我们感谢Lindback基金会的资金支持，而亚历山大西多连科医 ​​生和埃尔萨楚的富有成果的讨论和技术援助，以及罗伯特·史密斯教授的协助C.线虫检测。

注：在下面描述的步骤，实验室安全准则必须始终遵循。特别重要的是，当与高电压（&gt; 500 V）和处理化学品处理的安全性。 1，涂料的导电性基板与蜡烛的烟灰<ol><li>切割金属铜为矩形（75×43毫米，厚0.5毫米）。清洁浸没在铜蚀刻剂的铜基板为大约30秒，洗净用自来水进行约20秒，干燥的纸。 注意：如果使用方法1以下，更改尺寸为75×25毫米到适合的机器。 </li><li>扫铜衬底下的点燃石蜡蜡烛为30-45秒，以获得近似均匀的烟灰涂层（约40μm厚）。保持基板在约1cm焰内。请勿触摸脆弱的烟灰表面。 </li></ol> 2.保护与涂层的烟灰层注：烟灰层非常脆弱的，必须涂上保护层。两个简单的替代品（方法1和2所示）被认为在这里，但更可靠的协议，目前正在开发中。 <ol><li>方法1 <ol><li>加载样品放入金属蒸发或溅射系统。以下所述系统的操作过程，排空腔室，并且开始金受控沉积在烟灰层（150-200纳米）。让该装置冷却到室温。 </li><li>浸涂金属化基片在一个1-十二硫醇溶液（1％体积/体积，在95％乙醇中，ACS / USP级），用于化学罩内10分钟。然后，拿着该设备以一定的角度接近60°，轻轻地用只有几个乙醇滴洗表面。让设备干燥过夜。 </li></ol></li><li>方法2 <ol><li>在化学罩，涂敷煤烟基板后立即和同时衬底仍从蜡烛火焰温，沉积氟化液体的一些液滴上的一侧基板上，并倾斜衬底的角度接近90°。存放更多的水滴，让他们滚在整个油烟面。 注：当水滴落在一个点，烟灰会被冲离该区域。让的氟化液体扩散的液滴尽可能。 </li><li>烘烤的热板上（160℃，15分钟）的化学罩内的衬底。 </li><li>让基板放置过夜，在室温下在使用前。保存下去。 </li></ol></li></ol> 3.上电极的制作（从Abdelgawad 等人改编。12） <ol><li>通过绘制图形设计软件的电极。每个电极为2毫米长，0.3毫米宽，与电极之间的间隙为0.3mm。触头（卡入连接器中，见下文）之间的间隙为2.3毫米（ 图1）。 </li><li>修剪灵活的铜层压板（35微米厚）为国君格式（3.87×7.5cm的英寸）。使用其他尺寸的我f相的打印机兼容。加载层压到一台彩色打印机的手动进纸托盘。 </li><li>请务必使用“富黑”，或“登记黑”，在铜表打印时（见Abdelgawad 等 12查看详情），让黑色墨水的一层致密的铜基材上，蚀刻过程中保护印刷图案。让印刷基板完全干燥，过夜。 </li><li>内部的化学罩，预热（40℃），用50ml的铜蚀刻液的烧杯中。浸在烧杯中的印刷层压板，并轻轻摇动它在溶液中约10分钟。刻蚀时间取决于铜蚀刻剂溶液中。每隔几分钟，检查腐蚀，看看图案是否完好。 </li><li>小心地用水冲洗所述层压体，并用丙酮和乙醇中的化学引擎盖除去包衣。再次洗净，并轻轻擦干用纸巾层压板。 </li><li>小心地连接层压用电极为GLASS滑动件（75×25毫米，约1毫米厚），用双面胶带。避免气穴。 </li><li>附上氟烷的PFA薄膜，以使用磁带的电极。这用于防止电极与液滴的意外接触，从而损害顶电极由于短路。 </li></ol> 4.电子接口（电路如图2） <ol><li>焊接继电器和电容器C为通用电路板。 </li><li>装配了10继电器驱动器的其余部分在一个无焊面包板的电子电路。 </li><li>线各继电器驱动器的输入，以在所述控制板上的频道。 </li><li>小心管理单元的顶部电极到一个连接器（ 图3）。线的每个中继驱动器的输出到一个顶部电极，如该图所示。注意，有一对导线由继电器之间的接地连接器的接触，以最小化电噪声。 注：该连接器位于一个可调节的平台来控制T ON他的顶部和底部（碳黑涂覆）衬底之间的距离（0.1-0.5毫米）。 </li><li>使用程序来控制高电压（HV）的应用程序（约0.8秒），以4个电极在同一时间定时，移位1电极在运动（ 即方向，为0.8秒时，致动1234，然后2345，3456 等。，0.8秒的每个组，然后向后，使液滴移动在相反的方向上也同样）。 </li></ol> 5.滴可视化和处理<ol><li>以记录液滴的运动，可以使用可视化系统，它是由一个24X的 - 96X放大率组件结合了CCD照相机。视频记录器连接到使用S视频相机。 </li><li>吸管含C的 4微升滴线虫中的烟灰的基板的底部的介质。 </li><li>使顶端电极，以-0.3毫米的液滴之上。液滴应当接近中间，只是在第五电极的下方，以便于操作。 </li><li>把电子接口和高电压（500伏RMS）上，并调整顶部电极距离的液滴，直到它开始移动。不要让顶部电极接触到液滴。 </li><li>通过记录响应于电脉冲在设备上成功液滴转移的次数采集数据。一个成功的实验的特征在于，至少700微滴转移， 也就是说 ，每一个电脉冲后一个传送。 </li><li>连续地收集数据，直到微滴不响应再移动到5至10个脉冲。 注意：当表面开始退化，运动可以通过使顶电极更接近液滴被恢复。 </li></ol>

