Finger-actuated microfluidic device for the blood cross-matching test

Park, Juhwan,Park, Je-Kyun The Royal Society of Chemistry 2018 Lab on a chip Vol.18 No.8

<P>A blood cross-matching test should be carried out to prevent a hemolytic transfusion reaction as the final verification step. To simplify complicated procedures of a conventional blood cross-matching test requiring bulky systems and skilled people, we present a finger-actuated microfluidic device for the blood cross-matching test. Although finger actuation is a simple action that anyone can easily accomplish, there would be a variation in the individual finger actuation that may induce the user-dependent errors of the device. Therefore, the working principle of the finger-actuated microfluidic device is newly designed to reduce the user-dependent errors by indirectly controlling the pressure of fluidic channels. The constant volume was repeatedly dispensed by pushing and releasing a pressure chamber regardless of the different pushed depths of the pressure chamber, the pushing time interval, and the end-users. The dispensed volume was linearly increased according to the number of pushing times applied to the pressure chamber and determined by adjusting the diameter of an actuation chamber. In addition, multiple fluids can be dispensed with a desirable ratio by pushing and releasing the pressure chamber. Finally, a finger-actuated microfluidic device for the blood cross-matching test was developed, which can simultaneously actuate four fluidic channels. After loading 50 μL of whole blood samples from a donor and a recipient into two inlets of the device, the blood plasma from each individual was separated through the two plasma separation membranes. The blood cross-matching test results can be achieved by cross-reacting the donor's blood plasma with the recipient's whole blood as well as the donor's whole blood with the recipient's blood plasma by pushing and releasing only a single pressure chamber within 10 min.</P>

Pressed Paper-Based Dipstick for Detection of Foodborne Pathogens with Multistep Reactions

Park, Juhwan,Shin, Joong Ho,Park, Je-Kyun American Chemical Society 2016 ANALYTICAL CHEMISTRY - Vol.88 No.7

<P>This paper presents a pressed paper-based dipstick that enables detection of foodborne pathogens with multistep reactions by exploiting the delayed fluid flow and channel partition formation on nitrocellulose (NC) membrane. Fluid behaviors are easily modified by controlling the amount of pressure and the position of pressed region on the NC membrane. Detection region of the dipstick is optimized by controlling flow rate and delayed time based on Darcy's law. All the reagents required for assay are dried on the NC membrane and they are sequentially rehydrated at the prepartitioned regions when the device is dipped into sample solution. In this manner, multistep reactions can be facilitated by one-step dipping of the dipstick into the sample solution. As a proof of concept, we performed detection of two fatal foodborne pathogens (e.g., Escherichia coli O157:H7 and Salmonella typhimurium) with signal enhancement. In addition, we expanded the utilization of channel partitions by developing a pressed paper-based dipstick into dual detection format.</P>

Surface Defects States on a SiO2/Si Observed by REELS

Juhwan Kim,Beomsik Kim,Soojeong Park,Chanae Park,Yus Rama Denny,Soonjoo Seo,Hong Chol Chae,Hee Jae Kang 한국진공학회 2013 한국진공학회 학술발표회초록집 Vol.2013 No.2

Finger-Actuated Microfluidic Display for Smart Blood Typing

Park, Juhwan,Park, Je-Kyun American Chemical Society 2019 ANALYTICAL CHEMISTRY - Vol.91 No.18

<P>Accurate blood typing is required before transfusion. A number of methods have been developed to improve blood typing, but these are not user-friendly. Here, we have developed a microfluidic smart blood-typing device operated by finger actuation. The blood-typing result is displayed by means of microfluidic channels with the letter and the symbol of the corresponding blood type. To facilitate the mixing of blood and reagents, the two sample inlets are connected to a single actuation chamber. According to the agglutination aspect in the mixture, the fluids are directed to both the microslit filter channels and bypass channels, or only to the bypass channels. The dimension of the microslit filter being clogged by the red blood cell aggregates was optimized to achieve reliable blood-typing results. The flow rate ratio between two channels in the absence of agglutination was subjected to numerical analysis. With this device, blood typing was successfully performed by seven button pushes using less than 10 μL of blood within 30 s.</P> [FIG OMISSION]</BR>

Functional Components of Red Cabbage Seed Sprouts during Germination and Postharvest Storage as Affected by Irradiation of Seeds

Juhwan Park,Gui Ran Kim,Catherine K. Rico,Yu Ri Kim,Bumsoo Han,Hyun-Ku Kim,Joong-Ho Kwon 한국식품영양과학회 2011 한국식품영양과학회 학술대회발표집 Vol.2011 No.10

