Do Hwan Kim

Bio: Do Hwan Kim is an academic researcher from Hanyang University. The author has contributed to research in topics: Thin-film transistor & Organic semiconductor. The author has an hindex of 47, co-authored 176 publications receiving 11980 citations. Previous affiliations of Do Hwan Kim include Samsung & Brigham Young University–Idaho.

Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring

Abstract: Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa(-1), a fast response time of 15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

Full-colour quantum dot displays fabricated by transfer printing

Abstract: Scientists describe a size-selective quantum dot patterning technique that involves kinetically controlling the nanotransfer process without a solvent. The resulting printed quantum dot films exhibit excellent morphology and a well-ordered quantum dot structure. This technique allows fabrication of a 4-inch (or larger) thin-film transistor display with high colour purity and extremely high resolution.

Tuning charge transport in solution-sheared organic semiconductors using lattice strain

Abstract: A solution-processing method known as solution shearing is used to introduce lattice strain to organic semiconductors, thus improving charge carrier mobility. Solution-processed organic semiconductors show great promise for application in cheap and flexible electronic devices, but generally suffer from greatly reduced electronic performance — most notably charge-carrier mobilities — compared with their inorganic counterparts. Borrowing a trick from the inorganic semiconductor community, Giri et al. show how the introduction of strain into an organic semiconductor, through a simple solution-processing technique, modifies the molecular packing within the material and hence its electronic performance. For one material studied, the preparation of a strained structure is shown to more than double the charge-carrier mobility. Circuits based on organic semiconductors are being actively explored for flexible, transparent and low-cost electronic applications1,2,3,4,5. But to realize such applications, the charge carrier mobilities of solution-processed organic semiconductors must be improved. For inorganic semiconductors, a general method of increasing charge carrier mobility is to introduce strain within the crystal lattice6. Here we describe a solution-processing technique for organic semiconductors in which lattice strain is used to increase charge carrier mobilities by introducing greater electron orbital overlap between the component molecules. For organic semiconductors, the spacing between cofacially stacked, conjugated backbones (the π–π stacking distance) greatly influences electron orbital overlap and therefore mobility7. Using our method to incrementally introduce lattice strain, we alter the π–π stacking distance of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) from 3.33 A to 3.08 A. We believe that 3.08 A is the shortest π–π stacking distance that has been achieved in an organic semiconductor crystal lattice (although a π–π distance of 3.04 A has been achieved through intramolecular bonding8,9,10). The positive charge carrier (hole) mobility in TIPS-pentacene transistors increased from 0.8 cm2 V−1 s−1 for unstrained films to a high mobility of 4.6 cm2 V−1 s−1 for a strained film. Using solution processing to modify molecular packing through lattice strain should aid the development of high-performance, low-cost organic semiconducting devices.

Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains

Abstract: Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach—termed fluid-enhanced crystal engineering (FLUENCE)—that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm2 V−1 s−1 and 11 cm2 V−1 s−1. FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics. Solution printing of organic semiconductors could in principle be scaled to industrial needs, yet attaining aligned single-crystals directly with this method has been challenging. By using a micropillar-patterned printing blade designed to enhance the control of crystal nucleation and growth, thin films of macroscopic, highly aligned single crystals of organic semiconductors can now be fabricated.

Siloxane-terminated solubilizing side chains: bringing conjugated polymer backbones closer and boosting hole mobilities in thin-film transistors.

Abstract: We introduce a novel siloxane-terminated solubilizing group and demonstrate its effectiveness as a side chain in an isoindigo-based conjugated polymer. An average hole mobility of 2.00 cm2 V–1 s–1 (with a maximum mobility of 2.48 cm2 V–1 s–1), was obtained from solution-processed thin-film transistors, one of the highest mobilities reported to date. In contrast, the reference polymer with a branched alkyl side chain gave an average hole mobility of 0.30 cm2 V–1 s–1 and a maximum mobility of 0.57 cm2 V–1 s–1. This is largely explained by the polymer packing: our new polymer exhibited a π–π stacking distance of 3.58 A, while the reference polymer showed a distance of 3.76 A.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

Abstract: Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Graphene-Based Materials: Synthesis, Characterization, Properties, and Applications

Abstract: Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.