Smart Windows that Self-Illuminate on Rainy Days

– A joint research team from POSTECH and KAIST develops self-powering, color-changing humidity sensors
– Applicable to various fields including smart windows, health care and safety management


Smart windows that automatically change colors depending on the intensity of sunlight are gaining attention as they can reduce energy bills by blocking off sun’s visible rays during summer. But what about windows that change colors depending on the humidity outside during the monsoon season or on hot days of summer? Recently, a Korean research team has developed the source technology for smart windows that change colors according to the amount of moisture, without needing electricity.

The joint research team comprised of Professor Junsuk Rho of departments of mechanical and chemical engineering, Jaehyuck Jang and Aizhan Ismukhanova of Department of Chemical Engineering at POSTECH, and Professor Inkyu Park of KAIST’s Department of Mechanical Engineering. Together, they successfully developed a variable color filter using a metal-hydrogel-metal resonator structure using chitosan-based hydrogel, and combined it with solar cells to make a self-powering humidity sensor. These research findings were published as a cover story in the latest edition of Advanced Optical Materials, a journal specializing in nanoscience and optics.

200528_Back Cover

Sensors using light are already widely used in our daily lives in measuring the ECG, air quality, or distance. The basic principle is to use light to detect changes in the surroundings and to convert them into digital signals.

Fabri-Pero interference*1 is one of the resonance phenomena that can be applied in optical sensors and can be materialized in the form of multilayer thin films of metal-dielectric-metal. It is known that the resonance wavelength of transmitted light can be controlled according to the thickness and refractive index of the dielectric layer. However, the existing metal-dielectric-metal resonators had a big disadvantage in not being able to control the wavelengths of transmitted light once they are manufactured, making it difficult to use them in variable sensors.

The research team found that when the chitosan hydrogel is made into the metal-hydrogel-metal structure, the resonance wavelength of light transmitted changes in real time depending on the humidity of the environment. This is because the chitosan hydrogel repeats expansion and contraction as the humidity changes around it.


Using this mechanism, the team developed a humidity sensor that can convert light’s energy into electricity by combining a solar battery with a water variable wavelength filter made of metal-hydrogel-metal structured metamterial that changes resonance wavelength depending on the external humidity.

The design principle is to overlap the filter’s resonance wavelength with the wavelength where the absorption of the solar cells changes rapidly. This filter is designed to change the amount of light absorption of solar cells depending on the amount of moisture, and to lead to electric changes that ultimately detect the surrounding humidity.

Unlike the conventional optical humidity sensors, these newly developed ones work regardless of the type of light, whether it be natural, LED or indoor. Also, not only does it function without external power, but it can also predict humidity according to the filter’s color.


Professor Junsuk Rho who led the research commented, “This technology is a sensing technology that can be used in places like nuclear power reactors where people and electricity cannot reach.” He added, “It will create even greater synergy if combined with IoT technology such as humidity sensors that activate or smart windows that change colors according to the level of external humidity.”

The study was supported by the Samsung Research Funding & Incubation Center for Future Technology.

1.Fabry-Perot Interferometer
A device where multiple wavelengths enter a filter, and cause multiple interferences to occur in a particular space to transmit only certain wavelengths and reflect the others to select only the desired data.


Volcanic Eruptions Reduce Global Rainfall

– POSTECH Professor Seung-Ki Min’s joint research team identifies the mechanism behind the reduction in precipitation after volcanic eruptions
– Volcano-induced El Niño amplifies the reduction in precipitation. Safety of geoengineering that mimic volcanoes is not guaranteed.


Climate change is occurring all over the globe as 1°C increase in Earth’s surface temperature has led to the sea level rise, abrupt melting of the Arctic sea ice, and the increase in extreme weather events such as heat waves, droughts, and floods. To accurately predict the anthropogenic climate changes under the increase in greenhouse gases, it is important to understand the effects of natural factors such as solar and volcanic activities. A recent study has shown how global precipitation decreases when volcanoes erupt in the tropics.

Professor Seung-Ki Min and Dr. Seungmok Paik of Division of Environmental Science and Engineering at POSTECH and researchers from the French National Centre for Scientific Research, Swiss Federal Institute of Technology in Zurich, and University of Edinburgh have released new findings that the El Niño induced by volcanic eruptions plays a key role in the decrease in global precipitation. So far, studies have shown that volcanic activity reduces precipitation across the globe, but its specific mechanism had been unclear. These research results were recently published in Science Advances, a sister journal of Science.

