基于C8051F020的多通道手持式PCR扩增仪的设计

设计旨在研制一种新型的手持式PCR扩增仪,利用微电子机械系统(MEMS)技术制作PCR微加热芯片,采用聚二甲基硅氧烷(PDMS)材料制作一次性使用的微反应腔阵列,以C8051F020微控制器为核心搭建一个可以同时进行多路扩增的温控系统。它从根本上克服了传统台式PCR扩增仪的缺点,具有体积小、重量轻、反应速率快、节省反应试剂等诸多优点。     

微反应槽PCR芯片阵列前馈-串级控制系统

设计了内部不含温度传感元件、加热元件的低成本微反应槽聚合酶链式反应（PCR）芯片，研制了宏观集中控制与微观分散控制有机结合的芯片阵列温度控制系统。宏观集中控制装置以水为传热媒质，通过特制换热器给芯片提供聚合酶反应所需的基本温度；在柔性印刷电路板上形成与芯片阵列对应的微型加热器阵列，针对各芯片进行分散的温度补偿。采用前馈一串级控制策略实现微加热器阵列与换热器最佳配合，共同完成各芯片温度的快速、精确控制。     

空域PCR芯片/微装置中温度控制技术

基于微电子机械系统(MEMS)技术而发展起来的空域聚合酶链式反应(空域PCR)芯片/微装置由于其具有反应速度快、所需DNA样品体积小以及自动化程度高等优点,已经日益引起人们的关注。空域PCR芯片/微装置系统中精确的温度控制是DNA成功扩增的关键因素之一。主要介绍国内外空域PCR芯片/微装置中温度控制技术进展,包括空域PCR系统温度循环特征;薄膜电阻加热器/传感器的设计原则;空域PCR反应系统温度均一性等。     

低成本微反应槽PCR芯片阵列双重控制系统

设计了内部不含温度传感元件、加热元件的低成本微反应槽聚合酶链式反应（PCR）芯片．研制了宏观集中控制与微观分散控制有机结合的双重控制系统，该系统具备对PCR芯片的批量处理能力；宏观集中控制装置以水为传热媒质通过特制换热器给芯片提供聚合酶反应所需的基本温度；在柔性印刷电路板上形成与芯片阵列对应的微型加热器阵列，针对各芯片进行分散的温度补偿。     

PCR 扩增芯片中微加热器结构优化分析

针对PCR扩增芯片中微加热器的传热问题进行有限元分析,用计算机模拟了不同形状微加热器的温度分布,通过对比分析,得出了提高温度分布均匀性的加热器结构和布置规律;根据分析结果,设计出双螺旋环形微加热器,这种结构能在一定范围内提供均匀的温度分布,为完成高质量的片上PCR扩增提供所需的温度环境;同时该结构还能有效减小微加热器本身的自感效应,提高加热效率.     

基于纳米磁珠技术的新型微全分析DNA芯片的研究

在微全分析系统的研究中,样品提取及DNA分析技术是非常重要的一个环节.也是目前国内外研究的热点之一.文中介绍了一种新型的基于单芯片的样品制备和扩增方法.采用多层微加工技术制作SU-8模具,通过注模成型,制作出有立体微柱结构的PDMS(聚二甲基硅氧烷)芯片,在芯片微池内填充超顺磁性磁珠,利用固相提取(solid phase extraction,SPE)法,将细胞裂解、DNA提取、PCR反应等功能集成在一个PDMS芯片上.整个流程快速有效,操作简便且易于芯片系统集成,提取产物可以不必洗脱,直接作为下一步PCR反应的模板,在同一芯片上进行扩增反应,实现了样品预处理、DNA提取和PCR扩增的集成.     

聚二甲基硅氧烷球形微腔阵列的数字PCR芯片

数字聚合酶链式反应(dPCR)技术是一种核酸绝对定量技术,但现有dPCR平台因其昂贵的设备或复杂的操作限制了其实际应用.利用气体膨胀浇注成型技术,结合集成微腔阵列的模具,设计、制作了一种成本低廉、简单可靠的dPCR微流控芯片.独特的球形微腔为液滴存储提供了更稳定的几何形式,保证了样品数字离散化的可靠性和稳定性.同时,芯片还利用预脱气的聚二甲基硅氧烷(PDMS)实现自动进样和样品离散化,大大降低了对复杂昂贵设备的依赖,且提供了更高集成度.利用芯片进行了EGFR基因第19号外显子数字PCR定量检测,验证了该芯片的实用性.     

