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KAIST Team Develops Flexible PRAM
Phase change random access memory (PRAM) is one of the strongest candidates for next-generation nonvolatile memory for flexible and wearable electronics. In order to be used as a core memory for flexible devices, the most important issue is reducing high operating current. The effective solution is to decrease cell size in sub-micron region as in commercialized conventional PRAM. However, the scaling to nano-dimension on flexible substrates is extremely difficult due to soft nature and photolithographic limits on plastics, thus practical flexible PRAM has not been realized yet.
Recently, a team led by Professors Keon Jae Lee and Yeon Sik Jung of the Department of Materials Science and Engineering at KAIST has developed the first flexible PRAM enabled by self-assembled block copolymer (BCP) silica nanostructures with an ultralow current operation (below one quarter of conventional PRAM without BCP) on plastic substrates. BCP is the mixture of two different polymer materials, which can easily create self-ordered arrays of sub-20 nm features through simple spin-coating and plasma treatments. BCP silica nanostructures successfully lowered the contact area by localizing the volume change of phase-change materials and thus resulted in significant power reduction. Furthermore, the ultrathin silicon-based diodes were integrated with phase-change memories (PCM) to suppress the inter-cell interference, which demonstrated random access capability for flexible and wearable electronics. Their work was published in the March issue of ACS Nano: "Flexible One Diode-One Phase Change Memory Array Enabled by Block Copolymer Self-Assembly."
Another way to achieve ultralow-powered PRAM is to utilize self-structured conductive filaments (CF) instead of the resistor-type conventional heater. The self-structured CF nanoheater originated from unipolar memristor can generate strong heat toward phase-change materials due to high current density through the nanofilament. This ground-breaking methodology shows that sub-10 nm filament heater, without using expensive and non-compatible nanolithography, achieved nanoscale switching volume of phase change materials, resulted in the PCM writing current of below 20 uA, the lowest value among top-down PCM devices. This achievement was published in the June online issue of ACS Nano: "Self-Structured Conductive Filament Nanoheater for Chalcogenide Phase Transition." In addition, due to self-structured low-power technology compatible to plastics, the research team has recently succeeded in fabricating a flexible PRAM on wearable substrates.
Professor Lee said, "The demonstration of low power PRAM on plastics is one of the most important issues for next-generation wearable and flexible non-volatile memory. Our innovative and simple methodology represents the strong potential for commercializing flexible PRAM."
In addition, he wrote a review paper regarding the nanotechnology-based electronic devices in the June online issue of Advanced Materials entitled "Performance Enhancement of Electronic and Energy Devices via Block Copolymer Self-Assembly."
Picture Caption:
Low-power nonvolatile PRAM for flexible and wearable memories enabled by (a) self-assembled BCP silica nanostructures and (b) self-structured conductive filament nanoheater.
2015.06.15 View 14265 -
Science and Technology Policy Professor Chihyung Jeon Awarded Rachel Carson Fellowship
KAIST Graduate School of Science and Technology Policy Professor Chihyung Jeon has been awarded the Rachel Carson Fellowship 2015-2016.
Rachel Carson Center for Environment and Society is a research center for environmental humanities and social sciences, supported by the German Federal Ministry of Education and Research. It was founded by Ludwig-Maximilians-Universität, Munich, Germany and the Deutsches Museum as a joint initiative in 2009.
Rachel Carson Center supports researches in humanities and social sciences on the interactions between the environment and the society, following the footsteps of Rachel Cason, who raised awareness on the chemical environmental damage and started global environmental movement through her published book “Silent Spring” in 1962.
The center is awarding Rachel Carson Fellowships to established researchers to fund their writing and promote exchange of research. This year, 31 fellowships were awarded.
Professor Jeon will conduct research on "A Dredged Nation: The Four Rivers Restoration Project and the Envirotechnical Transformation of South Korea" and will also hold an additional post of International Curatorial Fellow at the Deutsches Museum.
2015.06.11 View 8404 -
The Acoustical Society of America Names Yang Hann Kim of KAIST the Recipient of the 2015 Rossing Prize in Acoustics Education
The award, given to Dr. Kim in recognition of his contributions to the advancement of acoustics education, will be presented during the 170th Meeting of the Acoustical Society of America on November 2-6, 2015 in Jacksonville, Florida.
