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Magnetically-focusing biochip structures for high-speed active biosensing with improved selectivity
Yoo, Haneul,Lee, Dong Jun,Kim, Daesan,Park, Juhun,Chen, Xing,Hong, Seunghun IOP 2018 Nanotechnology Vol.29 No.26
<P>We report a magnetically-focusing biochip structure enabling a single layered magnetic trap-and-release cycle for biosensors with an improved detection speed and selectivity. Here, magnetic beads functionalized with specific receptor molecules were utilized to trap target molecules in a solution and transport actively <I>to</I> and <I>away from</I> the sensor surfaces to <I>enhance the detection speed</I> and <I>reduce the non-specific bindings</I>, respectively. Using our method, we demonstrated the high speed detection of IL-13 antigens with the improved detection speed by more than an order of magnitude. Furthermore, the release step in our method was found to reduce the non-specific bindings and improve the selectivity and sensitivity of biosensors. This method is a simple but powerful strategy and should open up various applications such as ultra-fast biosensors for point-of-care services.</P>
Magnetically-refreshable receptor platform structures for reusable nano-biosensor chips
Yoo, Haneul,Lee, Dong Jun,Cho, Dong-guk,Park, Juhun,Nam, Ki Wan,Cho, Young Tak,Park, Jae Yeol,Chen, Xing,Hong, Seunghun IOP 2016 Nanotechnology Vol.27 No.4
<P>We developed a magnetically-refreshable receptor platform structure which can be integrated with quite versatile nano-biosensor structures to build <I>reusable</I> nano-biosensor chips. This structure allows one to easily remove used receptor molecules from a biosensor surface and reuse the biosensor for repeated sensing operations. Using this structure, we demonstrated reusable immunofluorescence biosensors. Significantly, since our method allows one to place receptor molecules very close to a nano-biosensor surface, it can be utilized to build reusable carbon nanotube transistor-based biosensors which require receptor molecules within a Debye length from the sensor surface. Furthermore, we also show that a single sensor chip can be utilized to detect two different target molecules simply by replacing receptor molecules using our method. Since this method does not rely on any chemical reaction to refresh sensor chips, it can be utilized for versatile biosensor structures and virtually-general receptor molecular species.</P>
Jang, Haneul,Yoo, Seonghyeon,Quevedo, Manuel,Choi, Hyunjoo Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.754 No.-
<P><B>Abstract</B></P> <P>In this study, copper/few-layered graphene (Cu/FLG) composite powder is prepared using two different approaches, chemical synthesis and mechanical milling, and the effect of the processing routes on the mechanical and thermal behaviors of hot-pressed pallets is examined. With both processing routes, the strength of the matrix is increased ∼3.90 and ∼2.82 times by grain refinement, and is further increased 1.14 times by incorporating 0.5 vol.% FLG. In addition, for both processing routes, the coefficient of thermal expansion is reduced from ∼17.07 to ∼15.15 (ppm/K) by incorporating 0.5 vol.% of FLG in both composites. Considering its cost-effectiveness, simplicity, and potential for mass-production, the mechanical process demonstrates the ability to produce Cu/FLG composites with a high mechanical and thermal performance that is comparable to solution-based chemical synthesis routes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Copper/few-layered graphene (FLG) composite is prepared by two methods of chemical synthesis and mechanical milling. </LI> <LI> The effect of processing routes on the mechanical and thermal behaviors of composites is examined. </LI> <LI> FLG is found to be effective to increase mechanical and thermal properties of composites regardless of processing routes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Three-dimensional, transient, nonisothermal model of all-vanadium redox flow batteries
Oh, Kyeongmin,Yoo, Haneul,Ko, Johan,Won, Seongyeon,Ju, Hyunchul Elsevier 2015 ENERGY Vol.81 No.-
