光寻址电位式传感器在有机磷检测上的应用

通过将乙酰胆碱酯酶用戊二醛交联法固定在光寻址电位式传感器的H+敏Si3N4膜上,即可用于检测有机磷农药。介绍了该传感器的工作原理及制作方法,并且分析探讨了缓冲溶液和乙酰胆碱底液的影响,还给出了在不同抑制时间和不同有机磷浓度下的响应特性。实验表明这是一种简捷灵敏、高效实用的有机磷农药检测新方法。     

AChE/PAMAM-Au/CNTs/GC传感器用于有机磷农药检测的研究

该文制备了一种多层AChE/PAMAM-Au/CNTs/GC乙酰胆碱酯酶的酶抑制电流型传感器应用于有机磷农药的检测,主要利用碳纳米管良好的导电性和吸附性,以及PAMAM(G4)-Au树枝状复合物特殊的结构及导电性能,利用有机磷农药对乙酰且日碱酯酶的抑制作用,以硫代乙酰胆碱(ATCh)为底物,实现了对有机磷农约的检测.实验表明,该方法快速简单,线性范围宽,灵敏度高.固定在传感器上的乙酰胆碱酯酶具有良好的酶动力学响应,其米氏常数(KMapp)为1.66 mmol/L.对有机磷农药呋喃丹的最低检测限达到4.0 nmol/L.     

光电协同催化生物传感器用于检测有机磷农药的研究

该文制备了AChE/PbO2/TiO2/Ti电流型生物传感器,并用原子力显微镜(AFM)对该电极的表面形貌进行了表征,结合流动注射技术将其用于有机磷农药(OPs)的检测.该文利用有机磷农药对乙酰胆碱酯酶的抑制作用,以硫代乙酰胆碱(ATCh)为底物,实现了对有机磷农药敌百虫的检测.实践表明,PbO2/TiO,修饰的酶生物传感器,具有光电协同催化性能,响应速度快,检测灵敏度高,稳定性好;固定在传感器上的乙酰胆碱酯酶具有良好的酶动力学响应,其表观米氏常数(KappM)为1.34mmol/L.对敌百虫的最低检测限达到1.0 nmol/L.     

聚环糊精-碳纳米管有机磷农药生物传感器

通过环糊精的聚合反应及其对碳纳米管的分散作用制备出不溶于水的聚环糊精-碳纳米管复合导电修饰材料,把CNT的稳定性、导电性和催化活性与环糊精分子的包络作用及生物相容性结合起来,得到一种可用于制备电化学生物传感器的碳纳米管-聚合物复合材料.在此基础上,通过优化固定化方法,在该复合材料上固定乙酰胆碱酯酶,制备出了灵敏度较高、线性范围较宽的有机磷农药生物传感器,该传感器可以在1.0～15.0mg/L浓度范围内检测农药甲胺磷的含量,检测下限为0.05mg/L.利用不同扫描速度下的循环伏安数据分析了传感器的电极反应机理,发现该传感器的电极过程由扩散步骤和电子转移步骤混合控制.     

液晶化学传感器制备及在有机磷农药检测中的应用研究

采用微接触印刷法在普通玻璃基底表面制备具有微沟槽结构的功能性有机膜,通过自组装法组装活性位点,采用铜网固定液晶膜制备成了新型的液晶化学传感器.研究结果表明,当传感器用于检测有机磷农药时,液晶分子E7由垂直排列状态向平行排列状态转变,液晶膜的颜色和亮度发生了改变;对常见有机磷农药,其最低检测限达到0.051 g/m3以下...     

