Polymer
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KAIST Develops Ultrathin Polymer Insulators Key to Low-Power Soft Electronics
Using an initiated chemical vapor deposition technique, the research team created an ultrathin polymeric insulating layer essential in realizing transistors with flexibility and low power consumption. This advance is expected to accelerate the commercialization of wearable and soft electronics.
A group of researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed a high-performance ultrathin polymeric insulator for field-effect transistors (FETs). The researchers used vaporized monomers to form polymeric films grown conformally on various surfaces including plastics to produce a versatile insulator that meets a wide range of requirements for next-generation electronic devices. Their research results were published online in Nature Materials on March 9th, 2015.
FETs are an essential component for any modern electronic device used in our daily life from cell phones and computers, to flat-panel displays. Along with three electrodes (gate, source, and drain), FETs consist of an insulating layer and a semiconductor channel layer. The insulator in FETs plays an important role in controlling the conductance of the semiconductor channel and thus current flow within the translators. For reliable and low-power operation of FETs, electrically robust, ultrathin insulators are essential. Conventionally, such insulators are made of inorganic materials (e.g., oxides and nitrides) built on a hard surface such as silicon or glass due to their excellent insulating performance and reliability.
However, these insulators were difficult to implement into soft electronics due to their rigidity and high process temperature. In recent years, many researchers have studied polymers as promising insulating materials that are compatible with soft unconventional substrates and emerging semiconductor materials. The traditional technique employed in developing a polymer insulator, however, had the limitations of low surface coverage at ultra-low thickness, hindering FETs adopting polymeric insulators from operating at low voltage.
A KAIST research team led by Professor Sung Gap Im of the Chemical and Biomolecular Engineering Department and Professor Seunghyup Yoo and Professor Byung Jin Cho of the Electrical Engineering Department developed an insulating layer of organic polymers, “pV3D3,” that can be greatly scaled down, without losing its ideal insulating properties, to a thickness of less than 10 nanometers (nm) using the all-dry vapor-phase technique called the “initiated chemical vapor deposition (iCVD).”
The iCVD process allows gaseous monomers and initiators to react with each other in a low vacuum condition, and as a result, conformal polymeric films with excellent insulating properties are deposited on a substrate. Unlike the traditional technique, the surface-growing character of iCVD can overcome the problems associated with surface tension and produce highly uniform and pure ultrathin polymeric films over a large area with virtually no surface or substrate limitations. Furthermore, most iCVD polymers are created at room temperature, which lessens the strain exerted upon and damage done to the substrates.
With the pV3D3 insulator, the research team built low-power, high-performance FETs based on various semiconductor materials such as organics, graphene, and oxides, demonstrating the pV3D3 insulator’s wide range of material compatibility. They also manufactured a stick-on, removable electronic component using conventional packaging tape as a substrate. In collaboration with Professor Yong-Young Noh from Dongguk University in Korea, the team successfully developed a transistor array on a large-scale flexible substrate with the pV3D3 insulator.
Professor Im said, “The down-scalability and wide range of compatibility observed with iCVD-grown pV3D3 are unprecedented for polymeric insulators. Our iCVD pV3D3 polymeric films showed an insulating performance comparable to that of inorganic insulating layers, even when their thickness were scaled down to sub-10 nm. We expect our development will greatly benefit flexible or soft electronics, which will play a key role in the success of emerging electronic devices such as wearable computers.”
The title of the research paper is “Synthesis of ultrathin polymer insulating layers by initiated chemical vapor deposition for low-power soft electronics” (Digital Object Identifier (DOI) number is 10.1038/nmat4237).
Picture 1: A schematic image to show how the initiated chemical vapor deposition (iCVD) technique produces pV3D3 polymeric films: (i) introduction of vaporized monomers and initiators, (ii) activation of initiators to thermally dissociate into radicals, (iii) adsorption of monomers and initiator radicals onto a substrate, and (iv) transformation of free-radical polymerization into pV3D3 thin films.
Picture 2: This is a transistor array fabricated on a large scale, highly flexible substrate with pV3D3 polymeric films.
