我们感谢东京技术学院的田中博士, 该研究所的时间分辨红外振动光谱学测量和奥哈拉教授和 k. 松博士在名古屋大学进行 XRD 测量。我们还感谢在名古屋大学的美国山口教授, 基尔大学的 Herges 教授和 r.j.d. 教授在普朗克斯学院的结构和动力学的重要讨论。
这项工作得到了日本科技 (JST) 的支持, 这项工程为 "分子技术和新功能的创造" (JPMJPR13KD、JPMJPR12K5 和 JPMJPR16P6) 和 "光能的化学转换" 提供了资金。此工作还部分由 jsp 授权编号 JP15H02103、JP17K17893、JP15H05482、JP17H05258、JP26107004 和 JP17H06375 支持。

1. 时间分辨红外振动光谱学
<ol><li>
样品准备
	<ol>
<li>解决方法: 将π扩展的 cyclooctatetraene (π-小床) 分子溶入二氯甲烷, 适当浓度 (1 毫摩尔/升)。</li>
		<li>LC 阶段: 用热板在100摄氏度的温度下, 将π型粉在氟化钙 (咖啡馆2) 衬底上熔化。在室温下冷却样品。 注意: 我们需要选择在中红外范围内透明的材料 (咖啡馆2或氟化钡 (曝气生物滤池2))。</li>
	</ol>
</li>
	<li>
设备设置
	<ol>
<li>开关钛蓝宝石 (钛宝石) 激光器和啁啾脉冲放大器。热稳定他们几个小时。</li>
		<li>请确保对齐正确。检查紫外线 (UV) 泵和中红外探头的功率和稳定性, 如有必要, 重新对准光路。时间分辨红外光谱的光学设置在图 5中提供。</li>
		<li>用液氮冷却 HgCdTe 红外探测器阵列。确保光谱仪正确定位, 以便在感兴趣的范围内检测出合理的光量。用聚苯乙烯或聚对苯二甲酸乙二醇酯等知名材料的吸收光谱对光谱仪进行标定。</li>
		<li>在样本持有者上安装一个显示大照片感应瞬态响应 (Si 晶片 (1 毫米) 或 Re (bpy) (CO)3Cl/CH3CN 解决方案) 的示例。将泵浦探头的延时定位到正值, 通过搅拌泵束来优化瞬态信号的数量, 以确保泵浦探头重叠。</li>
		<li>通过使用内置程序 (图 6) 对泵探头延迟进行远程扫描, 查找时间源设置。检查瞬态信号开始出现的位置。</li>
		<li>检查在稀土 (bpy) (CO)3Cl 中, 其偶极矩为正交的 co 拉伸对称和反对称振动的动力学。注意, 在正确满足魔术角度条件时, 两者都应该显示完全相同的动力学。</li>
	</ol>
</li>
	<li>
测量和数据采集
	<ol>
<li>解决方案: 安装家庭内置的流单元。如有必要, 设置带有惰性气体 (氮气 (N2) 或氩 (Ar)) 的冒泡装置。LC 阶段: 将自旋涂层的π-小床试样安装在电动舞台上, 连续移动试样上的激光点, 以尽量减少激光引起的损伤。</li>
		<li>Doublecheck 时间零位置与样品。</li>
		<li>正确设置泵探头延迟的扫描范围 (开始、结束和步骤)。</li>
		<li>选择保存数据的目录。</li>
		<li>使用内置的程序启动数据收集。 注意: 数据将自动记录在目录中。</li>
	</ol>
</li>
</ol>2. 时间分辨电子衍射
<ol><li>
样品衬底的制作
	<ol>
<li>购买硅 (001) 晶圆 (200 µm 厚), 双方都预先覆盖30纳米厚的硅氮化硅 (Si3N4, 或简单的罪恶) 薄膜 (图 11a)。在正方形 (15 x 15 毫米2) 中切下罪恶/Si/罪恶晶片。</li>