基于USB的有机磷农药检测系统设计

为实现在农业生产中对有机磷农药的残留量进行快速有效地检测,设计了一种基于USB的有机磷农药检测系统。首先简单介绍了有机磷农药检测系统的工作原理,然后利用ARM微控制器实现数据采集,并通过USB与上位机PC机通信,实现下位机与上位机数据的实时传输,最终实现有机磷农药检测系统的功能,该系统可以有准确有效地检测出溶液中有机磷农药的残留量。     

无透镜微流控成像流动细胞检测与计数系统

在未来面向个人化的生物医疗诊断中,实时的细胞检测与计数具有重要需求.现有的细胞检测和计数系统例如流式细胞仪和血细胞计数器不适用于小型化流动细胞实时检测和计数.通过将CMOS图像传感器芯片和微流控芯片结合,提出了一种用于流动细胞检测和计数的无透镜微流控成像系统,与用于计数静态细胞的其它无透镜微流控成像系统不同,该系统可以通过基于时域差分的运动检测算法检测和计数微流体通道中连续流动的细胞样本.测试结果表明:该系统可以对微流控通道中流动的人体骨髓基质细胞实现自动检测和计数,并具有-6.53％的低统计错误率.该系统提供了面向未来即时应用的细胞检测和计数解决方案.     

农药残留快速检测生物传感器研究进展

迄今为止,农药残留快速检测用途生物传感器主要有酶生物传感器和免疫生物传感器两大类,农药残留快速检测用途酶生 物传感器又包括胆碱酯酶、酪氨酸酶、碱性磷酸酶、酸性磷酸酶、过氧化物酶、有机磷水解酶和谷胱甘肽巯基转移酶等七种类型,主 要用于蔬菜、水果,以及食品中农药残留的快速检测。农药残留快速检测用途免疫生物传感器主要包括电化学、光学、压电和微机 械悬臂梁四种类型,可以直接用于饮用水、果汁和葡萄酒等农药残留快速检测。     

一种电容传感器金属材料表面缺陷检测方法

基于电容传感器原理,实现了一种简单有效的金属材料表面缺陷检测方法.首先介绍了电容传感器的工作原理,描述了单电极传感器用于检测金属材料表面缺陷时的基本方法,并给出了相应的电路模型.设计了系列实验验证该检测方法的可行性.实验结果表明：电容传感器对金属材料表面缺陷较敏感,通过单片集成电场成像集成器件MC33794能够快速简单实现该检测方法,为金属材料表面缺陷（如腐蚀）提供了一种快速、便捷、有效的检测方法.     

碳纳米管-表面活性剂修饰的H2O2酶电极

酶在电极上的固定是酶传感器制备中的重要环节,它直接影响酶传感器的检测性能.该文利用静电吸附的自组装法以碳纳米管为载体将酶固定在电极上来制备酶传感器,该酶传感器制备过程简单、稳定性好、组装到电极表面的酶的量多并可保持其生物活性,可检测浓度在1.0×10-6～5.4×10-5mol/L范围内的H2O2,最低检测限为5.3×10-7mol/L.这种制备方法为检测农药残留生物传感器的制备提供了一种新的方法.     

Inertial microfluidics for continuous particle filtration and extraction

In this paper, we describe a simple passive microfluidic device with rectangular microchannel geometry for continuous particle filtration. The design takes advantage of preferential migration of particles in rectangular microchannels based on shear-induced inertial lift forces. These dominant inertial forces cause particles to move laterally and occupy equilibrium positions along the longer vertical microchannel walls. Using this principle, we demonstrate extraction of 590 nm particles from a mixture of 1.9 μm and 590 nm particles in a straight microfluidic channel with rectangular cross-section. Based on the theoretical analysis and experimental data, we describe conditions required for predicting the onset of particle equilibration in square and rectangular microchannels. The microfluidic channel design has a simple planar structure and can be easily integrated with on-chip microfluidic components for filtration and extraction of wide range of particle sizes. The ability to continuously and differentially equilibrate particles of different size without external forces in microchannels is expected to have numerous applications in filtration, cytometry, and bioseparations.     