<P><B>Abstract</B></P> <P>A three-dimensional (3-D), transient, nonisothermal model of all-vanadium redox flow batteries (VRFBs) is developed by rigorously accounting for the electrochemical reactions of four types of vanadium ions (V<SUP>2+</SUP>, V<SUP>3+</SUP>, VO<SUP>2+</SUP>, and VO 2 + ) and the resulting mass and heat transport processes. Particular emphasis is placed on analyzing various heat generation mechanisms, including irreversible and reversible heat generation due to vanadium redox reactions and joule heating arising from the solid electrode and electrolyte ionic resistances. The 3-D model is validated against voltage evolution curves measured under charging and discharging processes. The model predictions compare well with the experimental data over a wide range of state of charge (SOCs), and further reveal key electrochemical and transport phenomena inside VRFBs through multidimensional contours of solid electrode/electrolyte potentials, species concentrations, and temperatures. This full 3-D comprehensive VRFB model can be applied to realistic multicell stacks to determine the optimal design and operating conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrochemical-thermal model for vanadium redox flow batteries is developed. </LI> <LI> The model was well validated against experimental data. </LI> <LI> Detailed distributions at various state of charges are shown. </LI> <LI> Heat is more generated near the outlet of negative electrode. </LI> </UL> </P>
Modeling and simulations of fuel cell systems for combined heat and power generation
Kang, Kyungmun,Yoo, Haneul,Han, Donghee,Jo, Ahrae,Lee, Junhee,Ju, Hyunchul Pergamon Press 2016 International journal of hydrogen energy Vol.41 No.19
<P><B>Abstract</B></P> <P>Combined heat and power (CHP) fuel cell systems have been under development for the past several decades to enable distributed power generation. These fuel cell systems consist of several subsystems, such as a fuel cell stack, a fuel processing system, heat exchangers, and a heat recovery system. Optimal integration of these subsystems is critical to develop highly efficient, cost effective fuel cell systems for CHP generation. In this paper, we describe the system modeling of a 20 kW fuel cell system, in which a PEM fuel cell stack is connected with fuel processors, i.e., a steam reformer with water gas shift and preferential oxidation reactors. The model is implemented within a commercial flow-sheet simulator, ASPEN HYSYS. We also analyze the effects of key operating parameters on the electrical and thermal efficiency of the 20 kW power systems. The simulation results indicate that the fuel delivery rate and air-fuel ratio supplied into the burner are major control factors to achieve a net electrical power of 20 kW and an acceptable CO concentration level (<10 ppm).</P> <P><B>Highlights</B></P> <P> <UL> <LI> The fuel-cell-based CHP system is modeled and simulated. </LI> <LI> The use of high y values leads to insufficient hydrogen yield. </LI> <LI> The CO fraction is maintained at a low concentration due to the high level y values. </LI> <LI> The heat flux from the burner is sensitive to the level of AFR. </LI> </UL> </P>
“Bio-switch Chip” Based on Nanostructured Conducting Polymer and Entrapped Enzyme
Kim, Daesan,Yoo, Haneul,Park, Jae Yeol,Hong, Seunghun American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.34
<P>We report a switchable biochip strategy where enzymes were entrapped in conducting polymer layers and; the enzymatic reaction of the entrapped enzymes was controlled in real-time via electrical stimuli on the polymer layers. This device is named here as a 'bio-switch chip' (BSC). We fabricated BSC structures using polypyrrole (Ppy) with entrapped glucose oxidase (GOx) and demonstrated the switching of glucose oxidation reaction in real-time. We found that the introduction of a negative bias voltage on the BSC structure resulted in the enhanced glucose oxidation reaction by more than 20 times than that without a bias voltage. Moreover, because the BSC structures could be fabricated on specific regions, we could control the enzymatic specific regions. In view of the fact that enzymes enable very useful and versatile biochemical reactions, the ability to control the enzymatic reactions via conventional electrical signals could open up various applications in the area, of biochips and other biochemical industries.</P>