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1.
We report a new technique for conducting immuno-diagnostics on a microfluidic platform. Rather than handling fluid reagents
against a stationary solid phase, the platform manipulates analyte-coated magnetic beads through stationary plugs of fluid
reagents to detect an antigenic analyte. These isolated but accessible plugs are pre-encapsulated in a microchannel by capillary
force. We call this platform microfluidic inverse phase enzyme-linked immunosorbent assay (μIPELISA). μIPELISA has distinctive
advantages in the family of microfluidic immunoassay. In particular, it avoids pumping and valving fluid reagents during assaying,
thus leading to a lab-on-a-chip format that is free of instrumentation for fluid actuation and control. We use μIPELISA to
detect digoxigenin-labeled DNA segments amplified from E. coli O157:H7 by polymerase chain reaction (PCR), and compare its detection capability with that of microplate ELISA. For 0.259 ng μl−1 of digoxigenin-labeled amplicon, μIPELISA is as responsive as the microplate ELISA. Also, we simultaneously conduct μIPELISA
in two parallel microchannels. 相似文献
2.
Dammika P. Manage Yuen C. Morrissey Alexander J. Stickel Jana Lauzon Alexey Atrazhev Jason P. Acker Linda M. Pilarski 《Microfluidics and nanofluidics》2011,10(3):697-702
Performing medical diagnosis in microfluidic devices could scale down laboratory functions and reduce the cost for accessible
healthcare. The ultimate goal of such devices is to receive a sample of blood, perform genetic amplification (polymerase chain
reaction—PCR) and subsequently analyse the amplified products. DNA amplification is generally performed with DNA purified
from blood, thus requiring on-chip implementation of DNA extraction steps with consequent increases in the complexity and
cost of chip fabrication. Here, we demonstrate the use of unprocessed whole blood as a source of template for genomic or viral
targets (human platelet antigen 1 (HPA1), fibroblast growth factor receptor 2 (FGFR2) and BK virus (BKV)) amplified by PCR on a three-layer microfluidic chip that uses a flexible membrane for pumping and valving.
The method depends upon the use of a modified DNA polymerase (Phusion™). The volume of the whole blood used in microchip PCR
chamber is 30 nl containing less than 1 ng of genomic DNA. For BKV on-chip whole blood PCR, about 3000 copies of BKV DNA were
present in the chamber. The DNA detection method, laser-induced fluorescence, used in this article so far is not quantitative
but rather qualitative providing a yes/no answer. The ability to perform clinical testing using whole blood, thereby eliminating
the need for DNA extraction or sample preparation prior to PCR, will facilitate the development of microfluidic devices for
inexpensive and faster clinical diagnostics. 相似文献
3.
A nucleic acid sensor capable of automated sample and reagent loading, real-time PCR, automated detection, and sample line cleaning was tested. Real-time PCR reactions were performed with Salmonella enterica in autoclaved and spent alfalfa sprout irrigation water. S. enterica boiled cells were detected over a range of approximately 104 to 108 CFU/reaction (rxn). It was possible to generate enough PCR product to visualize a band on a gel at the expected size over approximately five orders of magnitude from 3.2 × 103 to 108 CFU/rxn. Automated detection experiments yielded correct identification of 9/9 positive control reactions over a range of 104 to 108 CFU/rxn, correctly identified a negative control reaction, and a sample of 3.2 × 103 CFU/rxn was incorrectly identified as negative. Primer dimers were not seen in positive or negative control reactions with sprout irrigation water, suggesting that it may be possible to improve the detection limit simply by increasing the number of thermal cycles or by lowering the annealing temperature. The system required no interpretation of real-time PCR data by the operator. The entire process of loading, running the PCR, automated data interpretation, and sample line cleaning was completed in under 2 h and 20 min, significantly faster than it would take to ship a sample and have it tested by an independent laboratory. 相似文献
4.
5.