Tunable wide blue photoluminescence with europium decorated graphene

Park, Byeongho,Kim, Sun Jun,Lim, Juhwan,Some, Surajit,Park, Ji-eun,Kim, Sung-jin,Kim, Chulki,Lee, Taik Jin,Jun, Seong Chan The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.16

<▼1><P>Europium decorated graphene provides photoluminescence feature changes with an enhancement of blue emission located at 458 nm after thermal reduction.</P></▼1><▼2><P>The current paper describes europium decorated graphene (EuG) which provides high and wide blue emission at 400 nm and 458 nm. The chemical and structural properties of the products are characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy. Fourier transform infrared (FT-IR) and UV–Vis spectrometery are employed to analyze the optical properties. The photoluminescence features are investigated using the excitation/emission spectra and fluorescence microscopy images. The photoluminescence intensity of EuG with the bright fluorescent nature of europium is higher than that of reduced graphene oxide. The transition of trivalent europium (Eu<SUP>3+</SUP>) that leads to the radiation of light with a 590 nm wavelength can be turned into a 4f–4f transition of divalent (Eu<SUP>2+</SUP>) europium upon heating in the presence of the graphene sheet, which assists the reduction of the europium ion. The enhancement of the blue emission at 458 nm with quenching in the red at 590 nm is affected by the modification of properties (by → via) the europium–graphene composite concentration and external thermal energy. The result suggests a new possibility for the fluorescence characteristics of the lanthanide–graphene nanocomposite that can be applied to the display, optoelectronic devices, and bio-imaging fields. The temperature-tunable photoluminescence characteristics can be used as a non-contact thermal sensor.</P></▼2>

Electronic, Optical and Electrical Properties of Nickel Oxide Thin Films Grown by RF Magnetron Sputtering

Park, Chanae,Kim, Juhwan,Lee, Kangil,Oh, Suhk Kun,Kang, Hee Jae,Park, Nam Seok The Korean Vacuum Society 2015 Applied Science and Convergence Technology Vol.24 No.3

Nickel oxide (NiO) thin films were grown on soda-lime glass substrates by RF magnetron sputtering method at room temperature (RT), and they were post-annealed at the temperatures of $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ and $400^{\circ}C$ for 30 minutes in vacuum. The electronic structure, optical and electrical properties of NiO thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy spectroscopy (REELS), UV-spectrometer and Hall Effect measurements, respectively. XPS results showed that the NiO thin films grown at RT and post annealed at temperatures below $300^{\circ}C$ had the NiO phase, but, at $400^{\circ}C$, the nickel metal phase became dominant. The band gaps of NiO thin films post annealed at temperatures below $300^{\circ}C$ were about 3.7 eV, but that at $400^{\circ}C$ should not be measured clearly because of the dominance of Ni metal phase. The NiO thin films post-annealed at temperatures below $300^{\circ}C$ showed p-type conductivity with low electrical resistivity and high optical transmittance of 80% in the visible light region, but that post-annealed at $400^{\circ}C$ showed n-type semiconductor properties, and the average transmittance in the visible light region was less than 42%. Our results demonstrate that the post-annealing plays a crucial role in enhancing the electrical and optical properties of NiO thin films.

Pressed region integrated 3D paper-based microfluidic device that enables vertical flow multistep assays for the detection of C-reactive protein based on programmed reagent loading

Park, Juhwan,Park, Je-Kyun Elsevier 2017 Sensors and actuators. B Chemical Vol.246 No.-

<P><B>Abstract</B></P> <P>Although vertical flow assays (VFAs) have a number of advantages compared to lateral flow assays (LFAs) such as a short analysis time, no line interference, and no Hook effect, VFAs are not preferred as LFAs because of their complicated operation principle. In this study, we demonstrated VFAs with multistep reactions for the detection of C-reactive protein (CRP) based on the programmed reagent loading in a pressed region integrated 3D paper-based microfluidic device. The flow order of all reagents in a 3D paper-based microfluidic device was programmed based on the delayed flow caused by the pressed region as well as the geometry modification of the paper channel. After simultaneous loading of all the reagents required for assays, they are sequentially loaded into the analysis region with a programmed sequence. As a proof of concept, a high-sensitivity CRP (hs-CRP) detection with signal amplification was performed to predict the riskiness of cardiovascular disease within 15min. The detection limit was improved from 0.01 to 0.005μg/mL via a maximum 3.47-fold signal amplification. Additionally, the upper limit of hs-CRP detection increased to 5μg/mL without Hook effect. Finally, we successfully detected hs-CRP in a clinically relevant range (0.005–5μg/mL), while LFAs cannot cover due to the Hook effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Vertical flow assays (VFAs) with multistep reactions were performed in a 3D paper-based microfluidic device. </LI> <LI> Programmed loading of all reagents into the analysis region was achieved by utilizing a delayed flow in a pressed paper. </LI> <LI> Upper limit and sensitivity of the assays were increased without Hook effect compared to lateral flow assays (LFAs). </LI> <LI> C-Reactive protein was detected for the prediction of cardiovascular disease in a clinical range (0.005–5μg/mL). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

