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Native-like Spider Silk Produced in Metabolically Engineered Bacterium
Microscopic picture of 285 kilodalton recombinant spider silk fiber
Researchers have long envied spiders’ ability to manufacture silk that is light-weighted while as strong and tough as steel or Kevlar. Indeed, finer than human hair, five times stronger by weight than steel, and three times tougher than the top quality man-made fiber Kevlar, spider dragline silk is an ideal material for numerous applications. Suggested industrial applications have ranged from parachute cords and protective clothing to composite materials in aircrafts. Also, many biomedical applications are envisioned due to its biocompatibility and biodegradability.
Unfortunately, natural dragline silk cannot be conveniently obtained by farming spiders because they are highly territorial and aggressive. To develop a more sustainable process, can scientists mass-produce artificial silk while maintaining the amazing properties of native silk? That is something Sang Yup Lee at the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, the Republic of Korea, and his collaborators, Professor Young Hwan Park at Seoul National University and Professor David Kaplan at Tufts University, wanted to figure out. Their method is very similar to what spiders essentially do: first, expression of recombinant silk proteins; second, making the soluble silk proteins into water-insoluble fibers through spinning.
For the successful expression of high molecular weight spider silk protein, Professor Lee and his colleagues pieced together the silk gene from chemically synthesized oligonucleotides, and then inserted it into the expression host (in this case, an industrially safe bacterium Escherichia coli which is normally found in our gut). Initially, the bacterium refused to the challenging task of producing high molecular weight spider silk protein due to the unique characteristics of the protein, such as extremely large size, repetitive nature of the protein structure, and biased abundance of a particular amino acid glycine. “To make E. coli synthesize this ultra high molecular weight (as big as 285 kilodalton) spider silk protein having highly repetitive amino acid sequence, we helped E. coli overcome the difficulties by systems metabolic engineering,” says Sang Yup Lee, Distinguished Professor of KAIST, who led this project. His team boosted the pool of glycyl-tRNA, the major building block of spider silk protein synthesis. “We could obtain appreciable expression of the 285 kilodalton spider silk protein, which is the largest recombinant silk protein ever produced in E. coli. That was really incredible.” says Dr. Xia.
But this was only step one. The KAIST team performed high-cell-density cultures for mass production of the recombinant spider silk protein. Then, the team developed a simple, easy to scale-up purification process for the recombinant spider silk protein. The purified spider silk protein could be spun into beautiful silk fiber. To study the mechanical properties of the artificial spider silk, the researchers determined tenacity, elongation, and Young’s modulus, the three critical mechanical parameters that represent a fiber’s strength, extensibility, and stiffness. Importantly, the artificial fiber displayed the tenacity, elongation, and Young’s modulus of 508 MPa, 15%, and 21 GPa, respectively, which are comparable to those of the native spider silk.
“We have offered an overall platform for mass production of native-like spider dragline silk. This platform would enable us to have broader industrial and biomedical applications for spider silk. Moreover, many other silk-like biomaterials such as elastin, collagen, byssus, resilin, and other repetitive proteins have similar features to spider silk protein. Thus, our platform should also be useful for their efficient bio-based production and applications,” concludes Professor Lee.
This work is published on July 26 in the Proceedings of the National Academy of Sciences (PNAS) online.
2010.07.28 View 18588 -
A stream of generous donations to KAIST continues to grow.
Yi-Won Oh is nothing but an ordinary person who lives in Seoul. Ever since retirement, she has looked into ways to donate her savings for a bigger cause that will benefit the people in need and the nation as a whole.
On the inauguration day of President Nam Pyo Suh who took his second term in office, Ms. Oh joined the ceremony and pledged to donate her savings to KAIST, which amounted to 10 billion won.
“I’ve always thought that the best way for our country to become a developed nation that lacks natural resources and has a small land is to develop science and technology by producing excellent manpower through a quality education. I talked to President Suh a couple of times, and we shared our common belief that the future of our nation hinges on the advancement of science and technology in Korea,” said Ms. Oh.
She added, “I support for President Suh’s vision and leadership, who has brought reformative and innovative changes to KAIST. I have no doubt that KAIST will become a leading research university in the world and play an important role in the development of our nation. It is indeed my pleasure that I can make announcement to donate my money to KAIST on the day President Suh is assigned to lead such a distinguished university one more time.”
