共查询到20条相似文献,搜索用时 702 毫秒
1.
Erik Jung Dion Manessis Alexander Neumann Lars Böttcher Tanja Braun Jörg Bauer Herbert Reichl Bruno Iafelice Federica Destro Roberto Gambari 《Microsystem Technologies》2008,14(7):931-936
Microtechnology becomes a versatile tool for biological and biomedical applications. Microwells have been established long
but remained non-intelligent up to now. Merging new fabrication techniques and handling concepts with microelectronics enables
to realize intelligent microwells suitable for future improved cancer treatment. The described technology depicts the basis
for the fabrication of electronically enhanced microwell. Thin aluminium sheets are structured by laser micro machining and
laminated successively to obtain registration tolerances of the respective layers of <5 μm. The microwells lasermachined into
the laminate are with 50–350 μm diameter, allowing to contain individual cells within the microwell as well as provide access
holes for the layer-to-layer contacting. A permeable membrane attached to the bottom of the microwell plate is used for fluid
handling. The individual process steps are described and results on the microstructuring as well as on biocompatibility of
the materials are given. 相似文献
2.
Hyperthermia affects certain regulatory proteins, kinases or cyclins, resulting in alternations to the cell cycle and even
to apoptosis. Damage to the cell plasma membrane is a key factor in the killing of a cell by hyperthermia. Analysis at the
single-cell level is necessary for understanding the fundamental mechanisms of hyperthermia-induced cell death and the generation
of thermotolerance in surviving cells. Engineering approaches achieving precise control of cellular micropatterning provide
the potential for investigating the mechanisms of thermal injury to cells at the single-cell level. The main purpose of this
study is to fabricate a hydrogel chip with microwells for cellular patterning and to demonstrate the feasibility of measurement
of supraphysiological thermal injury in human carcinoma cells (HeLa cells) at the single-cell level. To accomplish this, measurement
of membrane injury by dye leakage post-thermal insult was performed and reported in this work. A hydrogel chip with microwells
with different diameters was fabricated. For cell concentrations at 0.5 × 106 cells/mL, the occupancy of cells on the microchip with 40 μm microwells was up to 86.6%, a value far higher than that found
on the 30 μm microwells (approximately 78.5%). Most microwells of 30 μm in diameter (about 70%) were occupied by a single
cell; hence, the hydrogel chip with 30 μm microwells was suitable for the applications of single-cell-based analysis. The
fluorescent images showed that calcein leakage occurred when cell membranes were damaged under supraphysiological temperatures
between 43 and 50°C. The normalized intensity of calcein decreased to 32% under a supraphysiological temperature of 43°C for
20 min. The intensity of calcein in cells was less than 20% under a supraphysiological temperature of 50°C. The feasibility
of the single-cell-based experiment of thermal injury in the microchip with hydrogel microwells was therefore successfully
demonstrated. 相似文献
3.
This study presents a particle manipulation and separation technique based on dielectrophoresis principle by employing an
array of isosceles triangular microelectrodes on the bottom plate and a continuous electrode on the top plate. These electrodes
generate non-uniform electric fields transversely across the microchannel. The particles within the flowing fluid experience
a dielectrophoretic force perpendicular to the fluid flow direction due to the non-uniform electric fields. The isosceles
triangular microelectrodes were designed to continuously exert a small dielectrophoretic force on the particles. Particles
experiencing a larger dielectrophoretic force would move further in the perpendicular direction to the fluid flow as they
traveled past each microelectrode. Polystyrene microspheres were used as the model particles, with particles of ∅20 μm employed
for studying the basic characteristics of this technique. Particle separation was subsequently demonstrated on ∅10 and ∅15 μm
microspheres. Using an applied sinusoidal voltage of 20 Vpp and frequency of 1 MHz, a mean separation distance of 0.765 mm between them was achieved at a flow rate of 3 μl/min (~1 mm/s),
an important consideration for high throughput separation capability in a micro-scale technology device. This unique isosceles
triangular microelectrodes design allows heterogeneous particle populations to be separated into multiple streams in a single
continuous operation. 相似文献
4.
