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Noninvasive Brain Stimulation Using a Modulated Microwave Signal
Taeyoon Seo,Seongwoog Oh,Dahee Jung,Yeowool Huh,Jeiwon Cho,Youngwoo Kwon 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.1
We propose a microwave signal generation system for brain stimulation. The existing brain stimulation system uses a signal of several tens of kHz, and the magnetic field distribution is wide. Microwave is used to locally limit the distribution of the electromagnetic field and to change the action potential of the cell with less power. The switch modulates the microwave signal to obtain a pulse envelope. The action potential of the cell can be controlled to the excitation/inhibition state by adjusting the repetition frequency. These results are confirmed by measuring the cell potential of the mouse brain.
Seo, Jungmok,Lee, Soonil,Han, Heetak,Jung, Hwae Bong,Hong, Juree,Song, Giyoung,Cho, Suk Man,Park, Cheolmin,Lee, Wooyoung,Lee, Taeyoon WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.30
<P><B>A gas‐driven ultrafast adhesion switching</B> of water droplets on palladium‐coated Si nanowire arrays is demonstrated. By regulating the gas‐ambient between the atmosphere and H<SUB>2</SUB>, the super‐hydrophobic adhesion is repeatedly switched between water‐repellent and water‐adhesive. The capability of modulating the super‐hydrophobic adhesion on a super‐hydrophobic surface with a non‐contact mode could be applicable to novel functional lab‐on‐a‐chip platforms.</P>
Guided Transport of WaterDroplets on Superhydrophobic–Hydrophilic Patterned Si Nanowires
Seo, Jungmok,Lee, Soonil,Lee, Jaehong,Lee, Taeyoon AmericanChemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.12
<P>We present a facile method to fabricate hydrophilic patterns in superhydrophobic Si nanowire (NW) arrays for guiding water droplets. The superhydrophobic Si NW arrays were obtained by simple dip-coating of dodecyltrichlorosilane (DTS). The water contact angles (CAs) of DTS-coated Si NW arrays drastically increased and saturated at the superhydrophobic regime (water CA >= 150 degrees) as the lengths of NW's increased. The demonstrated superhydrophobic surfaces show an extreme water repellent property and small CA hysteresis of less than 7 degrees, which enable the water droplets to easily roll off. The wettability of the DTS-coated Si NW arrays can be converted from superhydrophobic to hydrophilic via UV-enhanced photodecomposition of the DTS, and such wettability conversion was reproducible on the same surfaces by repeating the DTS coating and photodecomposition processes. The resulting water guiding tracks were successfully demonstrated via selective patterning of the hydrophilic region on superhydrophobic Si NW arrays, which could enable water droplets to move along defined trajectories.</P>
계층적 분류 및 회귀 그래프 신경망을 이용한 최적의 트러스 구조 예측 방법
임태윤(Taeyoon Lim),이승훈(Seunghun Lee),서민식(Minsik Seo),민승재(Seungjae Min) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
This paper proposes a graph neural network-based hierarchical classification and regression model to predict the optimal ground structure layout. A ground structure consists of a set of interconnected bars similar to a graph structure. The number of bars and joints depends on the size and configuration of the target design domains. Conventional neural networks, such as MLP and CNN, cannot handle such variable-dimensional data. Therefore, we adopted a graph neural network using the similarity between ground structure and graph. Only a few of the potential bar candidates remained after ground structure optimization converged. It causes the highly imbalanced distribution of bar areas, which is difficult to predict. Therefore, we construct the model to process a binary classification task to classify the presence or absence of remaining bars among potential bar candidates, and then sequentially process a regression task to predict the detailed value of the cross-sectional areas. To validate the proposed model, three types of ground structure optimization problems were defined: cantilever, simply supported, and L-shape beams. The model was evaluated with three evaluation metrics: classification, regression, and optimality. As a result, it predicts the presence or absence of the optimal ground structure with more than 95% accuracy and predicts the cross-sectional areas of the remaining bars with greater than 95% accuracy.
