Research
Fundamental thermal research for arising high-impact applications
- 연성물질 열전달 열특성 실험적 접근
- 차세대 의료기기 개발을 위한 의공학 & 생명과학 응용 (Development simultaneously for R&D and Business)
- 친환경 에너지 소자 개발을 위한 열전소재 개발
- 카본 물질을 사용한 다양한 분야로의 적용
Thread 7 – Carbon based materials (esp, Thermally Reduced Graphene Oxide) for applications
7.1 - Low cost synthesis of thermally reduced graphene oxide for Influenza Virus Sensor
A biocompatible, cost-effective, and scalable thermally reduced graphene oxide (TRGO) film was obtained from shellac using thermal treatment and its structural, chemical, and electrical properties were investigated. This TrGO film exhibited good crystallinity, low sheet resistance, and high carbon content. TRGO flakes obtained from the film were dispersed and drop cast onto indium tin oxide/glass electrodes to fabricate label-free electrochemical immunosensors for the quantitative detection of the influenza virus H1N1 via electrochemical impedance spectroscopy. These sensors exhibited high stability and reproducibility, both possibly ascribable to the high adhesion of TRGO due to its phenolic-OH moiety; the limits of detection were 26 and 33 plaque-forming units, respectively, in phosphate-buffered saline and diluted saliva. These cost-effective TRGO based sensors showed great potential as reliable and robust nanomaterial-based biosensors for widespread clinical applications
Material Science & Engineering C 108 (2020) 110465
7.2 - Enhanced Mechanical Properties of thermally reduced graphene oxide on carbon fiber
Shellac, an inexpensive natural thermoplastic resin was used as a natural precursor to grow thermally reduced graphene oxide (TRGO) directly on the surface of CFs at low temperatures without employing toxic chemicals. Owing to its wrinkled structure and large surface area, TRGO increased the interfacial strength of the composites not only at the molecular level by hydrogen and covalent bonding but also at the nano- and micro-scale by inducing the interlocking effect. In addition, The TRGO can be coated onto CF with better dispersions, increased surface roughness, which strengthened the interfacial interaction between CF and PA66. As a result, the CF-TRGO-PA66 composite prepared under the optimal conditions showed a dramatic improvement in its ILSS (by 60%) and flexural strength (by 152%) as compared to the bare composite. Hence, the synthesis method used in this study is a promising approach to prepare high-performance and low-cost composites.
Composite Part B 193 (2020) 108010
7.3 - Thermal Conductivity of Suspended Graphitic Films using Optothermal Technique
We have also used Raman spectroscopy based optothermal technique to measure the in-plane thermal conductivity of suspended 2D films. In this method, the laser of the Raman system is used as a heat source to determine the local temperature of the sample.
Advanced Materials 31 (2019) 1903039
Cell Matter 2 (2020) 1-9
7.4 - Fabricating low cost and high quality of TRGO(Thermally Reduced Graphene Oxide) flakes and suspension
The RGO(Reduced graphene oxide) flakes, the similar structure of graphene flakes, were utilized in lots of application such as polymer composites, bio-application and conductive ink. Nowadays, RGO flakes were normally produced using chemical exfoliation method (oxidation-reduction method) based on graphite. However, RGO flakes derived by chemical exfoliation method have lots of impurities(oxygen, sulfur, etc.) and less quality of mechanical, thermal, electrical properties. We developed thermally reduction method which can fabricate TRGO(Thermally reduced graphene oxide) flakes derived by bio-polymer materials. Based on this methods, we are planning to make high dispersion and quality of TRGO suspension.
7.5 - Thermal interface materials (TIMs) using TrGO
The microgap between the mating faces of heat-generating electronic components and heat sink is filled with air, resulting in very low thermal conductivity and high thermal interface resistance. Efficient heat dissipation is crucial importance for high-power and high-frequency devices to avoid working under overheating conditions which are harmful to device service life and reliability. To solve this problem, thermal interface materials (TIMs) are commonly applied to fill these microgaps. However, conventional TIM's performance have poor performance in the ability required by increasing integration density and power consumption. Therefore, our group is studying application to TIMs with eco-friendly and high thermal conductivity using rGO and shellac.
7.6 - Thermosyphon with high efficiency even at low temperatures
Thermosyphon is an equipment for exchanging heat with phase change of working fluid in sealed pipes. Thermosyphon use evaporation, condensation, and latent heat of working fluid. It has high heat exchange efficiency of 40 ~ 100 kW/mK. It is widely used in solar power generation, re-boiling systems, and electronic devices as it operates without external power. Our group use TrGO nanofluids to study thermosyphon with high efficiency from low temperature to high temperature.
7.7 - Several structures making with cellulose to applicate on electric devices
Cellulose is abundant material in nature, eco-friendly. And when use the nano-sized cellulose, it can help to make the composite strong, make it good mechanical properties. Furthermore, cellulose can be built as several strong structures. It can be transparent film, gel, porous 3D structure, and sponge. To apply on many kinds of electric devices flexible, transparent, and thin structure are needed. Porosity structure or making the dense conductive way help to increase the ability of them.
For example: EMI S (Electromagnetic interference shielding)
Many electric devices are used around, and each of them emit the EMW (electromagnetic wave) which can harmful to people and interrupt the connection among other devices. EMI S is for protecting the people from the EMW. EMW can be blocked with EMI shielding by EM reflection and EM absorption. People normally used metal material such as copper, aluminum as EMI shieling material. However, due to focus on high conductivity, these materials can make secondary reflection. Graphene is one of the solution because graphene have not only high conductivity than metal but also absorbance. So that, for effective EM shielding, we aim to make graphene-polymer composites which have lots of advantage such as high absorbing rate, high reflection rate, flexible material and so on.