Evaluation of passive mixing behaviors in a pillar obstruction poly(dimethylsiloxane) microfluidic mixer using fluorescence microscopy

The rapid mixing of fluids passing through a microfluidic channel is very important for various applications of microfluidic systems. It has been a great challenge to achieve highly efficient mixing in a microfluidic system because it is very difficult to generate turbulence in a submillimeter-size channel at low Reynolds numbers (Re). In this paper, we fabricated a pillar obstruction microfluidic mixer and evaluated its mixing efficiency at various flow rates. The mixing behavior of confluent streams was estimated using a fluorescence microscope. Three different sets of miscible solutions (phosphate-buffered solution, gold nanocolloids and 20% glycerol), with Rhodamine 6G aqueous solution, were used as sample laminar flows. According to our experimental results, the pillar obstruction microfluidic mixer shows an excellent mixing performance in the low Re range. Here, the mixing performance was strongly dependent on the characteristic viscosity changes of different sets of miscible solutions. The pillar obstruction microfluidic mixer designed here is expected to benefit a wide range of lab-on-a-chip applications because fabrication is very simple and the mixing efficiency is excellent at low Re.     

Potentiometric characterisation of a dual-stream electrochemical microfluidic device

A microfluidic device is presented with off-chip electrodes residing in a reservoir and connected via micro-capillaries to the Y-shaped microfluidic channel. The device is tested by potentiometric measurements involving dual-stream laminar flow of two aqueous solutions carrying different electrolytes at various concentrations. Open circuit potentials are measured for a series of solutions of alkali metal chlorides and tetraalkylammonium chlorides as well as for dilute hydrochloric acid. The open circuit potential for the microfluidic chip was calculated by taking into account the diffusion potential at finite ionic strength as well as the potential difference introduced by the reference electrode system. The liquid junction potential developed at the boundary of the co-flowing aqueous solutions may be manipulated to have greater or lesser relative contributions to the measured open circuit potential based on use of electrolyte salts having cation and anion pairs of similar or dissimilar mobilities in solution. A reasonable agreement between theoretical and experimental values of the open circuit potential is observed for these situations. The results show that simple microfluidic structures possess a rich environment for exploration and application of the solution chemistry of ions.     

Disposable microfluidic blood cuvette for measuring hemoglobin concentration

This paper presents a new air-bubble free microfluidic blood cuvette for the measurement of hemoglobin concentration. The microfluidic blood cuvette was filled with blood samples by capillary force, and hemoglobin levels in the blood were determined by measuring absorbance at the wavelength of 530 nm. Two different microfluidic blood cuvettes with dual and single sidewall microchannels were investigated. The microfluidic blood cuvette was fabricated using a polymethyl methacrylate substrate and a dry film photoresist. During the blood-filling process, air was trapped in the dual-sided wall-type cuvettes, while no air trapping occurred in the single sidewall-type cuvettes. The sensitivity of the hemoglobin measurements was more linear in a 105 μm deep microchannel than in a 35 μm deep microchannel.     

Investigation of wax and paper materials for the fabrication of paper-based microfluidic devices

Paper-based microfluidic devices hold great potential in today’s microfluidic applications. They offer low costs, simple and quick fabrication processes, ease of uses, etc. In this work, several wax and paper materials are investigated for the fabrication of paper-based microfluidic devices. A novel method of using wax as a suitable backing to a paper-based analytical device has been demonstrated. Governing equations for the mechanics of the fluid flow in paper-based channels with constant widths have been experimentally validated. Experimental results showing deviations from the governing equations have been verified using fluidic channels with varying widths. There lies the possibility of manipulation of the fluid flow in paper-based microfluidic devices solely using geometric factors. This opens up many potential applications that may require sequential delivery of reagents or samples. Lastly, properties of paper such as the average pore diameter and permeability can be deduced from experimental results.     

Fabrication of polystyrene microfluidic devices using a pulsed CO<Subscript>2</Subscript> laser system

In this article, we described a simple and rapid method for fabrication of droplet microfluidic devices on polystyrene substrate using a CO₂ laser system. The effects of the laser power and the cutting speed on the depth, width and aspect ratio of the microchannels fabricated on polystyrene were investigated. The polystyrene microfluidic channels were encapsulated using a hot press bonding technique. The experimental results showed that both discrete droplets and laminar flows could be obtained in the device.     

