Name: combining microfluidics and microrheology to determine rheological properties of soft matter during repeated phase transitions
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Description: Watch this Scientific Journal Video about Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions at JoVE.com

这项工作的资金由 DNI7 & 赌博公司和美国化学学会石油研究基金 (54462-) 提供。对美国化学学会石油研究基金的捐助者的承认是对这项研究的部分支持。作者想感谢马可 Caggioni 博士的有益讨论。

1. 微流控装置的制作
<ol><li>微流控邮票制作。 注: 此步骤要求使用挥发性材料, 应在化学油烟机中进行。<ol>
<li>使用带有与玻璃幻灯片 (75×50 mm) 相同尺寸的负打印设计、彩色白色的通道和背景色黑色 (请参见图 1)。在透明醋酸板材上打印此设计 (透明度), 分辨率为 1200年 dpi。</li>
		<li>如果透明度的黑暗部分仍然允许光通过, 层数底片和坚持使用双面胶带。</li>
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<ol>
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通过以下经过充分记录的微流控芯片制造技术29, 可以轻松地进行双层微流控设备 (图 1)。在装置的底部添加玻璃支撑, 以减少振动对探针运动的影响。玻璃滑动是非常稀薄的 (0.10 毫米) 为了容纳显微镜目标的工作距离。这使得该设备易受建筑物中的小振动和样品环境的影响, 然后用高速相机测量。玻璃支持成功地抵消了这些外部刺激。选择短工作距离目标, ?...