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The authors declare that they have no competing financial interests.

该协议中最关键的步骤是保护的烟灰层的，可直接与在移动液滴的成功相关联。金属化的烟灰层（上述的方法1）允许接近制造成功的100％。然而，最大的操作时间约为10分钟;可能的话，微滴级分通过在所述金属层的孔润湿烟灰。涂烟灰层的氟化液是最简单和最快的替代，需要最少的资源，但只有40％-50％的基板制作工作（20分最高）的 - 和涂层不均匀。实际上，该烟灰层是非常脆弱的，而且在粘?...

该液体的工作装置的小型化是非常重要的用于“芯片实验室”的平台的开发。在这个方向上，在过去二十年已经见证了在微流体领域的显著进展，具有各种应用。1-5用流体在封闭的通道（通道微流）的传输对比，DMF操纵上的电极阵列的微滴。其中，最有吸引力的这种技术的优点是没有可动部件运送流体，并且运动是通过关闭电信号即刻停止。 然而，雾滴的运动依赖于液滴内容，当然对于通用的“芯片实验室”的平台不希望的特性。含有蛋白质和其它分析物的微滴粘到设备的表面，成为不可移动。可以说，这一直是主要的限制为拓宽DMF的应用范围; 6-8替代方案，以尽量减少不希望的表面结垢涉及添加额外的化学物质，以液滴或它的周围，这有可能影响液滴的内容。 先前，我们小组开发出一种装置，以允许细胞和蛋白质在DMF中的传输，而无需额外的添加剂（现场DW的设备）。9这是通过基于蜡烛烟灰，10与设备的几何形状有利于液滴滚动表面相结合来实现并导致在熔滴上的向上的力，从而进一步降低液滴的表面相互作用。在这种方法中，液滴运动并不与表面润湿相关联。11 下面描述的详细方法的目标是产生一个微流体装置能够输送含有蛋白质，细胞和整个生物体的液滴，而无需额外的添加剂。在现场-DW设备铺平了道路液滴工作的化学家很大程度上独立完全控制平台RY。 在这里，我们还存在模拟表明，尽管所需的设备的操作的高电压，在整个液滴上的电压降是所施加的电压的一小部分，这表明在液滴内部bioanalytes的影响可以忽略。事实上，与秀丽隐杆线虫 （ 线虫 ），用于各种生物学研究线虫的初步试验，表明蠕虫游泳原状作为施加电压。