		<li>用 Ar 簇离子束照射41在 2.5 x 1016离子/cm2上, 在罪恶/Si/罪恶晶片的一侧, 尽管金属面具 (图 12), 这足以去除 30 nm 厚的罪膜 (图11 B、C)。 注: 去除罪膜的另一种方法是等离子蚀刻或离子束蚀刻。</li>
		<li>在浓度为28% 时制备氢氧化钾 (KOH) 水溶液。</li>
		<li>将硅片放入 KOH 溶液中, 温度为60-70 °c 1-2 天 (图 11D), 通过各向同性化学蚀刻42对硅晶片进行进一步蚀刻。 注: KOH 溶液中硅的蚀刻速率比罪快得多, 因此, 该罪薄膜仍然是自支撑膜 (图 11E)。</li>
		<li>在去离子水中用罪恶膜清洁晶片, 用氮气干燥。</li>
	</ol>
</li>
	<li>
样品准备
	<ol>
<li>在10毫克/毫升浓度的氯仿中溶解π-婴儿床分子。</li>
		<li>程序的旋转涂布机: 加速到 2000 rpm 在5秒, 保持旋转三十年代, 并停止旋转。自旋涂层π-床解决方案上的罪恶膜基板, 如图 11F所示。 注: 自旋涂层的适当硅片尺寸必须大于 10 x 10 毫米2, 因为表面张力有时会干扰较小晶片上的材料的自旋涂层, 例如, 用于透射电子显微术的 SiN 膜网格。</li>
		<li>将样品涂在100摄氏度温度的热板上, 并将其融化, 并逐渐冷却到室温 (图 11G)。</li>
	</ol>
</li>
	<li>
测量
	<ol>
<li>在样品架上装上螺钉, 将样品架放在真空室 (样品室) 中。</li>
		<li>密封真空室与盖子和开关在旋转泵, 以疏散室, 直到真空水平低于1000宾夕法尼亚州然后, 开关分子涡轮泵, 直到电子枪室是在真空水平的 ~ 10-6 Pa (通常超过12小时)。</li>
		<li>开关钛: 蓝宝石激光器和啁啾脉冲放大器, 并热稳定他们超过1小时。时间分辨电子衍射的实验设置在图 9中提供。将重复率设置为 500 Hz。</li>
		<li>打开电荷耦合器件 (CCD) 相机的惊悚片, 冷却到10摄氏度。</li>
		<li>接通电源, 并将电压调至75伏。 注: 电源泄漏电流不应在0.1 µA 范围内波动。</li>
		<li>特殊重叠。打开实验室编码的自动程序 (图 10A) 并设置曝光时间 (50 毫秒)。通过将开始类型设置为 Z 轴和 Y_overlap 的重叠, 然后按 开始按钮, 在样本保持器中找到带有针孔的电子光束位置, 方法是使用该程序。</li>
		<li>在针孔位置设置电子束, 并将泵浦激光器与反射泵光对准针孔。</li>
		<li>使用实验室编码的自动程序 (图 10B), 通过将开始类型设置为时间分辨和按下, 测量样本持有者上的具有无机材料 (Bi2Te3) 的时间零位置。开始按钮。对于此过程, 请将泵的通量调整为2兆焦耳/厘米2。</li>
		<li>将法拉第杯插入电子束的通过, 用实验室构建的型皮安计测量电子束的影响, 并通过旋转探头线上的可调钕滤波器来调整它。通过旋转泵浦线上的 waveplate 来调整泵浦脉冲的 thefluence。</li>
		<li>移动到采样位置并设置 CCD 摄像机的曝光时间。使用实验室编码的自动程序 (图 10B), 通过将开始类型设置为单并按启动按钮获得电子衍射图像。</li>
		<li>打开 CCD 相机的珀尔元件, 冷却到-20 摄氏度的温度。</li>
		<li>为时间分辨测量设置时间步骤和步骤数。使用实验室编码的自动程序 (图 10B), 通过将开始类型设置为时间解析并按启动按钮获得时间分辨电子衍射图像。</li>
		<li>使用实验室编码的自动程序 (图 10B), 通过将开始类型设置为时间解析, 获取具有时间解析背景的电子加速电源开关, 并按开始按钮。</li>
	</ol>
</li>
</ol>