软物质中的相变可以改变脚手架结构, 这在材料的处理和最终稳定性方面有影响1,2,3。在动态相变过程中, 软材料的表征为结构演化与平衡结构和流变特性之间的关系提供了重要的信息。例如, 许多家庭护理产品需要在消费者使用期间发生阶段性变化。此外, 在生产过程中, 加工步骤, 包括稀释和混合, 可以传递剪切影响的流变性能和最终显微组织的产品。了解整个相变的流变特性, 确保产品按设计进行。此外, 如果力改变材料在制造过程中的开始流变, 相变会产生意想不到的和不希望的结果, 改变预期的功能和效果。在临界凝胶点, 定义为物质从相关胶体或聚合物溶液过渡到样品生成凝胶网络的点, 材料性质随联想的细微变化而急剧变化。在关键凝胶点上对结构的任何修改都会影响最终产品4。在这些动态过渡过程中, 软材料具有弱的机械性能和测量, 使用经典的实验技术可以在测量噪声限制下5,6,7。为此, 在低模量范围 (10-3 -4 Pa) 中敏感的 microrheology 技术被用来表征弱初凝胶在动态演化过程中的特征。有些材料因外力而易受显微组织的变化, 这在表征过程中提出了挑战, 因为任何材料或流体的转移都可能影响结构, 最终材料的性能也会受到冲击。为了避免改变材料的显微结构, 我们开发了一种微流控装置, 可以在试样周围交换环境流体, 同时尽量减少剪切。通过交换流体环境, 在相变过程中测量流变特性和显微组织的变化, 并以最小的剪切贡献。该装置与多粒子跟踪 microrheology (等离子体) 结合在一种称为µ2流变学的技术中。该技术用于在凝胶的连续相变过程中, 对外部驱动力进行定量测定材料性能。该技术将说明使用纤维胶体凝胶, 氢化蓖麻油 (HCO)9,10,11。
凝胶支架由于其示例环境12,13,14,15, 可能会经历联想和离解的变化。胶凝和降解的驱动力是具体的材料, 必须为每个感兴趣的材料量身定做。µ2流变学可用于表征对外部刺激反应的凝胶系统, 包括胶体和聚合网络。改变 pH, 渗透压力或盐浓度是驱动力的例子, 可以引起材料微观结构的变化。例如, HCO 通过创建渗透压力梯度来经历控制的相变。当浓缩的 HCO 凝胶样品 (4 wt% HCO) 淹没在水中时, 胶体颗粒之间的吸引力减弱, 导致降解。或者, 当 HCO (0.125 wt% HCO) 的稀释溶液与亲水性材料 (称为凝胶剂, 主要由甘油和表面活性剂组成) 接触时, 吸引力会返回, 导致凝胶化。此凝胶系统将用于显示设备的操作, 作为测量单个示例9、10上的连续相转换的工具。为了表征这些凝胶支架在动态过渡过程中的特征, 以及在临界相变时的微妙初始凝胶结构, 我们利用等离子体来表征这些材料的高时空分辨率。
Microrheology 是用来确定凝胶的性质和结构, 特别是在关键的过渡, 一系列软材料, 包括胶体和聚合物凝胶5,6,9,16。微波等离子体是一种被动微观流变学技术, 它使用视频显微镜记录在样品中嵌入的荧光探针粒子的布朗运动。整个视频中的粒子位置精确地确定为使用经典跟踪算法17,18的像素的 1/10th 。从这些粒子轨迹计算了集合平均均方根位移 (本, Δr2(t))。该方法与材料性能有关, 如蠕变符合性, 使用广义斯托克斯-爱因斯坦关系17,19,20,21,22, 23。该材料的状态是通过计算该曲线的对数斜率作为滞后时间的函数来确定的, α,
<img alt="Equation 1" src="/files/ftp_upload/57429/57429eq1.jpg">
其中t为滞后时间, 并将其与临界松弛指数 ( n) 进行比较。n是使用时间固化叠加法确定的, 一种记录良好的技术, 它经过拉森和 Furst6进行了修改, 以分析等离子体数据。通过比较n到α材料的状态定量地被确定。当α > n材料为溶胶时, 当α < n材料为凝胶时。以前的工作使用 microrheology 来确定临界松弛指数9的 HCO 系统的特征。使用这些信息, 我们精确地确定在实验中材料何时从凝胶转变为溶胶。此外, 非高斯参数, αNG, 可以计算, 以确定系统的结构异质性的程度,
<img alt="Equation 2" src="/files/ftp_upload/57429/57429eq2.jpg">
其中Δx(t) 是x方向上的一维粒子移动。使用等离子体, 我们可以表征一个单相过渡, 但通过表征材料与微波微流体装置, 我们能够操纵周围的流体环境和收集数据的几个相变的单一凝胶样品。
该微流控装置的设计目的是研究单个凝胶样品的临界过渡, 以响应周围流体环境的变化而进行相变。当该装置在凝胶或溶胶状态下, 通过锁定样品以诱导相变, 同时最小化剪切时, 该设备会交换样品周围的流体。溶剂盆地位于样品室的正上方, 由六个对称间隔的入口通道连接。这种对称性允许液体从溶剂盆地交换到样品室, 同时在样品周围产生同样的压力, 将其锁定到位。已经有几项研究将这种技术用于单粒子和 DNA 捕获, 但这项工作将从单个分子到大约10µL24、25、26的样本量扩展。这种独特的设计还能在相变过程中实现实时的微观流变学特性。
µ2流变学是一种适用于许多软物质系统的健壮技术。本文所描述的技术是为胶体凝胶设计的, 但它可以很容易地适应其他材料, 如聚合物或胶束溶液。利用这一技术, 我们不仅确定了相变对平衡材料性能的影响, 而且还决定了不同加工步骤对材料的流变演化和最终脚手架结构的持久影响, 以及性能。