During the two to three years following Mount Pinatubo’s eruption in 1991, the average global temperature fell by about 0.2 degrees. This is because the massive dust including sulfur dioxide emitted by the eruption reflected the light from the sun and blocked its heat from reaching the Earth’s surface. Volcanic activities, along with this cooling effect, reduce the global terrestrial precipitation but its amplitude greatly varies depending on climate model simulations. For the first time, the joint research team confirmed that the main factor for the drop in precipitation after volcanic eruptions is the difference in El Niño’s response.


El Niño is a natural climate variability that occurs every three to eight years, with weakened trade winds in the equatorial Pacific Ocean and warmer sea surface temperatures in the equatorial eastern Pacific, causing extreme weather conditions across the globe including drought and heavy rains. Under El Niño’s influence, precipitation reduction occurs especially in the global monsoon regions, including Southeast Asia, India, South Africa, Australia and northern South America.

The team compared several climate model simulations and found that El Niño appeared in the year following a volcanic eruption in most models, with a significant drop in precipitation around the global monsoon region. In particular, the strength of El Niño was different for each simulation, and the stronger the El Niño, the more pronounced the reduction in precipitation occurred. The research team also found that the stronger the volcanic forcing and the greater the warm water volume in the western Pacific Ocean, a stronger El Niño developed, which in turn intensified the reduction in precipitation.


These findings are expected to be used to identify the side effects of geoengineering techniques and to predict the climate of the later years. In particular, it suggests that if geoengineering techniques are used to reduce global warming by spraying sulfur dioxide – the main component of volcanic ash – in the lower stratosphere to imitate artificial volcanoes, they could produce unexpected side effect of changing the precipitation patterns across the globe.

Professor Seung-Ki Min stated, “If geoengineering techniques are applied to mimic volcanoes and block sunlight, drought and water shortages may increase significantly in the monsoon regions – home to two-thirds of the world’s population.”

This research was supported by the Mid-career Researcher Program of the National Research Foundation of Korea.

A ‘15-minute’ quick diagnostic testing for newly emerging viruses introduced.

– Prof. Sung Key Jang of POSTECH developed a quick diagnostic testing for viral infections using aptamers.

– This new technology led to beginning of developing a new COVID-19 diagnostic system and a clinical treatment of the disease.

200323_장승기 교수 실험실

The novel coronavirus, named as COVID-19, began in Wuhan, China and is threatening all regions around the globe that the World Health Organization (WHO) has declared this outbreak a pandemic since the swine flu 11 years ago. When such a highly contagious and fatal new disease occurs, it is necessary to quickly identify infected individuals and quarantine them. The most important step in this procedure is to have a quick diagnosis of viral infection.

A research team from POSTECH recently developed a quick diagnostic testing for viral infections that can bring results in 15 minutes by using an aptamer (nucleic acid molecule), a kind of molecular capture. This new test can be applied to diagnosis of all novel viruses and is expected to be used in clinical applications as well.

Prof. Sung Key Jang, Dr. Junyoung Kwon, and Dr. Chandan Narayan of Department of Life Sciences, POSTECH with Aptamer Sciences (Inc.) developed a new method (designated as viro-SELEX) for discovering aptamers against membrane proteins. Using viro-SELEX, they were able to develop aptamers with high sensitivity and specificity for binding to target proteins which led to rapid 15-minute diagnosis of viral infections. Their new discovery is published in the renowned journals, Journal of Biomedical Nanotechnology and Analyst.

There are several ways to test viral infections including molecular assays, immunoassays, and virus cultivation. For COVID-19, molecular assays are used to diagnose, however, the whole diagnosis process is not convenient despite of its high sensitivity. It requires the samples to be sent to professional institutions for analysis, takes more than six hours to analyze, and is highly expensive. Virus cultivation takes even longer time to analyze from two to four weeks and is not appropriate for massive tests. Lastly, immunoassays for COVID-19 has not been developed yet. Unfortunately, there has not been a real-time diagnostic test for COVID-19 developed that can be tested on site where the samples are taken.

An aptamer is a nucleic acid that is composed of DNA or RNA. It is kind of a molecular capture that binds to various targets ranging from a low molecular weight compound to macromolecules such as proteins with high specificity and affinity. DNA aptamers are highly stable and therefore easy to transport and store. When the sequence of aptamer is known, it can be synthesized in mass at economical price. So, it is considered as a substitute for an antibody.

Aptamers are discovered through the process called, SELEX*1. However, it has been challenging to develop aptamers through the conventional SELEX method in cases of virus because its targeted molecules are membrane proteins.


