research
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Development of a Photonic Diode with Light Speed, Single-Direction Transfer
A photonic diode using a nitride semiconductor rod can increase the possibility of developing all-optical integrated circuits, an alternative to conventional integrated circuits.
Professor Yong-Hoon Cho's research team from the Department of Physics, KAIST, developed a photonic diode which can selectively transfer light in one way, using semiconductor rods.
The photonic diode has a diameter of hundreds of nanometers (nm) and a length of few micrometers. This size enables its use in large-scale integration (LSI). The diode’s less sensitivity towards polarized light angle makes it more useful.
In an integrated circuit, a diode controls the flow of electrons. If this diode controls light rather than electrons, data can be transferred at high speed, and its loss is minimized to a greater extent. Since these implementations conserve more energy, this is a very promising future technology.
However, conventional electronic diodes, made up of asymmetric meta-materials or photonic crystalline structures, are large, which makes them difficult to be used in LSI. These diodes could only be implemented under limited conditions due to its sensitivity towards polarized light angle.
The research team used nitride semiconductor rods to develop a highly efficient photonic diode with distinct light intensities from opposite ends.
The semiconductor rod yields different amount of energy horizontally. According to the research team, this is because the width of the quantum well and its indium quantity is continuously controlled.
Professor Cho said, "A large energy difference in a horizontal direction causes asymmetrical light propagation, enabling it to be operated as a photonic diode." He added that “If light, instead of electrons, were adopted in integrated circuits, the transfer speed would be expected as great as that of light.”
The research findings were published in the September 10th issue of Nano Letters as the cover paper.
Under the guidance of Professor Cho, two Ph.D. candidates, Suk-Min Ko and Su-Hyun Gong, conducted this research. This research project was sponsored by the National Research Foundation of Korea and KAIST’s EEWS (energy, environment, water, and sustainability) Research Center.
Figure Description: Computer simulated image of photonic diode made of semiconductor rod implemented in an all-optical integrated circuit
2014.09.23 View 10219 -
KAIST Researchers Fabricate Defect-free Graphene for Lithium-ion Batteries
Although graphene has been hailed as promising materials for lithium-ion batteries, making it for large-scale production has remained a challenging task for researchers. So far, high-quality graphene has been produced at the expense of large volume. It is possible to fabricate bulk quantities of graphene, but they will likely contain many defects.
Recently, a KAIST research team, headed by Professors Jung-Ki Park and Hee-Tak Kim from the Department of Chemical and Biomolecular Engineering, developed a fabrication method to produce a large amount of defect-free graphene (df-G) while preserving the structural integrity of the graphene.
This research result was published online in the July 11, 2014 issue of Nano Letters, entitled "Defect-free, Size-tunable Graphene for High-performance Lithium Ion Battery."
Phys.org, a science, research and technology news website, published an article on this research. To read article, please visit the link below:
Phys.org, August 22, 2014
“Scientists fabricate defect-free graphene, set record reversible capacity for Co3O4 node in Li-ion batteries”
http://phys.org/news/2014-08-scientists-fabricate-defect-free-graphene-reversible.html
2014.09.07 View 9382 -
Extracting Light from Graphite: Core Technology of Graphene Quantum Dots Display Developed
Professor Seokwoo Jeon of the Department of Materials Science and Engineering, Professor Yong-Hoon Cho of the Department of Physics, and Professor Seunghyup Yoo of the Department of Electrical Engineering announced that they were able to develop topnotch graphene quantum dots from graphite.
Using the method of synthesizing graphite intercalation compound from graphite with salt and water, the research team developed graphene quantum dots in an ecofriendly way.
The quantum dots have a diameter of 5 nanometers with their sizes equal and yield high quantum efficiency. Unlike conventional quantum dots, they are not comprised of toxic materials such as lead or cadmium. As the quantum dots can be developed from materials which can be easily found in the nature, researchers look forward to putting these into mass production at low cost.
The research team also discovered a luminescence mechanism of graphene quantum dots and confirmed the possibility of commercial use by developing quantum dot light-emitting diodes with brightness of 1,000 cd/m2, which is greater than that of cellphone displays.
Professor Seokwoo Jeon said, “Although quantum dot LEDs have a lower luminous efficiency than existing ones, their luminescent property can be further improved” and emphasized that “using quantum dot displays will allow us to develop not only paper-thin displays but also flexible ones.”