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			<td height="21" style="height:21px;width:205px;">150 x 15 mm Petri Dish</td>
			<td style="width:195px;">Corning, Inc.</td>
			<td style="width:131px;">351058</td>
			<td style="width:183px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">75 x 50 x 0.15 mm glass slide</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:131px;">Custom</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">75 x 50 x 1.0 mm glass slide</td>
			<td>Fisher Scientific</td>
			<td>12-550-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">75 x 25 x 1.0 mm glass Slide</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:131px;">12-550-A3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">22 x 22 Glass cover slips</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:131px;">12-542-B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Acetone, 99.5%</td>
			<td style="width:195px;">VWR Analytical</td>
			<td style="width:131px;">67-64-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Low intensity UV source</td>
			<td style="width:195px;">UVP</td>
			<td style="width:131px;">UVL-56</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Chloroform, 99.9%</td>
			<td style="width:195px;">Fisher Chemical</td>
			<td style="width:131px;">C298-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Cotton Swabs</td>
			<td style="width:195px;">Q-tips</td>
			<td style="width:131px;">83289205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Ethanol, 90%</td>
			<td style="width:195px;">Fisher Chemical</td>
			<td style="width:131px;">A962-4</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Fluoresbrite&#174; YG Carboxylate Microspheres 0.50&#181;m</td>
			<td style="width:195px;">Polysciences, Inc.&#160;</td>
			<td>15700-10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">High-Intensity UV Lamp</td>
			<td style="width:195px;">Spectroline Corp.</td>
			<td style="width:131px;">SB-100P</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Hot plate</td>
			<td style="width:195px;">Corning, Inc.</td>
			<td style="width:131px;">PC-420</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Hydrochloric Acid, 6N</td>
			<td style="width:195px;">Ricca Chemical Company</td>
			<td style="width:131px;">3750-32</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Methyltriethyoxysilane, 98%</td>
			<td style="width:195px;">Acros Organics</td>
			<td style="width:131px;">174622500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Microcentrifuge</td>
			<td style="width:195px;">Eppendorf</td>
			<td style="width:131px;">5424</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Plasma cleaner</td>
			<td style="width:195px;">Harrick Plasma, Inc.</td>
			<td style="width:131px;">PDC-32G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Polydimethylsiloxane (PDMS)</td>
			<td style="width:195px;">Robert McKwown Company</td>
			<td style="width:131px;">2065622</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Sonicator</td>
			<td style="width:195px;">Branson, Emerson Electric</td>
			<td style="width:131px;">1800</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Steel connectors, ID 0.023 inch</td>
			<td style="width:195px;">New England Small Tube Corp.</td>
			<td style="width:131px;">Custom</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Tetraethoxysilane, 98%</td>
			<td style="width:195px;">Alfa Aesar</td>
			<td style="width:131px;">A14965</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Thiol-ene Resin (UV curable)</td>
			<td style="width:195px;">Norland Products, Inc.&#160;</td>
			<td style="width:131px;">NOA81</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Transparency</td>
			<td style="width:195px;">Staples Inc.&#160;</td>
			<td style="width:131px;">21828</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Tygon tubing, ID 1/32 inch</td>
			<td style="width:195px;">McMaster-Carr</td>
			<td style="width:131px;">E-3603</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Vacuum oven</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:131px;">282A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Biopsy punch 8 mm</td>
			<td style="width:195px;">World Precision Instruments</td>
			<td style="width:131px;">504535</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Bioposy punch 0.5 mm</td>
			<td style="width:195px;">World Precision Instruments</td>
			<td>504528</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Syringe, 30 mL</td>
			<td style="width:195px;">BD</td>
			<td style="width:131px;">309659</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Syringe, 3 mL</td>
			<td style="width:195px;">BD</td>
			<td style="width:131px;">309651</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Needle, 18 gauge</td>
			<td style="width:195px;">BD</td>
			<td>305195</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Microcentrifuge tube, 1.5 mL</td>
			<td style="width:195px;">Eppendorf</td>
			<td>22-36-320-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">High-speed Camera</td>
			<td style="width:195px;">Vision Research</td>
			<td>Miro M120&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Microscope</td>
			<td style="width:195px;">Carl Zeiss AG</td>
			<td style="width:131px;">Zeiss Observer, Z1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Syringe pump</td>
			<td style="width:195px;">New Era Pump Systems</td>
			<td style="width:131px;">NE-300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Hydrogenated castor oil</td>
			<td style="width:195px;">Procter &#38; Gamble</td>
			<td style="width:131px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Af&#237;cio MP 6002 Printer</td>
			<td style="width:195px;">Ricoh Company, Ltd.</td>
			<td style="width:131px;">415877</td>
			<td></td>
		</tr>
	</tbody>
</table>

combining microfluidics and microrheology to determine rheological properties of soft matter during repeated phase transitions

软物质的显微结构直接影响宏观流变性能, 可通过在前相变化和应用剪切过程中的胶体重排等因素来改变。为了确定这些变化的程度, 我们开发了一种微流控装置, 它能使周围流体和微观流变学特性的交换引起的重复相变, 同时限制试样的剪切。此技术µ2流变学, 微流体和 microrheology 的组合。微流控装置是两层设计, 其对称入口流进入取样室, 在流体交换过程中捕获凝胶样品。吸力可以应用在远离样品室, 把液体拉入样品室。利用多粒子跟踪 microrheology (等离子体) 对材料的流变性能进行了表征。在微波等离子体中, 荧光探针粒子嵌入到材料中, 探针的布朗运动使用视频显微镜进行记录。对粒子的运动进行了跟踪, 计算了平均平方位移。利用广义斯托克斯-爱因斯坦关系, 该方法与宏观流变性质有关。通过与临界松弛指数的比较, 确定了材料的相位, 并用时间-固化叠加法确定。纤维胶体凝胶的测量表明了该技术的实用性。这种凝胶有一个微妙的结构, 可以不可逆转地改变时, 剪切应用。µ2流变数据表明, 材料在每次相变后反复 equilibrates 到相同的流变性质, 表明相转变在显微结构变化中不起作用。为了确定剪切的作用, 样品可以在注入到我们的微流控装置之前被剪切。µ2流变学是一种广泛适用的技术, 用于对软物质进行表征, 使在相变过程中, 单个样品中微细微结构的流变特性能够得到测定, 以响应周围环境条件。

两层微流控装置是用在微流控标记上进行阵列的 (图 1a、b) 构造的。图章的设计显示在图 1c中。不正确的实验设置会导致在周围流体交换过程中被动 microrheology 和微流控流的错误 (图 2)。在讨论部分中详细介绍了不正确的实验设置示例。在设备操作过程中, 围绕凝胶样品周围的流体...

Watch this Scientific Journal Video about Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions at JoVE.com

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

我们演示了一个微流控装置的制造和使用, 使多粒子跟踪 microrheology 测量, 以研究重复相变的流变效应对软物质。

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 ...

Research

Education

JoVE Core

JoVE Journal

Physics

Engineering

Unit 1

Temperature and Heat

SCIENTISTS IN ACTION

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

控制的大小，形状和稳定性超分子聚合物在水

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do ...

科研

工程学

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

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; ...

High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

高灵敏度核磁共振的千兆帕斯卡压力：一种新的工具，用于极端条件下探测电子和化工凝聚态的性质

Nuclear Magnetic Resonance (NMR) is one of the most important techniques for the study of condensed matter systems, their chemical structure, and their ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

通过光学吸收跃迁图案 - 制备与表征

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

Challenges in Rheological Characterization of Highly Concentrated Suspensions ÃƒÆ’Ã‚Â¢ÃƒÂ¢Ã¢â‚¬Å¡Ã‚Â¬ÃƒÂ¢Ã¢â€šÂ¬Ã‚Â A Case Study for Screen-printing Silver Pastes

挑战流变特性高度集中悬架 - 为例进行丝网印刷银浆

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets

由界面润湿片的热力学生长触发的液晶中的定向转变

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

用电解质浇注法对 WS2纳米器件电子态的电场控制

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

Fabrication of Soft Pneumatic Network Actuators with Oblique Chambers

斜腔软气动网络驱动器的研制

Soft pneumatic network actuators have become one of the most promising actuation devices in soft robotics which benefits from their large bending ...

Studying Large Amplitude Oscillatory Shear Response of Soft Materials

软材料大振幅振荡剪切响应的研究

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl ...

Rapid Manufacturing of Thin Soft Pneumatic Actuators and Robots

快速制造薄软气动执行器和机器人

This protocol describes a method for rapid manufacturing of soft pneumatic actuators and robots with an ultrathin form factor using a heat press and a ...