共查询到20条相似文献，搜索用时 15 毫秒
1.
Gang Li Yahui Luo Qiang Chen Lingying Liao Jianlong Zhao 《Biomicrofluidics》2012,6(1):014118-014118-16
This paper presents an easy-to-use, power-free, and modular pump for portable microfluidic applications. The pump module is a degassed particle desorption polydimethylsiloxane (PDMS) slab with an integrated mesh-shaped chamber, which can be attached on the outlet port of microfluidic device to absorb the air in the microfluidic system and then to create a negative pressure for driving fluid. Different from the existing monolithic degassed PDMS pumps that are generally restricted to limited pumping capacity and are only compatible with PDMS-based microfluidic devices, this pump can offer various possible configures of pumping power by varying the geometries of the pump or by combining different pump modules and can also be employed in any material microfluidic devices. The key advantage of this pump is that its operation only requires the user to place the degassed PDMS slab on the outlet ports of microfluidic devices. To help design pumps with a suitable pumping performance, the effect of pump module geometry on its pumping capacity is also investigated. The results indicate that the performance of the degassed PDMS pump is strongly dependent on the surface area of the pump chamber, the exposure area and the volume of the PDMS pump slab. In addition, the initial volume of air in the closed microfluidic system and the cross-linking degree of PDMS also affect the performance of the degassed PDMS pump. Finally, we demonstrated the utility of this modular pumping method by applying it to a glass-based microfluidic device and a PDMS-based protein crystallization microfluidic device. 相似文献
2.
This paper presents an easy-to-use, power-free, and modular pump for portable microfluidic applications. The pump module is a degassed particle desorption polydimethylsiloxane (PDMS) slab with an integrated mesh-shaped chamber, which can be attached on the outlet port of microfluidic device to absorb the air in the microfluidic system and then to create a negative pressure for driving fluid. Different from the existing monolithic degassed PDMS pumps that are generally restricted to limited pumping capacity and are only compatible with PDMS-based microfluidic devices, this pump can offer various possible configures of pumping power by varying the geometries of the pump or by combining different pump modules and can also be employed in any material microfluidic devices. The key advantage of this pump is that its operation only requires the user to place the degassed PDMS slab on the outlet ports of microfluidic devices. To help design pumps with a suitable pumping performance, the effect of pump module geometry on its pumping capacity is also investigated. The results indicate that the performance of the degassed PDMS pump is strongly dependent on the surface area of the pump chamber, the exposure area and the volume of the PDMS pump slab. In addition, the initial volume of air in the closed microfluidic system and the cross-linking degree of PDMS also affect the performance of the degassed PDMS pump. Finally, we demonstrated the utility of this modular pumping method by applying it to a glass-based microfluidic device and a PDMS-based protein crystallization microfluidic device. 相似文献
3.
A new method of surface modification is described for enabling the in situ formation of homogenous porous polymer monoliths (PPMs) within poly(dimethylsiloxane) (PDMS) microfluidic channels that uses 365 nm UV illumination for polymerization. Porous polymer monolith formation in PDMS can be challenging because PDMS readily absorbs the monomers and solvents, changing the final monolith morphology, and because PDMS absorbs oxygen, which inhibits free-radical polymerization. The new approach is based on sequentially absorbing a non-hydrogen-abstracting photoinitiator and the monomers methyl methacrylate and ethylene diacrylate within the walls of the microchannel, and then polymerizing the surface treatment polymer within the PDMS, entangled with it but not covalently bound. Four different monolith compositions were tested, all of which yielded monoliths that were securely anchored and could withstand pressures exceeding the bonding strength of PDMS (40 psi) without dislodging. One was a recipe that was optimized to give a larger average pore size, required for low back pressure. This monolith was used to concentrate and subsequently mechanical lyse B lymphocytes. 相似文献
4.
Christopher W. Gregory Katelyn L. Sellgren Kristin H. Gilchrist Sonia Grego 《Biomicrofluidics》2013,7(5)
A versatile method to fabricate a multilayer polydimethylsiloxane (PDMS) device with micropillar arrays within the inner layer is reported. The method includes an inexpensive but repeatable approach for PDMS lamination at high compressive force to achieve high yield of pillar molding and transfer to a temporary carrier. The process also enables micropillar-containing thin films to be used as the inner layer of PDMS devices integrated with polymer membranes. A microfluidic cell culture device was demonstrated which included multiple vertically stacked flow channels and a pillar array serving as a cage for a collagen hydrogel. The functionality of the multilayer device was demonstrated by culturing collagen-embedded fibroblasts under interstitial flow through the three-dimensional scaffold. The fabrication methods described in this paper can find applications in a variety of devices, particularly for organ-on-chip applications. 相似文献
5.