The research team generated recombinant baculoviruses*2 (surrogate viruses) containing target proteins on the viral envelope instead of purifying the membrane proteins. They applied the surrogate viruses in the SELEX process (designated as viro-SELEX.

Based on this new method, they generated new aptamers that bound to viral envelope proteins, HA, of influenza virus. Also, they were able to develop a diagnosis kit that changed a color, indicating the infection of virus like a pregnancy test kit by using a pair of aptamers which bound to different areas of HA. If this kit is used for diagnosis of viral infections, 15 minutes is enough to know the result.

“We can develop aptamers that bind to the spike proteins of COVID-19 with high specificity and affinity by using this newly developed viro-SELEX method. And using the aptamers, we can make a quick diagnosis kit. Moreover, these aptamers may also protect healthy cells from COVID-19 infection through interaction and inactivation of spike proteins. In other words, these aptamers could serve as lead molecules for developing a clinical treatment.” said, Prof. Sung Key Jang.

Meanwhile, the research team began developing a diagnostic test for COVID-19 with Korea Research Institute of Chemical Technology, which has the facility to cultivate COVID-19, and Aptamers Science Inc., which developed a KFDA-approved diagnosis of lung cancer for the first time in the world. Their goal is to establish a platform that can rapidly develop diagnosis and treatment of a novel virus such as COVID-19, MERS, and SARS.

1. SELEX, Systematic Evolution of Ligands by Exponential Enrichment
It is also known as in vitro evolution. It is a method for generating nucleic acids that can bind to targeted molecules with high affinity.

2. Baculoviruses
This virus is pathogenic to insects but not harmful to humans. It is often used for producing proteins in mass.

POSTECH Ranked Third Best Small University in the World, First in Asia

[Strong in University-Industry Collaboration]


POSTECH placed third on the 2019 World’s Best Small Universities list, recently published by the Times Higher Education (THE), a London-based leading publisher of higher education analysis and world university rankings.


THE announces world rankings annually for universities with fewer than 5,000 students. The same 13 performance indicators under five areas are used for small-scale global university evaluation as the global university assessment including, teaching, research, citations, industry income and international outlook. However, this evaluation only includes small universities due to their nature that prioritizes quality over quantity and customized education, which is not properly reflected in existing university evaluations.


Caltech placed first, followed by École Polytechnique and POSTECH placed third. POSTECH’s ranking is the highest among Asian universities.


Caltech, which continues to rank first, is an American engineering university of the highest level, established in California in 1891. It has produced outstanding scientists and engineers, such as Charles Richter, the developer of Richter scale and faculty members, including Albert Einstein, Linus Pauling and Richard Feynman. It is a frontrunner among small and strong universities. École Polytechnique, in second place, is a leading university among France’s small elite educational institutions labeled ‘Grandes Écoles.’ It is the epicenter of French mathematics, science and engineering research and boasts 222 years of history and tradition. Three presidents, including Giscard d’Estaing, numerous senior officials and CEOs from major French companies graduated from the university.


It has been analyzed that POSTECH ranked third due to its high marks in industry-university cooperation compared to other universities.


THE stated, “POSTECH was founded in 1986 to cultivate future engineers” and praised POSTECH for encouraging entrepreneurship by “providing students with entrepreneurship programs such as clubs for student startups, support for prospective entrepreneurs, patent training and leave of absence granted for launching startups.”

POSTECH students won 3rd place in the APRU Global Health Student Poster Contest (UG category)


POSTECH undergraduate students – Wonjun Jang, Sangeun Je, Do Yun Kim (CiTE), and Ahra Cho (IME) – won 3rd place in the undergraduate category of APRU Global Health Student Poster Contest with the entry titled “Treatment system for severe dementia patients using multi-sensory stimulation.” Among a total of 54 submissions from 24 universities in various countries, their poster was selected as one of the outstanding entries by an international panel of judges.


While they were taking the course titled Interaction Design Studio, Professor Eun Jeong Ma (CiTE), the course lecturer and advisor to the team, recommended the students to submit their project to the poster contest. For the project, they developed a personal multi-sensory simulation device, a multi-sensory controllable interface, and a dementia test application, which could be applied to severe dementia patients.


Jang stated, “I am grateful to Prof. Eun Jeong Ma for giving us this opportunity. I am also thankful for the fellow students working for the project together. During the course, I was trying to make ideas real and think about what users actually need. I’d be more than happy to help people in need by turning my own idea into reality.”


The awardees will attend the APRU Global Health Conference 2019, which will be held at the University of Hong Kong in November, and present their project at a poster session during the conference.