自热式连续流PCR芯片的模拟与设计

介绍了一种连续流式的聚合酶链式反应(PCR)芯片,采取主动加热、被动冷却的方式,可实现DNA片断的倍增。用ANSYS有限元分析软件对器件进行温场分布仿真及分析,在此基础上, 设计了一种基于玻璃-玻璃的PCR芯片,芯片上分布着宽90μm,深40μm的迂回微沟道。通过单侧局部区域加热的方法,即可形成3个较宽的恒温区(95, 72, 60℃)与PCR反应相对应,且恒温区内温差在5℃以内,可以满足PCR反应的需要。     

聚合酶链式反应微流控生物芯片的数值模拟

微通道内具有一定流速的DNA反应混和物能否达到聚合酶链式反应(PCR)指定的温度PCR微流控芯片研究的关键问题.本文应用有限体元法(FEV)数值模拟该芯片上3个恒温区的直型、弯型、逶迤型三类微通道内,微流体的温度场和速度场.结果表明:对于宽100 μm深50μm的微通道,速度在0.002 m/s～0.02 m/s范围内,180.的弯道以及温度场、温度梯度的存在对其速度场分布无影响,微流体仍旱现为层流;微流体大约经过60μm的距离,其温度场达到稳态,其速度场充分发展为层流;采用宽4 mm深2 mm的空气隔热槽能起到隔热的效果.     

微型聚合酶反应芯片的精确温度控制

微型PCR反应芯片是生物芯片的一个重要发展方向,是实现快速分子生物学检测的一个新兴技术.在微型PCR芯片中,变性、回火、延伸三个温度区的精确控制直接影响到生成产物的数量和特异性,因此至关重要.本文使用虚拟仪器技术构建温度测控系统,将其应用于微型PCR芯片的精确温度控制,该系统精度高,温度波动较小.通过Labview图形化编程软件和数据采集卡,大大缩短了系统组建时间,使温度数据采集和显示一次性完成.     

Electro-thermal analysis of an embedded boron diffused microheater for thruster applications

One of the important design criteria of micropropulsion systems in particular VLM is the type of microheater, its layout and placement with a view to achieve uniform heating of propellant, fast heat transfer efficiency with minimum input power. Thrust produced by microthruster not only depends on the structural geometry of the thruster and propellant flow rate, but also on the chamber temperature to produce super saturated dry stream at the exit nozzle. Detailed design of microheater in thermal and electrical domains using co-solvers available in MEMS software tools along with material’s thermal property, temperature dependence of electrical resistivity and thermal conductivity have been considered in the present work to achieve precise modeling and experimental accuracy of heater operation. The chamber temperature was analytically calculated and subsequently the required resistance and power were estimated. The boron diffused microheaters of meanderline configuration in silicon substrate has been designed and its finite element based electro-thermal modeling was employed to predict the heater characteristics. The variation of microheater temperature with time, applied voltage and along chamber length has been determined from the modeling. Subsequently the designed microheater was realized on silicon wafer by lithography and boron diffusion process and its detailed testing was evaluated. It was found that boron diffused resistor of 820 Ω can generate 405 K temperature with applied input power 2.4 W. Finally the simulated results were validated by experimental data.     

Simulation and experimental validation of a SU-8 based PCR thermocycler chip with integrated heaters and temperature sensor

We present a SU-8 based polymerase chain reaction (PCR) chip with integrated platinum thin film heaters and temperature sensor. The device is fabricated in SU-8 on a glass substrate. The use of SU-8 provides a simple microfabrication process for the PCR chamber, controllable surface properties and can allow on chip integration to other SU-8 based functional elements. Finite element modeling (FEM) and experiments show that the temperature distribution in the PCR chamber is homogeneous and that the chip is capable of fast thermal cycling. With heating and cooling rates of up to 50 and 30 °C/s, respectively, the performance of the chip is comparable with the best silicon micromachined PCR chips presented in the literature. The SU-8 chamber surface was found to be PCR compatible by amplification of yeast gene ribosomal protein S3 and Campylobacter gene cadF. The PCR compatibility of the chamber surfaces was enhanced by silanization.     

Bead-based polymerase chain reaction on a microchip

We present a bead-based approach to microfluidic polymerase chain reaction (PCR), enabling fluorescent detection and sample conditioning in a single microchamber. Bead-based PCR, while not extensively investigated in microchip format, has been used in a variety of bioanalytical applications in recent years. We leverage the ability of bead-based PCR to accumulate fluorescent labels following DNA amplification to explore a novel DNA detection scheme on a microchip. The microchip uses an integrated microheater and temperature sensor for rapid control of thermal cycling temperatures, while the sample is held in a microchamber fabricated from (poly)dimethylsiloxane and coated with Parylene. The effects of key bead-based PCR parameters, including annealing temperature and concentration of microbeads in the reaction mixture, are studied to achieve optimized device sensitivity and detection time. The device is capable of detecting a synthetically prepared section of the Bordetella pertussis genome in as few as 10 temperature cycles with times as short as 15?min. We then demonstrate the use of the procedure in an integrated device; capturing, amplifying, detecting, and purifying template DNA in a single microfluidic chamber. These results show that this method is an effective method of DNA detection which is easily integrated in a microfluidic device to perform additional steps such as sample pre-conditioning.     