This paper presents a low-cost, power-free, and easy-to-use spotter system for fabrication of microarrays. The spotter system uses embedded dispensing microchannels combined with a polydimethylsiloxane (PDMS) membrane containing regular arrays of well-defined thru-holes to produce precise, uniform DNA or protein microarrays for disease diagnosis or drug screening. Powered by pre-evacuation of its PDMS substrate, the spotter system does not require any additional components or external equipment for its operation, which can potentially allow low-cost, high-quality microarray fabrication by minimally trained individuals. Polyvinylpyrrolidone was used to modify the PDMS surface to prevent protein adsorption by the microchannels. Experimental results indicate that the PDMS spotter shows excellent printing performance for immobilizing proteins. The measured coefficient of variation (CV) of the diameter of 48 spots was 2.63% and that of the intensity within one array was 2.87%. Concentration gradient experiments revealed the superiority of the immobilization density of the PDMS spotter over the conventional pin-printing method. Overall, this low-cost, power-free, and easy-to-use spotting system provides an attractive new method to fabricate microarrays. 相似文献
6.
Systematic characterization of degas-driven flow for poly(dimethylsiloxane) microfluidic devices 总被引：1，自引：0，他引：1
Degas-driven flow is a novel phenomenon used to propel fluids in poly(dimethylsiloxane) (PDMS)-based microfluidic devices without requiring any external power. This method takes advantage of the inherently high porosity and air solubility of PDMS by removing air molecules from the bulk PDMS before initiating the flow. The dynamics of degas-driven flow are dependent on the channel and device geometries and are highly sensitive to temporal parameters. These dependencies have not been fully characterized, hindering broad use of degas-driven flow as a microfluidic pumping mechanism. Here, we characterize, for the first time, the effect of various parameters on the dynamics of degas-driven flow, including channel geometry, PDMS thickness, PDMS exposure area, vacuum degassing time, and idle time at atmospheric pressure before loading. We investigate the effect of these parameters on flow velocity as well as channel fill time for the degas-driven flow process. Using our devices, we achieved reproducible flow with a standard deviation of less than 8% for flow velocity, as well as maximum flow rates of up to 3 nL∕s and mean flow rates of approximately 1-1.5 nL∕s. Parameters such as channel surface area and PDMS chip exposure area were found to have negligible impact on degas-driven flow dynamics, whereas channel cross-sectional area, degas time, PDMS thickness, and idle time were found to have a larger impact. In addition, we develop a physical model that can predict mean flow velocities within 6% of experimental values and can be used as a tool for future design of PDMS-based microfluidic devices that utilize degas-driven flow. 相似文献
7.
John H. L. Beal Andrea Bubendorfer Tim Kemmitt Ingrid Hoek W. Mike Arnold 《Biomicrofluidics》2012,6(3)
A rapid, inexpensive method using alkoxysilanes has been developed to selectively coat the interior of polydimethylsiloxane (PDMS) microfluidic channels with an integral silicaceous layer. This method combines the rapid prototyping capabilities of PDMS with the desirable wetting and electroosmotic properties of glass. The procedure can be carried out on the open faces of PDMS blocks prior to enclosure of the channels, or by flowing the reagents through the preformed channels. Therefore, this methodology allows for high-throughput processing of entire microfluidic devices or selective modification of specific areas of a device. Modification of PDMS with tetraethoxysilane generated a stable surface layer, with enhanced wettability and a more stable electroosmotic flow rate than native PDMS. Modification of PDMS with 3-aminopropyltriethoxysilane generated a surface layer bearing amine functionalities allowing for further chemical derivatization of the PDMS surface. 相似文献
8.