<table border="0" cellpadding="0" cellspacing="0" width="1230">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Name of Material/ Equipment</td>
			<td style="width:119px;">Company</td>
			<td style="width:161px;">Catalog Number</td>
			<td style="width:720px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Paraffin candle</td>
			<td style="width:119px;"></td>
			<td style="width:161px;"></td>
			<td>Any paraffin candle</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Sputtering system</td>
			<td style="width:119px;">Denton Vacuum, Moorestown, NJ</td>
			<td style="width:161px;"></td>
			<td>Sputter coater Desk V HP equipped with an Au target.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">1-dodecanethiol</td>
			<td style="width:119px;">Sigma-Aldrich</td>
			<td align="right" style="width:161px;">471364</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Teflon</td>
			<td style="width:119px;">Dupont</td>
			<td style="width:161px;">AF-1600</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Fluorinert FC-40</td>
			<td style="width:119px;">Sigma-Aldrich</td>
			<td style="width:161px;">F9755</td>
			<td>Fluorinated liquid: Prepare Teflon-AF resin in Fluorinert FC-40, 1:100 (w/w), to create the hydrophobic coating.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Graphic design software -Adobe Illustrator</td>
			<td style="width:119px;">Adobe Systems</td>
			<td style="width:161px;"></td>
			<td>Other softwares might be used as well.</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:231px;">Copper laminate</td>
			<td style="width:119px;">Dupont</td>
			<td style="width:161px;">LF9110</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:231px;">Laser Printer</td>
			<td style="width:119px;">Xerox</td>
			<td style="width:161px;">Phaser 6360 or similar</td>
			<td>Check for the compatibility with &#34;rich black&#34; or &#34;registration black&#34; (see text).</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Copper Etchant</td>
			<td style="width:119px;">Transene</td>
			<td style="width:161px;">CE-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Perfluoroalkoxy (PFA) film</td>
			<td style="width:119px;">McMaster-Carr</td>
			<td style="width:161px;">84955K22</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Breadboard</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">70012450 or similar</td>
			<td>Large enough to allow the assemble of 10 drivers.</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Universal circuit board</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">70219535 or similar</td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:231px;">Connector</td>
			<td style="width:119px;">Allied Electronics</td>
			<td style="width:161px;">5145154-8 or similar</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Control board and control program (LabView software)</td>
			<td style="width:119px;">National Instruments</td>
			<td style="width:161px;">NI-6229 or similar</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">High-voltage amplifier</td>
			<td style="width:119px;">Trek</td>
			<td style="width:161px;">PZD700</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Resistor R 27 k&#8486;, 1/4 W</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">2964762</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:231px;">Capacitors C and C1, 100 nF, 60 V</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">8817183</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Transistor T, NPN</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">9350289</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Diode D, 1N4007</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">2660007</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Relay&#160;</td>
			<td style="width:119px;">Allied&#160;</td>
			<td align="right" style="width:161px;">8862527</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:231px;">Visualization system</td>
			<td style="width:119px;">Edmund Optics</td>
			<td style="width:161px;">VZM 200i or similar</td>
			<td>System magnification 24X- 96X. It is combined with a Hitachi KP-D20B 1/2 in CCD Color Camera.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Recorder</td>
			<td style="width:119px;">Sony</td>
			<td style="width:161px;">GV-D1000 NTSC or similar</td>
			<td>It is connected to the camera by an S-video cable.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:231px;">Simulations</td>
			<td style="width:119px;">COMSOL Multiphysics</td>
			<td style="width:161px;">V. 4.4</td>
			<td></td>
		</tr>
	</tbody>
</table>

taking advantage of reduced droplet-surface interaction to optimize transport of bioanalytes in digital microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

以前，我们已经使用现场DW的设备，以允许蛋白质在DMF中的运动。特别是，用牛血清白蛋白（BSA）的液滴可以在一个浓度2000倍高于先前报道的其他作者（无添加剂）移动。这是由于在液滴和表面之间的相互作用减小; 图4显示了含有荧光标记的牛血清白蛋白的液滴（见弗莱雷等 9为在实验的详细信息）。在左侧的第一图为液滴坐在烟灰涂覆的表面;中间的一个，电场...

Watch this Scientific Journal Video about Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics at JoVE.com

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

以减少液滴表面的相互作用来优化Bioanalytes运输中的数字微流体

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

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7.8K 次观看.  University of the Sciences. The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

视频: Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

科研

工程学

Characterization of Thermal Transport in One-dimensional Solid Materials

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including conductive, semi-conductive or nonconductive one-dimensional structures. This technique broadens the measurement scope of materials (conductive and nonconductive) and improves the accuracy and stability. If the sample (especially biomaterials, such as human head hair, spider silk, and silkworm silk) is not conductive, it will be coated with a gold layer to make it electronically conductive. The effect of parasitic conduction and radiative losses on the thermal diffusivity can be subtracted during data processing. Then the real thermal conductivity can be calculated with the given value of volume-based specific heat (&#961;cp), which can be obtained from calibration, noncontact photo-thermal technique or measuring the density and specific heat separately. In this work, human head hair samples are used to show how to set up the experiment, process the experimental data, and subtract the effect of parasitic conduction and radiative losses.

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials.

在一维固体材料的热传输的特性

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including ...