The Acoustical Society of America (ASA) announced today that Professor Yang Hann Kim of the Mechanical Engineering Department at the Korea Advanced Institute of Science and Technology (KAIST) was the 12th recipient of the Rossing Prize in Acoustics Education. Dr. Kim is the first recipient selected from a non-English-speaking nation.
The Rossing Prize in Acoustics Education was established in 2003 from a generous gift made to the ASA Foundation by Thomas D. Rossing to recognize an individual who has made significant contributions to the advancement of acoustics education through distinguished teaching, creation of educational materials, textbook writing, and other activities.
During 25 years of teaching and conducting research in acoustics, noise, and vibration at KAIST, Dr. Kim has advised 26 doctorates and published over 200 research papers in journals such as Journal of Acoustical Society of America, Journal of Sound and Vibration, and Journal of Mechanical Systems and Signal Processing. He also wrote two acoustics textbooks for university education, which has been widely read worldwide. The textbook titles are: Sound Propagation: An Impedance Based Approach (Wiley, July 2010) and with the co-author, Dr. Jung-Woo Choi, Sound Visualization and Manipulation (Wiley, September 2013).
Since 2009, Professor Kim has lectured an online course entitled “Introduction to Acoustics,” offering students and the general public throughout the world guidance to study acoustics through the basic concept of impedance, for example, on vibrations and waves.
Dr. Kim will receive the award during ASA’s 170th conference to be held on November 2-6, 2015 at the Hyatt Regency Jacksonville Riverfront Hotel in Jacksonville, Florida, USA.
For the list of previous recipients of the Rossing Prize in Acoustics Education,
see:http://acousticalsociety.org/funding_resources/prizes#rossing
2015.06.04 View 7788 -
President Steve Kang Receives the John Choma Education Award from the IEEE International Symposium on Circuits and Systems
The Institute of Electrical and Electronics Engineers (IEEE) International Symposium on Circuits and Systems (ISCAS) 2015 took place at the Cultural Centre of Belem in Lisbon, Portugal, on May 24-27, 2015.
President Steve Kang attended the conference and presented a paper entitled “Memrister-based Synapses and Neurons for Neuromorphic Computing” on May 26, 2015. On the same day, he received the John Choma Education Award.
The award was established to commemorate the lifetime achievement of the late Professor John Choma of the Electrical Engineering Department at the University of Southern California. Dr. Choma was an eminent scientist, scholar, and educator, who earned global recognition in the field of integrated circuits and very-large-scale-integration (VLSI).
The IEEE ISCAS selects, among its members, the recipient of the John Choma Education Award, who has made significant contributions to the education of circuits and systems.
President Kang advised 60 doctorates while teaching at the University of Illinois at Urbana-Champaign and the University of California at Santa Cruz and published 450 research papers in the past 40 years. He also received Meritorious Service Award, Charles Desoer Technical Achievement Award, and Mac Van Valkenburg Society Award, all from the IEEE ISCAS.
2015.06.03 View 6396 -
Professor Duck-Joo Lee Is Elected Vice Chairman of the American Helicopter Society
Professor Duck-Joo Lee of the Department of Aerospace Engineering at KAIST was elected to become the first Korean vice president of the American Helicopter Society (AHS). He will serve a two-year term, starting this July, and his responsibilities will cover Asia, Australia, and Russia.
AHS, established in 1943, is the biggest association in the field with 6,800 members. The society is intended to advance helicopter technology and vertical take-off and landing (VTOL) in airplane technology.
The AHS’s board of directors consists of thirty experts in rotorcrafts, including the president of Sikorsky Aircraft Corporation, a renowned American helicopter manufacturing company.
Professor Lee started his career as a researcher in NASA Ames Research Center in the United States, and is now an acknowledged scholar in the field of aircraft jet engines and helicopter Aero-Acoustics. He also worked as the Assistant Editor-in-Chief of Journal of the American Helicopter Society, the President of the first Asia-Australia Rotorcraft Forum, and the leader of National Task Force Team of Korean Military and Civil Helicopter.
2015.05.18 View 7365 -
Fast, Accurate 3D Imaging to Track Optically-Trapped Particles
KAIST researchers published an article on the development of a novel technique to precisely track the 3-D positions of optically-trapped particles having complicated geometry in high speed in the April 2015 issue of Optica.