作者没有什么可透露的。

在时间分辨电子衍射测量过程中, 关键步骤是保持高电压 (75 凯文) 而不存在电流波动, 因为光阴极与阳极板之间的距离只有10毫米。如果电流在实验之前或过程中波动超过0.1 µA 的范围, 则增加90凯文的加速度电压, 并将其再次设置为75凯文。这个调节过程必须要做, 直到电流在0.1 µA 的范围内波动。正确设计具有足够的电介质强度的电子源是研制这种机器的最重要的一点。
一般?...

液晶 (LCs) 具有多种功能, 广泛应用于科技应用领域1,2,3,4,5,6。LCs 的行为可以归结为他们的取向排序以及他们的分子的高机动性。lc 材料的分子结构通常以基团芯和长柔性碳链为特征, 保证 lc 分子的高流动性。在外部刺激下7,8,9,10,11,12,13,14,15, 如光、电场、温度变化或机械压力, LC 分子的小内和分子间运动会导致系统结构重新排列, 从而导致其功能行为。为了了解 lc 材料的作用, 确定 lc 相的分子尺度结构, 确定分子构象和填料变形的关键运动是重要的。
x 射线衍射 (XRD) 通常被用来作为一个强大的工具来确定 LC 材料的结构16,17,18。然而, 由功能刺激反应的核心产生的衍射模式常常被长碳链中的宽晕模式所掩盖。通过时间分辨衍射分析, 可以有效地解决这一问题, 通过 photoexcitation 对分子动力学进行直接观察。该技术利用 photoexcitation 前后衍射模式的差异, 提取 photoresponsive 芳香基团的结构信息。这些差异提供了消除背景噪声和直接观察兴趣结构变化的手段。对差分衍射模式的分析仅揭示了感光基团的调制信号, 从而排除了非 photoresponsive 碳链的有害衍射。在哈达、m et al19中提供了这种微分衍射分析方法的描述。
时间分辨衍射测量可以提供关于在材料的相变过程中发生的原子重排的结构信息20,21,22,23,24,25,26,27,28,29和分子之间的化学反应30,31,32,33,34。考虑到这些应用, ultrabright 和超短脉冲 X 射线35、36和电子37、38、39的开发取得了显著进展。,40源。然而, 时间分辨衍射只适用于简单的, 孤立的分子或单或多晶, 其中高度有序的无机晶格或有机分子产生良好的解析衍射模式提供结构信息。相比之下, 较复杂的软材料的超快结构分析由于它们的有序阶段较少而受到阻碍。在本研究中, 我们演示了利用时间分辨电子衍射以及瞬态吸收光谱和时间分辨红外 (IR) 振动光谱学来表征感光 LC 材料的结构动力学, 使用此衍射提取方法19。

