Name: thermal measurement techniques in analytical microfluidic devices
Uploaded: 2015-06-03T13:00:00.000+00:00
Duration: 8 min 29 s
Description: Watch this Scientific Journal Video about Thermal Measurement Techniques in Analytical Microfluidic Devices at JoVE.com

通过工业/大学合作研究中心的水处理设备和位于威斯康星州密尔沃基（IIP-0968887）和马凯特大学（IIP-0968844）的大学政策提供了由美国国家科学基金会为这项工作的部分资金支持。我们感谢格伦·沃克先生，宇晋Chang和香卡拉达克里希南有益的讨论。

1.热粒子探测（TPD） <ol><li>用薄膜的氮化硅膜和集成温度传感器通过微加工制备微制造硅器件，使用标准的半导体加工技术2。冲洗所制造的设备，用去离子（DI）水。 注意:该制造方法的热粒子检测器的微流体装置在现有出版物2进行说明。 </li><li>以生产微通道聚二甲基硅氧烷（PDMS）衬底，创建使用标准光刻技术的模具SU8处理5。 注意:通道尺寸被设计为每个特定的颗粒的尺寸。 <ol><li>使PDMS通过混合10:1的比例碱（30毫升）和固化剂（3毫升）中。倒到模具中的PDMS和由短暂暴露到真空（5-10分钟）除去气泡。 注:真空水平不是一个临界值，以脱气，并应继续进行，直到气体巴布文件被从混合PDMS完全去除。 </li><li>放置在热板上（〜70℃）的模具2小时，以固化的PDMS。然后剥去PDMS非常小心，以免损坏模具。 注:真空水平不是一个临界值。 </li></ol></li><li>使用手动冲头，冲头紧孔（1毫米）的PTFE管的一端。使用大的冲头（2毫米）的另一端，使PDMS的贮存器。放置在设备顶部的冲孔微通道，在显微镜下，并对准热电阻在微通道（ 图1A）的中心。 </li><li>在电气接口，连接电销在接触垫仓和收紧锁紧螺钉。确保高度可调节销（Pogo的引脚）坐在该装置上的正确的电极垫。 </li><li>稀释10微升的浓的PS珠在100微升去离子水在1.5ml管中。 </li><li>为了保证PS珠保持中性浮力，加2.7微升甘油（1.26克/厘米3），以DI水以匹配流体密度的聚苯乙烯（PS）珠密度（1.05克/厘米3）。 </li><li> PTFE管连接到所述通道的一端和另一端，以1毫升的玻璃注射器。填用0.5ml去离子水的玻璃注射器。 注:通过选择合适的冲规模将避免漏管做紧身。 </li><li>将充满的注射器上的计算机控制的注射泵的DI水。推水（5-20​​微升/分钟）到通道以填充整个通道与流体一路到储存器。 </li><li>负载10微升均衡珠溶液的贮存器，并通过改变对注射泵的流动方向引入珠溶液的微通道。 </li><li>由偏置DC电流为1mA通过计算机控制的源/米而测量由源/米的电阻和排序所测量的数据（ 图2）打开的RTD。 注:在实验过程中，传感器偏置;因此，该温度被连续地测量，直到计数实验结束。在RTD传感器通过施加直流电流范围为100微安到1毫安连续测量温度，直至计数实验结束电偏置。关键是要选择正确的电流电平，因为有噪声水平和检测到的信号幅度之间存在折衷。注射泵被用来产生在微通道的流动。选择一个适当的流动速率来执行TPD实验中限制到测量的速度。这个速度是设备和电气测量速度的热时间常数的函数。热粒子检测实验的结果示于图3。 </li><li>使用开发的数据处理软件（LabVIEW中），以使用的Callendar-凡杜森方程6所测量的电阻数据转换为温度。 </li></ol> 2.热液体物质使用微热量计的表征<ol><li>在此过程中，使用芯片上量热装置（ 图4A）3来测量热扩散系数和样品的比热。 注:在每个死亡，还有2微热量计室（ 图4B）。每室有2个入口和一个出口。且每个腔室具​​有加热器和RTD传感器集成。 </li><li>将装置保持器（ 图4C）上的微量热设备。该装置对准到微流体的入口和出口与支架配件。放置在设备顶部的PDMS密封层。 </li><li>该装置保持器上安装的电连接销和锁定保持器螺钉。 注:确保高度可调弹簧针与电接触垫对齐。 </li><li>安装有磁性闩锁到装置保持器（ 图4D）微流体界面层。连接PTFE铝管两者的入口和出口。一个入口连接到示例加载注射器泵并关闭另一个，作为焓没有在这种情况下进行测量。 </li><li>使用开发的计算机控制的程序中，以将样品加载到微通道和腔室。 注意:程序将使用停产流以释放过大的压力的薄膜悬浮室。 <ol><li>的300微升样品加载到玻璃注射器，并将其放置在注射器泵。使用非常缓慢（0.25微升/分钟）恒定流速为高粘度样品（ 例如 ，甘油和离子液体）。使用热扩散系数的测量和离子液体比热测量甘油样品。 </li></ol></li><li>测量<ol><li>热扩散系数的测量<ol><li>连接测量设置为如图5A所示。加载甘油样品到微热量计室。运行老天修改后的计算机控制程序<html>牛逼穿透时间的测量。 </li><li>使用校准的热穿透方程来计算测量热穿透时间7热扩散系数: <img alt="式（1）" src="/files/ftp_upload/52828/52828eq1.jpg" width="100" /> 其中，α是热扩散率，L是腔室的厚度，p是厚度校准因数由于制造工艺的变化，而​​t 0是热渗透时间。 </li></ol></li><li>比热测量<ol><li>使用TWA测量设置， 如图5B所示 。使用相同的样品装载程序并装入离子液体在腔室中。运行TWA程序来获得交流电的温度波动（∂Ť 交流 ）的振幅，并使用比热公式来计算特定， 中 c p，热每个离子液体样品8: 28eq2.jpg"WIDTH ="117"/&gt; 其中，C 0是输入功率校准因数，P 在被输入功率，ω是致动信号的频率，而m是液体样品的质量。 </li></ol></li></ol></li></ol> 3.量热生化检测纸基微流体装置<ol><li>使用微加工薄膜（40-50纳米镍）RTD传感器。制造步骤的RTD传感器在以前的作品中4解释。 </li><li>对于纸质通道制造4，用小刀绘图仪切纸微流体通道与设计的图案（L形）。将打印纸在切割垫的顶部，装入纸张和切割垫刀绘图仪，并使用适当的配方来切断微流体纸张通道4。 </li><li>对于设备和渠道整合，使用丙烯酸粘合剂层（5微米）到纸张上集成了RTD传感器。使用清洁提单拉德到纸张推送到设备和除去气泡（ 图6A）。丙烯酸类膜是粘接剂层，以保持纸在RTD传感器。 </li><li>酶的激活，使用50mM乙酸钠缓冲液以激活GOD酶。加入1毫克的GOD酶到1ml的醋酸钠缓冲液以使1mg / ml的溶液。调节溶液的pH至5.1。 注意:调节在乙酸钠缓冲液的乙酸的量，以保持溶液5.1的PH值。 </li><li>偏置RTD直流毫安1电流激活RTD，然后开始连续测量电阻源/米，而阻实验（〜4分钟）后稳定下来。 注: 图6B显示测量设置的基于纸张的测试量热。 </li><li>引入2微升制备GOD溶液到纸张微通道（固定点）经由吸移管的中心。检测到的温度（ 图7A）必须启动吨Ø减少。 注意:此冷却效果是由于RTD的更高的工作温度的样本的和蒸发一起。 </li><li>为了测量葡萄糖浓度，引入标准葡萄糖对照溶液9至通道入口和测量所引起的反应电阻变化。重复这个实验的所有不同的血糖控制解决方案（高，普通，低浓度），并保存电阻数据。 </li><li>使用电阻（TCR）的镍RTD和的Callendar-凡杜森方程的温度系数，转换所述电阻变化对温度。通过考虑葡萄糖的反应焓和GOD酶（ΔH = -80千焦耳/摩尔），并使用浓度方程10计算每个样品中的葡萄糖的浓度: <img alt="公式3" src="/files/ftp_upload/52828/52828eq3.jpg" width="83" /> 其中n p被检测摩尔浓度，C <sub&gt; p是该系统的热容量和ΔT计算温度。 </li></ol>