Evaporation is of great importance when dealing with microfluidic devices with open air/liquid interfaces due to the large
surface-to-volume ratio. For devices utilizing a thermal reaction (TR) reservoir to perform a series of biological and chemical
reactions, excessive heat-induced microfluidic evaporation can quickly lead to reaction reservoir dry out and failure of the
overall device. In this study, we present a simple, novel method to decrease heat-induced fluid evaporation within microfluidic
systems, which is termed as heat-mediated diffusion-limited (HMDL) method. This method does not need complicated thermal isolation
to reduce the interfacial temperature, or external pure water to be added continuously to the TR chamber to compensate for
evaporation loss. The principle of the HMDL method is to make use of the evaporated reaction content to increase the vapor
concentration in the diffusion channel. The experimental results have shown that the relative evaporation loss (V
loss/V
ini) based on the HMDL method is not only dependent on the HMDL and TR region’s temperatures (T
HMDL and T
TR), but also on the HMDL and TR’s channel geometries. Using the U-shaped uniform channel with a diameter of 200 μm, the V
loss/V
ini within 60 min is low to 5% (T
HMDL = 105°C, T
TR = 95°C). The HMDL method can be used to design open microfluidic systems for nucleic acid amplification and analysis such
as isothermal amplification and PCR thermocycling amplification, and a PCR process has been demonstrated by amplifying a 135-bp
fragment from Listeria monocytogenes genomic DNA. 相似文献
6.
This paper develops novel polymer transformers using thermally actuated shape memory polymer (SMP) materials. This paper applies
SMPs with thermally induced shape memory effect to the proposed novel polymer transformers as on-chip microfluidic vacuum
generators. In this type of SMPs, the morphology of the materials changes when the temperature of materials reaches its glass
transition temperature (T
g). The structure of the polymer transformer can be pre-programmed to define its functions, which the structure is reset to
the temporary shape, using shape memory effects. When subjected to heat, the polymer transformer returns to its pre-memory
morphology. The morphological change can produce a vacuum generation function in microfluidic channels. Vacuum pressure is
generated to suck liquids into the microfluidic chip from fluidic inlets and drive liquids in the microchannel due to the
morphological change of the polymer transformer. This study adopts a new smart polymer with high shape memory effects to achieve
fluid movement using an on-chip vacuum generation source. Experimental measurements show that the polymer transformer, which
uses SMP with a T
g of 40°C, can deform 310 μm (recover to the permanent shape from the temporary shape) within 40 s at 65°C. The polymer transformer
with an effective cavity volume of 155 μl achieved negative pressures of −0.98 psi. The maximum negative up to −1.8 psi can
be achieved with an effective cavity volume of 268 μl. A maximum flow rate of 24 μl/min was produced in the microfluidic chip
with a 180 mm long channel using this technique. The response times of the polymer transformers presented here are within
36 s for driving liquids to the end of the detection chamber. The proposed design has the advantages of compact size, ease
of fabrication and integration, ease of actuation, and on-demand negative pressure generation. Thus, this design is suitable
for disposable biochips that need two liquid samples control. The polymer transformer presented in this study is applicable
to numerous disposable microfluidic biochips. 相似文献
7.
8.
Bin Xiao Tao Dong Einar Halvorsen Zhaochu Yang Yulong Zhang Nils Hoivik Dandan Gu Nhut Minh Tran Henrik Jakobsen 《Microsystem Technologies》2011,17(1):115-125
This paper presents the design and fabrication of a micro Pirani gauge using VO
x
as the sensitive material for monitoring the pressure inside a hermetical package for micro bolometer focal plane arrays
(FPAs). The designed Pirani gauge working in heat dissipating mode was intentionally fabricated using standard MEMS processing
which is highly compatible with the FPAs fabrication. The functional layer of the micro Pirani gauge is a VO
x
thin film designed as a 100 × 200 μm pixel, suspended 2 μm above the substrate. By modeling of rarefied gas heat conduction
using the Extended Fourier’s law, finite element analysis is used to investigate the sensitivity of the pressure gauge. Also
the thermal interactions between the micro Pirani gauge and bolometer FPAs are verified. From the fabricated prototype, the
measured device TCR is about −0.8% K−1 and the sensitivity about 1.84 × 10−3 W K−1 mbar−1. 相似文献
9.