Centrifugal automation of a triglyceride bioassay on a low-cost hybrid paper-polymer device

We present a novel paper-polymer hybrid construct for the simple automation of fundamental microfluidic operations in a lab-on-a-disc platform. The novel design, we term a paper siphon, consists of chromatographic paper strips embedded along a siphon microchannel. The paper siphon relies on two main interplaying forces to create unique valving and liquid-sampling methods in centrifugal microfluidics. At sufficiently low speeds, the inherent wicking of the paper overcomes the rotationally induced centrifugal force to drive liquids towards inwards positions of the disc. At elevated speeds, the dominant centrifugal force will extract liquid from the siphon paper strip towards the edge of the disc. Distinct modes of flow control have been developed to account for water (reagent) and more viscous plasma samples. The system functionality is demonstrated by the automation of sequential sample preparation steps in a colorimetric triglyceride assay: plasma is metered from a whole blood sample and incubated with a specific enzymatic mixture, followed by detection of triglyceride levels through (off-disc) absorbance measurements. The successful quantification of triglycerides and the simple fabrication offer attractive directions for such hybrid devices in low-cost bioanalysis.     

Novel prototyping method for microfluidic devices based on thermoplastic polyurethane microcapillary film

Thermoplastic polyurethane microcapillary film (TPU-MCF), as a novel extruded product, inherently contains an array of circular micron-sized capillaries embedded inside the polymer matrix. With the aid of simple laser cutting and conventional sealing technologies, a rapid prototyping method for microfluidic devices is proposed based on the ready-made microstructure of MCFs. Two functionalized microfluidic devices: serpentine micromixer and multi-droplet generator, are rapidly fabricated to demonstrate the advantages and potential of employing this new method. The whole proof-of-concept fabrication process can be completed in 8–10 min in a simple way; each procedure is repeatable with stable performance control of microfluidic devices; and the material cost can be as low as $0.01 for each device. The TPU-MCF and this novel method are expected to provide a new perspective and alternative in microfluidic community with particular requirements.     

Microfluidic bolus induced gradient generator for live cell signalling

Major events in cell biology are initiated by the binding of ligands to cell surface receptors and/or their transport into cells. We present a study of a simple microchannel system that integrates a bolus generator and surface-adhered cell culture domains. Our system allows the delivery of small packets or boluses of biomolecules to a cell population. Owing to pressure driven microfluidic flow of the bolus, a gradient of cell surface bound ligands is established along the length of the microchannel. Experimental data for the epidermal growth factor (EGF) binding to its receptor on A431 cells are presented. We highlight the effect of changing Peclet number (or flowrate), bolus shape, bolus volume and ligand concentration on the gradient formed longitudinally in the microchannel. A mathematical model describing the transient convection, diffusion, dispersion and binding of ligands to cell surface receptors is developed. The model provides essential design guidelines for our system with good qualitative agreement with experimental data. The results suggest ways to modulate the amount of bound ligand and the gradient independently. This simple microsystem is suitable for generating longer range gradients involving larger cell populations as compared to existing microfluidic systems.     

A simple method of constructing microfluidic solid-state quantum dot molecular beacon array for label-free DNA detection

Solid-state molecular beacons show great potential for label-free biomarker detection, however, it is challenging to construct robust and homogenous quantum dot molecular beacon microarrays in a microfluidic platform. Here, we report a simple and cost-effective method of constructing a mercaptopropionic acid quantum dot (MPA-QD) microarray in a microfluidic platform using a PDMS through-hole structure. This method combines soft lithography and surface functionalization to achieve uniform QD immobilization in a microfluidic network. With the simple fabricated quantum dot microarray sensor integrated in the microfluidic device, label-free biomarker detection was performed with high efficiency, specificity and sensitivity. We performed cardiovascular biomarker detection, and our microfluidic QD molecular beacon platform achieved target DNA sequence identification at a low concentration of 1 nM/L.