<ol>
	<li>Zhang, H., Chon, C., Pan, X., Li, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+counting+particles+in+microfluidic+applications.">Methods for counting particles in microfluidic applications.</a> Microfluid Nanofluid. 7 (6), 739-749 (2009).</li><li>Vutha, A. K., Davaji, B., Lee, C. H., Walker, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microfluidic+device+for+thermal+particle+detection.">A microfluidic device for thermal particle detection.</a> Microfluid Nanofluid. 17 (5), 871-878 (2014).</li><li>Davaji, B., Bak, H. J., Chang, W. J., Lee, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Novel+On-chip+Three-dimensional+Micromachined+Calorimeter+with+Fully+Enclosed+and+Suspended+Thin-film+Chamber+for+Thermal+Characterization+of+Liquid+Samples.">A Novel On-chip Three-dimensional Micromachined Calorimeter with Fully Enclosed and Suspended Thin-film Chamber for Thermal Characterization of Liquid Samples.</a> Biomicrofluidics. 8 (3), 034101-034113 (2014).</li><li>Davaji, B., Lee, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+paper-based+calorimetric+microfluidics+platform+for+bio-chemical+sensing.">A paper-based calorimetric microfluidics platform for bio-chemical sensing.</a> Biosens. Bioelectron. 59, 120-126 (2014).</li><li>Liu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+research+of+high+aspect+ratio+microstructure+using+SU-8+resist.">Process research of high aspect ratio microstructure using SU-8 resist.</a> Microsystem Technologies. 10, 265-268 (2004).</li><li>Dusen, M. S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platinum-resistance+thermometry+at+low+temperatures.">Platinum-resistance thermometry at low temperatures.</a> J. Am. Chem. Soc. 47 (2), 326-332 (1925).</li><li>Arpaci, V. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Conduction Heat Transfer. , (1966).</li><li>Garden, J. L., Chteau, E., Chaussy, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+sensitive+ac+nanocalorimeter+for+microliter-scale+liquids+or+biological+samples.">Highly sensitive ac nanocalorimeter for microliter-scale liquids or biological samples.</a> Appl. Phys. Lett. 84, 3597-3599 (2004).</li><li>Kilo, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+New+Blood+Glucose+Monitoring+System+with+Auto-Calibration.">Evaluation of a New Blood Glucose Monitoring System with Auto-Calibration.</a> Diabetes Technol. Ther. 7 (2), 283-294 (2005).</li><li>Scheper, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Thermal Biosensors Bioactivity Bioaffinity (Advances in Biochemical Engineering/Biotechnology). , (1999).</li></ol>

没有利益冲突的声明。

Different thermal measurement techniques in microfluidic devices and their respective setup procedures are presented in this work. These thermal measurement methods such as thermal conductivity monitoring, thermal penetration time, amplitude of AC thermal fluctuations, and amplitude measurement of the generated heat are used to detect specific substances and investigate different reactions and interactions. 
The thermal time constant plays a key role in the aforementioned thermal measurement t...

三个不同的微观尺度的热测量技术呈现在这篇文章。微流体装置的三个不同的配置被用于热粒子检测（TPD），热特性（热导率和比热），和量热检测化学反应和相互作用。 热粒子探测检测和计数在微流体装置的粒子被广泛用于环境，工业和生物应用1。 TPD是热测量的在微流体装置2的新的应用中的一个。使用传热，用于检测和计数基于所述粒径的粒子降低了复杂性，成本和系统的大小。在其他方法中，复杂的光学或复杂的电气测量和先进的信号处理的软件用于检测颗粒。 热甜心液体物质cterization利用微热量计液体样品的热特性是热计量的微流体装置的第二个应用程序。执行微尺度量热将降低样品消耗和通过提供更高的重复性相比于常规，散装量热方法提高精度。的程序使用芯片上的微量热设备的热导率和比热测量在别处3呈现。对于热导率测量的热渗透时间技术和热波分析（TWA）为在微流体装置的比热测量的细节在协议部分中描述。 量热生物化工检测纸张为基础的微流控设备热测量的另一种应用是生化检测在纸基微流体。在毛细作用的纸的多孔结构承载的液体，避免了在微通道气泡引发问题。在纸基微流体装置中最常见的检测机制是光学或电化学技术。光学检测患有高复杂性和先进的图像处理软件的必要性量化检测到的信号。电化学检测也受到限制，因为它们只能被应用到产生活性的副产物的反应。最近推出的量热纸基生化传感器平台4取纸基微流体系统和无标记的热检测机构的优点。量热检测用葡萄糖氧化酶（GOD）酶在纸基微流体平台葡萄糖的程序都在协议部分。 本文的目的是展示在微流体装置的热测量技术的功能。该器件preparatioN，液体样品处理和电阻温度检测器（RTD）传感器激励和测量列于下一个章节。