Sponsored by Graphene Research Center in KAIST Institute for NanoCentury, the research finding was published online in the April 20th issue of Advanced Optical Materials.
Picture 1: Graphene quantum dots and their synthesis
Picture 2: Luminescence mechanism of graphene quantum dots
Picture 3: Structure of graphene quantum dots LED and its emission
2014.09.06 View 15887 -
Development of Gold Nanowire Probe Needle with an Increased Sensitivity
Professor Bongsoo Kim
The newly developed nano-probe needle’s thickness estimates only at 0.1 micrometers with an increased 1,000-fold sensitivity and spatial resolution of 1mm.
Professor Bongsoo Kim and his research team from the Department of Chemistry, KASIT, including the first author, Dr. Mijeong Kang, succeeded in measuring nerve signals of a mouse using the world’s thinnest nano-probe needle made of single-crystal gold nanowires.
The newly developed nano-probe needle possesses the thickness of 100 nanometers (nm), which shows 1,000 times more sensitivity than the conventional nerve probe needles, as well as accurately measures nerve signals with an extremely fine resolution of less than 1mm. Unlike the existing probe needles that cause neural tissues to be damaged during insertion, the new nano-probe needle minimizes the damage and thus can detect large nerve signals.
The brain neural probe, which collects and analyzes electrical nerve signals generated in the brain, is the most essential element in brain research. A neural probe should minimize tissue damages, but needs to possess a good electrical sensitivity.
The researchers first applied heat on the gold, which is the necessary material for a probe, until it turned to a vapor phase. Then, the gold evaporation slug was transported to a colder board and left to form single-crystal gold nano structures by condensation. Because the new gold nanowire, produced by using this principle, is a flawless single crystal structure, it shows strong and flexible properties.
Professor Kim and his team applied the nano-probe needle into the brain of a mouse that has been administered a drug to induce epilepsy. They were able to find the exact area in the brain that triggers epilepsy. Furthermore, the researchers also detected neural signal changes in the brain of the mouse when it encountered the intrusion of a stranger mouse.
Professor Bongsoo Kim commented the meaning of his research:
“The new nano-probe needle is able to detect signals from a single nerve cell with high sensitivity while preserving the nerve cells intact. The probe needle will be useful for creating a precise three-dimensional brain map, as well as providing electrical treatment for brain diseases such as dementia and Parkinson's disease.”
This research results were published online in the August 12, 2014 edition of ACS Nano.
2014.09.06 View 6496 -
Regulatory T Cells Influence Liver Damage of Hepatitis A Patients
Liver damage becomes more severe with the decrease of regulatory T cells
“This research will aid the development of hepatitis A targeted drug,” said a KAIST researcher.
The KAIST Graduate School of Medical Science and Engineering’s Professor Eui-Cheol Shin and his research team have identified the mechanism, explaining how the regulatory T cells are responsible for the body’s immune system and how they have induced liver damage of hepatitis A patients.
The research results were published online in the July 9th edition of ‘Gut,’ the world’s most prominent journal in the field of gastroenterology.
Hepatitis A is an acute form of hepatitis caused by hepatitis A virus. The virus spreads through oral contact and enters the body via digestive organs.
Regulatory T cells play an important role in maintaining the homeostasis of the body’s immune system by inhibiting the activation of other immune cells. In the case of chronic viral infections, regulatory T cells are known to contribute to the duration of the infection, weakening the immune response to virus infections. However, there has been no information on what roles the regulatory T cells perform in the case of acute viral infections.
The research team used the fluorescence flow cytometry technique to determine the number and characteristics of a variety of immune cells, including regulatory T cells, in the blood of hepatitis A patients.
Consequently, the researchers confirmed that the decrease in the regulatory T cells immune inhibitory ability was consistent with a significant reduction in the number of regulatory T cells in the blood of hepatitis A patients. Furthermore, it was identified that the more noticeable decrease of regulatory T cells led to the occurrence of a more severe liver injury.
The analysis of hepatitis A patient’s blood proved that the cause of the decrease in the number and function of regulatory T cells was the increased expression of cell surface protein ‘Fas,’ which induces cell death.
