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1.
A vision-based on-chip sensor for sensing local pressure inside a microfluidic device is proposed and evaluated in this paper. The local pressure is determined from the change of color intensity in the sensing chamber which is pre-filled with colored fluid. The working principle of the sensor is based on polydimethylsiloxane deformation. The pressure at the point of interest is guided into a deformation chamber, where the structural stiffness is softened by chamber geometry, and thus, the chamber deforms as a result of pressure changes. Such deformation is transmitted to the sensing chamber, a same-layer concentric inside the deformation chamber. The deformation in the sensing chamber causes the colored fluid flowing in or out the chamber and leads to different color intensity from the top view through a microscope. Experimental evaluations on static and dynamic responses by regulated input pressures were conducted. The correlation in static response is 0.97 while the dynamic responses are successfully observed up to 16 Hz. The greatest advantage is that the local pressure can be directly seen without any additional hardware or electricity. The whole sensor is on a single-layer microfluidic design, so that the fabrication is simple, consistent, and low-cost. The single-layer design also provides the convenience of easy integration for existing microfluidic systems. 相似文献
2.
由于天线结构局部变形并出现凹区,造成口径场产生畸变,从而导致了天线旁瓣性能下降。文章以某车载雷达天线为例,根据其在微波暗室的测试结果以及天线方向图与其口径场之间的关系,通过理论分析,探讨口径场分布影响天线旁瓣性能的主要机理。 相似文献
3.
In this report, we describe in detail a microfluidic analyzer, which is able to conduct blood coagulation tests using whole blood samples. Sample preparation steps, such as whole blood aliquoting and metering, plasma separation, decanting, and mixing with reagents were performed in sequence through microfluidic functions integrated on a disk. Both prothrombin time (PT) and activated partial thromboplastin time (aPTT) were carried out on the same platform and the test results can be reported in 5 min. Fifty clinical samples were tested for both PT and aPTT utilizing the microfluidic disk analyzer and the instrument used in hospitals. The test results showed good correlation and agreement between the two instruments. 相似文献
4.
A microfabricated calorimeter (μ-calorimeter) with an enclosed reaction chamber is presented. The 3D micromachined reaction chamber is capable of analyzing liquid samples with volume of 200 nl. The thin film low-stress silicon nitride membrane is used to reduce thermal mass of the calorimeter and increase the sensitivity of system. The μ-calorimeter has been designed to perform DC and AC calorimetry, thermal wave analysis, and differential scanning calorimetry. The μ-calorimeter fabricated with an integrated heater and a temperature sensor on opposite sides of the reaction chamber allows to perform thermal diffusivity and specific heat measurements on liquid samples with same device. Measurement results for diffusivity and heat capacitance using time delay method and thermal wave analysis are presented. 相似文献
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6.
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
7.
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
8.
M. A. Fallah V. Huck V. Niemeyer A. Desch J. I. Angerer T. A. J. McKinnon A. Wixforth S. W. Schneider M. F. Schneider 《Biomicrofluidics》2013,7(4)
The role of von Willebrand factor (VWF) as a shear stress activated platelet adhesive has been related to a coiled-elongated shape conformation. The forces dominating this transition have been suggested to be controlled by the proteins polymeric architecture. However, the fact that 20% of VWF molecular weight originates from glycan moieties has so far been neglected in these calculations. In this study, we present a systematic experimental investigation on the role of N-glycosylation for VWF mediated platelet adhesion under flow. A microfluidic flow chamber with a stenotic compartment that allows one to mimic various physiological flow conditions was designed for the efficient analysis of the adhesion spectrum. Surprisingly, we found an increase in platelet adhesion with elevated shear rate, both qualitatively and quantitatively fully conserved when N-deglycosylated VWF (N-deg-VWF) instead of VWF was immobilized in the microfluidic channel. This has been demonstrated consistently over four orders of magnitude in shear rate. In contrast, when N-deg-VWF was added to the supernatant, an increase in adhesion rate by a factor of two was detected compared to the addition of wild-type VWF. It appears that once immobilized, the role of glycans is at least modified if not—as found here for the case of adhesion—negated. These findings strengthen the physical impact of the circulating polymer on shear dependent platelet adhesion events. At present, there is no theoretical explanation for an increase in platelet adhesion to VWF in the absence of its N-glycans. However, our data indicate that the effective solubility of the protein and hence its shape or conformation may be altered by the degree of glycosylation and is therefore a good candidate for modifying the forces required to uncoil this biopolymer. 相似文献
9.