We present a novel image-based method to measure the on-chip microfluidic pressure and flow rate simultaneously by using the integrated optofluidic membrane interferometers (OMIs). The device was constructed with two layers of structured polydimethylsiloxane (PDMS) on a glass substrate by multilayer soft lithography. The OMI consists of a flexible air-gap optical cavity which upon illumination by monochromatic light generates interference patterns that depends on the pressure. These interference patterns were captured with a microscope and analyzed by computer based on a pattern recognition algorithm. Compared with the previous techniques for pressure sensing, this method offers several advantages including low cost, simple fabrication, large dynamic range, and high sensitivity. For pressure sensing, we demonstrate a dynamic range of 0-10 psi with an accuracy of ±2% of full scale. Since multiple OMIs can be integrated into a single chip for detecting pressures at multiple locations simultaneously, we also demonstrated a microfluidic flow sensing by measuring the differential pressure along a channel. Thanks to the simple fabrication that is compatible with normal microfluidics, such OMIs can be easily integrated into other microfluidic systems for in situ fluid monitoring. 相似文献
9.
Sheng Yan Jun Zhang Huaying Chen Gursel Alici Haiping Du Yonggang Zhu Weihua Li 《Biomicrofluidics》2014,8(6)
Microfluidic diagnostic devices often require handling particles or cells with different sizes. In this investigation, a tunable hydrophoretic device was developed which consists of a polydimethylsiloxane (PDMS) slab with hydrophoretic channel, a PDMS diaphragm with pressure channel, and a glass slide. The height of the hydrophoretic channel can be tuned simply and reliably by deforming the elastomeric diaphragm with pressure applied on the pressure channel. This operation allows the device to have a large operating range where different particles and complex biological samples can be processed. The focusing performance of this device was tested using blood cells that varied in shape and size. The hydrophoretic channel had a large cross section which enabled a throughput capability for cell focusing of ∼15 000 cells s−1, which was more than the conventional hydrophoretic focusing and dielectrophoresis (DEP)-active hydrophoretic methods. This tunable hydrophoretic focuser can potentially be integrated into advanced lab-on-a-chip bioanalysis devices. 相似文献
10.
Jeroen A. van Kan Ce Zhang Piravi Perumal Malar Johan R. C. van der Maarel 《Biomicrofluidics》2012,6(3)
An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60 nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and λ−DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels. 相似文献
11.
David W. Inglis 《Biomicrofluidics》2010,4(2)
Poly(dimethylsiloxane) or PDMS is an excellent material for replica molding, widely used in microfluidics research. Its low elastic modulus, or high deformability, assists its release from challenging molds, such as those with high feature density, high aspect ratios, and even negative sidewalls. However, owing to the same properties, PDMS-based microfluidic devices stretch and change shape when fluid is pushed or pulled through them. This paper shows how severe this change can be and gives a simple method for limiting this change that sacrifices few of the desirable characteristics of PDMS. A thin layer of PDMS between two rigid glass substrates is shown to drastically reduce pressure-induced shape changes while preserving deformability during mold separation and gas permeability. 相似文献
12.
Polydimethylsiloxane (DMS) is a popular material for microfluidics, but it is hydrophobic and is prone to non-specific protein adsorption. In this study, we explore methods for producing stable, protein resistant, tetraglyme plasma polymer coatings on PDMS by combining extended baking processes with multiple plasma polymer coating steps. We demonstrate that by using this approach, it is possible to produce a plasma polymer coatings that resist protein adsorption (<10 ng/cm2) and are stable to storage over at least 100 days. This methodology can translate to any plasma polymer system, enabling the introduction of a wide range of surface functionalities on PDMS surfaces. 相似文献
13.
Walter Schrott Zdeněk Slouka Petr ?ervenka Ji?í Ston Marek Nebyla Michal P?ibyl Dalimil ?nita 《Biomicrofluidics》2009,3(4)
Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy (AFM) analysis of the surface reveals a “peak and ridge” structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings. 相似文献
14.
Ever-increasing hardware capabilities and computation powers have enabled acquisition and analysis of big scientific data at the nanoscale routine, though much of the data acquired often turn out to be redundant, noisy and/or irrelevant to the problems of interest, and it remains nontrivial to draw clear mechanistic insights from pure data analytics. In this work, we use scanning probe microscopy (SPM) as an example to demonstrate deep data methodology for nanosciences, transitioning from brute-force analytics such as data mining, correlation analysis and unsupervised classification to informed and/or targeted causative data analytics built on sound physical understanding. Three key ingredients of such deep data analytics are presented. A sequential excitation scanning probe microscopy (SE-SPM) technique is first developed to acquire high-quality, efficient and physically relevant data, which can be easily implemented on any standard atomic force microscope (AFM). Brute-force physical analysis is then carried out using a simple harmonic oscillator (SHO) model, enabling us to derive intrinsic electromechanical coupling of interest. Finally, principal component analysis (PCA) is carried out, which not only speeds up the analysis by four orders of magnitude, but also allows a clear physical interpretation of its modes in combination with SHO analysis. A rough piezoelectric material has been probed using such a strategy, enabling us to map its intrinsic electromechanical properties at the nanoscale with high fidelity, where conventional methods fail. The SE in combination with deep data methodology can be easily adapted for other SPM techniques to probe a wide range of functional phenomena at the nanoscale. 相似文献
15.