Prof. Moo Hwan Kim, Appointed as the 8th President of POSTECH

POSTECH Foundation (Chairman Jeong-Woo Choi) appointed Professor Moo Hwan Kim of Division of Advanced Nuclear Engineering (DANE) / Mechanical Engineering as the eighth president of POSTECH at the second board of trustees meeting of 2019 academic year held on July 17th. He succeeds President Doh-Yeon Kim, whose term expires on August 31st. The new president’s term in office is four years from September 1, 2019 to August 31, 2023.


Regarding the appointment, the board stated, “The newly appointed president Moo Hwan Kim presented the vision of fully realizing POSTECH’s founding tenets by playing up the strengths of a small elite university, in building a model where each unit grows through self-driven innovation. We affirm that he has the capacity to realize this vision.”


Professor Moo Hwan Kim was born in Busan and attended Kyunggi High School, then went onto receive both his bachelor’s and master’s degrees in nuclear engineering at Seoul National University in 1980 and 1982. He continued his studies at University of Wisconsin-Madison and received his Ph.D. there in 1986 then joined the POSTECH faculty in the following year.


He is an expert in the field of nuclear safety technology and has held leadership positions in various departments at POSTECH, including vice president of student affairs, admissions, external relations and communications, and planning, and as a professor of Division of Advanced Nuclear Engineering (DANE). He also served as the president of Korea Institute of Nuclear Safety (KINS) from 2013 for three consecutive years.


The board further remarked, “We have agreed that the newly appointed president Kim is well-equipped to be POSTECH’s president as he possesses excellent leadership and communication skills and demonstrates strong initiative. The board added, “With this new appointment, we encourage all members of the POSTECH community, including professors, staff, students, alumni, and the foundation to do their best in fulfilling the founding tenets of POSTECH and in growing into a global university.”

POSTECH Doctoral Student Gwanho Yoon Awarded the SPIE Scholarship in the U.S.

– Anticipated to contribute to future of optical engineering
– Selected in Forbes ‘30 Under 30 Asia 2019’



Gwanho Yoon, a doctoral student in mechanical engineering at POSTECH (Pohang University of Science and Technology, President Doh-Yeon Kim), has been awarded the 2019 Optics and Photonics Education Scholarship by SPIE (Society of Photo-Optical Instrumentation Engineers), the largest academic society in the field of optical engineering.


Yoon, working in the Nanophotonics Lab led by Professor Junsuk Rho, has been specializing in various researches on metasurface, widely known as the “invisibility cloak” technology. This research has attracted much attention because it also leads to future technologies through augmented and virtual reality technology, 3D hologram display and ultra-thin flat lens.


Yoon stated, “Even though metasurface outperforms conventional optical technology, only laboratory-scale production was possible due to its high production cost and difficulty in large-scale production. But this research develops quick and inexpensive metasurface production technology, allowing us to make an important contribution to commercialization of metasurface.”


Yoon made headlines in April when he was selected as one of the ’30 Under 30 Asia 2019′ leaders in the Healthcare and Science category by Forbes, an American business magazine.


This SPIE scholarship, awarded to students who are expected to contribute significantly to the future of optical engineering, was awarded to a total of 84 students from all over the world in 2019 and Yoon was the sole recipient in Korea and amongst the four in Asia.


Yoon’s advisor Professor Roh added, “Since this scholarship is known to be rarely awarded to non-US countries and especially not to Asian universities, I believe that SPIE has weighed Yoon’s potential at a higher level.”

A Wearable Vibration Sensor for Accurate Voice Recognition

[The research group led by Professor Kilwon Cho and Professor Yoonyoung Chung developed a skin-attachable vibration sensor for voice recognition]


A voice-recognition feature can be easily found on mobile phones these days. Often times, we experience an incident where a speech recognition application is activated in the middle of a meeting or a conversation in the office. Sometimes, it is not activated at all regardless of numbers of times we call out the application. It is because a mobile phone uses a microphone which detects sound pressure to recognize voice, and it is easily affected by surrounding noise and other obstacles.


Professor Kilwon Cho of Chemical Engineering and Professor Yoonyoung Chung of Electronic and Electric Engineering from POSTECH successfully developed a flexible and wearable vibration responsive sensor. When this sensor is attached to a neck, it can precisely recognize voice through vibration of the neck skin and is not affected by ambient noise or the volume of sound.


The conventional vibration sensors recognize voice through air vibration and the sensitivity decreases due to mechanical resonance and damping effect, therefore are not capable of measuring voices quantitatively. So, ambient sound or obstacles such as mouth mask can affect its accuracy of voice recognition and it cannot be used for security authentication.