Microinjection molded disposable microfluidic lab-on-a-chip for efficient detection of agglutination 总被引:1,自引:0,他引:1
Previous diagnosing methods based on agglutination have a limitation in view of emergency and point-of-care diagnoses due
to the requirement of large scale equipments and much agglutination time. In this paper, we propose a low cost microfluidic
lab-on-a-chip for more efficient detection of agglutination. In the present lab-on-a-chip, two inlet microwells, flow guiding
microchannels, chaotic micromixer and reaction microwell are fully integrated. Mold inserts for the lab-on-a-chip were manufactured
by UV photolithography and nickel electroplating process. The complete lab-on-a-chip was realized by the microinjection molding
of cyclic olefin copolymer and the subsequent thermal bonding. The improved serpentine laminating micromixer, developed by
our group, integrated in the lab-on-a-chip showed the high-level of chaotic mixing, thereby enabling us to get a reliable
mixing of sample and reagent. The performance of the fabricated lab-on-a-chip was demonstrated by agglutination experiments
with simulated bloods of 10 μl and simulated sera of 10 μl. The results of agglutination inside the reaction microwell were
clearly read by means of the level of light transmission. The present microfluidic lab-on-a-chip could be widely applied to
various clinical diagnostics based on agglutination tests. 相似文献
5.
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
6.
Junjie Zhu Robert Cameron Canter Gyunay Keten Pallavi Vedantam Tzuen-Rong J. Tzeng Xiangchun Xuan 《Microfluidics and nanofluidics》2011,11(6):743-752
Particle and cell separations are critical to chemical and biomedical analyses. This study demonstrates a continuous-flow
electrokinetic separation of particles and cells in a serpentine microchannel through curvature-induced dielectrophoresis.
The separation arises from the particle size-dependent cross-stream dielectrophoretic deflection that is generated by the
inherent electric field gradients within channel turns. Through the use of a sheath flow to focus the particle mixture, we
implement a continuous separation of 1 and 5 μm polystyrene particles in a serpentine microchannel under a 15 kV/m DC electric
field. The effects of the applied DC voltages and the serpentine length on the separation performance are examined. The same
channel is also demonstrated to separate yeast cells (range in diameter between 4 and 8 μm) from 3 μm particles under an electric
field as low as 10 kV/m. The observed focusing and separation processes for particles and cells in the serpentine microchannel
are reasonably predicted by a numerical model. 相似文献
7.
Customized trapping of magnetic particles 总被引:1,自引:1,他引:0
This paper presents an efficient technique for trapping of magnetic particles in confined spatial locations using customized
designs of micro-coils (MCs). Large magnetic field gradients of up to 20 T/mm and large magnetic forces in the range of 10−8 Newton on magnetic particles with diameter of 1 μm have been achieved using MCs with several planar geometrical configurations.
A large magnetic field gradient is generated and enhanced by two structural parameters: the small width and high aspect ratio
of each single conductor and the ferromagnetic pillars positioned at high-flux density locations. This arrangement creates
very steep magnetic potential wells, in particular at the vicinity of the pillars. The system allowed capturing of suspended
magnetic particles as far as 1,000 μm from the center of the device. Magnetic particles/cells have been trapped and confined
in single and in arrays of deep magnetic potential wells corresponding to the MCs configuration. 相似文献
8.
