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

Thread I – Heat transfer medical device (열전달 기반 의료기기)


Heat transfer in body affects various tissue activities and functions, having broad implications in various medical therapies. Compared with robots (dynamics & control) and artificial bone & tooth (solid mechanics), medical devices that utilize heat transfer as a core mean to produce a certain clinical effect have far less been explored. Our group is developing medical devices that rapidly manipulate body temperature and thereby produce a desired clinical or therapeutic effect at an unprecedented speed and efficiency. 



Thread II – Super-fast, high-resolution, high-power cooling instruments (초고속, 고분해능, 고출력 냉각기)

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. 



Thread III – Heat Conducting Plastics (고열전도도 플라스틱)


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 IV – Heat-to-Electricity Organic Generator (유기발전소자)

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 V – Electricity Conducting Soft Matter (전도성 연성 물질)

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.
Gun-Ho Kim and K. P. Pipe, Physical Review B 86, 085208 (2012).