LPV) will launch inside a 150-ton class port cleaning ship that the Ulsan Port Authority will deploy in December. The ship will operate off the coast of Ulsan and will be the first LNG-fueled public service vessel run by the government.
LATTICE Technology, a tech-startup established in 2012 by two KAIST professors, announced last week that the company signed a contract with the Ulsan Port Authority to install the LPV into the hull of the port cleaning ship.
The company setup by Professors Daejun Chang and Pål G. Bergan in the Department of Mechanical Engineering accomplished the feat seven years after they first registered their original technology patent.
The free-shaped pressure vessel developed by the two professors is applicable to any type of ship structure, a technological breakthrough addressing the wasted installing space of the conventional pressure vessel types that either spherical or cylindrical designs would result in.
The LPV has an internal lattice structure for load carrying caused by pressure, providing 50 percent more capacity than that of a cylindrical pressure vessel.
According to Professor Chang, the essence of the LPV is an internal, modular structure that carries the load by balancing the pressure on opposite walls. He said that the LPV has a number of merits thanks to the lattice structure. While its structural redundancy improves safety, it is fully scalable in any direction as well as being able to mitigate the sloshing load, resulting in a negligible level of fatigue risk. Its modularity also cuts the production cost. The technology has already earned seven internationally authorized certificates, and the company has already built four prototype tanks.
The LPV has significant market potential in the energy storage industry, especially transportation sectors. One imminent application is LNG fuel storage on ships. This cryogenic fuel is expected to replace the conventional marine fuel or heavy fuel oil that is the source of a number of polluting emissions (SOx, NOx, CO2, and particle matters).
This LPV technology will contribute to the efficient storage LNG in volume. As liquid hydrogen increasingly emerges to decarbonate the energy mix, the storage and transportation of liquid hydrogen will be also a critical issue. The researchers expect that this LPV technology will be further applied into the entire supply chain of various fields including production, transportation, storage, and utilization of such decarbonated energy sources.
Professor Chang said, “Pressure vessels are one of the most common devices for storing materials and energy. The areas for which the LPV can create value will expand into various industrial sectors.”
The research team plans to conduct further research and development to realize various LPV applications to store LNG, LPG, liquid hydrogen, carbon dioxide, and steam for ships, land facilities, vehicles, trains, and automobiles.
Figure 1: The internal strucutre of a lattice pressure vessel. The middle part of the tank is repetition of a modular lattice strucutre while the end part is specially designed.
Figure 2: Lattice pressure vessels in shapes and sizes. Unlike conventional cylinders, the lattice pressure vessel can freely assume different shapes and be scaled up through the repetition of modular internal units.
Figure 3: A cylinder tank of 24 m3 and a lattice pressure vessel of 22 m3. They are similar in volume but show a big difference in installation space.
Figure 4: LNF-fueld cruised ships with six cylinders and one lattice pressure vessel. Thanks to its high-volume efficiency, the lattice pressure vessel doubles the stroage volume with one sixth of the piping, instruments, and operational complexity.
2018.05.30 View 8112 -
Get Treatment Anywhere and Any Time with Wearable PBM Patch
(PhD Candidate Yongmin Jeon)
There have been many cases in which OLEDs are applied to electronic devices, and now they have even been extended to therapeutic fields. A KAIST research team succeeded in developing a wearable photobiomodulation (PBM) patch to treat wounds. This technology will allow injuries to be treated regardless of location or time.
Professor KyungCheol Choi from the School of Electrical Engineering, in collaboration with Seoul National University Bundang Hospital’s team, conducted research on PBMs which are a clinical method widely used in hospitals. They are considered to be a safe, noninvasive, and nonsurgical method that require relatively low light power.
Conventionally, light-emitting diodes (LEDs) have been used in PBM applications; however, LED devices are usually inflexible and difficult to irradiate light uniformly. They may also produce localized heat. Due to these constraints, it was difficult to enhance the clinical effects of LED devices as they cannot stick to the human body.
Choi’s team developed a wearable patch using flexible OLEDs, allowing people to be treated outside of hospitals. A thin film has been developed for the patch, containing not only flexible OLEDs but also batteries and anti-superheating devices.
Moreover, its thickness is less than 1mm and its weight is less than 1g. This lightweight and ultra-thin patch with a bending radius is 20mm can be used more than 300 hours.