In this study, a poly-methyl-methacrylate (PMMA) microfluidic chip with a 45° cross-junction microchannel is fabricated using
a CO2 laser machine to generate chitosan microfibers. Chitosan solution and sodium tripolyphosphate (STPP) solution were injected
into the cross-junction microchannel of the microfluidic chip. The laminar flow of the chitosan solution was generated by
hydrodynamic focusing. The diameter of laminar flow, which ranged from 30 to 50 μm, was controlled by changing the ratio between
chitosan solution and STPP solution flow rates in the PMMA microfluidic chip. The laminar flow of the chitosan solution was
converted into chitosan microfibers with STPP solution via the cross-linking reaction; the diameter of chitosan microfibers
was in the range of 50–200 μm. The chitosan microfibers were then coated with collagen for cell cultivation. The results show
that the chitosan microfibers provide good growth conditions for cells. They could be used as a scaffold for cell cultures
in tissue engineering applications. This novel method has advantages of ease of fabrication, simple and low-cost process. 相似文献
9.
An integrated flow-cell for full sample stream control 总被引:1,自引:1,他引:0
In this study, we present a novel three-dimensional hydrodynamic sheath flow chip that allows full control of a sample stream.
The chip offers the possibility to steer each of the four side sheath flows individually. The design of the flow-cell exhibits
high flexibility in creating different sample stream profiles (width and height) and allows navigation of the sample stream
to every desired position inside the microchannel (vertical and horizontal). This can be used to bring the sample stream to
a sensing area for analysis, or to an area of actuation (e.g. for cell sorting). In addition, we studied the creation of very
small sample stream diameters. In microchannels (typically 25 × 40 μm2), we created sample stream diameters that were five
to ten times smaller than the channel dimensions, and the smallest measured sample stream width was 1.5 μm. Typical flow rates
are 0.5 μl/min for the sample flow and around 100 μl/min for the cumulated sheath flows. The planar microfabricated chip,
consisting of a silicon–glass sandwich with an intermediate SU-8 layer, is much smaller (6 × 9 mm2) than the previously presented
sheath flow devices, which makes it also cost-effective. We present the chip design, fluidic simulation results and experiments,
where the size, shape and position of the sample stream have been established by laser scanning confocal microscopy and dye
intensity analysis. 相似文献
10.
This paper describes a method to control and detect droplet size gradient by step-wise flow rate ramping of water-in-oil droplets
in a microfluidic device. The droplets are generated in a cross channel device with two oil inlets and a water inlet. The
droplet images are captured and analyzed in a time sequence in order to quantify the droplet generation frequency. It is demonstrated
that by controlling the ramping of the oil flow rates it is possible to manipulate the ramping of droplet sizes. Increasing
or decreasing of droplet sizes is achieved for a step-wise triangular ramping profile of the oil flow rate. The dynamic behavior
of droplets due to the step-wise flow pulses is investigated. Uniform linear size ramping of water-in-oil droplets from 73
to 83 μm in diameter is generated with an oil flow ramping range from 1 to 11 μL/min in a minimum of five steps while water
flow rate is held constant at 2 μL/min. 相似文献
11.
Tim Van Gestel Feng Han Doris Sebold Hans Peter Buchkremer Detlev St?ver 《Microsystem Technologies》2011,17(2):233-242
A solid oxide fuel cell (SOFC) with a thin-film yttria-stabilized zirconia (YSZ) electrolyte was developed and tested. This
novel SOFC shows a similar multilayer set-up as other current anode-supported SOFCs and is composed of a Ni/8YSZ anode, a
gas-tight 8YSZ electrolyte layer, a dense Sr-diffusion barrier layer and a LSCF cathode. To increase the power density and
lower the SOFC operating temperature, the thickness of the electrolyte layer was reduced from around 10 μm in current cells
to 1 μm, using a nanoparticle deposition method. By using the novel 1 μm electrolyte layer, the current density of our SOFC
progressed to 2.7, 2.1 and 1.6 A/cm2 at operation temperatures of 800, 700 and 650°C, respectively, and out-performs all similar cells reported to date in the
literature. An important consideration is also that cost-effective dip-coating and spin-coating methods are applied for the
fabrication of the thin-film electrolyte. Processing of 1 μm layers on the very porous anode substrate material was initially
experienced as very difficult and therefore 8YSZ nanoparticle coatings were developed and optimized on porous 8YSZ model substrates
and transferred afterwards to regular anode substrates. In this paper, the preparation of the novel SOFC is shown and its
morphology is illustrated with high resolution SEM pictures. Further, the performance in a standard SOFC test is demonstrated. 相似文献
12.