Professor Shin said, “This study is the first case which proposes the mechanism for clinical aspects in not only hepatitis A, but also acute virus infection.” He added on the future prospect of the research that: “In the future, we can prevent tissue damage by inhibiting cell death of regulatory T cells for severe acute viral infections that do not have an effective treatment for the virus itself.”
[Picture]
The picture shows the process of fluorescence flow cytometry technique to study regulatory T cell in the blood of hepatitis A patients.
2014.08.11 View 9611 -
The Journal of Clinical Investigation: Researchers Uncover the Secret Lymphatic Identity of the Schlemm's Canal
The Journal of Clinical Investigation (JCI), a peer-reviewed, top-tier medical journal published by the American Society for Clinical Investigation, carried a commentary entitled “Schlemm’s Canal: More Than Meets the Eye, Lymphatics in Disguise” in the July 25, 2014 issue.
In the commentary, the authors compared a research paper (“Lymphatic regular PROX1 determines Schlemm’s canal integrity and identity”) by Professor Gou-Young Koh of the Graduate School of Medical Science and Engineering at KAIST with research work from the University of Helsinki (article entitled “The Schlemm’s canal is a VEGF-C/VEGFR-3 responsive lymphatic-like vessel”).
The JCI released a press statement dated July 25, 2014 on its commentary. It mentioned that glaucoma, one of the leading causes of blindness worldwide, elevates eye pressure owing to poor drainage of aqueous humor. A specialized structure called “Schlemm’s canal” funnels aqueous humor from the eye back into circulation, which is critical to prevent pressure buildup in the eye. The article discussed the role of Schlemm’s canal in the context of lymphatic vascular characteristics by reviewing two research group’s papers back-to-back.
For the full text of the press release, please visit the link below:
Press Release from the Journal of Clinical Investigation, July 25, 2014
“Researchers uncover the secret lymphatic identity of the Schlemm’s canal”
http://www.eurekalert.org/pub_releases/2014-07/joci-rut072414.php
2014.07.28 View 7693 -
Discovery of New Therapeutic Targets for Alzheimer's Disease
A Korean research team headed by Professor Dae-Soo Kim of Biological Sciences at KAIST and Dr. Chang-Jun Lee from the Korea Institute of Science and Technology (KIST) successfully identified that reactive astrocytes, commonly observed in brains affected by Alzheimer’s disease, produce abnormal amounts of inhibitory neurotransmitter gamma-Aminobutyric acid (GABA) in reaction to the enzyme Monoamine oxidase B (Mao-B) and release GABA through the Bestrophin-1 channel to suppress the normal signal transmission of brain nerve cells.
By suppressing the GABA production or release from reactive astrocytes, the research team was able to restore the model mice's memory and learning impairment caused by Alzheimer’s disease. This discovery will allow the development of new drugs to treat Alzheimer’s and other related diseases.
The research result was published in the June 29, 2014 edition of Nature Medicine (Title: GABA from Reactive Astrocytes Impairs Memory in Mouse Models of Alzheimer’s Disease).
For details, please read the article below:
Technology News, July 10, 2014
"Discovery of New Drug Targets for Memory Impairment in Alzheimer’s Disease"
http://technews.tmcnet.com/news/2014/07/10/7917811.htm
2014.07.16 View 8337 -
KAIST develops TransWall, a transparent touchable display wall
At a busy shopping mall, shoppers walk by store windows to find attractive items to purchase. Through the windows, shoppers can see the products displayed, but may have a hard time imagining doing something beyond just looking, such as touching the displayed items or communicating with sales assistants inside the store. With TransWall, however, window shopping could become more fun and real than ever before.
Woohun Lee, a professor of Industrial Design at KAIST, and his research team have recently developed TransWall, a two-sided, touchable, and transparent display wall that greatly enhances users' interpersonal experiences.
With an incorporated surface transducer, TransWall offers audio and vibrotactile feedback to the users. As a result, people can collaborate via a shared see-through display and communicate with one another by talking or even touching one another through the wall. A holographic screen film is inserted between the sheets of plexiglass, and beam projectors installed on each side of the wall project images that are reflected.
TransWall is touch-sensitive on both sides. Two users standing face-to-face on each side of the wall can touch the same spot at the same time without any physical interference. When this happens, TransWall provides the users with specific visual, acoustic, and vibrotactile experiences, allowing them to feel as if they are touching one another.