These patches are usable at a temperature below 42℃ to eliminate the risk of low-temperature burns. They also meet the safety regulations of the International Organization for Standardization (ISO) at red wavelengths (600–700 nm).
The wearable PBM patches showed excellent effects with in vitro wounds because they stimulated cell proliferation over 58% of control as well as cell migration over 46% of control under various conditions.
Yongmin Jeon, who led this research, said, “The wearable PBM is effective and convenient, so people can simply purchase it at a pharmacy without having to visit a hospital. If we can adjust the power and wavelength of the OLEDs, its application can be extended to skin care, cancer treatment, Alzheimer’s disease treatment, and mental healthcare.”
Professor Choi added, “We have applied the advantages of flexible OLEDs, which are often used for fabricating displays, to PBMs. This technology will open the way to commercialize portable and highly-efficient wearable photobiomodulation devices.”
This research was published in the front cover of Advanced Materials Technologies on May, 2018.
Figure 1. The patch attached to a human face, a hand and examples of treatment applications
Figure 2. The migration of cells into the scratched area
2018.05.25 View 7643 -
Recombinant E. Coli As a Biofactory for the Biosynthesis of Diverse Nanomaterials
(Distinguished Professor Lee and PhD candidate Choi)
A metabolic research group at KAIST and Chung-Ang University in Korea has developed a recombinant E. coli strain that biosynthesizes 60 different nanomaterials covering 35 elements on the periodic table. Among the elements, the team could biosynthesize 33 novel nanomaterials for the first time, advancing the forward design of nanomaterials through the biosynthesis of various single and multi-elements.
The study analyzed the nanomaterial biosynthesis conditions using a Pourbaix diagram to predict the producibility and crystallinity. Researchers studied a Pourbaix diagram to predict the stable chemical species of each element for nanomaterial biosynthesis at varying levels of reduction potential (Eh) and pH. Based on the Pourbaix diagram analyses, the initial pH of the reaction was changed from 6.5 to 7.5, resulting in the biosynthesis of various crystalline nanomaterials that were previously amorphous or not synthesized.
This strategy was extended to biosynthesize multi-element nanomaterials. Various single and multi-element nanomaterials biosynthesized in this research can potentially serve as new and novel nanomaterials for industrial applications such as catalysts, chemical sensors, biosensors, bioimaging, drug delivery, and cancer therapy.
A research group consisting of PhD candidate Yoojin Choi, Associate Professor Doh Chang Lee, and Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering at KAIST and Associate Professor Tae Jung Park of the Department of Chemistry at Chung-Ang University reported the synthesis. This study, entitled “Recombinant Escherichia coli as a biofactory for various single- and multi-element nanomaterials,” was published online in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) on May 21.
A recent successful biosynthesis of nanomaterials under mild conditions without requiring physical and chemical treatments has triggered the exploration of the full biosynthesis capacity of a biological system for producing a diverse range of nanomaterials as well as for understanding biosynthesis mechanisms for crystalline versus amorphous nanomaterials.
There has been increased interest in synthesizing various nanomaterials that have not yet been synthesized for various applications including semiconducting materials, enhanced solar cells, biomedical materials, and many others. This research reports the construction of a recombinant E. coli strain that co-expresses metallothionein, a metal binding protein, and phytochelatin synthase that synthesizes the metal-binding peptide phytochelatin for the biosynthesis of various nanomaterials. Subsequently, an E. coli strain was engineered to produce a diverse range of nanomaterials, including those never biosynthesized before, by using 35 individual elements from the periodic table and also by combining multi-elements.
Distinguished Professor Lee said, “An environmentally-friendly and sustainable process is of much interest for producing nanomaterials by not only chemical and physical methods but biological synthesis. Moreover, there has been much attention paid to producing diverse and novel nanomaterials for new industrial applications. This is the first report to predict the biosynthesis of various nanomaterials, by far the largest number of various single- and multi-elements nanomaterials. The strategies used for nanomaterial biosynthesis in this research will be useful for further diversifying the portfolio of nanomaterials that can be manufactured.”
Figure: The biosynthesis of diverse nanomaterials using recombinant E. coli. This schematic diagram shows the overall conceptualization of the biosynthesis of various single and multi-element nanomaterials using recombinant E. coli under incubation with corresponding elemental precursors. The 35 elements that were tested to biosynthesize nanomaterials are shown in black circles on the periodic table.
2018.05.23 View 11571