This paper describes a novel concept of integrated on-chip fiber free laser-induced fluorescence detection system. The poly-dimethylsiloxane
(PDMS) chip was fabricated using soft lithography and was bonded with a glass substrate of 150 μm thickness that reduced the
distance of channel-to-sidewall to less than 180 μm. The cells and particles detection was conducted by an external single
fiber close to the glass substrate that transmitted laser light for simultaneous excitation and receipt of the emission light
signals. The performance of the proposed device was demonstrated using fluorescence beads, stained white blood cells, and
yeast cells. The experimental results showed the simplicity and flexibility of the proposed device configuration which can
provide convenient on-chip integration interface for fast, high throughput, and low-cost laser-induced fluorescence detection
micro flow cytometer. 相似文献
13.
N. Katsarakis M. Bender L. Singleton G. Kiriakidis C. M. Soukoulis 《Microsystem Technologies》2002,8(2-3):74-77
Two-dimensional metallic photonic band-gap crystals, consisting of square and triangular lattices of nickel pillars, were
fabricated by the LIGA process. In particular, PMMA slabs with a thickness of up to 800 μm were irradiated with synchrotron
radiation and the holes produced were then filled with nickel via electroforming. The lattice constant, i.e., the center-to-center
distance between the pillars, is either 60 μm or 40 μm for the square and triangular structures respectively. The metal filling
ratio is 10% for the square and 20% for the triangular structures. Transmission and reflection measurements demonstrate that
the metallic photonic band-gap crystals show a cutoff frequency in the far infrared regime between 2 and 5 THz. It is concluded
that LIGA is a promising method for the fabrication of 2-D metallic photonic band-gap structures, which could be potentially
used as passive filters in THz devices.
Received: 10 August 2001/Accepted: 24 September 2001 相似文献
14.
S. R. A. de Loos J. van der Schaaf R. M. Tiggelaar T. A. Nijhuis M. H. J. M. de Croon J. C. Schouten 《Microfluidics and nanofluidics》2010,9(1):131-144
Most heterogeneously catalyzed gas–liquid reactions in micro channels are chemically/kinetically limited because of the high
gas–liquid and liquid–solid mass transfer rates that can be achieved. This motivates the design of systems with a larger surface
area, which can be expected to offer higher reaction rates per unit volume of reactor. This increase in surface area can be
realized by using structured micro channels. In this work, rectangular micro channels containing round pillars of 3 μm in
diameter and 50 μm in height are studied. The flow regimes, gas hold-up, and pressure drop are determined for pillar pitches
of 7, 12, 17, and 27 μm. Flow maps are presented and compared with flow maps of rectangular and round micro channels without
pillars. The Armand correlation predicts the gas hold-up in the pillared micro channel within 3% error. Three models are derived
which give the single-phase and the two-phase pressure drop as a function of the gas and liquid superficial velocities and
the pillar pitches. For a pillar pitch of 27 μm, the Darcy-Brinkman equation predicts the single-phase pressure drop within
2% error. For pillar pitches of 7, 12, and 17 μm, the Blake-Kozeny equation predicts the single-phase pressure drop within
20%. The two-phase pressure drop model predicts the experimental data within 30% error for channels containing pillars with
a pitch of 17 μm, whereas the Lockhart–Martinelli correlation is proven to be non-applicable for the system used in this work.
The open structure and the higher production rate per unit of reactor volume make the pillared micro channel an efficient
system for performing heterogeneously catalyzed gas–liquid reactions. 相似文献
15.