Professor Lee said, "TransWall concept enables people to see, hear, or even touch others through the wall while enjoying gaming and interpersonal communication. TransWall can be installed inside buildings, such as shopping centers, museums, and theme parks, for people to have an opportunity to collaborate even with strangers in a natural way."
He further added that "TransWall will be useful in places that require physical isolation for high security and safety, germ-free rooms in hospitals, for example." TransWall will allow patients to interact with family and friends without compromising medical safety.
TransWall was exhibited at the 2014 Conference on Computer-Human Interaction (CHI) held from April 26, 2014 to May 1, 2014 in Toronto, Canada.
YouTube Link:
http://www.youtube.com/watch?v=1QdYC_kOQ_w&list=PLXmuftxI6pTXuyjjrGFlcN5YFTKZinDhK
2014.07.15 View 7180 -
Artificial Antibody-based Therapeutic Candidate for Lung Cancer Developed
Professor Hak-Sung Kim of Biological Sciences at KAIST publishes a cover article on artificial antibody in "Molecular Therapy".
Repebody-based lung cancer therapeutic drug candidate developed Repebody-based protein demonstrates the possibility of the development of a new drug
KAIST Biological Sciences Department’s Professor Hak-Sung Kim, in collaboration with Professor Eun-Kyung Cho from the College of Medicine at Chungnam National University, has successfully developed an artificial antibody-based, or repebody, cancer therapeutic candidate. These research results were published as a cover paper of the July edition of Molecular Therapy.
The repebody developed by Professor Kim and his team strongly binds to interleukin-6, a cancer-causing factor. It has also been confirmed that the repebody can significantly inhibit the proliferation of cancer cells in non-small-cell lung cancer animal model.
Numerous multinational pharmaceutical and biotechnology companies have invested astronomical amounts of money in research for the development of protein therapeutics with low side effects and high efficacy. More than 20 kinds of such therapeutics are currently under clinical trials, and over 100 drugs are under clinical demonstration. Among these, the majority is antibody-based therapeutics, and most of the investments are heavily concentrated in this field. However, antibody production cost is very high because it has large molecular weights and complex structural properties, and this makes it difficult to engineer. Consequently, the development costs a great deal of time and money.
In order to overcome the existing limitations of antibody-based therapeutics, Professor Kim and his team have developed a new artificial antibody, or repebody, which was published in Proceedings of the National Academy of Sciences (PNAS) in 2012. Based on this research, they have succeeded in developing a therapeutic candidate for treating non-small-cell lung cancer with a specifically strong cohesion to the cancer-causing factor, interleukin-6.
Interleukin-6 is a crucial substance within the body that is involved in immune and inflammatory-related signals. When abnormally expressed, it activates various carcinogenic pathways and promotes tumor growth and metastasis. Because of its importance, multinational pharmaceutical companies are heavily investing in developing therapeutics that can inhibit the signaling of interleukin-6.
In this study, Professor Kim and his team observed that a repebody consists of repeated modules, and they conceived a module-based affinity amplification technology that can effectively increase the binding affinity with the disease target. The developed therapeutic candidate has been confirmed in cell and animal experiments to show low immunogenicity, as well as to strongly inhibit the proliferation of non-small-cell lung cancer.
Furthermore, by investigating the complex structure of the repebody with interleukin-6, Professor Kim has identified its mechanism, which demonstrated the potential for therapeutic development. The researchers are currently carrying out pre-clinical trials for acquiring permission to perform clinical trials on animals with non-small-cell lung cancer. The repebody can be developed into a new protein drug after demonstrating its safety and efficacy.
Professor Hak-Sung Kim and his team have confirmed that the repebody can be utilized as a new protein drug, and this will be a significant contribution to Korea’s protein drugs and biotechnology industry development.
The research was supported by the Future Pioneer Industry project and sponsored by the Ministry of Science, ICT and Future Planning.