Picture 3: This photograph shows an electronic component fabricated on a conventional packaging tape, which is attachable or detachable, with pV3D3 polymeric films embedded.
2015.03.10 View 12442 -
Rechargeable Lithium Sulfur Battery for Greater Battery Capacity
Professor Do Kyung Kim from the Department of Material Science and Engineering and Professor Jang Wook Choi from the Graduate School of EEWS have been featured in the lead story of the renowned nanoscience journal Advanced Materials for their research on the lithium sulfur battery. This new type of battery developed by Professor Kim is expected to have a longer life battery life and [higher] energy density than currently commercial batteries.
With ample energy density up to 2100Wh/kg—almost 5.4 times that of lithium ion batteries—lithium sulfur batteries can withstand the sharp decrease in energy capacity resulting from charging and discharging—which has been considered the inherent limitation of the conventional batteries.
Professor Kim and his research team used one-dimensional, vertical alignment of 75nm tick, 15μm long sulfur nanowires to maximize electric conductivity. Then, to prevent loss of battery life, they carbon-coated each nanowire and prohibited direct contact between the sulfur and electrolyte.
The result was one of the most powerful batteries in terms of both energy performance and density. Compared to conventional batteries which suffer from continuous decrease in energy capacity after being discharged, the lithium sulfur battery maintained 99.2% of its initial capacity after being charged and discharged 300 times and up to 70% even after 1000 times.
Professor Kim claims that his new battery is an important step forward towards a high-performance rechargeable battery which is a vital technology for unmanned vehicles, electric automobiles and energy storage. He hopes that his research can solve the problems of battery-capacity loss and contribute to South Korea’s leading position in battery technology. Professor Kim’s research team has filed applications for one domestic and international patent for their research.
2013.12.11 View 11039 -
Paving the Way to Next Generation Display
A new type of LCD that does not require polymer orientation films has been developed by researchers within the country. This technology will enable the creation of thiner and higher definition display.
Prof. Hee Tae Jung form KAIST’s biochemical engineering department led the research and Hyun Soo Jung, Hwan Jin Jeon doctoral students (1st co-authors), Doctor Yun Ho Kim from Korea Chemistry Research Center, and Prof. Shin Woong Kang from Jeon Buk University ( co-author) have participated in this research. This research has been funded by the WCU program and middle-grade researcher support program. The results of the research has been published as the online update of ‘‘Nature Asia Materials(NPG Asia Materials)” which is a sister magazine of the world renowned academic magazine ‘Nature’.
The flat display industry is the core industry leading the 21st century’s IT industry. The LCD is the main area of research. Korea is the leader of this industry, holding more than 50% of the world market. Many technologies are combined to make the electro-optic devices of the LCD function. The most important technology, which determines the indicating element’s quality and function is the technology to align the liquid crystals in one direction.
Currently, all LCD products are created by mechanically cutting into the surface of the polymer film and orienting the liquid crystal material along these cuts. However, the creation of polymer orientation films cost much time and money, and the high temperature processes necessary to stabilize the polymers does not allow for the free selection of circuit boards, and thus does not allow for the use in flexible display.
Prof. Hee Tae Jung devised a method to orient liquid display without the use of a polymer film using ITOs. Prof. Jung’s base technology has been tested on ITOs to maintain the necessary transparency and conductivity after forming a pattern with high decomposition rates and slenderness ratios.
The technology developed by the research team can horizontally or vertically align the transparent conductors without the use of polymer orientation films. Thus, the manufacturing processes have become much shortened and the LCDs can be made in much thinner from a few micrometers to a few centimeters. Also, it has a lower functioning voltage and faster response speed, showing the prospects of a high definition ultra-fast screen display development. Furthermore, this technology can be used for any type of board, and can be adjusted to a nanometer scale. This enables for its use in LCD based flexible or multi-domain modes.
Also, the transparent conductor patterning technology devised by the research team can be used not only for displays, but also for touch panels with highly increased sensitivity.
Prof. Jung said, “It was a long desire of the industry and academia to find a way to replace the polymer orientation film. This new technology does not need any polymer orientation films, and we can still use the original boards used for LCDs. This mean a lot to the industry. Also, this technology will increase the sensitivity of the touch panels for tablet PCs and smart phones. It can be used in many areas of future electronics base technology.”
2012.04.04 View 9839 -
Low Cost and Simple Gene Analysis Technology Developed
Professor Park Hyun Kyu of the Department of Biology and Chemical Engineering has developed a ‘real time CPR’ using Methylene Blue (nucleic acid bonding molecule with Electro-Chemical property).
The current gene analysis being used in the field is the real time PCR (Polymerase Chain Reaction) which takes advantage of the luminescent property of the gene and therefore requires expensive machines and chemicals to run.
By contrast, the electro-chemical method is easy to use and low cost and, most importantly, it allows the machine to become small and portable.
Professor Park’s research team used the decrease in the electro-chemical signal when the Methylene Blue reacts with nucleic acid and applied this to PCR which allowed for the real time analysis of the nucleic acid amplification process.
With the result of the experiment as the basis, the team was able to perform a trial with Chlamydia trachomatis, a pathogen that causes sexually transmitted disease.
The result showed that the electro-chemical method showed the same performance level as the real time PCR, which proved that the technology can be applied to diagnosing various diseases and gene research.
2011.04.30 View 9068
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Explanation for the polymerized nucleic acid enzyme's abnormal activation found
KAIST’s Professor Park Hyun Kyu of the Department of Bio Chemical Engineering revealed on the 23rd of December 2010 that his team had successfully developed the technology that uses the metal ions to control the abnormal activation of nucleic acids’ enzymes and using this, created a logic gate, which is a core technology in the field of future bio electrons.
The polymerized nucleic acid enzyme works to increase the synthesis of DNA and kicks into action only when the target DNA and primers form complimentary pairs (A and T, C and G).
Professor Park broke the common conception and found that it is possible for none complimentary pairs like T-T and C-C to initiate the activation of the enzyme and thus increase the nucleic acid production, given that there are certain metal ions present.
What Professor Park realized is that the enzymes mistake the uncomplimentary T-T and C-C pairs (with stabilized structures due to the bonding with mercury and silver ions) as being complimentary base pairs. Professor Park described this phenomenon as the “illusionary polymerase activity.”
The research team developed a logic gate based on the “illusionary polymerase activity’ phenomenon.” The logic gate paves the way to the development of future bio electron needed for bio computers and high performance memories.
Professor Park commented, “The research is an advancement of the previous research carried on about metal ions and nucleic acid synthesis. Our research is the first attempt at merging the concepts of the two previously separately carried out researches and can be adapted for testing presence of metal ions and development of a new single nucleotide polymorphic gene analysis technology.”
Professor Park added that, “Our research is a great stride in the field of nano scale electron element research as the results made possible the formation of accurate logic gates through relatively cost efficient and simple system designs.”
On a side note, the research was funded by Korea Research Foundation (Chairman: Park Chan Mo) and was selected as the cover paper for the December issue of ‘Angewandte Chemie International Edition’.
2011.01.18 View 9949 -
Prof. Lee"s Team Succeeds in Producing Plastics Without Use of Fossil Fuels
A team of scientists led by Prof. Sang-Yup Lee of the Department of Biological Sciences at KAIST have succeeded in producing the polymers used for everyday plastics through bioengineering, rather than through the use of fossil fuel based chemicals, the university authorities said on Tuesday (Nov. 24).
This groundbreaking research, which may now allow for the production of environmentally conscious plastics, has been published in two papers in the journal Biotechnology and Bioengineering.
Polymers are molecules found in everyday life in the form of plastics and rubbers. The team consisted of scientists from KAIST and Korean chemical company LG Chem focused their research on polylactic acid (PLA), a bio-based polymer which holds the key to producing plastics through natural and renewable resources.
"The polyesters and other polymers we use everyday are mostly derived from fossil oils made through the refinery or chemical process," said Lee. "The idea of producing polymers from renewable biomass has attracted much attention due to the increasing concerns of environmental problems and the limited nature of fossil resources. PLA is considered a good alternative to petroleum based plastics as it is both biodegradable and has a low toxicity to humans."
Until now PLA has been produced in a two-step fermentation and chemical process of polymerization, which is both complex and expensive. Now, through the use of a metabolically engineered strain of E.coli, the team has developed a one-stage process which produces polylactic acid and its copolymers through direct fermentation. This makes the renewable production of PLA and lactate-containing copolymers cheaper and more commercially viable.
"By developing a strategy which combines metabolic engineering and enzyme engineering, we"ve developed an efficient bio-based one-step production process for PLA and its copolymers," said Lee. "This means that a developed E. coli strain is now capable of efficiently producing unnatural polymers, through a one-step fermentation process,"
This combined approach of systems-level metabolic engineering and enzyme engineering now allows for the production of polymer and polyester based products through direct microbial fermentation of renewable resources.
"Global warming and other environmental problems are urging us to develop sustainable processes based on renewable resources," concluded Lee. "This new strategy should be generally useful for developing other engineered organisms capable of producing various unnatural polymers by direct fermentation from renewable resources".
2009.11.30 View 13873 -
KAIST President Suh Honored with 2009 ASME Medal
KAIST President Nam-Pyo Suh has chosen as the 2009 winner of the ASME Medal presented by the American Society of Mechanical Engineers, university authorities said on Thursday (July 2).
President Suh received the honor for "seminal contributions to the advancement of engineering through research in tribology, polymer processing, metal processing, design and manufacturing, as well as contributions to engineering education and research infrastructure."
The selection of President Suh was unanimously approved by the 13-member Board of Governors of the ASME. Suh became the first scientist of Asian descent in the award"s 89-year-long history.
Founded in 1880, the ASME is a non-profit professional organization promoting the art, science and practice of mechanical and multidisciplinary engineering and allied sciences. The organization is known for setting codes and standards for mechanical devices. As of 2009, it has 120,000 members worldwide.
Only one ASME medal is awarded annually to recognize "eminently distinguished achievement." The award consists of a $17,000 honorarium, a gold medal, certificate and travel supplement for two days. It will be presented to President Suh during the 2009 International Mechanical Engineering Congress and Exposition, which will be held in Lake Buena Vista, Florida, November 13-10, 2009.
President Suh is an internationally known educator, engineer and inventor. Born in Korea, he immigrated to the U.S. in 1954 to join his father, who was teaching at Harvard. He earned both his bachelor"s and master"s degrees from MIT before coming to Carnegie Tech for his doctoral education in mechanical engineering.
While teaching at MIT, he founded the MIT-Industry Polymer Processing Program in 1973 and the Laboratory for Manufacturing and Productivity. He left these positions in 1984 to serve with the U.S. National Science Foundation as its assistant director for engineering, until 1988.
He invented many new materials, products and manufacturing processes, earning more than 60 U. S. patents and founding several companies. He has written seven books and more than 300 scholarly papers. Among dozens of honors throughout his career, President Suh most recently received the 2007 Lifetime Achievement from the Society of Plastics Engineers.
The ASME conducts one of the world"s largest technical publishing operations through its ASME Press, holds numerous technical conferences and hundreds of professional development courses each year, and sponsors numerous outreach and educational programs.
2009.07.02 View 12691 -
President Nam-Pyo Suh Receives Lifetime Achievement Award from SPE
President Nam-Pyo Suh has been selected as a recipient of the Lifetime Achievement Award by the Society of Plastic Engineers (SPE).
The SPE is the largest professional organization that promotes polymer-related R&D.
The SPE announced that it recognizes President Suh’s many contributions to the field of polymer processing. President Suh established the first university/industry cooperative research program at MIT known as the MIT-Industry Polymer Processing Program, which became a model in establishing similar programs at many other universities by NSF. Among the many new materials, products and manufacturing processes invented by him are: Microcellular plastics, known as MuCell and used commercially worldwide, USM high pressure foam molding technology, electrostatic charge-decay NDE technique for polymeric materials, and foam/straight plastic lamination process (a major industrial product).
2007.04.12 View 13050