<table><tbody><tr><td>Chirped pulse amplifier</td><td>Spectra Physics Inc.</td><td>Spitfire ACE</td><td>For time-resolved IR vibration spectroscopy</td></tr><tr><td>Chirped pulse amplifier&amp;nbsp;</td><td>Spectra Physics Inc.</td><td>Spitfire XP</td><td>For time-resolved electron diffractometry</td></tr><tr><td>Femtosecond laser</td><td>Spectra Physics Inc.</td><td>Tsunami</td><td>For time-resolved IR vibration spectroscopy</td></tr><tr><td>Femtosecond laser</td><td>Spectra Physics Inc.</td><td>Tsunami</td><td>For time-resolved electron diffractometry</td></tr><tr><td>Optical parametric amplifier</td><td>Light Conversion Ltd.</td><td>TOPAS prime</td><td></td></tr><tr><td>64-channel mercury cadmium tellurium IR detector array</td><td>Infrared Systems Development Corporation</td><td>FPAS-6416-D</td><td></td></tr><tr><td>FT-IR spectrometer</td><td>Shimadzu Corporation</td><td>IR Prestige-21</td><td></td></tr><tr><td>High voltage supply</td><td>Matsusada precision</td><td>HER-100N0.1</td><td></td></tr><tr><td>Rotary pump</td><td>Edwards</td><td>RV12</td><td></td></tr><tr><td>Molecular turbo pumps</td><td>Agilent Technologies Japan, Ltd.</td><td>Twis Torr 304FS</td><td></td></tr><tr><td>Vacuum gauges</td><td>Pfeiffer vacuum systems gmbh</td><td>PKR251</td><td>For ICF70 flange</td></tr><tr><td>Vacuum monitors</td><td>Pfeiffer vacuum systems gmbh</td><td>TPG261</td><td></td></tr><tr><td>Fiber coupled CCD camera</td><td>Andor Technology Ltd.</td><td>iKon-L HF</td><td></td></tr><tr><td>BaF2 and CaF2 substrates</td><td>Pier optics</td><td></td><td>Thickness 3 mm</td></tr><tr><td>AgGaS2 crystal</td><td>Phototechnica Corporation</td><td></td><td>Custom-order</td></tr><tr><td>BBO crystals</td><td>Tokyo Instruments, Inc.</td><td></td><td>SHG &amp;theta;=29.2 deg&lt;br/&gt; THG &amp;theta;=44.3 deg</td></tr><tr><td>calcite crystals</td><td>Tokyo Instruments, Inc.</td><td></td><td>Thickness 1mm</td></tr><tr><td>Optical mirrors</td><td>Thorlabs</td><td>PF10-03-F01&lt;br/&gt; PF10-03-M01&lt;br/&gt; UM10-45A</td><td>Al coat mirrors&lt;br/&gt; Au coat mirrors&lt;br/&gt; Ultrafast mirrors</td></tr><tr><td>Optical mirrors</td><td>HIKARI,Inc.</td><td></td><td>Broadband mirrors</td></tr><tr><td>Dichroic mirrors</td><td>HIKARI,Inc.</td><td></td><td>Custom-order&lt;br/&gt; Reflection: 266 nm&lt;br/&gt; Transmission: 400, 800 nm</td></tr><tr><td>Optical chopper</td><td>Newport Corporation</td><td>3501 optical chopper</td><td></td></tr><tr><td>Optical shutters</td><td>Thorlabs Inc.</td><td>SH05/M&lt;br/&gt; SC10</td><td></td></tr><tr><td>Optical shutters</td><td>SURUGA SEIKI CO.,LTD.</td><td>F116-1</td><td></td></tr><tr><td>Beam splitters</td><td>Thorlabs Inc.</td><td>BSS11R</td><td></td></tr><tr><td>Fused-silica lenses</td><td>Thorlabs Inc.</td><td>LA4663&lt;br/&gt; LA4184</td><td></td></tr><tr><td>BaF2 lens</td><td>Thorlabs Inc.</td><td>LA0606-E</td><td></td></tr><tr><td>Polarized mirrors</td><td>Sigmakoki Co.,Ltd</td><td></td><td>Custom-order&lt;br/&gt; Designed for 800 nm&lt;br/&gt; Reflection: s-polarized light&lt;br/&gt; Transmission : p-polarized light</td></tr><tr><td>Half waveplate</td><td>Thorlabs Inc.