Figure 1. Professor Kim’s article published as the cover article of July edition of Molecular Therapy
Figure 2. Clinical proof of the repebody’s inhibition of cancer growth using animal models
2014.07.14 View 12081 -
KAIST Researchers Develops Sensor That Reads Emotional States of Users
A piloerection monitoring sensor attached on the skin
The American Institute of Physics distributed a press release dated June 24, 2014 on a research paper written by a KAIST research team, which was published in its journal entitled Applied Physics Letters (APL). APL features concise, up-to-date reports in significant new findings in applied physics.
According to the release, “KAIST researchers have developed a flexible, wearable 20 mm x 20 mm polymer sensor that can directly measure the degree and occurrence on the skin of goose bumps, which is caused by sudden changes in body temperature or emotional states.”
The lead researcher was Professor Young-Ho Cho from the Department of Bio and Brain Engineering at KAIST.
If you would like to read the press release, please go to the link below:
American Institute of Physics, June 24, 2014
“New technology: The goose bump sensor”
http://www.eurekalert.org/pub_releases/2014-06/aiop-ntt062314.php
2014.06.26 View 8216 -
The First Demonstration of a Self-powered Cardiac Pacemaker
As the number of pacemakers implanted each year reaches into the millions worldwide, improving the lifespan of pacemaker batteries has been of great concern for developers and manufacturers. Currently, pacemaker batteries last seven years on average, requiring frequent replacements, which may pose patients to a potential risk involved in medical procedures.
A research team from the Korea Advanced Institute of Science and Technology (KAIST), headed by Professor Keon Jae Lee of the Department of Materials Science and Engineering at KAIST and Professor Boyoung Joung, M.D. of the Division of Cardiology at Severance Hospital of Yonsei University, has developed a self-powered artificial cardiac pacemaker that is operated semi-permanently by a flexible piezoelectric nanogenerator.
The artificial cardiac pacemaker is widely acknowledged as medical equipment that is integrated into the human body to regulate the heartbeats through electrical stimulation to contract the cardiac muscles of people who suffer from arrhythmia. However, repeated surgeries to replace pacemaker batteries have exposed elderly patients to health risks such as infections or severe bleeding during operations.
The team’s newly designed flexible piezoelectric nanogenerator directly stimulated a living rat’s heart using electrical energy converted from the small body movements of the rat. This technology could facilitate the use of self-powered flexible energy harvesters, not only prolonging the lifetime of cardiac pacemakers but also realizing real-time heart monitoring.
The research team fabricated high-performance flexible nanogenerators utilizing a bulk single-crystal PMN-PT thin film (iBULe Photonics). The harvested energy reached up to 8.2 V and 0.22 mA by bending and pushing motions, which were high enough values to directly stimulate the rat’s heart.
Professor Keon Jae Lee said:
“For clinical purposes, the current achievement will benefit the development of self-powered cardiac pacemakers as well as prevent heart attacks via the real-time diagnosis of heart arrhythmia. In addition, the flexible piezoelectric nanogenerator could also be utilized as an electrical source for various implantable medical devices.”
This research result was described in the April online issue of Advanced Materials (“Self-Powered Cardiac Pacemaker Enabled by Flexible Single Crystalline PMN-PT Piezoelectric Energy Harvester”: http://onlinelibrary.wiley.com/doi/10.1002/adma.201400562/abstract).
Youtube link: http://www.youtube.com/watch?v=ZWYT2cU_Mog&feature=youtu.be
Picture Caption: A self-powered cardiac pacemaker is enabled by a flexible piezoelectric energy harvester.
2014.06.25 View 15719 -
Professor Won Do Heo on LED Light Technology for Controlling Proteins in Living Cells
With the newly developed LED technology, Professor Won Do Heo at the College of Life Science and Bioengineering, KAIST, was able to suppress cell migration and division when cells are exposed to LED light. This suggests a breakthrough to apply in future cancer cell research.
Professor Heo talked about the impact of his research in the following excerpt from a news article:
“We are already conducting research on the spread of cancer, as well as brain science in animal models with the Light-Activated Reversible Inhibition by Assembled Trap. I believe this technology will be a breakthrough in investigating cancer treatments and the function of neurons in a complex neural network, which existing technologies have not been able to do.”
From EE Times Europe, June 19, 2014
“LED Light Technology Controls Proteins in Living Cells”
http://www.ledlighting-eetimes.com/en/led-light-technology-controls-proteins-in-living-cells.html?cmp_id=7&news_id=222909336
2014.06.22 View 7530