Johannes R. Peham Lisa-Maria Recnik Walter Grienauer Michael J. Vellekoop Christa Nöhammer Herbert Wiesinger-Mayr 《Microsystem Technologies》2012,18(3):311-318
This work presents the combination and acceleration of PCR and fluorescent labelling within a disposable microfluidic chip.
The utilised geometry consists of a spiral meander with 40 turns, representing a cyclic-flow PCR system. The used reaction
chemistry includes Cy3-conjugated primers leading to a one-step process accelerated by cyclic-flow PCR. DNA of three different
bacterial samples (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) was processed and successfully amplified and labelled with detection limits down to 102 cells per reaction. The specificity of species identification was comparable to the approach of separate PCR and labelling.
The overall processing time was decreased from 6 to 1.5 h. We showed that a disposable polycarbonate chip, fabricated by injection
moulding is suitable for the significant acceleration of DNA microarray assays. The reaction output led to high-sensitivity
bacterial identification in a short time, which is crucial for an early and targeted therapy against infectious diseases. 相似文献
10.
11.
Cheng-Che Chung I-Fang Cheng Chi-Chang Lin Hsien-Chang Chang 《Microfluidics and nanofluidics》2011,10(2):311-319
We studied an imaging-based technique for the rapid quantification of bio-particles in a dielectrophoretic (DEP) microfluidic
chip. Label-free particles could be successively sorted and trapped in a continuous flow manner under the applied alternating
current (AC) conditions. Both 2 and 3 μm polystyrene beads at a concentration of 1.0 × 107 particles ml−1 could be rapidly quantified within 5 min in our DEP system. Capturing efficiencies higher than 95% could be 2 μm polystyrene
beads with a linear flow speed, applied voltage and frequency of 0.89 mm s−1, 20 Vp-p and 5 MHz. Yeast cells (Candida glabrata and Candida albicans) could also be captured even at a lower concentration of 2.5 × 105 cells ml−1. Images of aggregative particles taken from the designed trapping area were further processed based on the intensity of relative
greyscale followed by correction of the particle numbers. The imaging-based quantification method showed higher agreement
than that of the conventional counting chamber method and proved the stability and feasibility of our AC DEP system. 相似文献
12.
This paper describes a flow reversal phenomenon for fluids with moderate conductivity. Fluids with conductivities of 2 × 10−4 S/m, 0.02 S/m and up to 0.1 S/m were experimented at frequencies ranging from 1 to 110 kHz. Flow reversal was observed only
at ~1 kHz and 5.3 V
rms for σ = 0.02 S/m, and our analysis indicates that AC electrothermal effect could be responsible. Analysis of the system impedance
and simulation of power consumption show that the distribution of electric power consumption is dependent on conductivity
and AC frequency. At low frequencies, possibly more electric power is consumed at surface/electrolyte interface rather than
within the fluid, which consequently changes the location of temperature maximum and the directions of temperature gradients.
The direction of AC electrothermal force is reoriented, causing the flow reversal. Numerical simulation is also performed
and agrees within the experiments. 相似文献
13.
Jung-Hao Wang Chih-Hung Wang Chun-Che Lin Huan-Yao Lei Gwo-Bin Lee 《Microfluidics and nanofluidics》2011,10(3):531-541
This study reports on an integrated microfluidic system capable of counting CD4+/CD8+ T lymphocytes from a whole blood sample, which may be further applied for the rapid screening of the human immunodeficiency
virus (HIV) infection. This system is composed of a sample incubation module for fluorescence-labeling of the target cells
and a micro-fabricated flow cytometry module for cell counting. First, a pneumatically driven, vortex-type micro-mixer has
been adopted for the fluorescence-labeling of CD4+/CD8+ T lymphocytes from whole blood. After the labeling process, different laser-excited fluorescent signals are detected and
are used for counting of CD4+/CD8+ T lymphocytes as they pass through the detection region of the microflow cytometer. A concentration of 963 cells/μl is counted
for cultured CD4+ T lymphocytes with a reference concentration of 1000 cells/μl. The ratio of CD4+/CD8+ T lymphocytes is then calculated. Experimental results show that the results from the microsystem are in agreement with the
ones from large-scale flow cytometers. In addition, the entire diagnostic procedure, including the sample incubation and the
cell counting, can be automatically performed within 35 min. Therefore, this may become a powerful tool for further biomedical
applications, especially for fast screening of HIV infection. 相似文献
14.
Zongbo Zhang Yi Luo Xiaodong Wang Yingsong Zheng Yanguo Zhang Liding Wang 《Microsystem Technologies》2010,16(4):533-541
Bonding is a bottleneck for mass-production of polymer microfluidic devices. A novel ultrasonic bonding method for rapid and
deformation-free bonding of polymethyl methacrylate (PMMA) microfluidic chips is presented in this paper. Convex structures,
usually named energy director in ultrasonic welding, were designed and fabricated around micro-channels and reservoirs on
the substrates. Under low amplitude ultrasonic vibration, localized heating was generated only on the interface between energy
director and cover plate, with peak temperature lower than T
g (glass transition temperature) of PMMA. With the increasing of temperature, solution of PMMA in isopropanol (IPA) increases
and bonding was realized between the contacting surfaces of energy director and cover plate while no solution occurs on the
surfaces of other part as their lower temperature. PMMA microfluidic chips with micro-channels of 80 μm × 80 μm were successfully
bonded with high strength and low dimension loss using this method. 相似文献
15.
L. Zhu N. Kroodsma J. Yeom J. L. Haan M. A. Shannon D. D. Meng 《Microfluidics and nanofluidics》2011,11(5):569-578
This article introduces an on-demand microfluidic hydrogen generator that can be integrated with a micro-proton exchange membrane
(PEM) fuel cell. The catalytic reaction, reactant circulation, gas/liquid separation, and autonomous control functionalities
are all integrated into a single microfluidic device. It generates hydrated hydrogen gas from an aqueous ammonia borane solution
which is circulated and exchanged between the microfluidic reactor and a rechargeable fuel reservoir without any parasitic
power consumption. Ammonia borane is chosen instead of sodium borohydride because of its faster hydrogen generation rate,
higher hydrogen storage capability, stability, and better catalyst durability. The self-circulation of the ammonia borane
solution was achieved using directional growth and selective venting of hydrogen bubbles in micro-channels, which leads to
agitation and addition of fresh solution without consumption of electrical power. The self-regulation mechanism ensures that
hydrogen can be supplied to a fuel cell according to the exact demand of the current output of the fuel cell. The circulation
flow rate of ammonia borane solution is also automatically regulated by the venting rate of hydrogen at the gas outlet. Design,
fabrication, and testing results of a prototype system are described. The hydrogen generator is capable of generating hydrogen
gas at a maximum rate of 0.6 ml/min (2.1 ml/min cm2) and circulating aqueous ammonia borane at a maximum flow rate of ~15.7 μl/min. The device has also been connected with a
micro-PEM fuel cell to demonstrate the feasibility of its practical applications in a high-impedance system. 相似文献
16.
μ-PIM is a promising technology for micro-manufacture, by which complex structured micro components can be produced economically.
In this paper, iron micro gear arrays with different diameters were produced by μ-PIM. The influence of die temperature (T
m), the injection pressure (P
i) and the injection speed (V
i) on the replication quality has been studied. The results showed that the replication quality was mainly affected by the
T
m. Micro gears with best shape retention were obtained when T
m was set to be 80°C, P
i for 100 MPa and V
i for 60 cm3/s. The green compacts were debinded and subsequently sintered. Micro gears with good shape retention and 0.0053 wt. % residual
carbon were obtained after debinding and sintering process. The micro hardness turned out 8 GPa measured by a nano-mechanical
test instrument. 相似文献
17.
Microfluidic-based biosensors toward point-of-care detection of nucleic acids and proteins 总被引:1,自引:1,他引:0
Seokheun Choi Michael Goryll Lai Yi Mandy Sin Pak Kin Wong Junseok Chae 《Microfluidics and nanofluidics》2011,10(2):231-247
This article reviews state-of-the-art microfluidic biosensors of nucleic acids and proteins for point-of-care (POC) diagnostics.