<table><tbody><tr><td>Polydimethylsiloxane (PDMS)&amp;nbsp;</td><td>Dow Corning</td><td>Sylgard 184</td><td></td></tr><tr><td>PS beads - 90 &amp;#956;m</td><td>Corpuscular</td><td>100265</td><td></td></tr><tr><td>PS beads - 200 &amp;#956;m</td><td>Corpuscular</td><td>100271</td><td></td></tr><tr><td>Glycerol</td><td>SigmaAldrich</td><td>G5516</td><td></td></tr><tr><td>GOD enzyme</td><td>SigmaAldrich</td><td>G7141</td><td></td></tr><tr><td>Glucose Control Solution - Low</td><td>Bayer contour</td><td>Low Control</td><td></td></tr><tr><td>Glucose Control Solution - Normal</td><td>Bayer contour</td><td>Normal Control</td><td></td></tr><tr><td>Glucose Control Solution - High</td><td>Bayer contour</td><td>High Control</td><td></td></tr><tr><td>Chromatography filter paper</td><td>Whatman</td><td>3001-845</td><td></td></tr><tr><td>Glass</td><td>VWR&amp;nbsp;</td><td>48393-106</td><td></td></tr><tr><td>Acrylic Film</td><td>Nitto Denko</td><td>5600</td><td></td></tr><tr><td>Glass syringe (1 ml)</td><td>Hamilton</td><td>1001</td><td></td></tr><tr><td>Syringe pump</td><td>New Era</td><td>NE-500</td><td></td></tr><tr><td>knife plotter</td><td>Silhouette</td><td>portrait</td><td></td></tr><tr><td>Current Preamplifier</td><td>Stanford Research</td><td>SR-570</td><td></td></tr><tr><td>Ocilloscope</td><td>Agilent</td><td>DSO 2420A</td><td></td></tr><tr><td>Signal Generator</td><td>HP</td><td>HP3324A</td><td></td></tr><tr><td>Lock-in Amplifire</td><td>Stanford Research</td><td>SRS-830</td><td></td></tr><tr><td>Source/meter 2400</td><td>Keithley</td><td>2400</td><td></td></tr><tr><td>Source/meter 2600</td><td>Keithley</td><td>2436A</td><td></td></tr></tbody></table>

thermal measurement techniques in analytical microfluidic devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. Micromachining techniques allow reduction of the thermal mass of fabricated structures and introduce the possibility to perform high sensitivity thermal measurements in the micro-scale and nano-scale devices. Combining thermal measurement techniques with microfluidic devices allows performing different analytical measurements with low sample consumption and reduced measurement time by integrating the miniaturized system on a single chip. The procedures of thermal measurement techniques for particle detection, material characterization, and chemical detection are introduced in this paper.

图3示出了测得的热信号的曲线图。在与相应的光学图像的小珠的存在下所产生的信号显示了成功的检测，在微通道的微球PS珠。液体穿过微通道的导热性发生变化，由于PS的珠的存在。这种变化在通道的热导率是影响在微通道的热传递。在微通道的热传递的变化是由热电阻的电阻波动（ 图3A和B）的形式进行检测。 检测到的信号也可以受?...

Watch this Scientific Journal Video about Thermal Measurement Techniques in Analytical Microfluidic Devices at JoVE.com

Thermal Measurement Techniques in Analytical Microfluidic Devices

Here, we present three protocols for thermal measurements in microfluidic devices.