Single-cell analysis has been widely applied in various biomedical applications, such as cancer diagnostics, immune status monitoring, and drug screening. To perform an accurate and rapid cellular analysis, various magnetic-activated cell sorting techniques are available in the markets. However, large sample requirement and uneven magnetic field distribution limit its application in single-cell trapping and following analysis. To address these problems, we developed a microfluidic microwell device for immunomagnetic single-cell trapping. By adding a microwell layer between the microchannel and magnet, the magnetic field along the device becomes more uniform. Besides, magnetic beads can be retained in the array of microwell after the high-speed washing step, whereas untrapped beads would be flushed away, resulting in high single-particle trapping efficiency (62%) and purity (99.6%). To achieve large-area single-cell trapping, we introduced a “sweeping” loading protocol to further expand the single-particle trapping range. In the microwell region near to the edge of the magnet, over 3000 single magnetic beads were trapped in a 10 mm2 area. Finally, we demonstrated immunomagnetic-labeled THP-1 cells can successfully be trapped at single-cell level in the microwell. The cell trapping process can be done in 10 min. We believe the platform with an accurate and efficient single-cell trapping functionality could potentially be used for various cellular analyses at the single-cell level. 相似文献
16.
Noel M. Elman Karen Daniel Farzad Jalali-Yazdi Michael J. Cima 《Microfluidics and nanofluidics》2010,8(4):557-563
We report the design, fabrication, and testing of super permeable nano-channel membranes, characterized by the absolute control
in the pore size at the nano-scale dimensions, large surface area, very high permeability, mechanical stability and durability.
The membranes were fabricated using a unique nanotechnology process that combines laser interferometric lithography to define
nano-channels (pores) and micro-machining to produce free-standing amorphous silicon membranes, allowing rapid and cost-effective
mass production. The suspended membranes were defined as 50 nm thick a-Si, characterized by a very high porosity of approximately
20%, achieved by definition of large arrays of nano-channels. The dimensions of each individual nano-channel was 65 nm wide,
250 nm long. The measured apparent permeability was 0.14 ± 0.05 cm/min for each individual 70 μm × 70 μm membrane, representing
one of the highest permeability values ever reported for this scale. 相似文献
17.
This study presents a sheathless and portable microfluidic chip that is capable of high-throughput focusing bioparticles based
on 3D travelling-wave dielectrophoresis (twDEP). High-throughput focusing is achieved by sustaining a centralized twDEP field
normal to the continuous through-flow direction. Two twDEP electrode arrays are formed from upper and lower walls of the microchannel
and extend to its center, which induce twDEP forces to provide the lateral displacements in two directions for focusing the
bioparticles. Bioparticles can be focused to the center of the microchannel effectively by twDEP conveyance when the characteristic
time due to twDEP conveying in the y direction is shorter than the residence time of the particles within twDEP electrode
array. Red blood cells can be effectively focused into a narrow particle stream (~10 μm) below a critical flow rate of 10 μl/min
(linear flow velocity ~5 mm/s), when under a voltage of 14 Vp–p at a frequency of 500 kHz is applied. Approximately 90% focusing efficiency for red blood cells can be achieved within two
6-mm-long electrode arrays when the flow rate is below 12 μl/min. Blood cells and Candida cells were also focused and sorted successfully based on their different twDEP mobilities. Compared to conventional 3D-paired
DEP focusing, velocity is enhanced nearly four folds of magnitude. 3D twDEP provides the lateral displacements of particles
and long residence time for migrating particles in a high-speed continuous flow, which breaks through the limitation of many
electrokinetic cell manipulation techniques. 相似文献
18.