Optical tweezers have been used as an invaluable tool for exerting micro-scale force on microscopic particles and manipulating three-dimensional (3-D) positions of particles. Optical tweezers employ a tightly-focused laser whose beam diameter is smaller than one micrometer (1/100 of hair thickness), which generates attractive force on neighboring microscopic particles moving toward the beam focus. Controlling the positions of the beam focus enabled researchers to hold the particles and move them freely to other locations so they coined the name “optical tweezers.”
To locate the optically-trapped particles by a laser beam, optical microscopes have usually been employed. Optical microscopes measure light signals scattered by the optically-trapped microscopic particles and the positions of the particles in two dimensions. However, it was difficult to quantify the particles’ precise positions along the optic axis, the direction of the beam, from a single image, which is analogous to the difficulty of determining the front and rear positions of objects when closing an eye due to a lack of depth perception. Furthermore, it became more difficult to measure precisely 3-D positions of particles when scattered light signals were distorted by optically-trapped particles having complicated shapes or other particles occlude the target object along the optic axis.
Professor YongKeun Park and his research team in the Department of Physics at the Korea Advanced Institute of Science and Technology (KAIST) employed an optical diffraction tomography (ODT) technique to measure 3-D positions of optically-trapped particles in high speed. The principle of ODT is similar to X-ray CT imaging commonly used in hospitals for visualizing the internal organs of patients. Like X-ray CT imaging, which takes several images from various illumination angles, ODT measures 3-D images of optically-trapped particles by illuminating them with a laser beam in various incidence angles.
The KAIST team used optical tweezers to trap a glass bead with a diameter of 2 micrometers, and moved the bead toward a white blood cell having complicated internal structures. The team measured the 3-D dynamics of the white blood cell as it responded to an approaching glass bead via ODT in the high acquisition rate of 60 images per second. Since the white blood cell screens the glass bead along an optic axis, a conventionally-used optical microscope could not determine the 3-D positions of the glass bead. In contrast, the present method employing ODT localized the 3-D positions of the bead precisely as well as measured the composition of the internal materials of the bead and the white blood cell simultaneously.
Professor Park said, “Our technique has the advantage of measuring the 3-D positions and internal structures of optically-trapped particles in high speed without labelling exogenous fluorescent agents and can be applied in various fields including physics, optics, nanotechnology, and medical science.”
Kyoohyun Kim, the lead author of this paper (“Simultaneous 3D Visualization and Position Tracking of Optically Trapped Particles Using Optical Diffraction Tomography”), added, “This ODT technique can also apply to cellular-level surgeries where optical tweezers are used to manipulate intracellular organelles and to display in real time and in 3-D the images of the reaction of the cell membrane and nucleus during the operation or monitoring the recovery process of the cells from the surgery.”
The research results were published as the cover article in the April 2014 issue of Optica, the newest journal launched last year by the Optical Society of America (OSA) for rapid dissemination of high-impact results related to optics.
Figure 1: This picture shows the concept image of tweezing an optically-trapped glass bead on the cellular membrane of a white blood cell.
Figure 2: High-speed 3-D images produced from optical diffraction tomography technique
2015.04.24 View 11357 -
Anti-Cancer Therapy Delivering Drug to an Entire Tumor Developed
KAIST’s Department of Bio and Brain Engineering Professor Ji-Ho Park and his team successfully developed a new highly efficacious anti-cancer nanotechnology by delivering anti-cancer drugs uniformly to an entire tumor. Their research results were published in Nano Letters online on March 31, 2015.
To treat inoperable tumors, anti-cancer medicine is commonly used. However, efficient drug delivery to tumor cells is often difficult, treating an entire tumor with drugs even more so.
Using the existing drug delivery systems, including nanotechnology, a drug can be delivered only to tumor cells near blood vessels, leaving cells at the heart of a tumor intact. Since most drugs are injected into the bloodstream, tumor recurrence post medication is frequent.
Therefore, the team used liposomes that can fuse to the cell membrane and enter the cell. Once inside liposomes the drug can travel into the bloodstream, enter tumor cells near blood vessels, where they are loaded to exosomes, which are naturally occurring nanoparticles in the body. Since exosomes can travel between cells, the drug can be delivered efficiently into inner cells of the tumor.
Exosomes, which are secreted by cells that exist in the tumor microenvironment, is known to have an important role in tumor progression and metastasis since they transfer biological materials between cells. The research team started the investigation recognizing the possibility of delivering the anti-cancer drug to the entire tumor using exosomes.