在分析微流体装置的热测量技术

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

thermal-measurement-techniques-in-analytical-microfluidic-devices

Universidad San Sebastian

Research

JoVE Journal

Engineering

9.6K 次观看.  Marquette University. Here, we present three protocols for thermal measurements in microfluidic devices. 

视频: Thermal Measurement Techniques in Analytical Microfluidic Devices

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators 1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.
Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides 3, asymmetric split-ring resonators 4, and photonic band gap structures integrated into parallel-plate waveguides 5. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.
The sensor design we use here is based on a simple parallel-plate waveguide 6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove 6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index 9.
Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves 10. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.

The procedure for implementing a refractive index sensor for terahertz frequencies based on a grooved parallel-plate waveguide geometry is described here. The method yields a measurement of the refractive index of a small volume of liquid through monitoring of the shift in the resonant frequency of the waveguide structure

太赫兹微流控测量中的一个平行板波导传感器

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic ...

科研

工程学

Fluorescence detection methods for microfluidic droplet platforms

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints.1
In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation.2-4 Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented.
Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

荧光检测方法，为微流体液滴平台

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that ...

生物工程

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 &#176;C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

We demonstrate use of a fiber optic distributed sensor for mapping the temperature field of mixing air jets. The Rayleigh scattering-based sensor generates thousands of data points along a single fiber to provide exceptional spatial resolution that is unattainable with traditional sensors such as thermocouples.

对于高分辨率温度场测绘光纤分布式传感器

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists ...

High Throughput Microfluidic Rapid and Low Cost Prototyping Packaging Methods

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging techniques.
The one-time use packaging technique employs UV-based and temperature curing epoxies to connect microtubes to access holes, wire-bonding for integrated circuit connections, and silver epoxy for electrical connections. This method is based on a robust assembly technique that can support relatively high pressure close to 1 psi and does not need any support to strengthen the microfluidic architecture.
Reusable packaging techniques consist of PDMS-based microtube interconnectors and anisotropic adhesive films for electrical connections. These devices are more sensitive and fragile. Consequently, Plexiglas support is added to the microfluidic structure to improve the electrical contact when anisotropic adhesive films are used, and also to strengthen the microfluidic architecture. In addition, a micromanipulator is needed to maintain tubes while using a thin PDMS layer to connect them to the access holes. Different PDMS layer thicknesses, ranging from 0.45-3 mm, are tested to compare the best adherence versus injection rates. Applied injection rates are varied from 50-300 &#956;l/hr for 0.45-3 mm PDMS layers, respectively. These techniques are mainly applicable for low-pressure applications. However, they can be extended for high-pressure ones through plasma-oxygen process to permanently seal the PDMS to glass substrates. The main advantage of this technique, besides the fact that it is reusable, consists of keeping the device observable when the microchannel length is very short (in the range of 3 mm or lower).

In this article we describe different techniques for microfluidic rapid prototyping platforms. The proposed techniques are based on ultraviolet (UV) sensitive and temperature curing epoxies, polydimethylsiloxane (PDMS) based tubing, wire-bonding, and anisotropic adhesive films. The assembling procedures presented are developed for both one-time use devices as well as reusable microfluidic systems.

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging ...

Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being leveraged for developing sophisticated photonic sensors. Silicon photonic sensors seek to exploit the strong confinement of light in nano-waveguides to transduce changes in physical state to changes in resonance frequency. In the case of thermometry, the thermo-optic coefficient, i.e., changes in refractive index due to temperature, causes the resonant frequency of the photonic device such as a Bragg grating to drift with temperature. We are developing a suite of photonic devices that leverage recent advances in telecom compatible light sources to fabricate cost-effective photonic temperature sensors, which can be deployed in a wide variety of settings ranging from controlled laboratory conditions, to the noisy environment of a factory floor or a residence. In this manuscript, we detail our protocol for the fabrication and testing of photonic thermometers.

We describe the process of fabrication and testing of photonic thermometers.

光子温度计的制作与测试

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

化学

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter magnetic sphere is irradiated with 1150 nm or 1412 nm incident light, as selected using a narrow bandpass filter; additionally, two-dimensional absorbance images, which are the transverse projections of the absorption coefficient, are acquired via a near-infrared camera. When the three-dimensional distributions of temperature can be assumed to be spherically symmetric, they are estimated by applying inverse Abel transforms to the absorbance profiles. The temperatures were observed to consistently change according to time and the induction heating power.