Molter T.W. Holl M.R. Dragavon J.M. McQuaide S.C. Anderson J.B. Young A.C. Burgess L.W. Lidstrom M.E. Meldrum D.R. 《Automation Science and Engineering, IEEE Transactions on》2008,5(1):32-42
A novel system that has enabled the measurement of single-cell oxygen consumption rates is presented. The experimental apparatus includes a temperature controlled environmental chamber, an array of microwells etched in glass, and a lid actuator used to seal cells in the microwells. Each microwell contains an oxygen sensitive platinum phosphor sensor used to monitor the cellular metabolic rates. Custom automation software controls the digital image data collection for oxygen sensor measurements, which are analyzed using an image-processing program to yield the oxygen concentration within each microwell versus time. Two proof-of-concept experiments produced oxygen consumption rate measurements for A549 human epithelial lung cancer cells of 5.39 and 5.27 fmol/min/cell, closely matching published oxygen consumption rates for bulk A549 populations. 相似文献
19.
A quasi-three-dimensional (quasi-3-D) cell-based biosensor platform microfabricated from SU-8 has been developed and characterized. In this work, SH-SY5Y human neuroblastoma cells were integrated with SU-8 microfabricated microwells with diameters of 100 μm. SH-SY5Y cells were differentiated with 1 mM dibutyryl cAMP and 2.5 μM 5-bromodeoxyuridine. Voltage-gated calcium channel (VGCC) function of SH-SY5Y cells cultured within the microwells (quasi-3-D) versus those cultured on the SU-8 planar substrates (2-D) was evaluated by confocal microscopy with a calcium fluorescent indicator, Calcium Green-1. In response to 50 mM high K+ depolarization, cells in microwells were less responsive in terms of increase in intracellular Ca2+ in comparison to cells on 2-D substrates. This study shows that VGCC function of cells within SU-8 microwells was indeed different from that of cells on planar SU-8 surfaces, suggesting that SU-8 microstructure did affect SH-SY5Y cell differentiation with respect to VGCC function and that high-aspect-ratio microstructures are not merely “folded” 2-D structures. Furthermore, these results are consistent with previous 2-D/3-D comparative studies carried out in polymer scaffolds and support the hypothesis that cell calcium dynamics on 2-D substrates may be exaggerated. Overall, this work is supportive of SU-8 micropattern as a viable platform for engineering a quasi-3-D cell culture system for cell-based biosensing against drugs for VGCCs. 相似文献
20.
Xiaowen Huang Li Li Qin Tu Jianchun Wang Wenming Liu Xueqin Wang Li Ren Jinyi Wang 《Microfluidics and nanofluidics》2011,10(6):1333-1341
Ethanol consumption is associated with the risk of breast cancer progression; however, the mechanism of relationship has not
yet been fully explained. Research on breast cancer cell migration after ethanol stimulation may give hope for a better understanding
of the disease and oncotherapy. Conventional cell migration assays such as Boyden chamber and wound-healing assays are easy
to conduct for this purpose; however, these assays have inherent limitations. In this study, we quantified the effect of ethanol
on MCF-7 hunam breast cancer cells using a microfluidics-based wound-healing assay. Wounds were prepared by partially digesting
a confluent cell sheet using parallel laminar flows in the presence of protease trypsin. The cells at the leading edge of
the wound remained intact. Cell image analysis indicates that all the cells cultured in the microdevice took on a good morphology
and monolayer growth status. Cell viability assay demonstrates that cell viability decreased with the increase in ethanol
concentration and treatment time. For 0, 22, 43, and 65 mmol/l of ethanol, cell viability after being cultured for 24 h was
100%, 99.6%, 99.4%, and 98.4%, respectively. Studying MCF-7 human breast cancer cell migration when treated with different
ethanol concentrations revealed that the cell migration distance is directly proportional with ethanol concentration. After
being cultured for 24 h at 37°C and 5% CO2, the maximal cell migration distance was 231, 283, and 332 μm for 22, 43, and 65 mmol/l ethanol, respectively; all results
were higher than the blank test (i.e., ethanol-free test, 218 μm). These findings will be beneficial in developing microfluidic
device applications for future research on breast tumor therapy in a biomimetic microenvironment and for developing new methods
for breast cancer therapy. 相似文献