</td><td>WPH05M-808</td><td></td></tr><tr><td>Mirror mounts</td><td>Thorlabs Inc.</td><td>POLARIS-K1&lt;br/&gt; KM100</td><td>Kinematic mirror mounts</td></tr><tr><td>Mirror mounts</td><td>Sigmakoki Co.,Ltd</td><td>MHAN-30M&lt;br/&gt; MHAN-30S</td><td>Gimbal mirror mounts</td></tr><tr><td>Mirror mounts</td><td>Newport Corporation</td><td>ACG-3K-NL</td><td>Gimbal mirror mounts</td></tr><tr><td>Variable ND filters</td><td>Thorlabs Inc.</td><td>NDC-25C-2M</td><td></td></tr><tr><td>Beam splitter mounts</td><td>Thorlabs Inc.</td><td>KM100S</td><td></td></tr><tr><td>Lens mounts</td><td>Thorlabs Inc.</td><td>LMR1/M</td><td></td></tr><tr><td>Rotational mounts</td><td>Thorlabs Inc.</td><td>RSP1/M</td><td></td></tr><tr><td>Retroreflector</td><td>Edmund Optics</td><td>63.5MM X 30&quot; EN-AL&amp;nbsp;</td><td></td></tr><tr><td>spectrometers</td><td>ocean photonics</td><td>USB-4000</td><td></td></tr><tr><td>Power meter</td><td>Ophir</td><td>30A-SH</td><td>Used for intensity monitor of CPA</td></tr><tr><td>Power meter</td><td>Thorlabs Inc.</td><td>S120VC&lt;br/&gt; PM100USB</td><td>Used for intensity measurements of pump pulse</td></tr><tr><td>Photodiodes</td><td>Thorlabs Inc.</td><td>DET36A/M&lt;br/&gt; DET25K/M</td><td></td></tr><tr><td>DC power supply</td><td>TEXIO</td><td>PW18-1.8AQ</td><td>Used for magnetic lens</td></tr><tr><td>Magnetic lens</td><td>Nissei ETC Co.,Ltd</td><td></td><td>Custom-order</td></tr><tr><td>Stages</td><td>Newport Corporation</td><td>M-MVN80V6&lt;br/&gt; LTAHLPPV6</td><td>Used for magnetic lens</td></tr><tr><td>Stage controller</td><td>Newport Corporation</td><td>SMC100</td><td></td></tr><tr><td>Stages&amp;nbsp;</td><td>Sigmakoki Co.,Ltd</td><td>SGSP20-35(X)&lt;br/&gt; SGSP20-85(X)</td><td>Used for sample position</td></tr><tr><td>Stages&amp;nbsp;</td><td>Sigmakoki Co.,Ltd</td><td>SGSP26-200(X)&lt;br/&gt; OSMS26-300(X)</td><td>Used for delay time generator</td></tr><tr><td>Stage controller</td><td>Sigmakoki Co.,Ltd</td><td>SHOT-304GS</td><td></td></tr><tr><td>Picoammeter</td><td></td><td></td><td>Laboratory built</td></tr><tr><td>spin coater</td><td>MIKASA Co.,Ltd</td><td>1H-D7</td><td></td></tr><tr><td>hot plate</td><td>IKA&amp;reg;&amp;nbsp;</td><td>C-MAG HP7</td><td></td></tr><tr><td>SiN wafer</td><td>Silson Ltd</td><td></td><td>Custom-order</td></tr><tr><td>KOH aqueous solution (50%)</td><td>Hiroshima Wako Co.,Ltd.</td><td>168-20455</td><td></td></tr><tr><td>Chloroform</td><td>Hiroshima Wako Co.,Ltd.</td><td>038-18495</td><td></td></tr><tr><td>Dichloromethane</td><td>Hiroshima Wako Co.,Ltd.</td><td>132-02456</td><td></td></tr><tr><td>Personal computers for the controlling programs</td><td>Epson Corporate</td><td>Endeavor MR7300E-L</td><td>32-bit operation system</td></tr><tr><td>Program for the control the equipment</td><td>National Instruments Corporation</td><td>Labview2016</td><td></td></tr><tr><td>Program for the data analysis</td><td>The MathWorks, Inc.</td><td>Matlab2015b</td><td></td></tr></tbody></table>