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

实时直流偏置的动态法切换时间改善严重欠阻尼边缘化场静电MEMS致动器

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

How to Build a Vacuum Spring-transport Package for Spinning Rotor Gauges

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to 1.0 Pa. In this application, the SRGs are frequently transported to laboratories for calibration. Events can occur during transportation that change the rotor surface conditions, thus changing the calibration factor. To assure calibration stability, a spring-transport mechanism is often used to immobilize the rotor and keep it under vacuum during transport. It is also important to transport the spring-transport mechanism using packaging designed to minimize the risk of damage during shipping. In this manuscript, a detailed description is given on how to build a robust spring-transport mechanism and shipping container. Together these form a spring-transport package. The spring-transport package design was tested using drop-tests and the performance was found to be excellent. The present spring-transport mechanism design keeps the rotor immobilized when experiencing shocks of several hundred g (g = 9.8 m/sec2 and is the acceleration due to gravity), while the shipping container assures that the mechanism will not experience shocks greater than about 100 g during common shipping mishaps (as defined by industry standards).

Here we describe how to build a robust spring-transport mechanism for a spinning rotor gauge. This device securely immobilizes the rotor and keeps it under vacuum during transportation. We also describe packaging that minimizes the risk of damage during transport. Tests show our design works for typical shocks during transport.

如何建立一个真空Spring的运输包装为纺转子规

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10-4 Pa to ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

钛白粉用于染料敏化太阳能电池的数码印刷

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

拉伸压缩模式下的超声疲劳试验

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement during previous phase changes and applied shear. To determine the extent of these changes, we have developed a microfluidic device that enables repeated phase transitions induced by exchange of the surrounding fluid and microrheological characterization while limiting shear on the sample. This technique is &#181;2rheology, the combination of microfluidics and microrheology. The microfluidic device is a two-layer design with symmetric inlet streams entering a sample chamber that traps the gel sample in place during fluid exchange. Suction can be applied far away from the sample chamber to pull fluids into the sample chamber. Material rheological properties are characterized using multiple particle tracking microrheology (MPT). In MPT, fluorescent probe particles are embedded into the material and the Brownian motion of the probes is recorded using video microscopy. The movement of the particles is tracked and the mean-squared displacement (MSD) is calculated. The MSD is related to macroscopic rheological properties, using the Generalized Stokes-Einstein Relation. The phase of the material is identified by comparison to the critical relaxation exponent, determined using time-cure superposition. Measurements of a fibrous colloidal gel illustrate the utility of the technique. This gel has a delicate structure that can be irreversibly changed when shear is applied. &#181;2rheology data shows that the material repeatedly equilibrates to the same rheological properties after each phase transition, indicating that phase transitions do not play a role in microstructural changes. To determine the role of shear, samples can be sheared prior to injection into our microfluidic device. &#181;2rheology is a widely applicable technique for the characterization of soft matter enabling the determination of rheological properties of delicate microstructures in a single sample during phase transitions in response to repeated changes in the surrounding environmental conditions.

We demonstrate the fabrication and use of a microfluidic device that enables multiple particle tracking microrheology measurements to study the rheological effects of repeated phase transitions on soft matter.

微流体和 Microrheology 相结合测定软物质在重复相变过程中的流变特性

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

生物医学微流体折射率匹配器件的研制

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...

Crack Monitoring in Resonance Fatigue Testing of Welded Specimens Using Digital Image Correlation

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It is intended as a practical and reproducible procedure to identify macroscopic cracks at an early stage and monitor crack propagation during fatigue tests. It consists of strain field measurements at the weld using DIC. Images are taken at fixed load cycle intervals. Cracks become visible in the computed strain field as elevated strains. This way, the whole width of a small-scale specimen can be monitored to detect where and when a crack initiates. Subsequently, it is possible to monitor the development of the crack length. Because the resulting images are saved, the results are verifiable and comparable. The procedure is limited to cracks initiating at the surface and is intended for fatigue tests under laboratory conditions. By visualizing the crack, the presented procedure allows direct observation of macrocracks from their formation until rupture of the specimen.

Digital image correlation is used in fatigue tests on a resonance testing machine to detect macroscopic cracks and monitor crack propagation in welded specimens. Cracks on the specimen surface become visible as increased strains.

使用数字图像相关性对焊接试样共振疲劳测试中的裂纹监测

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It ...

Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a closed feedback loop that operates between the target manipulator and a ranging sensor. The target fabrication process is explained in detail. Representative results of MeV-level proton beams generated by irradiation of 600 nm thick gold foils at a rate of 0.2 Hz are given. The method is compared with other replenishable target systems and the prospects of increasing the shot rates to above 10 Hz are discussed.

A protocol is presented for automated irradiation of thin gold foils with high intensity laser pulses. The protocol includes a step-by-step description of the micromachining target fabrication process and a detailed guide for how targets are brought to the laser&#39;s focus at a rate of 0.2 Hz.

用于密集激光辐照实验的微制造目标的自动交付

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a ...