The team injected the light-sensitive anti-cancer drug using their new delivery technique into experimental mice. The researchers applied light to the tumor site to activate the anti-cancer treatment and analyzed a tissue sample. They observed the effects of the anti-cancer drug in the entire tumor tissue.
The team’s results establish a ground-breaking foothold in drug delivery technology development that can be tailored to specific diseases by understanding its microenvironment. The work paves the way to more effective drug delivery systems for many chronic diseases, including cancer tumors that were difficult to treat due to the inability to penetrate deep into the tissue.
The team is currently conducting experiments with other anti-cancer drugs, which are being developed by pharmaceutical companies, using their tumor-penetrating drug delivery nanotechnology, to identify its effects on malignant tumors.
Professor Park said, “This research is the first to apply biological nanoparticles, exosomes that are continuously secreted and can transfer materials to neighboring cells, to deliver drugs directly to the heart of tumor.”
Picture: Incorporation of hydrophilic and hydrophobic compounds into membrane vesicles by engineering the parental cells via synthetic liposomes.
2015.04.07 View 11088 -
Polymers with Highly Improved Light-transformation Efficiency
A joint Korean research team, led by Professor Bum-Joon Kim of the Department of Chemical and Biomolecular Engineering at KAIST and Professor Young-Woo Han of the Department of Nanofusion Engineering at Pusan National University, has developed a new type of electrically-conductive polymer for solar batteries with an improved light-transformation efficiency of up to 5%. The team considers it a viable replacement for existing plastic batteries for solar power which is viewed as the energy source of the future.
Polymer solar cells have greater structural stability and heat resistance compared to fullerene organic solar cells. However, they have lower light-transformation efficiency—below 4%—compared to 10% of the latter. The low efficiency is due to the failure of blending among the polymers that compose the active layer of the cell. This phenomenon deters the formation and movement of electrons and thus lowers light-transformation efficiency.
By manipulating the structure and concentration of conductive polymers, the team was able to effectively increase the polymer blending and increase light-transformation efficiency. The team was able to maximize the efficiency up to 6% which is the highest reported ratio.
Professor Kim said, “This research demonstrates that conductive polymer plastics can be used widely for solar cells and batteries for mobile devices.”
The research findings were published in the February 18th issue of the Journal of the American Chemical Society (JACS).
Picture: Flexible Solar Cell Polymer Developed by the Research Team
2015.04.05 View 9911 -
KAIST Develops a Credit-Card-Thick Flexible Lithium Ion Battery
Since the battery can be charged wirelessly, useful applications are expected including medical patches and smart cards.
Professor Jang Wook Choi at KAIST’s Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and Dr. Jae Yong Song at the Korea Research Institute of Standards and Science jointly led research to invent a flexible lithium ion battery that is thinner than a credit card and can be charged wirelessly.
Their research findings were published online in Nano Letters on March 6, 2015. Lithium ion batteries are widely used today in various electronics including mobile devices and electronic cars. Researchers said that their work could help accelerate the development of flexible and wearable electronics.
Conventional lithium ion batteries are manufactured based on a layering technology, stacking up anodes, separating films, and cathodes like a sandwich, which makes it difficult to reduce their thickness. In addition, friction arises between layers, making the batteries impossible to bend. The coating films of electrodes easily come off, which contributes to the batteries’ poor performance.
The research team abandoned the existing production technology. Instead, they removed the separating films, layered the cathodes and anodes collinearly on a plane, and created a partition between electrodes to eliminate potential problems, such as short circuits and voltage dips, commonly present in lithium ion batteries.
After more than five thousand consecutive flexing experiments, the research team confirmed the possibility of a more flexible electrode structure while maintaining the battery performance comparable to the level of current lithium ion batteries.
Flexible batteries can be applied to integrated smart cards, cosmetic and medical patches, and skin adhesive sensors that can control a computer with voice commands or gesture as seen in the movie “Iron Man.”
Moreover, the team has successfully developed wireless-charging technology using electromagnetic induction and solar batteries.
They are currently developing a mass production process to combine this planar battery technology and printing, to ultimately create a new paradigm to print semiconductors and batteries using 3D printers.
Professor Choi said, “This new technology will contribute to diversifying patch functions as it is applicable to power various adhesive medical patches.”