Fabrication and characterization of a polymethyl methacrylate continuous-flow PCR microfluidic chip using CO2 laser ablation

An improved microfabrication method was used to fabricate a continuous-flow PCR (polymerase chain reaction) microfluidic chip on the PMMA substrate using the low-power CO₂ laser ablation technique. The use of the low-power CO₂ laser and the PMMA material could reduce the cost and the time of the fabrication process, especially at the step of laboratory research because of the high flexibility of the laser fabrication technique and the low cost of PMMA. A CO₂ laser output power of 4.5 W and a laser scanning velocity of 76.2 mm/s were chosen to fabricate the chip in this work. The micromachining quality could satisfy the microfluidic requirement of the PCR mixture within the microchannel. Good temperature distribution and gradient were obtained on the PMMA chip with a home-built integrated heating system. An amplification of DNA template with a 990 base pair fragment of Pseudomonas was successfully performed with this chip to characterize its availability and performance with various flow rates.     

SOI-CMOS compatible low-power gas sensor using sputtered and drop-coated metal-oxide active layers

In this paper, a Silicon-On-Insulator (SOI) solid-state gas-sensor with an original design of a polysilicon loop-shaped microheater fabricated on a thin-stacked dielectric membrane is presented. The microheater ensures high thermal uniformity and very low power consumption (25 mW for heating at 400°C). Sensitive films are based on tin and tungsten oxides deposited either by RF sputtering or drop coating methods. The fabricated sensors are tested to a wide variety of contaminant species and promising results are obtained. The use of completely CMOS compatible TMAH-based bulk micro-machining techniques during the fabrication process, allows easy smart gas sensor integration in SOI-CMOS technology. This makes SOI-based gas-sensing devices particularly attractive for use in handheld battery-operated gas monitors.     

A high flow rate thermal bubble-driven micropump with induction heating

A thermal bubble-driven micropump with magnetic induction heating is successfully demonstrated in this paper. Energy is transferred from the planar coil outside the microchamber to the metal heating plate inside the microchamber through the electromagnetic field, and Joule heat is induced by the eddy current in the heating plate. Sequential photographs of bubble nucleation, growth and shrink in open environment were recorded by a CCD camera. One advantage of the micropump is that there is no physical contact between the heating plate and the external power supply circuit, which resulted in an easy fabrication process. What’s more, compared with other thermal bubble-driven micropump with resistive microheater, the flow rate and the pump stroke have been improved significantly due to its larger dimension of the heating plate and larger bubbles volume. The experiments show that the maximum flow rate of this micropump is about 102.05 μL/min, which can expand the potential applications, especially for microfluidic system that requires higher flow rate.     

Low power highly sensitive platform for gas sensing application

This paper reports a low power miniaturized MEMS based integrated gas sensor with 36.84 % sensitivity (ΔR/R₀) for as low as 4 ppm (NH₃) gas concentration. Micro-heater based gas sensor device presented here consumes very low power (360 °C at 98 mW/mm²) with platinum (Pt) micro-heater. Low powered micro-heater is an essential component of the metal oxide based gas sensors which are portable and battery operated. These micro-heaters usually cover less than 5 % of the gas sensor chip area but they need to be thermally isolated from substrate, to reduce thermal losses. This paper elaborates on design aspects of micro fabricated low power gas sensor which includes ‘membrane design’ below the microheater; the ‘cavity-to-active area ratio’; effect of silicon thickness below the silicon dioxide membrane; etc. using FEM simulations and experimentation. The key issues pertaining to process modules like fragile wafer handling after bulk micro-machining; lift-off of platinum and sensing films for the realization of heater, inter-digitated-electrodes (IDE) and sensing film are dealt with in detail. Low power platinum microheater achieving 700 °C at 267 mW/mm² are fabricated. Temperature calculations are based on experimentally calculated thermal coefficient of resistance (TCR) and IR imaging. Temperature uniformity and localized heating is verified with infrared imaging. Reliability tests of the heater device show their ruggedness and repeatability. Stable heater temperature with standard deviation (σ) of 0.015 obtained during continuous powering for an hour. Cyclic ON–OFF test on the device indicate the ruggedness of the micro-heater. High sensitivity of the device for was observed for ammonia (NH₃), resulting in 40 % response for ~4 ppm gas concentration at 230 °C operating temperature.     

Numerical and experimental study of a droplet-based PCR chip

A two-temperature continuous-flow polymerase chain reaction (PCR) polymer chip has been constructed that takes advantage of droplet technology to avoid sample contamination and adsorption at the surface. Samples contained in aqueous droplets are continuously moved by an oil carrier-fluid through various temperature zones, introducing the possibility of real-time quantitative PCR. In the present paper, we investigate many of the factors affecting droplet-based PCR chip design, including thermal mass, flow rate, and thermal resistance. The study focuses particularly on the fluid and substrate temperature distribution within the PCR chip and the droplet residence times in critical temperature zones. The simulations demonstrate that the flow rate strongly affects the temperature field within the carrier-fluid. Above a critical flow rate, the carrier-fluid fails to achieve the required temperatures for DNA amplification. In addition, the thermal resistances of the different layers in the chip are shown to have a major impact on the temperature profile in the channel.