Others: super capacitor, humidity sensor, gas sensor, PCM (phase change materials)
7.8 - Micro/nano fiber Applications
The micro/nano fibers represent a relevant class of materials with a vast possibility of applications due to their unique properties, such as large specific area, selective permeability, surface adsorption properties and tailorable surface functionalization. The micro/nanofibers can applicated in medical consumables, aerospace industry, transistors, textiles, air and water filter, sensor, wound dressings, drug delivery systems, energy storage.
Solution Blow Spinning(SBS) technique is one of the simplest method to make micro/nano fibers. In our lab, we aim to produce micro/nanofiber based composite material to adopt in variety area with SBS technique.
Thread 6 – Antibacterial property of TrGO and metallic substance
In areas where hygienic management is essential, such as the medical field and the restaurant business, tools are always made and developed with materials that have antibacterial effects. However, after going through a period of popularity of Covid19, we learned a lesson about the need to use materials that have antibacterial effects in real life. The research was conducted in the belief that it would be possible to cope with the upcoming pandemic virus if it was easily manufactured and supplied not only to certain locations such as elevator switches and door handles but also to many other places.
Using E. coli, we are studying the characteristics of antibacterial actions that do not grow well on the surface of certain substances. In particular, it is well known that rGO has an excellent effect on antibacterial activity. We are doing research to determine the cause of rGO by dividing the effect of these antibacterial actions into two categories: physical and chemical. In addition, research is being conducted to find optimized conditions for antibacterial action by focusing on the material properties of rGO.
Thread 5 - Peltier module-based Cooling device or Heat system design
A study on the development of device and heat system that satisfies the unmet needs that were not previously present. Based mainly on Peltier, our group is designing a device which can precisely control the temperature. We also study how to improve energy efficiency with existing methods of using the Peltier.
Now we are designing Peltier refrigerator which can be improved its COP and design the Biological Experimental Setup.
Thread 4 – Electricity Conducting Soft Matter
Charge carrier mobility strongly affects the performance of many electronic devices. Analogous to the mean-free-path of charge carriers in crystalline inorganic materials, the degree of carrier localization, often quantified by carrier localization length, determines charge carrier mobility in organic semiconductors. In contrast to previous models, in which carrier localization length was assumed to be a certain small constant, we developed a theoretical model that can quantitatively determine carrier localization length from ordinary data such as Seebeck coefficient and electrical conductivity. Based on this model, we aim to develop an experimental methodology to determine carrier localization length in a relatively easy manner.
Thread 3 – Heat-to-Electricity Organic Generator
Gun-Ho Kim et al., Nature Materials (2013)
More than half of total energy produced during 2015 in the USA was rejected directly to waste heat. Traditional heat engines such as turbine and combustion engine have practical difficulties in utilizing such abundant waste heat as they need a high temperature & high pressure heat source to operate. Solid-state heat engines based on thermoelectric technology can directly convert heat to electricity, and therefore can operate even by few Kelvin difference in temperature between heat source and sink. Current thermoelectric solid-state heat engines are limited to niche applications (e.g., generator in a spacecraft), since their base elements are not only rare in the earth crust (e.g., Bi, Te) but also often toxic and brittle. Organic materials are made of earth abundant elements (e.g., C, H, O), and have superior manufacturability, scalability, and flexibility all of which are suitable to harvest waste heat over large areas. Efficient organic thermoelectric materials will allow inexpensive & paintable solid-state heat engine, and move thermoelectric technologies from current niche applications to the main stream, where they may become a widespread means for waste heat recovery or refrigeration. We aim to build fundamental understandings of charge and heat carrier transports in organic materials, and develop high-performance & low-cost solid-state organic heat engine.
Thread 2 – Heat Conducting Plastics
Gun-Ho Kim et al., Nature Materials (2015)
Despite their low thermal conductivity (~0.2 W/m-K), the low cost, low weight, desirable mechanical properties and superior manufacturability of polymers make them widely used even in products that need to dissipate heat efficiently. For example, the annual market size of plastic LED heatsink was $500 million USD in 2015 and is expected to reach $2 billion USD in 2020 (link). Blending polymers with high thermal conductivity fillers (e.g., alumina particles) has typically been used in industry, while alignment or crystallization of polymer chains was shown to produce high values of thermal conductivity at small nano-scales. In contrast to previous approaches, we aim to develop strategies of enhancing the intrinsic thermal conductivity of bulk amorphous polymers, which do not require exotic fabrication processes. For example, we showed that holding two chains with strong intermolecular interactions produced extended chain conformation and a continuous thermal network, resulting in a high thermal conductivity in amorphous polymer blends, 1.5 W/m-K.
Thread 1 – Super-fast, high-resolution, high-power cooling instruments
Our group develops novel cooling devices with a high spatial resolution (100 µm), controllable high ramping rate (up to -10˚C/sec), and high cooling power. The combination of these three characteristics (high resolution, high ramping rate, high power) provides unique opportunities to various fields. For example; life scientists can selectively cool a local set of cells to study in-vivo regional thermotaxis responses; doctors can rapidly anesthetize nerves without using chemical drugs; and chemists can rapidly synthesize materials with unprecedented precision. Our cooling device is analogous to Laser except the fact that it cools rather than heats.