KAIST plans to create and operate a fund dubbed “Yi-Won Oh Scholarship and Grant for Young Chair Professors.” Through the fund, talented students suffering financial difficulties and promising, young professors will have a richer opportunity to study and research.
2010.07.21 View 10256 -
International Center was built to promote greater exchanges and collaborations between the international community and KAIST.
On July 9, 2010, KAIST held an opening ceremony for the construction of International Center. The Center will serve as an internal and external liaison for the university, providing a source of assistance to faculty, administrators, and students on matters related to international activities and initiatives. It will also pursue greater exchanges and collaborations between the international community and KAIST.
The facility accommodates various meetings, exhibitions, library, language services, and other amenities. The International Cooperation Team of KAIST will be moved into this building and provide a variety of services, such as immigration regulations, cultural adjustment, employment, to assist international students, scholars, faculty, and staff at KAIST, as well as Korean students seeking opportunities to study, work, or travel abroad. An international nursery school will also be inside the building so that foreign faculty and students with children can have convenience and quality child care while they are teaching or studying.
At the center will be held many different kinds of international event—one among them is KAIST-ONE, a festival held twice a year in spring and fall to introduce and share culture, education, and food of the global community at KAIST.
2010.07.19 View 11917 -
A new facility at KAIST opened on July 6, 2010.
Ryu Geun-Chul Sports Complelx will allow students, faculty and staff to pause a moment and exhale in the hustle and bustle of their daily lives.
An opening ceremony celebrating the completion of a new facility for the KAIST family was held on July 6, 2010 at the campus. Had it not been for contributions of many people and organizations throughout the nation, among others, Dr. Geun-Chul Ryu, POSCO, Woori Bank, members of KAIST community, parents, and other citizens, it would be impossible to build the facility, said the university.
The Complex, a three-story building with a basement, has an indoor court for basketball and volleyball with 3,000 individual seats, 200 meters of running track, indoor golf range, a fitness center, and other convenient facilities.
Any members of KAIST community can visit the building and relax their body and mind stressed with work and study. It also provides a large space for ceremonial and cultural gatherings such as 2010 KAIST commencement ceremony.
The official name of the building is “Ryu Geun-Chul Sports Complelx,” which was created in appreciation of Dr. Geun-Chul Ryu’s generous act who had donated 57.8 billion won worth of real estate to KAIST in August 2008.
2010.07.07 View 13192 -
President of Israel visited KAIST on June 9, 2010.
President of Israel, Shimon Peres, visited KAIST today on June 9, 2010 to witness the development of science and technology in Korea and explore ways of establishing collaboration and cooperation with industries and universities between Korea and Israel. President Peres led a delegation consisted of the Israeli Mister of Industry, Trade, and Labor, the Minister of Communication, and 60 business leaders from the top companies in the security, infrastructure, communication, high-tech, and water industries.
Upon their arrival to the campus, the Israeli delegation was greeted by KAIST’s humanoid robot, “HUBO,” and then moved to its branch campus, IT Convergence Campus, for a ride of Online Electric Vehicle (OLEV) that has been developed by KAIST. The OLEV receives the necessary power through the cable lines buried underground, so it can be provided with a constant and continuous supply of electricity while running or stopping.
Between roads and OLEVs is nothing but space. There is no electrical wires intricately crossed underbody of the electric car or above the road. The pick-up equipment installed beneath the body of the electric car collects magnetic fields created around the underground cables, which then converts the filed into electricity. The OLEV’s wireless, non-contact charging system made it possible for a battery currently used for hybrid or pure electric cars on the market to be smaller and cheaper.
President Peres expressed a great interest in the technology applied to the OLVE, quoting, “the OLEV system is indeed very impressive.” He talked about efforts being made in Israel with respect to the development of electric cars. The country plans to replace the conventional transportation system with electric cars by constructing a network of battery exchange stations and roadside charge points which allow the cars to be charged whenever they are parked.
“Despite the different approach taken by the two nations for the development of electric cars, I believe that transforming the automobile industry from combustion engine to electric system is the right direction we should all follow. Without addressing the current transportation system that heavily dependent on natural resources, we will not be able to promote “green growth on a global scale,” added President Peres.
In addition to electric cars, President Peres took up a considerable portion of his time to exchange ideas on how to expand cooperative relations between universities in Korea and Israel, specifically in the area of space, biotechnology, nanotechnology, high-tech, renewable and alternative energy, and the EEWS initiatives that have been implemented by KAIST to find answers to global issues such as climate change and depletion of natural resources. The EEWS stands for energy, environment, water, and sustainability.
In response, the president of KAIST pledged to set up a stronger and greater tie with research universities in Israel, particularly called for more collaboration between KAIST and Technion-Israel Institute of Technology.
Also, the Israeli delegation had a tour for several Korean research and development centers in Daedeok Innopolis, located in the City of Daejeon, which is the 2nd largest science and research complex in Korea.
Shimon Peres, the 9th president of Israel, held many of important government positions in Israel, among other things, Prime Minster and Minister of Defense. He won Nobel Peace Prize in 1994, together with Yitzhak Rabin and Yasser Arafat for the conclusion of a peace agreement, Oslo Accords, between Israel and Palestine Liberation Organization.
2010.06.09 View 17041 -
The 6th president of KAIST passed away on May 7, 2010.
Dr. Sang-Soo Lee was the first president of Korea Advanced Institute of Science (KAIS) and the 6th president of KAIST, who died of a chronic disease at the age of 85. The KAIS was the matrix of KAIST today. Graduated from the physics department of Seoul National University in 1949, he later received a doctoral degree in optics from Imperial College of Science and Technology, University of London.
Dr. Lee has greatly contributed to the development of science and technology in Korea in the capacity of a policy administrator, educator, scientist, researcher, and engineer. He held numerous prestigious offices including President of Korea Atomic Energy Research Institute in 1967, of KAIS in 172, and of KAIST in 1989. Dr. Lee also worked as a professor at the physics department of KAIST for 20 years from 1972-1992.
The Society of Photographic Instrumentation Engineers (SPIE), an international society for optics and photonics, was founded in 1955 to advance light-based technologies. Dr. Sang-Soo Lee was a member of the SPIE that issued a news release expressing its sincere condolences to his death. The following is the full text of the news release: http://spie.org/x40527.xml
In memoriam: Sang Soo Lee
10 May 2010
Sang Soo Lee, known as the "Father of Optics" in Korea passed away on May 7, 2010, in Korea. He was 84.
Lee received a B.S. in Physics from Seoul National University in Korea and a Ph.D. from Imperial College of Science and Technology, University of London, UK. Receiving the first Ph.D. in Optics in Korea, Dr. Lee devoted his life to lay the foundation for optical science and engineering for more than four decades as an educator, researcher, and administrator in science policy.
"He was one of the architects of the extraordinary and rapid emergence of Korea as a world leader in science and technology, or perhaps with the rich history of contributions centuries ago, re-emergence would be more appropriate." said Eugene G. Arthurs, SPIE Executive Director.
During his teaching career, Dr. Lee mentored 50 doctoral and more than 100 masters" degree candidates. in the areas of laser physics, wave optics, and quantum optics. Many of his former students have become leaders in academia, government-funded research institutes, and industry both in Korea and abroad. He published more than 250 technical papers and authored five textbooks, including "Wave Optics", "Geometrical Optics", "Quantum Optics", and "Laser Speckles and Holography".
Lee was the first president of the Korea Advanced Institute of Science and Technology (KAIST), and the first president to establish a new government funded graduate school. He played a pivotal role in founding the Optical Society of Korea (OSK) in 1989 and served as its first president.
Lee was an active member of the international scientific community. In addition to his pioneering scholastic achievements at KAIST, he served as the Vice President of the International Commission for Optics (ICO), a Council Member of the Third World Academy of Sciences, and a Council Member of UN University, serving as an ambassador for the optics community, which showed a significant example of how a developing country like Korea can serve international optics community.
Dr. Lee was a Fellow of the International Society for Optical Engineering (SPIE), the Optical Society of America (OSA), and the Korean Physical Society (KPS). He was the recipient of many awards and honors, including the National Order of Civil Merit that is the Presidential Medal of Honor from the Republic of Korea (2000), the Songgok Academic Achievement Prize, the Presidential Award for Science, and the Medal of Honor for Distinguished Scientific Achievement in Korea. In 2006, he was awarded OSA"s Esther Hoffman Beller Medal.
2010.05.19 View 14261 -
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium.
Their research paper was published in Nature Physics for the issue of April 2010.
If we take Helium 4 and cool it down at temperatures below 2.176 Kelivin, liquid helium 4 undergoes a phase transition and becomes superfluid with a zero viscosity. The superfluidity was observed in solid helium through an experiment performed by researchers of Pennsylvania State University in 2004. One of the researchers then was Professor Eun-Seong Kim in the Department of Physics, KAIST.
Professor Kim and his research staff, Hyung-Soon Choi, Ph.D., recently published their research results in Nature Physics (April 2010), a highly esteemed journal in the field, on the phenomena of hysteresis and relaxation dynamics observed in supersolid Helium.
For the paper, please download the attached .pdf file.
Nature Physics link: http://www.nature.com
2010.04.13 View 13070 -
News Article: Naro space rocket getting ready for second launch, April 12, 2010
News Article on KIAST published on April 12, 2010
The Korea Herald, 2010-04-12 17:07
Naro space rocket getting ready for second launch
By Bae Hyun-jung (tellme@heraldm.com)
The Ministry of Education, Science and Technology is checking on the second launch of Naro, Korea’s first space rocket, as all the necessary parts were transferred to the launch center last week.
The Science Technology Satellite No. 2 was transferred last Thursday from the KAIST Satellite Technology Research Center in Daejeon to the Naro Space Center in South Jeolla Province, said ministry officials.
The solid-fuel second-stage rocket reached the center last Monday and the liquid-fuel first-stage rocket did so on March 23. The latter was manufactured in Russia’s Khrunichev State Space Science and Production Center.
The satellite, a small one weighing 100 kilograms, was co-developed by the Korea Aerospace Research Institute, KAIST SaTReC and the Gwangju Institute of Science and Technology.
It is to revolve around the Earth for two years collecting data on climate change by gauging the hydrogen content in the atmosphere, said officials.
“With all the crucial parts ready here in the center, we have officially kicked off our final investigation before setting the details of the second Naro launch,” said a ministry official.
Second Vice Minister Kim Joong-hyun last week visited the Naro center to attend the overall inspection on all facilities related to the rocket launch.
The date has not yet been set for the second launch but will be fixed within this month, said officials.
With the general inspection completed on the facilities, the first-stage rocket and the satellite will be assembled and the combination will be joined by the second-stage rocket in May.
The first launching attempt ended in failure in August due to faulty electrical wiring or a mechanical problem in the fairing separation mechanism, according to panels.
The two fairings -- used to cover and protect the satellite placed on top of the Naro -- failed to separate timely and thus stopped the satellite from gaining sufficient velocity to reach its planned orbit.
Korea has so far spent 502.4 billion won ($428.1 million) on the Naro project since it began in August 2002.
2010.04.13 View 14329
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"The 2010 Artificial Intelligence Robot War Competition" begins to receive applications
[Event Notice]
“The 2010 Artificial Intelligence Robot War Competition” begins to receive applications
A good opportunity to gauge the intelligence of your robots
“The 2010 Artificial Intelligence (AI) Robot War Competition” will be held in October 2010, and the Competition has been receiving applications from contestants since April 1st. The deadline for the application will be May 31st, 2010.
Qualified contestants must be a minimum of two, but less than six, team members, and they will compete in one of the two fields: System on Chip (SoC) Taekwon Robot and Humanoid Robot (HURO). Winners will be decided based on the intelligence capabilities presented by a robot’s platform that mimics key functions of the human brain.
SoC Taekwon Robot will compete against one another by using a camera installed on its head to recognize visual images, locations, distances, and gestures of the other competing robot.
HURO competition is a new entry begun this year, and winners will be determined in accordance with the robot’s ability to perform given missions and fights. Missions are to go through a track installed with obstacles, recognize colors and shapes of barriers, and knock down barriers to earn scores. Fighting will be performed in the form of a Korean martial art, Tae-kwon-do.
The Korean government has nominated Robotics as one of the key growth engines to develop IT industry and Korean economy. Robotics converge many of different engineering fields, such as machinery, materials, components, and embedded software. In particular, the SoC is an essential technology for Korea to continuously take lead in the semi-conductor industry in the world, which is an important element for robotics.
SoC stands for System on Chip, an integrated chip that assembles various chips and components to be fabricated together on a single chip, instead of building them on a circuit board. The SoC technology has advantages of higher performance, smaller space requirements, lower memory requirements, higher system reliability, and lower consumer costs.
An artificial intelligence SoC robot is autonomous because it can adapt itself to changes in various environments and reach a given goal without constantly receiving external orders.
For details of the event, please refer to the website of www.socrobotwar.org.
2010.04.06 View 13373
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Interesting research results were published on the use of Twitter.
The number of “followers” on your Twitter account does not necessarily mean that “Your opinions matter much” to other people.
A KAIST graduate researcher, Mi-Young Cha, joined an interesting project that studies the influence of a popular social media, Twitter. Most of Twitter users today consider the number of followers as a measurement of their influence on the social sphere. According to the research paper, however, this connection does not seem to standing together. For details, please click the link below for an article published by the New York Times.
Dr. Cha received all of her post secondary education degrees in Computer Science, including her Ph.D. in 2008, from KAIST. Since 2008 till now, she has been a post doctoral researcher at Max Planck Institute for Software Systems (MPI-SWS) based in Germany.
[New York Times Article, March 19, 2010]
http://www.nytimes.com/external/readwriteweb/2010/03/19/19readwriteweb-the-million-follower-fallacy-audience-size-d-3203.html
2010.04.05 View 13876
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New drug targeting method for microbial pathogens developed using in silico cell
A ripple effect is expected on the new antibacterial discovery using “in silico” cells
Featured as a journal cover paper of Molecular BioSystems
A research team of Distinguished Professor Sang Yup Lee at KAIST recently constructed an in silico cell of a microbial pathogen that is resistant to antibiotics and developed a new drug targeting method that could effectively disrupt the pathogen"s growth using the in silico cell.
Hyun Uk Kim, a graduate research assistant at the Department of Chemical and Biomolecular Engineering, KAIST, conducted this study as a part of his thesis research, and the study was featured as a journal cover paper in the February issue of Molecular BioSystems this year, published by The Royal Society of Chemistry based in Europe.
It was relatively easy to treat infectious microbes using antibiotics in the past. However, the overdose of antibiotics has caused pathogens to increase their resistance to various antibiotics, and it has become more difficult to cure infectious diseases these days.
A representative microbial pathogen is Acinetobacter baumannaii. Originally isolated from soils and water, this microorganism did not have resistance to antibiotics, and hence it was easy to eradicate them if infected. However, within a decade, this miroorganism has transformed into a dreadful super-bacterium resistant to antibiotics and caused many casualties among the U.S. and French soldiers who were injured from the recent Iraqi war and infected with Acinetobacter baumannaii.
Professor Lee’s group constructed an in silico cell of this A. baumannii by computationally collecting, integrating, and analyzing the biological information of the bacterium, scattered over various databases and literatures, in order to study this organism"s genomic features and system-wide metabolic characteristics. Furthermore, they employed this in silico cell for integrative approaches, including several network analysis and analysis of essential reactions and metabolites, to predict drug targets that effectively disrupt the pathogen"s growth. Final drug targets are the ones that selectively kill pathogens without harming human body.
Here, essential reactions refer to enzymatic reactions required for normal metabolic functioning in organisms, while essential metabolites indicate chemical compounds required in the metabolism for proper functioning, and their removal brings about the effect of simultaneously disrupting their associated enzymes that interact with them.
This study attempted to predict highly reliable drug targets by systematically scanning biological components, including metabolic genes, enzymatic reactions, that constitute an in silico cell in a short period of time.
This research achievement is highly regarded as it, for the first time, systematically scanned essential metabolites for the effective drug targets using the concept of systems biology, and paved the way for a new antibacterial discovery. This study is also expected to contribute to elucidating the infectious mechanism caused by pathogens.
"Although tons of genomic information is poured in at this moment, application research that efficiently converts this preliminary information into actually useful information is still lagged behind. In this regard, this study is meaningful in that medically useful information is generated from the genomic information of Acinetobacter baumannii," says Professor Lee. "In particular, development of this organism"s in silico cell allows generation of new knowledge regarding essential genes and enzymatic reactions under specific conditions," he added.
This study was supported by the Korean Systems Biology Project of the Ministry of Education, Science and Technology, and the patent for the development of in silico cells of microbial pathogens and drug targeting methods has been filed.