Surface modification is a critical issue in various applications of polydimethylsiloxane (PDMS)-based microfluidic devices. Here, we describe a novel method through which PDMS-based microchannels were successfully modified with fragmented poly(l-lactic acid) (PLLA) nanosheets through a simple patchwork technique that exploited the high level of adhesiveness of PLLA nanosheets. Compared with other surface modification methods, our method required neither complicated chemical modifications nor the use of organic solvents that tend to cause PDMS swelling. The experimental results indicated that the modified PDMS exhibited excellent capacity for preventing the adhesion and activation of platelets. This simple yet efficient method can be used to fabricate the special PDMS microfluidic devices for biological, medical, and even hematological purposes. 相似文献
16.
Linfeng Xu Hun Lee Mariana Vanderlei Brasil Pinheiro Phil Schneider Deekshitha Jetta Kwang W. Oh 《Biomicrofluidics》2015,9(1)
We propose a blood separation microfluidic device suitable for point-of-care (POC) applications. By utilizing the high gas permeability of polydimethylsiloxane (PDMS) and phaseguide structures, a simple blood separation device is presented. The device consists of two main parts. A separation chamber with the phaseguide structures, where a sample inlet, a tape-sealed outlet, and a dead-end ring channel are connected, and pneumatic chambers, in which manually operating syringes are plugged. The separation chamber and pneumatic chambers are isolated by a thin PDMS wall. By manually pulling out the plunger of the syringe, a negative pressure is instantaneously generated inside the pneumatic chamber. Due to the gas diffusion from the separation chamber to the neighboring pneumatic chamber through the thin permeable PDMS wall, low pressure can be generated, and then the whole blood at the sample inlets starts to be drawn into the separation chamber and separated through the phaseguide structures. Reversely, after removing the tape at the outlet and manually pushing in the plunger of the syringe, a positive pressure will be created which will cause the air to diffuse back into the ring channel, and therefore allow the separated plasma to be recovered at the outlet on demand. In this paper, we focused on the study of the plasma separation and associated design parameters, such as the PDMS wall thickness, the air permeable overlap area between the separation and pneumatic chambers, and the geometry of the phaseguides. The device required only 2 μl of whole blood but yielding approximately 0.38 μl of separated plasma within 12 min. Without any of the requirements of sophisticated equipment or dilution techniques, we can not only separate the plasma from the whole blood for on-chip analysis but also can push out only the separated plasma to the outlet for off-chip analysis. 相似文献
17.
Jacob C. K. Leung Rhodri W. Taylor-Kamall Arthur J. Hilliker Pouya Rezai 《Biomicrofluidics》2015,9(3)
Drosophila melanogaster (fruit fly) is a model organism and its behaviours including oviposition (egg-laying) on agar substrates have been widely used for assessment of a variety of biological processes in flies. Physical and chemical properties of the substrate are the dominant factors affecting Drosophila''s oviposition, but they have not been investigated precisely and parametrically with the existing manual approaches. As a result, many behavioral questions about Drosophila oviposition, such as the combined effects of the aforementioned substrate properties (e.g., exposure area, sugar content, and stiffness) on oviposition and viability, and their threshold values, are yet to be answered. In this paper, we have devised a simple, easily implementable, and novel methodology that allows for modification of physical and chemical composition of agar substrates in order to quantitatively study survival and oviposition of adult fruit flies in an accurate and repeatable manner. Agar substrates have been modified by surface patterning using single and hexagonally arrayed through-hole polydimethylsiloxane (PDMS) membranes with various diameters and interspacing, as well as by substrate stiffness and sugar content modification via alteration of chemical components. While pure PDMS substrates showed a significant lethal effect on flies, a 0.5 mm diameter through-hole access to agar was found to abruptly increase the survival of adult flies to more than 93%. Flies avoided ovipositing on pure PDMS and on top of substrates with 0.5 mm diameter agar exposure areas. At a hole diameter of 2 mm (i.e., 0.25% exposure area) or larger, eggs were observed to be laid predominately inside the through-holes and along the edges of the PDMS-agar interface, showing a trending increase in site selection with 4 mm (i.e., 1% exposure area threshold) demonstrating natural oviposition rates similar to pure agar. The surface-modified agar-PDMS hybrid devices and the threshold values reported for the substrate physical and chemical conditions affecting oviposition are novel; therefore, we advocate their use for future in-depth studies of oviposition behaviour in Drosophila melanogaster with accuracy and repeatability. The technique is also useful for development of novel assays for learning and decision-making studies as well as miniaturized devices for self-assembly of eggs and embryonic developmental investigations. 相似文献
18.