Microfluidics is capable of analyzing small sample volumes (10−9–10−18 l) and minimizing costly reagent consumption as well as automating sample preparation and reducing processing time. The merger
of microfluidics and advanced biosensor technologies offers new promises for POC diagnostics, including high-throughput analysis,
portability and disposability. However, this merger also imposes technological challenges on biosensors, such as high sensitivity
and selectivity requirements with sample volumes orders of magnitude smaller than those of conventional practices, false response
errors due to non-specific adsorption, and integrability with other necessary modules. There have been many prior review articles
on microfluidic-based biosensors, and this review focuses on the recent progress in last 5 years. Herein, we review general
technologies of DNA and protein biosensors. Then, recent advances on the coupling of the biosensors to microfluidics are highlighted.
Finally, we discuss the key challenges and potential solutions for transforming microfluidic biosensors into POC diagnostic
applications. 相似文献
18.
Multi-layered ceramic substrates with embedded micro patterns are becoming increasingly important, for example, in harsh environment
electronics, enabling microsystems and microfluidic devices. Fabrication of these embedded micro patterns, such as micro channels,
cavities and vias, is a challenge. This study focuses on the process aspects of patterning micro features on low temperature
co-firable ceramic (LTCC) green substrates using micro hot embossing. Green ceramic tapes that possessed near-zero shrinkage
in the x–y plane were used, six layers of which were stacked and laminated as a substrate. The process parameters that impact on the
embossing fidelity were investigated and optimized in this study. Micro features with channel-width as small as several micrometers
were formed on green ceramic substrates. The dynamic thermo-mechanical analysis indicated that extending the holding time
at a certain temperature range would harden the substrates with little effect on improving the embossing fidelity. Ceramic
substrates with embossed micro patterns were obtained after co-firing; the shrinkage ratios of the embossed depth and channel-width
were 8–15 and 12–17%, respectively. The changes of pitches between two embossed channels were within ±1.0% due to the interlocking
effect of the ceramic tapes. 相似文献
19.
Neus Godino Detlef Snakenborg Jörg P. Kutter Jenny Emnéus Mikkel Fougt Hansen F. Xavier Muñoz F. Javier del Campo 《Microfluidics and nanofluidics》2010,8(3):393-402
This work presents the fabrication and characterisation of a versatile lab-on-a-chip system that combines magnetic capture
and electrochemical detection. The system comprises a silicon chip featuring a series of microband electrodes, a PDMS gasket
that incorporates the microfluidic channels, and a polycarbonate base where permanent magnets are hosted; these parts are
designed to fit so that wire bonding and encapsulation are avoided. This system can perform bioassays over the surface of
magnetic beads and uses only 50 μL of bead suspension per assay. Following detection, captured beads are released simply by
sliding a thin iron plate between the magnets and the chip. Particles are captured upstream from the detector and we demonstrate
how to take further advantage of the system fluidics to determine enzyme activities or concentrations, as flow velocity can
be adjusted to the rate of the reactions under study. We used magnetic particles containing β-galactosidase and monitored
the enzyme activity amperometrically by the oxidation of 4-aminophenol, enzymatically produced from 4-aminophenyl-β-d-galactopyranoside. The system is able to detect the presence of enzyme down to approximately 50 ng mL−1. 相似文献
20.
Chih-Hui Chiu Ya-Fu Peng You-Wei Lin 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2011,15(10):2029-2040
In this study, a robust intelligent backstepping tracking control (RIBTC) system combined with adaptive output recurrent cerebellar
model articulation controller (AORCMAC) and H
∞ control technique is proposed for wheeled inverted pendulums (WIPs) with unknown system dynamics and external disturbance.
The AORCMAC is a nonlinear adaptive system with simple computation, good generalization capability and fast learning property.
Therefore, the WIP can stand upright when it moves to a designed position stably. In the proposed control system, an AORCMAC
is used to copy an ideal backstepping control, and a robust H
∞ controller is designed to attenuate the effect of the residual approximation errors and external disturbances with desired
attenuation level. Moreover, the all adaptation laws of the RIBTC system are derived based on the Lyapunov stability analysis,
the Taylor linearization technique and H
∞ control theory, so that the stability of the closed-loop system and H
∞ tracking performance can be guaranteed. The proposed control scheme is practical and efficacious for WIPs by simulation results. 相似文献