보강토 옹벽용 지오그리드의 현장 내시공성 및 강도 감소계수 평가에 관한 연구

박주환(Park Juhwan),천병식(Chun Byungsik) 한국지반환경공학회 2012 한국지반환경공학회논문집 Vol.13 No.7

최근 국내에서 기존 RC옹벽보다 시공실적이 증가하고 있는 보강토 옹벽은 보강자재, 시공방법, 전면블럭의 형태에 따라 다양하지만 공법에 대한 안전성이 충분히 검증되지 않아 설계와 시공관리에 어려움이 많으며, 보강토 옹벽에 사용되는 보강재 등은 제조사별로 규격과 형상이 다양하고 영세한 업체에서 제작하였거나 일부 값이 싼 품질이 낮은 제품이 수입되고 있지만 이를 설계에 적용할 수 있는 적절한 기준이 제시되지 못하고 있는 실정이다. 이에 본 연구는 보강토 옹벽의 보강재인 옹벽용 그리드에 대하여 현장 내시공성 시험을 통해 다양한 형태의 옹벽용 그리드의 내시공성 감소계수를 제안하고, 국내외 연구결과 분석과 국내 시판되고 있는 제조사별로 제시한 옹벽용 그리드의 물성치를 조사 분석하였다. 결론적으로, 뒤채움재의 입경과 모난 정도의 차이, 입도 분포에 따라 감소계수에 미치는 영향이 크므로 일정규모 이상의 현장에서는 현장내시공성 시험을 거쳐 뒤채움재 별로 차별화된 감소계수를 적용하고, 보강벽체의 활용성에 따라 연성과 강성그리드를 잘 선정하여 적용함으로서 효과적으로 보강토 옹벽의 안전성을 높일 수 있음을 확인하였다. Recently the installation of reinforced earth retaining walls in the domestic construction site has increased, surpassing conventional RC walls. These reinforced walls have various types depending on the reinforcing material, installation method and the form of face panel. However, there are difficulties in design and construction management due to the unproved safety of construction method. In case of reinforcing materials, despite the fact that they come in all different sizes and types produced by small businesses or partially imported with cheap price and low quality, no proper standards for designing the walls have been suggested. In order to apply reinforced retaining wall system to broad cases and design the walls effectively considering site conditions, specific design and construction guidelines for efficient construction management are needed. In conclusion, this study verified that reduction factors can be greatly affected by grain sizes and stiffness of backfill materials and granularity range, therefore in case of relatively large construction site, it is required to redesign the reinforced retaining wall by evaluating site installation resistance test, applying respective reduction factors to each backfill material and select the right geogrid depending on the usage of retaining wall so as to enhance the safety of reinforced earth retaining walls with efficiency.

Electronic, Optical and Electrical Properties of Nickel Oxide Thin Films Grown by RF Magnetron Sputtering

Chanae Park,Juhwan Kim,Kangil Lee,Suhk Kun Oh,Hee Jae Kang,Nam Seok Park 한국진공학회(ASCT) 2015 Applied Science and Convergence Technology Vol.24 No.3

Nickel oxide (NiO) thin films were grown on soda-lime glass substrates by RF magnetron sputtering method at room temperature (RT), and they were post-annealed at the temperatures of 100℃, 200℃, 300℃ and 400℃ for 30 minutes in vacuum. The electronic structure, optical and electrical properties of NiO thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy spectroscopy (REELS), UV-spectrometer and Hall Effect measurements, respectively. XPS results showed that the NiO thin films grown at RT and post annealed at temperatures below 300℃ had the NiO phase, but, at 400℃, the nickel metal phase became dominant. The band gaps of NiO thin films post annealed at temperatures below 300℃ were about 3.7 eV, but that at 400oC should not be measured clearly because of the dominance of Ni metal phase. The NiO thin films post-annealed at temperatures below 300℃ showed p-type conductivity with low electrical resistivity and high optical transmittance of 80% in the visible light region, but that post-annealed at 400℃ showed n-type semiconductor properties, and the average transmittance in the visible light region was less than 42%. Our results demonstrate that the post-annealing plays a crucial role in enhancing the electrical and optical properties of NiO thin films.