一种压阻式微悬臂梁免疫传感器及其动力学分析

针对传统光学读出微悬臂梁传感器所需测量系统复杂的局限,将生物素—亲和素系统的放大效应与压阻式微悬臂梁传感技术结合起来,成功构建了一种读出方式简单的压阻式微悬臂梁免疫传感器。利用构建的传感器对相思子毒素进行检测,检测限达8μg/L,反应在20 min内基本完成,具有很好的特异性和重现性,能满足水样、土壤、食品等实际模拟样品检测的要求。建立了压阻式微悬臂梁免疫传感器检测相思子毒素的反应动力学模型,并对实际检测数据进行了拟合分析,相关系数R值在0.971 1以上(P0.001)。根据拟合方程求出的传感器对不同浓度相思子毒素反应达到平衡的响应电压ΔU e、响应时间t0均与实测值非常接近。     

Design and optimization of laminated piezoresistive microcantilever sensors

Microcantilevers-based sensors (MCSs) are a new approach to detecting and measuring physical, chemical, and biological signals in the nano- to femto-range level. Piezoresistive readout systems for MCSs have the advantages of full integration, low cost, ease of use, and the capability of manipulating large arrays. This paper presents a design method for laminated piezoresistive MCSs to obtain optimal performance by optimizing the dimensions of the microcantilevers and the doping concentration of the piezoresistors. Laminated theory was employed to deduce the closed-form solutions to static stress and natural frequency. Expressions for predicting sensitivity and resolution were derived by combining stress distribution with power densities of 1/f noise and Johnson noise. Finite element method (FEM) was performed to verify the theoretical results. The thickness of the laminated MCSs and the doping concentration were optimized by using static analyses and power densities of noise to generate the best sensitivity and resolution. A method based on non-linear programming is given to facilitate the solving process. These methods and some conclusions are also applicable to developing other types of piezoresistive sensors that use laminated structures.     

Design and analysis of piezoresistive microcantilever for surface stress measurement in biochemical sensor

Piezoresistive microcantilever has been proposed to measure the surface stress generated by biochemical analytes. Such in situ measurement is desirable for biochemical sensors with on-chip microsystem integration. A two-dimensional model is presented to analyze the four-layer piezoresistive microcantilever subject to the surface stress effect generated by biochemical reaction and the thermal effect induced by the piezoresistive layer. Analysis shows that both effects are detrimental to sensor measurement. Conventional wisdom by changing the aspect ratio of a microcantilever is futile to achieve higher sensitivity. An improved design by having the stripe pattern on the immobilized layer is developed to increase the measurement sensitivity. Higher sensitivity can also be obtained by having thicker bottom insulation layer and thinner piezoresistive layer. It is shown that the microcantilever design is superior to the stress concentration region (SCR) design commonly seen in atomic force microscopy (AFM).     

Experimental and numerical investigation of capillary flow in SU8 and PDMS microchannels with integrated pillars

Microfluidic channels with integrated pillars are fabricated on SU8 and PDMS substrates to understand the capillary flow. Microscope in conjunction with high-speed camera is used to capture the meniscus front movement through these channels for ethanol and isopropyl alcohol, respectively. In parallel, numerical simulations are conducted, using volume of fluid method, to predict the capillary flow through the microchannels with different pillar diameter to height ratio, ranging from 2.19 to 8.75 and pillar diameter to pitch ratio, ranging from 1.44 to 2.6. The pillar size (diameter, pitch and height) and the physical properties of the fluid (surface tension and viscosity) are found to have significant influence on the capillary phenomena in the microchannel. The meniscus displacement is non-uniform due to the presence of pillars and the non-uniformity in meniscus displacement is observed to increase with decrease in pitch to diameter ratio. The surface area to volume ratio is observed to play major roles in the velocity of the capillary meniscus of the devices. The filling speed is observed to change more dramatically under different pillar heights upto 120 μm and the change is slow with further increase in the pillar height. The details pertaining to the fluid distribution (meniscus front shapes) are obtained from the numerical results as well as from experiments. Numerical predictions for meniscus front shapes agree well with the experimental observations for both SU8 and PDMS microchannels. It is observed that the filling time obtained experimentally matches very well with the simulated filling time. The presence of pillars creates uniform meniscus front in the microchannel for both ethanol and isopropyl alcohol. Generalized plots in terms of dimensionless variables are also presented to predict the performance parameters for the design of these microfluidic devices. The flow is observed to have a very low Capillary number, which signifies the relative importance of surface tension to viscous effects in the present study.     