K.H. Swainger 《Journal of The Franklin Institute》1948,245(6):501-516
The equilibrating stresses on an orthogonal element in a strained body induce normal strains defined as relative displacement per unit length of deformed body. This vector “straining”-displacement must be a point function for continuity of the solid. The work done by the forces on the faces of an orthogonal element of unit volume in the loaded body during a differential increase of deformation is found. Integration gives the total work done on the element, from the initial unstrained state up to the current state of deformation. 相似文献
10.
O. Yassine C. P. Gooneratne D. Abu Smara F. Li H. Mohammed J. Merzaban J. Kosel 《Biomicrofluidics》2014,8(3)
This study describes the development and testing of a magnetic microfluidic chip (MMC) for
trapping and isolating cells tagged with superparamagnetic beads (SPBs) in a microfluidic
environment for selective treatment and analysis. The trapping and isolation are done in two
separate steps; first, the trapping of the tagged cells in a main channel is achieved by soft
ferromagnetic disks and second, the transportation of the cells into side chambers for isolation is
executed by tapered conductive paths made of Gold (Au). Numerical simulations were performed to
analyze the magnetic flux and force distributions of the disks and conducting paths, for trapping
and transporting SPBs. The MMC was fabricated using standard microfabrication processes. Experiments
were performed with E. coli (K12 strand) tagged with 2.8 μm SPBs.
The results showed that E. coli can be separated from a sample solution by trapping
them at the disk sites, and then isolated into chambers by transporting them along the tapered
conducting paths. Once the E. coli was trapped inside the side chambers, two
selective treatments were performed. In one chamber, a solution with minimal nutrition content was
added and, in another chamber, a solution with essential nutrition was added. The results showed
that the growth of bacteria cultured in the second chamber containing nutrient was significantly
higher, demonstrating that the E. coli was not affected by the magnetically driven
transportation and the feasibility of performing different treatments on selectively isolated cells
on a single microfluidic platform. 相似文献
11.
In this paper, a novel oscillating flow polymerase chain reaction (PCR) device was designed and fabricated to amplify SPPS150 and salmonella typhi. In this new design, the samples are shuttled (oscillating flow) inside a microfluidic chip to three different temperature zones required for DNA amplification. The amplification cycle time has markedly been reduced as the reagent volume used was only about 25% of that used in conventional PCRs. Bubble formation and adsorption issues commonly associated to chip based PCR were also eliminated. Based on the performance evaluated, it is demonstrated that this oscillating flow PCR has the advantages of both the stationary chamber and continuous flow PCR devices. 相似文献
12.
This study determines the optimal vascular designs for perfusing engineered tissues. Here, "optimal" describes a geometry that minimizes vascular volume fraction (the fractional volume of a tissue that is occupied by vessels) while maintaining oxygen concentration above a set threshold throughout the tissue. Computational modeling showed that optimal geometries depended on parameters that affected vascular fluid transport and oxygen consumption. Approximate analytical expressions predicted optima that agreed well with the results of modeling. Our results suggest one basis for comparing the effectiveness of designs for microvascular tissue engineering. 相似文献
13.
人脸由于其非刚性明显,受到运动背景变化、形变程度复杂、特征丢失等因素的影响,使得在进行三维动态人脸形变估计时,面临着估计不准,误差较大的问题。为了解决这些问题,提出一种基于特征缺失修复的人脸三维运动形变估计算法,将非刚体人脸运动的形变估计过程中,运用特征补偿方法,补偿由于噪声、形变程度复杂带来的特征丢失缺陷,运用较多的人脸形变特征进行形变分析,准确计算人脸的形变程度。实验结果表明,这种方法得到的解误差较小,效果明显。 相似文献
14.
A microfluidic device that is able to perform dielectric spectroscopy is developed. The device consists of a measurement chamber that is 250 μm thick and 750 μm in radius. Around 1000 cells fit inside the chamber assuming average quantities for cell radius and volume fraction. This number is about 1000 folds lower than the capacity of conventional fixtures. A T-cell leukemia cell line Jurkat is tested using the microfluidic device. Measurements of deionized water and salt solutions are utilized to determine parasitic effects and geometric capacitance of the device. Physical models, including Maxwell-Wagner mixture and double shell models, are used to derive quantities for sub-cellular units. Clausius-Mossotti factor of Jurkat cells is extracted from the impedance spectrum. Effects of cellular heterogeneity are discussed and parameterized. Jurkat cells are also tested with a time domain reflectometry system for verification of the microfluidic device. Results indicate good agreement of values obtained with both techniques. The device can be used as a unique cell diagnostic tool to yield information on sub-cellular units. 相似文献
15.