Kim, Dayeong,Seo, Jungmok,Shin, Sera,Lee, Soonil,Lee, Kilsoo,Cho, Hyeonjin,Shim, Wooyoung,Lee, Han-Bo-Ram,Lee, Taeyoon American Chemical Society 2015 Chemistry of materials Vol.27 No.14
<P>Adhesion control of various liquid droplets on a liquid-repellent surface is a fundamental technique in novel open channel microfluidic systems. Herein, we demonstrate reversible liquid droplet adhesion switching on superamphiphobic Pd-decorated Ag dendrites (Pd/Ag dendrites). Although adhesion between liquids and the superamphiphobic surfaces was extremely low under ambient air, high adhesion was instantly achieved by exposure of the dendrites to 8% hydrogen gas. Transition from low to high adhesion and the reverse case were successfully repeated more than 10 times by switching from atmospheric ambient air to 8% hydrogen gas. This is the first technique that allows real-time reversible adhesion change with various liquid droplets to a surface using gas-induced structural changes and can potentially be used to realize various functions for droplet-based microfluidics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-14/acs.chemmater.5b01038/production/images/medium/cm-2015-01038d_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b01038'>ACS Electronic Supporting Info</A></P>
Lee, Jaehong,Seo, Jungmok,Kim, Dayeong,Shin, Sera,Lee, Sanggeun,Mahata, Chandreswar,Lee, Hyo-Sung,Min, Byung-Wook,Lee, Taeyoon American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.12
<P>The fabrication of well-ordered metal nanoparticle structures onto a desired substrate can be effectively applied to several applications. In this work, well-ordered Ag nanoparticle line arrays were printed on the desired substrate without the use of glue materials. The success of the method relies on the assembly of Ag nanoparticles on the anisotropic buckling templates and a special transfer process where a small amount of water rather than glue materials is employed. The anisotropic buckling templates can be made to have various wavelengths by changing the degree of prestrain in the fabrication step. Ag nanoparticles assembled in the trough of the templates via dip coating were successfully transferred to a flat substrate which has hydrophilic surface due to capillary forces of water. The widths of the fabricated Ag nanoparticle line arrays were modulated according to the wavelengths of the templates. As a potential application, the Ag nanoparticle line arrays were used as SERS substrates for various probing molecules, and an excellent surface-enhanced Raman spectroscopy (SERS) performance was achieved with a detection limit of 10<SUP>–12</SUP> M for Rhodamine 6G.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-12/am5000382/production/images/medium/am-2014-000382_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5000382'>ACS Electronic Supporting Info</A></P>
Magnetic Nanoparticle-Assisted Microwave Hyperthermia Using an Active Integrated Heat Applicator
Kim, Kihyun,Seo, Taeyoon,Sim, Kyunjong,Kwon, Youngwoo IEEE 2016 IEEE transactions on microwave theory and techniqu Vol.64 No.7
<P>Magnetic nanoparticle (MNP)-assisted microwave hyperthermia using an active integrated heat applicator is presented in this paper. The effect of MNPs on microwave hyperthermia has been analyzed by coupled electromagnetic-thermal analysis considering the frequency-and temperature-dependent properties of biological tissues. For enhanced heating efficiency and material sensitivity, the optimum microwave frequency for hyperthermia has been identified using the presented analysis and confirmed with experiments. In order to demonstrate MNP-assisted hyperthermia, an active integrated applicator is developed. A microwave signal generation module, which has a voltage-controlled oscillator and a power amplifier, has been fabricated in monolithic microwave integrated circuits and integrated on the microwave heat applicator based on a spiral radiator. A dual-channel logarithmic power detector and a directional coupler have been also employed to monitor power levels during hyperthermia, which allows understanding of the heating mechanism. In vitro heating experiments on phantoms, pork muscles, and tumors with and without MNPs show a large difference in temperature rises, which demonstrates the effectiveness of MNPs for low-power and material-specific hyperthermia. Combined with MNP targeting on the cancer cells, MNP-assisted microwave hyperthermia can be a promising method for a low-power and cancer-specific treatment with minimal collateral damage.</P>