Experimental evaluation of sensitivity and non-linearity in polysilicon piezoresistive pressure sensors with different diaphragm sizes

MEMS-based piezoresistive pressure sensors are widely popular due to advantages such as small size, low cost, simple fabrication, and DC output. In this work, the design simulation, fabrication process, and characterization of four pressure sensors with square diaphragms of edge-length 1,060, 1,280, 1,480, and 1,690 µm are reported. Several design principles such as appropriate boundary condition, piezoresistor placement, and fracture stress are considered in the design phase. The sensors have novel shaped polysilicon piezoresistors and equal diaphragm thickness of 50 µm. The sensors are fabricated simultaneously by putting the different designs on the same mask set so that the best design can be determined after characterization. The uncompensated and unamplified output response of the different sensors are reported at three temperatures (?5, 25 and 55 °C). Out of the four sensors with different diaphragm sizes, the sensor with a diaphragm edge length of 1,280 μm is found to have optimum characteristics. For the diaphragm with edge-length of 1,280 µm, in the pressure range of 0–30 Bar, sensitivity of 3.35–3.73 mV/Bar, non-linearity of <0.3 %, and hysteresis of <0.1 % are obtained. The different sensors can be used in the specified pressure range for suitable applications.     

Amperometric glucose biosensor based on integration of glucose oxidase with platinum nanoparticles/ordered mesoporous carbon nanocomposite

This article reports a new amperometric glucose biosensor based on ordered mesoporous carbon (OMC) supported platinum nanoparticles (Pt/OMC) modified electrode. The Pt/OMC nanocomposite modified electrode exhibited excellent electrocatalytic activities towards the reduction and oxidation of H₂O₂ as well. This feature allowed us to use it as bioplatform on which glucose oxidase (GOD) was immobilized by entrapment in electropolymerized pyrrole film for the construction of the glucose biosensor. The biosensor showed good analytical performances in terms of low detection (0.05 mM), high sensitivity (0.38 μA/mM) and wide linear range (0.05-3.70 mM). In addition, the effects of pH value, applied potential, electroactive interference and the stability of the biosensor were discussed. The applicability to blood analysis was also evaluated.     

Modelling and simulation of dynamically integrated manufacturing systems

Fluctuations in demand patterns and products?? mixes, driven by continuous changes in customer requirements, are inducing significant changes on the operations of manufacturing organisations. How to respond to such changes rapidly and at minimum cost constitutes a major challenge for manufacturers. The DIMS project (Dynamically Integrated Manufacturing Systems) has developed an agent-based approach that enables manufacturing systems to be modelled using multi-agent systems such that optimal and timely responses to changes are generated from the interactions taking place within the multi-agents systems. This approach also incorporates a distributed discrete event simulation mechanism that enables ??what-if?? system configurations that have been generated through agent interactions to be evaluated dynamically for system restructure. This paper presents the approach with particular focus on the distributed simulation mechanism.     

Effect of horizontal diaphragm flexibility on the P-delta analysis

This paper investigates the importance of including the effects of the flexibility of the horizontal diaphragms when using the P-delta method of analysis, especially when considering the loads applied to intermediate frames on trusses that are not part of the lateral force resisting system. Analyses were conducted for structural systems with a variable number of stories, number of bays and diaphragm stiffnesses and supported by rigid jointed plane frames or vertical trusses.     

压阻式加速度计双端固支梁结构的设计与分析

介绍一种压阻式加速度计双端固支梁的结构,并建立其三维实体有限元模型。分析了在惯性载荷作用下的弹性梁的应力及应变,并对弹性结构进行了模态分析。讨论影响灵敏度、固有频率等主要指标的因素,用有限元方法进行分析、模拟,以达到优化设计的目的。     

微悬臂梁DNA生物传感器纳米力学分析的重力模型及其应用

基于微悬臂梁技术的DNA生物传感器的纳米挠度与核苷长度、嫁接密度、杂交率、重力、盐溶液浓度、时间、温度变化、缓冲液流场特性等诸多因素有关.利用Zhang两变量方法,建立了静态模式中自重作用下微梁正应力、切应力、层间挤压应力及其挠度预测的解析模型.作为应用,采用McKendry实验参数,研究了重力因素对静态纳米挠度的影响,发现参考梁技术中生物层自重对纳米挠度的影响可以忽略,但单梁技术中非生物层自重对纳米挠度的影响不可以忽略;同时,利用DNA生物传感器表面应力的Zhang解析模型,考虑自重和表面应力因素,给出了微梁的最优尺寸,从而可使单梁技术中自重因素对静态挠度的影响降到最低.     

锇聚合物修饰的低浓度葡萄糖传感器制备与响应特性研究

将锇氧化还原聚合物与辣根过氧化酶共价交联修饰薄膜金电极,使用戊二醛交联固定葡萄糖氧化酶制得葡萄糖传感器,对传感器的制备条件和其对低浓度葡萄糖的响应特性进行了研究.在-0.1 V(vs.Ag|AgCl)电位下,该传感器的背景电流小于1 nA,检出限为1 μM,小于400 μM范围内灵敏度为2900 nA μM-1 (相关系数R=0.998),且能够消除抗坏血酸对葡萄糖测定的干扰,实现了低浓度葡萄糖的测定,为实现血糖的无创监测奠定了基础.     