Francesco Del Giudice Francesco Greco Paolo Antonio Netti Pier Luca Maffettone 《Biomicrofluidics》2016,10(4)
Microrheometry is very important for exploring rheological behaviours of several systems when conventional techniques fail. Microrheometrical measurements are usually carried out in microfluidic devices made of Poly(dimethylsiloxane) (PDMS). Although PDMS is a very cheap material, it is also very easy to deform. In particular, a liquid flowing in a PDMS device, in some circumstances, can effectively deform the microchannel, thus altering the flow conditions. The measure of the fluid relaxation time might be performed through viscoelasticity induced particle migration in microfluidics devices. If the channel walls are deformed by the flow, the resulting measured value of the relaxation time could be not reliable. In this work, we study the effect of channel deformation on particle migration in square-shaped microchannel. Experiments are carried out in several PolyEthylene Oxyde solutions flowing in two devices made of PDMS and Poly(methylmethacrylate) (PMMA). The relevance of wall rigidity on particle migration is investigated, and the corresponding importance of wall rigidity on the determination of the relaxation time of the suspending liquid is examined. 相似文献
19.
In recent years, there has been a dramatic increase in the use of poly(dimethylsiloxane) (PDMS) devices for cell-based studies. Commonly, the negative tone photoresist, SU8, is used to pattern features onto silicon wafers to create masters (SU8-Si) for PDMS replica molding. However, the complexity in the fabrication process, low feature reproducibility (master-to-master variability), silane toxicity, and short life span of these masters have been deterrents for using SU8-Si masters for the production of cell culture based PDMS microfluidic devices. While other techniques have demonstrated the ability to generate multiple devices from a single master, they often do not match the high feature resolution (∼0.1 μm) and low surface roughness that soft lithography masters offer. In this work, we developed a method to fabricate epoxy-based masters that allows for the replication of features with high fidelity directly from SU8-Si masters via their PDMS replicas. By this method, we show that we could obtain many epoxy based masters with equivalent features to a single SU8-Si master with a low feature variance of 1.54%. Favorable feature transfer resolutions were also obtained by using an appropriate Tg epoxy based system to ensure minimal shrinkage of features ranging in size from ∼100 μm to <10 μm in height. We further show that surface coating epoxy masters with Cr/Au lead to effective demolding and yield PDMS chambers that are suitable for long-term culturing of sensitive primary hippocampal neurons. Finally, we incorporated pillars within the Au-epoxy masters to eliminate the process of punching media reservoirs and thereby reducing substantial artefacts and wastage. 相似文献
20.
The ability to pump and manipulate fluid at the micron-scale is a basic requirement for microfluidic platforms. Many current manipulation methods, however, require expensive and bulky external supporting equipment, which are not typically compatible for portable applications. We have developed a contactless metal electro-osmotic micropump capable of pumping conductive buffers. The pump operates using two pairs of gallium metal electrodes, which are activated using an external voltage source and separated from a main flow channel by a thin micron-scale polydimethylsiloxane (PDMS) membrane. The thin contactless membrane allows for field penetration and electro-osmotic flow within the microchannel, but eliminates electrode damage and sample contamination commonly associated with traditional DC electro-osmotic pumps that utilize electrodes in direct contact with the working fluid. Our previous work has demonstrated the effectiveness of this method in pumping deionized water. However, due to the high resistivity of PDMS, this method proved difficult to apply towards manipulating conductive buffers. To overcome this limitation, we fabricated conductive carbon black (CB) powder directly into the contactless PDMS membranes. The increased electrical conductivity of the contactless PDMS membrane significantly increased micropump performance. Using a microfluidic T-channel device and an electro-osmotic flow model, we determined the influence that CB has on pump pressure for CB weight percents varying between 0 and 20. The results demonstrate that the CB increases pump pressure by two orders of magnitude and enables effective operations with conductive buffers. 相似文献