[目的/意义] 学科核心期刊载文量下降现象需要引起重视,有必要在此背景下分析论文篇幅与被引之间的关系。[方法/过程] 本文提出篇幅影响因子的概念,采用普通回归与分位数回归,基于CNKI引文数据库,对CSSCI数据库收录的17 275篇经济学期刊进行了系统分析。[结果/结论] 研究结果表明：学科期刊载文量下降现象需要引起足够的重视;篇幅影响因子与论文篇幅无关;论文篇幅与被引无关;关于论文篇幅与被引关系的研究方法有待改善;建议将载文量作为CSSCI评价指标。 相似文献
16.
The solid phase polymerase chain reaction (PCR) on a gel-based microarray system was studied under various durations of individual stages of the PCR cycle and spatial restriction of the reaction volume. Combining the experimental study with numerical modeling, we demonstrated that the diffusion of the PCR product in and out of a microarray element during the annealing and melting stages, respectively, is the main factor responsible for distinctive features of the studied type of PCR. The restriction of reaction volume leads to faster PCR signal growth. Particularly, the capillary array, whereby gel-based microarray elements are located on a glass bar inserted into capillary chamber, was found to be a suitable format for the development of the platform. 相似文献
17.
This paper presents a method for the evaluation of the tensile strength of composite materials made of a soft matrix with hard inclusions. The tensile strength is calculated as the force per unit area required for the onset of plastic flow in the material. In addition to the tensile strength, the severity of the core deformation and the rate of void formation are also estimated. The results are based on an upper-bound analysis with a two parameter family of velocity fields which accounts for both non-homogeneity of deformation and void formation.The model of the composite and the family of the velocity field used here have already appeared in published articles. Moreover, the application of the present method to estimate the tensile strength in cases when ductile deformation prevails (i.e. when there is no void formation) would lead to the same results as in the previous studies based on the same model and velocity fields.New here is the completeness of the analysis. All possible flow patterns, including for the first time void forming flows, were considered. This made it possible to show that the conditions required to ensure that one or another flow pattern prevails (i.e. those conditions found here and in other articles based on the same model) are not only necessary but also sufficient, at least from a theoretical point of view.The results of this paper have not yet been confirmed experimentally. Although the general trends are in the expected direction, so far no attempt has been made to find the degree of correlation between the theory and the behavior of real materials. 相似文献
18.
本文利用GPS技术对南宁市天雹水库进行变形观测,并利用TEQC软件对GPS观测数据进行了初步处理,证实了GPS变形监测数据有着良好的质量和可靠性,然后利用徕卡后处理软件LGO对整个监测网数据进行了基线解算和网平差,最后对比了非完全多项式模型和三维坐标转换的结果,得出多项拟合法的计算过程更为简单,结果满足变形监测的要求。 相似文献
19.
对2款外部尺寸相同、内部毛细芯结构不同的均热板进行理论分析与数值分析.结果表明,1)内部具有烧结铜粉柱体的均热板热性能更加优良,这是由于烧结铜粉柱体缩短了工质的回流通路与时间;2)数值分析对均热板结构优化与热性能的提高具有指导意义. 相似文献
20.
In the present study, we report a simple and economical precipitation method for the quantitative determination of small,
dense LDL-cholesterol (sdLDL-C) in serum that is considered to be an emerging risk factor for cardiovascular disease. This
method consisted of precipitation of lipoproteins of density <1.044 g/ml using heparin-MnCl2 and quantification of cholesterol existed in the supernatant using reagents for routine cholesterol assay instead of the
costly direct low density lipoprotein-cholesterol assay kit. The supernatant contained sdLDL and high-density lipoprotein
(HDL) that was confirmed by polyacrylamide gel electrophoresis. sdLDL-C concentration can be calculated by subtracting the
HDL-C value from the total cholesterol concentration of the supernatant. sdLDL-C values obtained by this modified method were
similar to those obtained by direct assay of sdLDL-C and there was significant correlation between the two methods. In conclusion,
this method is highly economical, do not require special equipments and is useful to evaluate atherogenic risk. 相似文献