In this study, the research group demonstrated that the voice pressure is proportional to the acceleration of neck skin vibration at various sound pressure levels from 40 to 70 dBSPL and they developed a vibration sensor utilizing the acceleration of skin vibration. The device, which is consisted of an ultrathin polymer film and a diaphragm with tiny holes, can sense voices quantitively by measuring the acceleration of skin vibration.


They also successfully exhibited that the device can accurately recognize voice without vibrational distortion even in the noisy environment and at a very low voice volume with a mouth mask worn.


This research can be further extended to various voice-recognition applications such as an electronic skin, human-machine interface, wearable vocal healthcare monitoring device.


Professor Kilwon Cho explained the meaning of this study in his interview. “This research is very meaningful in a way that it developed a new voice-recognition system which can quantitively sense and analyze voice and is not affected by the surroundings. It took a step forward from the conventional voice-recognition system that could only recognize voice qualitatively.”


This research was supported by the Center for Advanced Soft Electronics under the Global Frontier Research Program of The Ministry of Science and ICT, Korea. Further results of this study can be found on the website of Nature Communications, published on the 18th of June.

A new microorganism for algae biomass to produce alternative fuels

– Professor Gyoo Yeol Jung and his research team utilized algae that grow three times faster than starch crops and succeeded in producing biofuel and biochemicals

– They developed a new artificial microorganism as a microbial platform for the biorefinery of brown macroalgae which is possible to accelerate biochemical production rate


The biorefinery technology uses biomass as a feedstock and converts it to energy and other beneficial byproducts. It is drawing attention as an eco-friendly and sustainable technology to prepare for depletion of fossil fuels. However, the types of biomass that can be used for this technology are very limited. Starch crops such as corns are utilized as biomass (mainly glucose), but they are easily consumed by microorganism. Such processes have limitations in satisfying the growing demands of bioproducts, for example, the consumption of food resources and limited cultivation capabilities.


To overcome such limitations, the joint research team of POSTECH and Seoul National University developed a new microorganism, which they named as Vibrio sp. dhg. In their study, they successfully demonstrated that Vibrio sp. dhg can be a promising microbial platform for the biorefinery of brown macroalgae which can replace starch-crop biomass. Their research is published in the latest publication of the world-renowned journal, Nature Communications on June 6th, 2019.


Continuing efforts on studying utilization of non-edible biomass have been made and brown macroalgae have been suggested as an alternative feedstock. Brown macroalgae grow two to three times faster than the starch crops and only require light and seawater to grow. Although they are only consumed in a few countries such as Korea, they are not eaten in most of the countries. Because of these advantages, they seem to be a reasonable alternative choice. However, there was no industrial microorganism that can easily metabolize polysaccharides like alginic acid in algae and it was difficult to develop the process for utilizing algae as biomass.


To solve this problem, Prof. Gyoo Yeol Jung and his research team at POSTECH and Prof. Sang Woo Seo and his research group at Seoul National University successfully developed a new microorganism, Vibrio sp. dgh, that can rapidly metabolize alginic acid in algae and genetic engineering techniques optimized for this new microorganism based on omics analysis. In addition, they succeeded in developing biorefinery processes that directly produce ethanol (biofuel), 2,3-butanediol (raw material for plastics), lycopene (physiologically active substance) and other various chemical products by artificially manipulating the metabolic pathway of Vibrio sp. dhg.


Especially, the new artificial microorganism they found has many advantages and brings great expectations of its future usage. For example, Vibrio sp. dhg can not only use brown macroalgae as biomass but also other various biomass more efficiently than the conventional industrial microorganisms (E. coli, yeast). Also, their growth rate is two times faster and they convert biomass more rapidly. Therefore, it is expected to be used for improving the efficiency of microbial fermentation process using not only algae but also conventional gluose-based biomass.

Prof. Jung who led the research team explained, “The microorganism that we found, Vibrio sp. dhg can rapidly metabolize algae-derived carbon sources. So, it can be utilized in producing eco-friendly value-added chemicals. Also, it can convert raw materials to high value-added chemicals exceptionally faster than the existing industrial microorganism. Therefore, we expect that this will exceedingly improve the efficiency and economic feasibility of microbial fermentation process which has been studied globally.”


This research was supported by the C1 Gas Refinery Program, the Global Research Laboratory Program, the Bio & Medical Technology Development Program (Korea Bio Grand Challenge) through the National Research Foundation of Korea and Creative-Pioneering Researchers Program through Seoul National University.