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Preconcentration of lipid vesicles using concentration polarization in a microfluidic chip
Lee, S.J.,Rhee, H.,Jeon, T.J.,Kim, D. Elsevier Sequoia 2016 Sensors and actuators. B Chemical Vol.229 No.-
This paper presents the first lipid vesicle preconcentrator using concentration polarization in a microfluidic chip. Concentration polarization is a well-known electrokinetic phenomenon, occurring near a micro/nanochannel interface. The preconcentrator is composed of a straight microchannel and a nanoporous membrane (Nafion strip) in it, which serves as a preconcentrating zone. We visualized the concentrated lipid vesicles near the Nafion strip and characterized the concentrating performance for different applied voltages. The maximum performance is the concentration ratio of 160 with 100V in 10min. This performance is at least comparable with the previous work and we believe that it has the advantages of lab-on-a-chip system compatibility and a relatively easy fabrication. Our concentration polarization platform on a PDMS chip is versatile so that the same device can be applied to other biomolecule preconcentration.
Ngoc-Viet Nguyen,Jian-Sheng Wu,Chun-Ping Jen 한국바이오칩학회 2018 BioChip Journal Vol.12 No.4
This paper investigated the effects of ionic strength in the medium on a preconcentrator for a protein sample with low concentration. The preconcentration chip was designed and fabricated using a polydimethylsiloxane replica through standard lithophotography. A glass substrate is silanized prior to functionalizing the nanoparticles for self-assembly at a designed region. Due to the overlap of electrical double layers in a nanofluidic channel, a concentration polarization effect can be achieved using an electric field. A nonlinear electrokinetic flow is induced, resulting in the fast accumulation of proteins in front of the induced ionic depletion zone, so called exclusion-enrichment effect. Thus, the protein sample can be driven by electroosmotic flow and accumulated at a specific location. The chip is used to collect fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) diluted in phosphate- buffered saline (PBS) buffer solution. Different concentrations of the buffer media were studied herein. Fluorescence intensity images show that the buffer concentration of 4 mM is more appropriate than all the other ones. The sample of FITC-BSA with an initial concentration of 10 μM in the 4 mM PBS solution increases its concentration at the desired region by up to 50 times within 30 min, demonstrating the results in this investigation.
ppb 수준의 가스상 황화합물 분석을 위한 극저온 농축주입장치의 제작과 성능평가
서용수,장기호,이은희,김윤신,이재근 한국냄새환경학회 2009 실내환경 및 냄새 학회지 Vol.8 No.1
Semi-automatic cryogenic-preconcentrator is constructed with time controlling function in preconcentration and desorption stage. GC-FPD and cryogenic-preconcentrator were to analyze gaseous sulfur compounds (hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide) in ppbv level. The objective of this study was to offer reliable methods for sulfur gas analysis in all procedures (keeping, concentration, desorption, and detection). The cryo-concentrator was able to concentrate 4 L gas sample of 40 % relative humidity. The recovery rate of the system was in the range of 92~100 % at 30 seconds of pre-heating time, and method detection limits were shown up 0.16~0.20 ng which is able to quantify 1 ppbv level with 0.5 L gas sample. The storage time of 5 ppbv sample in polyethylene bag led to serious loss (e.g; H₂S: loss of 30% after storage 3 days). It was estimated that the analytical bias was affected more sensitively by storage time after sampling than by cryo-injection procedures in the analysis of hydrogen sulfide and methanethiol.
온도센서를 사용하지 않는 MEMS 마이크로히터 온도제어시스템
Bae, Byung-Hoon,Yeon, Jung-Hoon,Flachsbart Bruce R.,Shannon Mark A. 대한전기학회 2006 전기학회논문지C Vol.55 No.11
In this paper, we present a temperature-controlled system for MEMS electrical resistance heaters without a temperature sensor. To rapidly control the heater temperature, the microheater system developed consists of a power supply, power amplifier, digital ${\underline{P}}roportional-{\underline{I}}ntegral-{\underline{D}}ifferential$ (PID) controller, and a quarter bridge circuit with the microheater and three resistors are nominally balanced. The microheaters are calibrated inside a convection oven to obtain the temperature coefficient with a linear or quadratic fit. A voltage amplifier applies the supply voltage proportional to the control signal from the PID controller. Small changes in heater resistance generate a finite voltage across the quarter bridge circuit, which is fed back to the PID controller to compare with the set-point and to generate the control signal. Two MEMS microheaters are used for evaluating the developed control system - a NiCr serpentine microheater for a preconcentrator and a Nickel microheater for ${\underline{P}}olymerase\;{\underline{C}}hain\;{\underline{R}}eaction$ (PCR) chip.
온도센서를 사용하지 않는 MEMS 마이크로히터 온도제어시스템
裵炳勳(Byunghoon Bae),廉楨勳(Junghoon Yeom),Bruce R. Flachsbart,Mark A. Shannon 대한전기학회 2006 전기학회논문지C Vol.55 No.11
In this paper, we present a temperature-controlled system for MEMS electrical resistance heaters without a temperature sensor. To rapidly control the heater temperature, the microheater system developed consists of a power supply, power amplifier, digital Proportional-Integral-Differential (PID) controller, and a quarter bridge circuit with the microheater and three resistors are nominally balanced. The microheaters are calibrated inside a convection oven to obtain the temperature coefficient with a linear or quadratic fit. A voltage amplifier applies the supply voltage proportional to the control signal from the PID controller. Small changes in heater resistance generate a finite voltage across the quarter bridge circuit, which is fed back to the PID controller to compare with the set-point and to generate the control signal. Two MEMS microheaters are used for evaluating the developed control system - a NiCr serpentine microheater for a preconcentrator and a Nickel microheater for Polymerase Chain Reaction (PCR) chip.
저농도 다종 휘발성유기화합물의 농축 및 분리를 위해 금속유기구조체가 임베딩된 하이브리드 가스 크로마토그래피 컬럼 칩
이영석(Yeongseok Lee),황순호(Sunho Hwang),이준우(Junwoo Lee),임시형(Si-Hyung Lim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
With the reported hazards of volatile organic compounds (VOCs) in the ppb range present indoors, many researchers have been working on platforms based on microelectromechanical systems (MEMS) devices for air quality monitoring. Platforms have three main devices: a micro gas preconcentrator (μ-PC) to convert low concentrations to high concentrations, a micro gas chromatography column (μ-GC) to separate multiple VOCs over time, and a miniaturized detector. However, current platforms are still not commercially viable in terms of size, weight, and price. This study reports on a hybrid GC column chip embedded with metal-organic framework that acts as an adsorbent and stationary phase, enabling the preconcentration and separation of multiple volatile organic compounds at low concentrations. The hybrid performance was verified using benzene, toluene, ethylbenzene, and xylene. The hybrid function is expected to reduce size, weight, and price by replacing the μ-PC and μ-GC of platform with one single hybrid chip.