A novel alternating current multiple array electrothermal micropump for lab-on-a-chip applications

The AC electrothermal technique is very promising for biofluid micropumping, due to its ability to pump high conductivity fluids. However, compared to electroosmotic micropumps, a lack of high fluid flow is a disadvantage. In this paper, a novel AC multiple array electrothermal (MAET) micropump, utilizing multiple microelectrode arrays placed on the side-walls of the fluidic channel of the micropump, is introduced. Asymmetric coplanar microelectrodes are placed on all sides of the microfluidic channel, and are actuated in different phases: one, two opposing, two adjacent, three, or all sides at the same time. Micropumps with different combinations of side electrodes and cross sections are numerically investigated in this paper. The effect of the governing parameters with respect to thermal, fluidic, and electrical properties are studied and discussed. To verify the simulations, the AC MAET concept was then fabricated and experimentally tested. The resulted fluid flow achieved by the experiments showed good agreement with the corresponding simulations. The number of side electrode arrays and the actuation patterns were also found to greatly influence the micropump performance. This study shows that the new multiple array electrothermal micropump design can be used in a wide range of applications such as drug delivery and lab-on-a-chip, where high flow rate and high precision micropumping devices for high conductivity fluids are needed.     

Nano-islands integrated evanescence-based lab-on-a-chip on silica-on-silicon and polydimethylsiloxane hybrid platform for detection of recombinant growth hormone

Integration of nano-materials in optical microfluidic devices facilitates the realization of miniaturized analytical systems with enhanced sensing abilities for biological and chemical substances. In this work, a novel method of integration of gold nano-islands in a silica-on-silicon-polydimethylsiloxane microfluidic device is reported. The device works based on the nano-enhanced evanescence technique achieved by interacting the evanescent tail of propagating wave with the gold nano-islands integrated on the core of the waveguide resulting in the modification of the propagating UV-visible spectrum. The biosensing ability of the device is investigated by finite-difference time-domain simulation with a simplified model of the device. The performance of the proposed device is demonstrated for the detection of recombinant growth hormone based on antibody-antigen interaction.     

CMC聚合物对重金属离子的吸附性能

通过正交试验得出制备羧甲基纤维素(CMC)聚合物的最佳工艺条件:丙烯酸(AA)/羧甲基纤维素=10,引发剂(硫酸铵)和交联剂(N,N'-亚甲基双丙烯酰胺)用量分别为单体的0.0014倍和0.0015倍.吸胀平衡后,将CMC聚合物在400~450℃下完全灰化16h,消解并用火焰原子吸收法测定聚合物对Zn2+、Cu2+、Pb2+、Cd2+、Cr2+、Ni2+和Mn2+的吸附性能.结果表明,CMC聚合物对重金属离子具有一定的吸附能力,其吸附量随着溶液pH值和重金属离子质量浓度的增加而增大,当pH为9时达到最大;并且CMC聚合物对Pb2+和Cu2+的吸附量要大于其他金属离子.     

A specific colorimetric assay for Dapsone in biological fluids

The original Bratton and Marshall method for sulfanilamide assay has been modified for differential assay of Dapsone even in the presence of other diazotisable compounds. The property of Dapsone diazo derivative to precipitate out upon its coupling with N-(1-naphthyl) ethylene diamine has been taken advantage to differentiate this sulphone from that of other diazotisable compounds. The present assay method also enables one to assay free DDS and its acid labile metabolites in biological samples even in the presence of other diazotisable compounds. The use of the organic solvent to extract the azo colour complex renders greater sensitivity and specificity for DDS assay.     

A hybrid dielectrophoretic system for trapping of microorganisms from water

Assessment of the microbial safety of water resources is among the most critical issues in global water safety. As the current detection methods have limitations such as high cost and long process time, new detection techniques have transpired among which microfluidics is the most attractive alternative. Here, we show a novel hybrid dielectrophoretic (DEP) system to separate and detect two common waterborne pathogens, Escherichia coli (E. coli), a bacterium, and Cryptosporidium parvum (C. parvum), a protozoan parasite, from water. The hybrid DEP system integrates a chemical surface coating with a microfluidic device containing inter-digitated microelectrodes to impart positive dielectrophoresis for enhanced trapping of the cells. Trimethoxy(3,3,3-trifluoropropyl) silane, (3-aminopropyl)triethoxysilane, and polydiallyl dimethyl ammonium chloride (p-DADMAC) were used as surface coatings. Static cell adhesion tests showed that among these coatings, the p-DADMAC-coated glass surface provided the most effective cell adhesion for both the pathogens. This was attributed to the positively charged p-DADMAC-coated surface interacting electrostatically with the negatively charged cells suspended in water leading to increased cell trapping efficiency. The trapping efficiency of E. coli and C. parvum increased from 29.0% and 61.3% in an uncoated DEP system to 51.9% and 82.2% in the hybrid DEP system, respectively. The hybrid system improved the cell trapping by encouraging the formation of cell pearl-chaining. The increment in trapping efficiency in the hybrid DEP system was achieved at an optimal frequency of 1 MHz and voltage of 2.5 V_pp for C. parvum and 2 V_pp for E. coli, the latter is lower than 2.5 V_pp and 7 V_pp, respectively, utilized for obtaining similar efficiency in an uncoated DEP system.     

A neural network-based detection and mitigation system for unintended acceleration

Modern vehicles are equipped with a growing number of electronic devices, which significantly improve the driving experience. However, the complicated architecture of electronic systems also increases the difficulty of fault diagnosis since process models are often unavailable. This paper presents a novel detection and mitigation system for vehicle related anomalies originating in unintended acceleration (UA), which has become one of the most complained-about vehicle problems in recent history. The detection system consists of several neural network-based models, which are created by analyzing historical vehicle data at specific moments such as acceleration peaks and gear shifting. These data-driven models describe the boundary of normal vehicle behavior in the data space. A priori knowledge of complete vehicle structures is not necessary for building them. The detection system combines these models to decide if a UA event has occurred. When a UA event is detected, a mitigation system cuts the engine power and adjusts the braking force accordingly. The whole system was validated in the Simulink/dSPACE environment. UA errors were simulated so that they occurred randomly when human subjects drove virtual cars in a simulated environment. Random noise of sensors were also considered and incorporated to add realism. Various traffic scenarios were included in tests. Test results show that the integrated system is capable of detecting UA in one second with high accuracy and reducing the risk of accidents.     

Design and optimization of a double-enzyme glucose assay in microfluidic lab-on-a-chip

An electrokinetic driven microfluidic lab-on-a-chip was developed for glucose quantification using double-enzyme assay. The enzymatic glucose assay involves the two-step oxidation of glucose, which was catalyzed by hexokinase and glucose-6-phosphate dehydrogenase, with the concomitant reduction of NADP⁺ to NADPH. A fluorescence microscopy setup was used to monitor the different processes (fluid flow and enzymatic reaction) in the microfluidic chip. A two-dimensional finite element model was applied to understand the different aspects of design and to improve the performance of the device without extensive prototyping. To our knowledge this is the first work to exploit numerical simulation for understanding a multisubstrate double-enzyme on-chip assay. The assay is very complex to implement in electrokinetically driven continuous system due to the involvement of many species, which has different transport velocity. With the help of numerical simulation, the design parameters, flow rate, enzyme concentration, and reactor length, were optimized. The results from the simulation were in close agreement with the experimental results. A linear relation exists for glucose concentrations from 0.01 to 0.10 g l⁻¹. The reaction time and the amount of enzymes required were drastically reduced compared to off-chip microplate analysis.     

边缘检测在火灾检测系统中的应用

对Robert边缘检测算子,Sobel边缘检测算子,Laplace边缘检测算子,Canny边缘检测算子这四种经典的边缘检测算子进行理论分析.然后在OpenCV应用平台下进行实验及结果分析.比较其各自的优缺点,从而选择效果最佳的边缘检测算子,应用在火灾检测系统的软件设计中.     

A "place n play" modular pump for portable microfluidic applications

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.     

光电编码器自动沿面检测系统

设计出了一套光电编码器自动沿面检测系统. 对沿面检测的意义和传统方法进行了简要说明;详细阐述了所设计系统中的硬件电路和数据捕捉的算法. 检测结果表明,此系统操作方便、界面友好、原理正确、设计合理、能够满足使用条件.     

地表水源热泵系统水体初始温度分布模型

以滞留水体为地表水源热泵系统为研究对象,进行水温初始温度分布分析.根据水温控制方程和水流控制方程建立了二维初始水温模型,求得了水体初始水温的数值分布,并对计算结果和实际测试数据进行了对比分析.该温度分布模型可以应用于地表水源热泵初始水体的适应性研究,为动态负荷下水体水温变化规律的研究奠定了基础.     

A colorimetric method for the estimation of cholesterol from high density lipoprotein and its subclasses

The technique involves estimation of cholesterol after a double precipitation procedure to separate subfractions of high density lipoprotein (HDL). Cholesterol estimation by a colorimetric method compares favourably with the enzymatic method. This simple method is acceptable for the routine estimation of HDL-Cholesterol (HDL-C) and its subclasses.     

系统论在管网检漏中的探索与应用

通过对影响管网漏损各因素的梳理,对管网漏水的直接因素及其影响大小、漏水状态和漏水量、不同口径管道,不同材质管道漏水情况进行了全面对比分析,运用系统论的方法从管理、技术、服务等方面提出了解决措施,同时针对管网漏损控制系统性和长期性的特点,谈了一些在日常管理运行中的体会.