Picture 1: Medical patch (left) and flexible secondary battery (right)
Picture 2: Diagram of flexible battery
Picture 3: Smart card embedding flexible battery
2015.03.24 View 10705 -
President Kang to Present at the World Economic Forum
President Sung-Mo Kang of KAIST will attend the World Economic Forum (WEF) as a member of the Global University Leaders Forum (GULF) to represent KAIST. GULF is attended by the world leaders of education and research. Its members represent 26 universities drawn from around the world including Harvard University. KAIST is the only Korean university to be invited.
WEF will be held in Davos, Switzerland, for four days, starting on 21 January 2015. He will discuss the future of higher education, the issues and solutions of science and society at GULF.
By attending GULF, KAIST expects to strengthen its network with top universities around the world and raise KAIST’s profile on an international basis. President Kang said, “The invitation for KAIST to attend the GULF is an evidence of its raised global status.” He continued, “I will show the innovative and challenging achievements KAIST has made to the leaders of the world.”
The theme of the 2015 World Economic Forum Annual Meeting 2015 is “The New Global Context” to discuss the integration of economic growth and society, employment and work force, environment and resource scarcity, the future of the Internet, and international crime and anti-corruption.
The World Economic Forum was established in 1971 by Klaus Schwab who is also its Executive Chairman. More than 2,500 people including German Chancellor Angela Merkel, French President François Hollande, Chinese Premier Li Keqiang, Google President Eric Schmidt, and Microsoft CEO Satya Nadella will attend this year's forum.
2015.01.22 View 8058 -
Professor Sung-Yong Kim Receives the Young Scientist Award
Professor Sung-Yong Kim of the Department of Ocean Systems Engineering at KAIST received the Young Scientist Award for 2014 conferred by the Korean Society of Oceanography (KSO). The award was presented at the KSO’s fall conference that took place on November 6, 2014 at the campus of the Naval Academy of the Republic of Korea in Jinhae.
Professor Kim has been recognized for his outstanding research in coastal oceanography and environmental fluid mechanics. His research papers are frequently published in prestigious journals such as the Journal of Geophysical Research-Oceans by the American Geophysical Union.
2014.11.11 View 7111 -
Kiseok Song, a Ph.D. candidate in the Electrical Engineering Department, receives the 2014 Marconi Society Young Scholar Award
Established
in 1974 to commemorate the eminent Italian inventor and electrical engineer,
Guglielmo Marconi, the Marconi Society has recognized significant contributions
in science and technology by awarding the Marconi Prize, with an annual USD
100,000 grant, to a living scientist who has made great advancements in
communications technology.
Along
with the Marconi Prize, the Society has been presenting the Young Scholars
Awards over the past six years to reward young and emerging scientists’ brilliant
academic and research achievements as well as their entrepreneurship. For this
year’s seventh Young Scholar Awards, a KAIST doctoral student was selected as
one of the two recipients.
Kiseok
Song, a Ph.D. candidate in the Department of Electrical Engineering, KAIST, has
been named as a 2014 Marconi Society Paul Baran Young Scholar. The Marconi Society said that Song was being recognized for "his
academic achievements and leadership in the field of communications and
information science,” according to a press release distributed by the Society on August 28, 2014.
Studying
under the advice of Professor Hoi-Jun Yoo of the Department of Electrical
Engineering at KAIST, Song has developed bio-medical System on a Chip (SoC)
such as smart wireless bio-medical systems combined with optimized SoCs,
compact bio-medical patch systems connected to smart phones, smart electro-acupuncture
and transdermal drug delivery, and multi-modal non-invasive glucose monitors.
The
press release quoted Professor Yoo’s comment on the meaning of Song’s research:
“All
of these bio-medical systems open a new healthcare paradigm to improve people’s
quality of life in combination with the current mobile smart phones.”
In
addition to Song, Himanshu Asnani, a Stanford Ph.D. candidate and system engineer
at Ericsson Silicon Valley, received the other award. The award
ceremony will be held at the Marconi Society’s annual award gala at the
National Academies of Science Building in Washington D.C., on October 2, 2014.
For
details, please read the following press release:
The
Marconi Society, Press Release, August 28, 2014
“Kiseok
Song Receives the 2014 Marconi Society Young Scholar Award”
http://www.marconisociety.org/press/2014Song.html
2014.09.08 View 7846