[Picture 1 Cells in silico]
[Picture 2 A process of generating drug targets without harming human body while effectively disrupting the growth of a pathogen, after predicting metabolites from in silico cells]
2010.04.05 View 16853
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Photonic crystals allow the fabrication of miniaturized spectrometers
By Courtesy of Nanowerk
Photonic crystals allow the fabrication of miniaturized spectrometers
(Nanowerk Spotlight) Spectrometers are used in materials analysis by measuring the absorption of light by a surface or chemical substance. These instruments measure properties of light over a specific portion of the electromagnetic spectrum. In conventional spectrometers, a diffraction grating splits the light source into several beams with different propagation directions according to the wavelength of the light. Thus, to achieve sufficient spatial separation for intensity measurements at a small slit, a long light path – i.e., a large instrument – is required.
However, for lab-on-a-chip or microTAS (total analysis system) applications, the spectrometer must be integrated into a sub-centimeter scale device to produce a stand-alone platform. To achieve this, researchers at the Korea Advanced Institute of Science and Technology (KAIST) propose a new paradigm in which the spectrometer is based on an array of photonic crystals with different bandgaps.
"Because photonic crystals refelct light of different wavelengths selectively depending on their bandgaps, we can generate reflected light spanning the entire wavelength range for analysis at different spatial positions using patterned photonic crystals," Seung-Man Yang, Director of the National Creative Research Initiative Center for Intergrated Optofluidic Systems and Professor of the Department of Chemical & Biomolecular Engineering at KAIST, tells Nanowerk. "Therefore, when the light source impinges on the patterned photonic crytals, we can construct the spectrum using the reflection intensity profile from the constituent photonic crystals."
Photonic crystals – also known as photonic band gap material – are similar to semiconductors, only that the electrons are replaced by photons (i.e. light). By creating periodic structures out of materials with contrast in their dielectric constants, it becomes possible to guide the flow of light through the photonic crystals in a way similar to how electrons are directed through doped regions of semiconductors. The photonic band gap (that forbids propagation of a certain frequency range of light) gives rise to distinct optical phenomena and enables one to control light with amazing facility and produce effects that are impossible with conventional optics.
To demonstrate this new concept based on patterned photonic crystals, Yang and his group used non-close-packed colloidal crystals of silica particles dispersed in photocurable resin. Due to the repulsive interparticle potential, monodisperse silica particles spontaneously crystallize into non-close-packed face-centered cubic (fcc) structures at volume fractions above 0.1. Therefore, the particle volume fraction determines both the lattice constant and the bandgap position.
a) Optical image of an ETPTA film containing porous photonic crystal stripe patterns with 20 different bandgaps. b) Reflectance spectra from the 20 strips. c) Optical microscope image of the middle region with the parallel stripe pattern (denoted as white-dotted box in a). d) Cross-sectional SEM images of first, sixth, eleventh and seventeenth strips. The scale bars in a, c and d are 1 cm, 2mm and 2 µm, respectively. (reprinted with permission from Wiley-VCH Verlag)
Reporting their findings in a recent issue of Advanced Materials ("Integration of Colloidal Photonic Crystals toward Miniaturized Spectrometers"), the KAIST team has demonstrated the integration of colloidal photonic crystals with 20 different bandgaps into freestanding films (prepared by soft lithography), and their application as a spectrometer.
Yang explains that the team was able to precisely control the photonic bandgap by varying the particle size and volume fration.
"The prepared colloidal composite structures showed high physical rigidity and chemical resistivity" he says. "The composite structure is suitable for spectroscopic use due to the small full widths at half maximum (FWHMs) of the reflectance spectra, which mean that there is little overlap of the reflectance spectra of neighboring photonic crystal strips."
"On the other hand" says Yang, "porous photonic crystals showed large FWHMs and high reflectivities, which should prove useful in many practical photonic applications that require high optical performance and physical rigidity as well as simple and inexpensive preparation."
In addition to fabricating miniaturized spectrometers, which can for instance be integrated into small lab-on-a-chip devices, these integrated photonic crystals can be potentially used for tunable band reflection mirrors, optical switches, and tunable lasing cavities. Moreover, patterned photonic crystals with RGB colors are well-suited for use in reflection-mode microdisplay devices.
Yang points out that, although the spectrometric resolution can be reduced by employing the smaller bandgap interval and photonic bandwidth, there is a limitation. "Now, we are studying photonic crystals with continuous modulation of bandgap position. We expect that the photonic crystals can reduce the resolution to 0.01 nm."
By Michael Berger. Copyright 2010 Nanowerk
2010.03.17 View 14441