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

感应加热小磁球周围水近红外测温技术

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This ...

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer.
At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

管道单、两相流局部瞬时对流换热的测量

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer ...

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren system is constructed from a Hoffman modulation contrast microscope, which provides easy access to the rear focal plane of the objective lens, by removing the slit plate and replacing the modulator with a knife-edge. The working principle of microscale schlieren technique relies on detecting light deflection caused by variation of refractive index1-3. The deflected light either escapes or is obstructed by the knife-edge to produce a bright or a dark band, respectively. If the refractive index of the mixture varies linearly with its composition, the local change in light intensity in the image plane is proportional to the concentration gradient normal to the optical axis. The micro-schlieren image gives a two-dimensional projection of the disturbed light produced by three-dimensional inhomogeneity.
To accomplish quantitative analysis, we describe a calibration procedure that mixes two fluids in a T-microchannel. We carry out a numerical simulation to obtain the concentration gradient in the T-microchannel that correlates closely with the corresponding micro-schlieren image. By comparison, a relationship between the grayscale readouts of the micro-schlieren image and the concentration gradients presented in a microfluidic device is established. Using this relationship, we are able to analyze the mixing inhomogeneity from associate micro-schlieren image and demonstrate the capability of microscale schlieren technique with measurements in a microfluidic oscillator4. For optically transparent fluids, microscale schlieren technique is an attractive diagnostic tool to provide instantaneous full-field information that retains the three-dimensional features of the mixing process.

Herein, we describe a procedure that employs microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. Through calibration, distribution of concentration gradient can be derived from the micro-schlieren image.

由微型条纹分析技术在微流控设备混合不均匀

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren ...

A Microfluidic Device for Quantifying Bacterial Chemotaxis in Stable Concentration Gradients

Chemotaxis allows bacteria to approach sources of attractant chemicals or to avoid sources of repellent chemicals. Bacteria constantly monitor the concentration of specific chemoeffectors by comparing the current concentration to the concentration detected a few seconds earlier. This comparison determines the net direction of movement. Although multiple, competing gradients often coexist in nature, conventional approaches for investigating bacterial chemotaxis are suboptimal for quantifying migration in response to concentration gradients of attractants and repellents. Here, we describe the development of a microfluidic chemotaxis model for presenting precise and stable concentration gradients of chemoeffectors to bacteria and quantitatively investigating their response to the applied gradient. The device is versatile in that concentration gradients of any desired absolute concentration and gradient strength can be easily generated by diffusive mixing. The device is demonstrated using the response of Escherichia coli RP437 to gradients of amino acids and nickel ions.

This protocol describes the development of a microfluidic device for investigating bacterial chemotaxis in stable concentration gradients of chemoeffectors.

一个微流体装置量化细菌趋稳定的浓度梯度

Chemotaxis allows bacteria to approach sources of attractant chemicals or to avoid sources of repellent chemicals. Bacteria constantly monitor the ...

生物学

Soft Lithographic Procedure for Producing Plastic Microfluidic Devices with View-ports Transparent to Visible and Infrared Light

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable microfluidic devices. Here, a protocol for the fabrication of plastic microfluidic devices is demonstrated, where soft lithographic techniques are used to embed transparent Calcium Fluoride (CaF2) view-ports in connection with observation chamber(s). The method is based on a replica casting approach, where a polydimethylsiloxane (PDMS) mold is produced through standard lithographic procedures and then used as the template to produce a plastic device. The plastic device features ultraviolet/visible/infrared (UV/Vis/IR) -transparent windows made of CaF2 to allow for direct observation with visible and IR light. The advantages of the proposed method include: a reduced need for accessing a clean room micro-fabrication facility, multiple view-ports, an easy and versatile connection to an external pumping system through the plastic body, flexibility of the design, e.g., open/closed channels configuration, and the possibility to add sophisticated features such as nanoporous membranes.

A protocol for the fabrication of plastic microfluidic devices with transparent view-ports for visible and infrared light imaging is described.

生产塑料微流控装置与查看端口对可见光和红外透明软光刻过程

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable ...