Name: thermal scanning conductometry (tsc) as a general method for studying and controlling the phase behavior of conductive physical gels
Uploaded: 2018-01-23T13:30:00.000+00:00
Duration: 10 min 1 s
Description: Watch this Scientific Journal Video about Thermal Scanning Conductometry TSC as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels at JoVE.com

这项工作的财政支助由国家科学中心提供, 作为赠款 No。DEC-2013/11/D/ST3/02694

1. TSC 测量试验场的制备
<ol><li>为了测量 TSC 方法的全部特性, 使用具有四电极电池的商用电导 (或者两个电极电池可以用于低电导率) 和温度传感器。将其连接至 PC, 并记录样品的导电性和温度 (4%% 甲基-46-o--基)-α-d-喃在基溴-TEABr 中的 1 M 摩尔浓度-Glyc 用于研究案例, 请参阅3款用于离子凝胶样品的制备) 以及计算机时间。</li>
	<li>对于自动读数, 使用制造商提供的软件与电导, 并设置测量模式连续与间隔读数每1秒。</li>
	<li>准备氮气线 (用液氮填充高压氮气罐并开始蒸发以获得氮气线中的气态氮), 并将压力设置为2条和所需的流量, 然后降低氮气的初始温度在冰箱的帮助下。</li>
	<li>将小瓶上的螺钉帽紧紧地安装在导电传感器上, 并用一条聚四氟乙烯胶带固定 (关键是挥发性样品) (参见图 2)。</li>
</ol>2. 电解质溶液的制备
<ol><li>通过混合适量的甘油 (用作溶剂) 和基溴化物 (TEABr) 来制备电解质 (使用水垢对所需浓度的化合物进行相应的称量以进行调查), 用作溶质, 在玻璃瓶在100° c 下紧紧地封闭和加热15分钟。</li>
	<li>下一步, 搅拌1分钟的混合物, 再加热100° c 5 分钟, 以确保所有的溶质溶解和混合物是均匀的。</li>
	<li>使用这些准备好的电解质溶液进行测量, 并随后准备 ionogels。</li>
</ol>3. 低分子量离子凝胶的制备
<ol><li>从电解质溶液中制备 ionogels (见2节), 加入178.6 毫克的低分子量胶至4毫升的1米 TEABr/Glyc 电解质溶液, 以获得 4%% 的离子凝胶样品。 注: 所用的胶的化学合成在别处被描述了11。</li>
	<li>要溶解胶, 将其添加到带有电解液溶液的玻璃瓶中, 并在130° c 处加热20分钟, 以增加搅拌以协助溶解。</li>
	<li>在完全溶解胶后, 将混合物加热5分钟以确保样品均匀。</li>
	<li>接下来, 在10° c 的干燥冷却块中快速冷却样品, 以确保物理凝胶。在该过程之后, 应获得均匀、透明或不透明的凝胶阶段 (图 3)。 注: 在第一次凝胶完成后, 样品在高温下转向溶胶相时变成液体, 但回到室温后, 它又转向凝胶相。凝胶溶胶相变所需的温度低于晶体胶溶解所需的温度。通过改变冷却阶段的动力学, 可以影响获得的 ionogel 的物理性能, 如显微组织、光学外观或凝胶溶胶相变温度 (Tgs)。</li>
</ol><img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56607/56607fig3.jpg"> 图 3 :所调查的示例的物理外观.1M TEABr/Glyc 电解质 (a), 4% ionogel 与 1M TEABr/Glyc 电解质在透明阶段 (b), 4% ionogel 与 1M TEABr/Glyc 电解质在不透明阶段 (c)。<a href="//cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56607/56607fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
4.原位Ionogels 热扫描电导
<ol><li>要准备样品为 TSC 测量, 加热 ionogel 在 Tgs温度之上, 94.85 ° c 在被研究的案件。把它转移到冷聚丙烯小瓶后, 它变成溶胶相。由于溶胶的快速冷却, 凝胶相形成。</li>
	<li>将电导传感器 (与瓶子上的螺钉盖) 插入瓶中, 将其推入凝胶中, 拧紧螺钉盖, 并将其固定在聚四氟乙烯胶带上。</li>
	<li>执行 TSC 测量并记录电导率、温度和时间, 以准备导电性vs温度、温度vs时间和电导率 v 时间依赖性.在加热冷却循环 (至少2次) 中重复测量在所调查的温度范围 (9.85-99.85 ° c)。 注意: 请记住 1st周期用于消除由准备过程引起的样本的所有差异。</li>
	<li>以不同的冷却速率 (7 ° c/分钟, 4 ° c/分钟, 和1° c/分钟) 进行测量, 以探讨它是如何影响研究 ionogels 的导电和热性能的。 注意: 演示如何将 TSC 方法用作获取具有目标属性的 ionogels 的工具, 在本手稿中进行了一系列基于胶1、甘油和 TEABr 的非水 ionogel 的实验. </li>
</ol>5. TSC 测量示例
<ol><li>将调查的 ionogel 插入小瓶中, 并在电导率传感器中推进。</li>
	<li>执行 1st加热冷却循环, 以改善电极接触, 并消除 ionogel 组织中的所有缺陷, 将样品放置在瓶子中, 并将其视为在凝胶中包括的划痕、裂纹和气泡。</li>
	<li>测量 2nd和 3rd加热冷却周期中的电导率和温度, 以调查 ionogel 的性能和系统的重现性。将加热速率设置为2° c/分钟, 冷却速率为7° c/分钟, 凝胶温度为10° c。因此, 获得透明的凝胶相。</li>
	<li>执行 4th和 5th加热冷却循环, 加热和冷却速率等于2° c/分钟, 凝胶温度等于10° c。因此, 获得了透明和不透明的凝胶阶段的混合物。</li>
	<li>执行 6th和 7th加热冷却周期, 加热和冷却速率等于2° c/分钟, 凝胶温度等于60° c。因此, 获得一个不透明的, 白色的凝胶阶段。</li>
	<li>对记录的数据执行对 1st派生的分析, 以查看示例之间的差异。</li>
	<li>在每个凝胶温度下保持样品20分钟, 以确保凝胶过程完成。</li>
</ol>

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作者没有透露

热扫描电导是一种新的实验方法, 它被证明是一种有效和有效的方法来调查动态变化的系统, 如 ionogels 的基础上低分子量胶, 电解质, 或离子液体。然而, 它的适用性不仅限于 ionogels。TSC 方法可以很容易地与其他类型的导电软物质系统, 如水凝胶, 乳液, 药膏, 或任何其他电荷含有的载体, 电导传感器可以插入。该方法的局限性在于它依赖于电导率传感器本身, 以及它可以使用的样本类型, 但是该协议?...

热可逆 Ionogels 物理胶凝是一个过程, 允许结构的自组装胶分子存在的溶剂分子。由于这种现象的相互作用的非共价键性质 (如氢键、范德华相互作用、色散力、静电力、ππ叠加、等), 这些系统是热可逆的。这种热可逆性, 连同胶的极低浓度和可以被创造的系统的各种各样, 是物理凝胶的一些主要好处在化工部分。由于物理凝胶状态的独特性质, ionogels 的特点是可取的特点, 如易于回收, 长周期寿命, 增强的物理性能 (例如离子电导率), 易于生产, 并降低生产成本。考虑到上述物理凝胶的优点 (已经有广泛的不同应用范围1,2,3,4), 这些都被认为是用来替代电解质固化和获得 ionogels5,6,7,8。然而, 经典的电导是不敏感和准确的, 足以跟踪这样的动态变化的系统。因此, 它无法检测凝胶基质中离子的相变和增强动力学9。这种不敏感的原因是温度稳定所需要的时间, 在此期间, 在开始测量之前, 样品的动态变化正在进行。此外, 测量的温度的数量是有限的顺序, 而不是显着延长实验时间。因此, 为了充分准确地刻画 ionogels, 需要一种新的方法, 它可以跟踪性能的动态变化作为温度的函数, 并能实时记录数据。进行凝胶过程的方式决定了所创建的 ionogel 的性质。在冷却阶段定义了分子间非共价键相互作用;通过改变凝胶温度和冷却速率, 人们可以强烈地影响这些相互作用。因此, 当凝胶发生时, 在冷却过程中测量系统是极其重要的。经典的方法, 这是不可能的, 因为温度稳定时间的测量, 和快速冷却率所需的成功凝胶。然而, 用热扫描电导方法这项任务是非常简单的, 提供准确和可重现的结果, 并允许研究不同的热变化动力学的影响应用于样品的样品属性10. 因此, 具有目标属性的 ionogels 可以同时进行研究和制造。
热扫描电导 (TSC) 热扫描电导应该提供一个可重现的, 准确的, 快速的反应实验方法的动态变化和热可逆系统的电导率测量, 如 ionogels 基于低分子量胶.然而, 它也可以用于电解质, 离子液体, 和任何其他导电样品, 可以放在测量细胞, 并具有电导率的传感器的测量范围。此外, 该方法除研究应用外, 还成功地用于制造具有显微组织、光学外观或热稳定性等目标性质的 ionogels, 并能准确、简便地实现相变温度。利用 TSC 法进行热处理的动力学和历史, 对物理凝胶系统的一些基本特性进行了全面的控制。此外, 该室还配备了一个摄像机, 以检查样品的状态和记录的变化, 特别是在凝胶和溶解过程中的样品。TSC 方法的另一个优点是它的简单性, 因为该系统可以建立在一个标准的电导, 可编程温度控制器, 气体氮气线的加热/冷却介质, 冰箱, 测量室, 和 PC,可以在大多数实验室中找到。
TSC 实验场 热扫描电导实验装置可以建立在几乎每个实验室, 成本相对较低。作为回报, 你得到一个准确的, 可重现的, 快速的方法来测量液体和半固态导电样品在不同的外部条件。在我们的实验室中建立的 TSC 实验装置的详细方案在图 1中给出。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56607/56607fig1v2.jpg"> 图 1: 测量站点的框图.热扫描电导方法的工作实验装置组成。<a href="//cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56607/56607fig1v2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
对于温度的变化, 采用自制的温度控制器, 可采用可编程的温度控制器, 可以用定义的变化率线性改变温度。对于热隔离, 已经建立了一个特殊的腔室。使用隔离室的目的是尽量减少样品中的温度水平梯度, 并保证快速冷却速率。该室由一个直径为40毫米的玻璃圆筒和300毫米的长度组成。在底部, 气体氮气进口加热器位于, 入口的末端装备了压均匀地传播热或冷气体。这也是温度传感器 PT100 的地方在可变温度控制器 (职训局) 位于。样品的温度由位于电导传感器中的温度传感器独立记录。此外, 该室还配备了一个摄像机, 以检查样品的状态和记录的变化, 特别是在凝胶和溶解过程中的样品。采用 250 L 高压贮罐中液氮蒸发所获得的气态氮作为加热和冷却介质。在氮气线的工作压力设置为6条, 并减少到2酒吧在测量现场。这样的设置允许在4和28升/分钟之间的流量取得没有任何干扰, 这使得冷却率为10° c/分钟。为了降低氮气的初始温度, 采用了外部制冷机, 降低了温度为10° c。这使得从室温开始的温度变化具有良好的线性度。在快速冷却期间, 氮气的温度降低到-15 ° c, 以协助高冷却率。由于低温, 必须使用气态氮, 而不是干燥的空气, 以避免结冰的冰箱。
样品入了 9 毫米内径和长度 58 毫米的小瓶 , 由聚丙烯制成 , 并且装备了螺丝盖帽 , 有橡胶圆环为严密的关闭。小瓶可以使用由120° c。(请参见图 2)。
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56607/56607fig2.jpg"> 图 2: 聚丙烯小瓶的图片及其在电导率传感器上的安装.(1) 聚丙烯小瓶, (2) 带橡胶圈的螺丝盖, 2a-安装在导电性传感器上的螺钉盖, (3) 装有电导传感器的小瓶, 用聚四氟乙烯胶带固定的螺钉盖。<a href="//cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56607/56607fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

<table><tbody><tr><td>SevenCompact S230 conductometer</td><td>Mettler-Toledo</td><td></td><td>equiped with InLab 710 sensor</td></tr><tr><td>home-build VTC</td><td></td><td></td><td></td></tr><tr><td>LabX PH 3.2 software</td><td>Mettler-Toledo</td><td></td><td>software used for data aqusition</td></tr><tr><td>tetraethylammonium bromide</td><td>Sigma-Aldrich</td><td>140023</td><td></td></tr><tr><td>glycerol</td><td>Sigma-Aldrich</td><td>G5516</td><td></td></tr><tr><td>methyl-4,6-O-(p-nitrobenzylidene)-a-D-glucopyranose</td><td></td><td></td><td>synthezied according to Gronwald, O., Shinkai, S., J. chem. Soc., Perkin Trans. 2 1933-1937 (2001).</td></tr><tr><td>[im]HSO&lt;sub&gt;4&lt;/sub&gt;</td><td></td><td></td><td>synthezeid by group of prof. Mohammad Ali Zolfigol, Faculty of Chemistry&lt;br/&gt; Bu-Ali Sina University&lt;br/&gt; Hamedan, I.R.Iran&amp;nbsp; according to Bielejewski, M., Ghorbani, M., Zolfigol, M., Tritt-Goc, J., Noura, S., Narimani, M., Oftadeh, M. RSC Adv. 6, 108896-108907 (2016).</td></tr><tr><td>polypropylene vial</td><td>Paradox Company, Cracow, Poland</td><td>PTC 088</td><td>www.insectnet.eu</td></tr></tbody></table>

thermal scanning conductometry (tsc) as a general method for studying and controlling the phase behavior of conductive physical gels

热扫描电导协议是研究基于低分子量胶的离子凝胶的一种新方法。该方法的目的是跟踪 ionogels 的动态变化状态, 并提供更多的信息和细节的微妙变化的导电性能随着温度的增减。此外, 该方法还允许在恒定温度下进行长期 (即天、周) 测量, 以调查系统的稳定性和耐久性以及老化效应。TSC 方法的主要好处在古典电导是能力执行测量在胶凝过程期间, 是不可能的以古典方法由于温度稳定, 通常需要很长时间在个人测量。获得物理凝胶相是一个众所周知的事实, 冷却阶段必须是快速的;此外, 根据冷却速度, 可以实现不同的显微结构。TSC 方法可以进行任何冷却/加热速率, 可由外部温度系统保证。在我们的情况下, 我们可以实现线性温度变化率在0.1 和大约10° c/分钟之间。热扫描电导设计为循环工作, 在加热和冷却阶段之间不断变化。这种方法可以研究热可逆凝胶溶胶相变的重现性。此外, 它允许在同一样本上的不同实验协议的性能, 可以刷新到初始状态 (如果有必要) 不从测量单元中删除。因此, 测量可以更快、更有效地执行, 并且具有更高的重现性和精确性。此外, TSC 方法也可以作为一种工具, 制造 ionogels 的目标性质, 如微观结构, 即时表征导电性能。

有机离子凝胶构成了一种新型的功能材料, 可以成为高分子凝胶电解质的替代溶液。然而, 为了达到这个目的, 这些凝胶必须被深入研究和理解。凝胶过程的热可逆特性, 以及温度和相位发生的动态变化特性, 需要一种新的实验方法, 使数据的记录和温度的细微变化的检测更改.热扫描电导是唯一的方法, 允许记录的电导率和温度的样品在加热冷却循环, 和线性变化的温度。TSC ?...

Watch this Scientific Journal Video about Thermal Scanning Conductometry TSC as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels at JoVE.com

Thermal Scanning Conductometry TSC as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels

冷却过程的动力学定义了基于低分子量胶的离子凝胶的性质。这份手稿描述了热扫描电导 (TSC) 的使用, 它得到完全控制的凝胶过程, 连同原位测量样品的温度和电导率。

热扫描电导 (TSC) 作为研究和控制导电物理凝胶相行为的一般方法

The thermal scanning conductometry protocol is a new approach in studying ionic gels based on low molecular weight gelators. The method is designed to ...

thermal-scanning-conductometry-tsc-as-general-method-for-studying

Universidad San Sebastian

Research

JoVE Journal

Environment

Thermal Scanning Conductometry (TSC) as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels

7.6K 次观看.  Institute of Molecular Physics Polish Academy of Sciences. 冷却过程的动力学定义了基于低分子量胶的离子凝胶的性质。这份手稿描述了热扫描电导 (TSC) 的使用, 它得到完全控制的凝胶过程, 连同原位测量样品的温度和电导率。

视频: Thermal Scanning Conductometry TSC as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

扫描探针单电子电容谱

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

科研

工程学

Phase Diagram Characterization Using Magnetic Beads as Liquid Carriers

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for the purpose of investigating phase change of those liquid segments. The magnetic beads were externally controlled using a magnet, allowing for the beads to bridge the air valve between the adjacent liquid segments. A hydrophobic coating was applied to the inner surface of the tube to enhance the separation between two liquid segments. The applied magnetic field formed an aggregate cluster of magnetic beads, capturing a certain liquid amount within the cluster that is referred to as carry-over volume. A fluorescent dye was added to one liquid segment, followed by a series of liquid transfers, which then changed the fluorescence intensity in the neighboring liquid segment. Based on the numerical analysis of the measured fluorescence intensity change, the carry-over volume per mass of magnetic beads has been found to be ~2 to 3 &#181;l/mg. This small amount of liquid allowed for the use of comparatively small liquid segments of a couple hundred microliters, enhancing the feasibility of the device for a lab-in-tube approach. This technique of applying small compositional variation in a liquid volume was applied to analyzing the binary phase diagram between water and the surfactant C12E5 (pentaethylene glycol monododecyl ether), leading to quicker analysis with smaller sample volumes than conventional methods.

Here, we present a protocol to investigate multi-component phase diagrams using externally controlled magnetic beads as liquid carriers in a lab-in-tube approach. This approach can aid in applications that seek to gather further information on phase change in complex liquid systems.

相图表征使用磁珠用作液体载体

Magnetic beads with ~1.9 &#181;m average diameter were used to transport microliter volumes of liquids between contiguous liquid segments with a tube for ...

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal&#8211;semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 &#937;&#8722;1 cm&#8722;1, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS2 and WS2.

We describe the approaches for the device fabrication and electrical characterization of molybdenum diselenide (MoSe2) layer semiconductor nanostructures with different thicknesses. In addition, the fabrication of ohmic contacts for MoSe2-layer nanocrystals by the focused-ion beam deposition method using platinum (Pt) as a contact metal is described.

欧姆接触制造用聚焦离子束技术和电气特性的半导体层的纳米结构

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor ...

Characterizing Electron Transport through Living Biofilms

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980&#39;s to investigate thin film conductive polymers.

A protocol for measuring electrical conductivity of living microbial biofilms under physiologically relevant conditions is presented.

通过活生物膜表征电子传输

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under ...

化学

Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and absence of white light exposure. By instituting a controlled temperature ramp, the gelation of these materials can be precisely monitored as they proceed through this structural evolution, which effectively mirrors the conditions experienced during the solution deposition phase of organic electronic device fabrication. Using small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) along with appropriate fitting protocols we quantify the evolution of select structural parameters throughout this process. Thorough analysis indicates that continued light exposure throughout the gelation process significantly alters the structure of the ultimately formed gel. Specifically, the aggregation process of poly(3-hexylthiophene-2,5-diyl) (P3HT) nano-scale aggregates is negatively affected by the presence of illumination, ultimately resulting in the retardation of growth in conjugated polymer microstructures and the formation of smaller scale macro-aggregate clusters.

A protocol for the analysis of gels formed from the optoelectronic conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) using small and ultra-small angle neutron scattering in both the presence and absence of illumination is presented.

利用中子散射监测光照对共轭高分子凝胶结构的影响

We demonstrate a protocol to effectively monitor the gelation process of a high concentration solution of conjugated polymer both in the presence and ...

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 ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

直接溶液还原法快速合成金、钯、铂气凝胶的研究

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Fabrication and Characterization of a Conformal Skin-like Electronic System for Quantitative, Cutaneous Wound Management

Recent advances in the development of electronic technologies and biomedical devices offer opportunities for non-invasive, quantitative assessment of cutaneous wound healing on the skin. Existing methods, however, still rely on visual inspections through various microscopic tools and devices that normally include high-cost, sophisticated systems and require well trained personnel for operation and data analysis. Here, we describe methods and protocols to fabricate a conformal, skin-like electronics system that enables conformal lamination to the skin surface near the wound tissues, which provides recording of high fidelity electrical signals such as skin temperature and thermal conductivity. The methods of device fabrication provide details of step-by-step preparation of the microelectronic system that is completely enclosed with elastomeric silicone materials to offer electrical isolation. The experimental study presents multifunctional, biocompatible, waterproof, reusable, and flexible/stretchable characteristics of the device for clinical applications. Protocols of clinical testing provide an overview and sequential process of cleaning, testing setup, system operation, and data acquisition with the skin-like electronics, gently mounted on hypersensitive, cutaneous wound and contralateral tissues on patients.

This article presents methods to fabricate and characterize a conformal, skin-like electronic system and protocols for the use in clinical applications, particularly on cutaneous wound management.

制作定量，皮肤伤口管理一个形皮肤般的电子系统与表征

Recent advances in the development of electronic technologies and biomedical devices offer opportunities for non-invasive, quantitative assessment of ...

生物工程

Viscoelastic Characterization of Soft Tissue-Mimicking Gelatin Phantoms using Indentation and Magnetic Resonance Elastography

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the biomechanics-related mechanisms of disease, injury, and development. The mechanical testing method is the most straightforward way for tissue characterization and is considered as verification for in vivo measurement. Among the many ex vivo mechanical testing techniques, the indentation test provides a reliable way, especially for samples that are small, hard to fix, and viscoelastic such as brain tissue. Magnetic resonance elastography (MRE) is a clinically used method to measure the biomechanical properties of soft tissues. Based on shear wave propagation in soft tissues recorded using MRE, viscoelastic properties of soft tissues can be estimated in vivo based on wave equation. Here, the viscoelastic properties of gelatin phantoms with two different concentrations were measured by MRE and indentation. The protocols of phantom fabrication, testing, and modulus estimation have been presented.

This article presents a demonstration and summary of protocols of making gelatin phantoms that mimic soft tissues, and the corresponding viscoelastic characterization using indentation and magnetic resonance elastography.

使用压痕和磁共振弹性成像对软组织模拟明胶模型进行粘弹性表征

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the ...

Hydrogel Arrays Enable Increased Throughput for Screening Effects of Matrix Components and Therapeutics in 3D Tumor Models

Cell-matrix interactions mediate complex physiological processes through biochemical, mechanical, and geometrical cues, influencing pathological changes and therapeutic responses. Accounting for matrix effects earlier in the drug development pipeline is expected to increase the likelihood of clinical success of novel therapeutics. Biomaterial-based strategies recapitulating specific tissue microenvironments in 3D cell culture exist but integrating these with the 2D culture methods primarily used for drug screening has been challenging. Thus, the protocol presented here details the development of methods for 3D culture within miniaturized biomaterial matrices in a multi-well plate format to facilitate integration with existing drug screening pipelines and conventional assays for cell viability. Since the matrix features critical for preserving clinically relevant phenotypes in cultured cells are expected to be highly tissue- and disease-specific, combinatorial screening of matrix parameters will be necessary to identify appropriate conditions for specific applications. The methods described here use a miniaturized culture format to assess cancer cell responses to orthogonal variation of matrix mechanics and ligand presentation. Specifically, this study demonstrates the use of this platform to investigate the effects of matrix parameters on the responses of patient-derived glioblastoma (GBM) cells to chemotherapy.

The present protocol describes an experimental platform to assess the effects of mechanical and biochemical cues on chemotherapeutic responses of patient-derived glioblastoma cells in 3D matrix-mimetic cultures using a custom-made UV illumination device facilitating high-throughput photocrosslinking of hydrogels with tunable mechanical features.

水凝胶阵列可提高 3D 肿瘤模型中基质成分和治疗药物筛选效果的通量

Cell-matrix interactions mediate complex physiological processes through biochemical, mechanical, and geometrical cues, influencing pathological changes ...