Modelling and analysis of ozone episodes

Air pollution is one of the primary environmental concerns in France due to the public health question. People wish to be informed of the air pollution level in real time or to be warned in advance of a peak of pollution.The goal of this study is to show the feasibility of developing an operational system to forecast the air pollution level. In our case, this level depends on the ozone concentration in the atmosphere.This prediction has been made by using a fuzzy logic based method. One advantage of this kind of model is to be able to extract information on the phenomena.Results obtained with this method are encouraging and some supplementary work needs to be done.     

Fabrication and evaluation of a passive SU8-based micro direct glucose fuel cell

Microsystem Technologies - A passive micro direct glucose fuel cell (μDGFC) using SU8-current collector structures of 8 × 14&nbsp;mm with a grid that allows the delivery...     

高聚物微流控芯片上集成化气动微阀的研制

报道了一种新型的聚甲基丙烯酸甲酯(PMMA)/聚二甲基硅氧烷(PDMS)复合芯片。该芯片采用PMMA-PDMS…PDMS-PMMA的四层构型,以在芯片上集成气动微阀。具有液路和控制通道网路的PMMA基片与PDMS弹性膜间采用不可逆封接,分别形成液路半芯片和控制半芯片,而2个半芯片则依靠PDMS膜间的粘性实现可逆封接,组成带有微阀的全芯片。这种制备方法解决了制备PMMA-PDMS-PMMA三层结构芯片的封接难题,封接过程简单可靠。其控制部分和液路部分可以单独更换,可进一步降低使用成本,尤其适合一次性应用场合。初步实验表明:该微阀具有良好的开关性能和耐用性。     

Modelling and analysis of non-linear time series

The modelling of non-linear time series is reviewed and new results are introduced by employing some ideas from the identification of non-linear control systems. Both global and local conditions for stationary and invertibility are established for the general non-linear time-series model and it is shown how these results provide a framework for time-series estimators. Methods of computing multistep-ahead predictions are studied and the usefulness of polynomial models is discussed.     

An electrochemical biosensor for determination of hydrogen peroxide using nanocomposite of poly(methylene blue) and FAD hybrid film

An electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) has been developed by the hybrid film of poly(methylene blue) and FAD (PMB/FAD). The PMB/FAD hybrid film was performed in PBS (pH 7) containing methylene blue and FAD by cyclic voltammetry. Repeatedly scanning potential range of −0.6-1.1 V, FAD was immobilized on the electrode surface by electrostatic interaction while methylene blue was electropolymerized on electrode surface. This modified electrode was found surface confined and pH dependence. It showed good electrocatalytic reduction for H₂O₂, KBrO₃, KIO₃, and NaClO as well as electrocatalytic oxidation for NADH. At an applied potential of −0.45 V vs. Ag/AgCl, the sensor showed a rapid and linear response to H₂O₂ over the range from 0.1 μM to 960 μM, with a detection limit of 0.1 μM and a significant sensitivity of 1109 μA mM⁻¹ cm⁻² (S/N = 3). It presented excellent stability at room temperature, with a variation of response current less than 5% over 30 days.     

A new numerical approach and visco-refined zigzag theory for blast analysis of auxetic honeycomb plates integrated by multiphase nanocomposite facesheets in hygrothermal environment

Engineering with Computers - The current work suggests a mathematical model for the dynamic response of sandwich plates subjected to a blast load using a numerical method. The sandwich structure is...     

Performance analysis of an integrated voice/data cut-through switching network

In this paper, the performance of an integrated voice/data cut-through switching network is studied. We first derive cut-through probabilities of voice and data packets at intermediate nodes. Then, the Laplace transform for the network delay is obtained. According to our numerical results, the cut-through switching method is superior in its delay characteristics to the conventional packet switching3for voice and data in integrated voice/data networks.     

Modelling and finite-time stability analysis of psoriasis pathogenesis

A new systems model of psoriasis is presented and analysed from the perspective of control theory. Cytokines are treated as actuators to the plant model that govern the cell population under the reasonable assumption that cytokine dynamics are faster than the cell population dynamics. The analysis of various equilibria is undertaken based on singular perturbation theory. Finite-time stability and stabilisation have been studied in various engineering applications where the principal paradigm uses non-Lipschitz functions of the states. A comprehensive study of the finite-time stability properties of the proposed psoriasis dynamics is carried out. It is demonstrated that the dynamics are finite-time convergent to certain equilibrium points rather than asymptotically or exponentially convergent. This feature of finite-time convergence motivates the development of a modified version of the Michaelis–Menten function, frequently used in biology. This framework is used to model cytokines as fast finite-time actuators.