novel techniques for observing structural dynamics of photoresponsive liquid crystals

本文讨论了用时间分辨红外 (IR) 振动光谱和时间分辨电子衍射对液晶 (LC) 相中分子的实验测量。液晶相是固体和液相之间存在的重要物质状态, 在自然系统以及有机电子学中是常见的。液晶是 orientationally 有序的, 但松散的包装, 因此, 可通过外部刺激修改 LCs 分子成分的内部构象和对齐。尽管先进的时间分辨衍射技术已经揭示了单晶体和多晶体的皮秒尺度分子动力学, 但对填料结构的直接观测和软材料的超快动力学却受到模糊衍射图案。在这里, 我们报告时间分辨红外振动光谱学和电子衍射获取一个柱状 LC 材料轴承感光核心基团的超快快照。时间分辨红外振动光谱与电子衍射相结合的差分检测分析是软材料结构表征和光致动力学的有力工具。

我们选择了一个鞍形π-小床骨架43,44作为 LC 分子的感光核心单元, 因为它形成了一个明确定义的柱状堆叠结构, 因为中央八-元的小床环预计会显示一个由于激发态芳香19,45, 光致构象变为扁平形式。此材料的合成过程在以前的出版物19中提供。合成 LC 分子由π形芯单元?...

Watch this Scientific Journal Video about Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals at JoVE.com

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

在这里, 我们提出了时间分辨红外振动光谱和电子衍射差分检测分析的协议, 使对 photoexcited 分子在柱状体周围局部结构变形的观测液晶, 对这种感光材料的结构与动力学的关系给出了一个原子视角。

观测 Photoresponsive 液晶结构动力学的新方法

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational ...

novel-techniques-for-observing-structural-dynamics-photoresponsive

Research

JoVE Journal

Chemistry

8.7K 次观看.  Okayama University. 在这里, 我们提出了时间分辨红外振动光谱和电子衍射差分检测分析的协议, 使对 photoexcited 分子在柱状体周围局部结构变形的观测液晶, 对这种感光材料的结构与动力学的关系给出了一个原子视角。

视频: Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

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 ...

科研

工程学

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

自由形式的光驱动器 - 制作和开动控制在微观尺度

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

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

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve desired molecular orientation states in LC displays, the "static" surface property of LCs, so-called surface anchoring, has been intensively studied. As a rule of thumb, once the initial orientation of LCs is "locked" by specific surface treatments, such as rubbing or treatment with a specific alignment layer, it hardly changes with temperature. Here, we present a system exhibiting an orientational transition upon temperature variation, which conflicts with the consensus. Right on the transition, the bulk LC molecules experience the orientational rotation, with 90&#176; between the planar (P) orientation at high temperatures and the vertical (V) orientation at low temperatures in the first-order transitional manner. We have tracked thermodynamic surface anchoring behavior by means of polarizing optical microscopy (POM), dielectric spectroscopy (DS), high-resolution differential scanning calorimetry (HR-DSC), and grazing incidence X-ray diffraction (GI-XRD) and reached a plausible physical explanation: that the transition is triggered by a growth of surface wetting sheets, which impose the V orientation locally against the P orientation in the bulk. This landscape would provide a general link explaining how the equilibrium bulk orientation is affected by surface-localized orientation in many LC systems. In our characterization, POM and DS are advantageous by offering information on the spatial distribution of the orientation of LC molecules. HR-DSC gives information about the precise thermodynamic information on transitions, which cannot be addressed by conventional DSC instruments due to limited resolution. GI-XRD provides information on surface-specific molecular orientation and short-range orderings. The goal of this paper is to present a protocol for preparing a sample that exhibits the transition and to demonstrate how the thermodynamic structural variation, both in the bulk and on surfaces, can be analyzed through the abovementioned methods.

Here, we present a protocol to trigger an orientational transition of a liquid crystal in response to temperature. Methodologies are described for preparing a sample in order to observe the transition and the detailed transitional evolution.

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 ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

光诱导的宏观振荡运动液晶网络的制备

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The devices are patterned from epoxy glue using soft lithography and are suitable for in situ X-ray diffraction experiments at room temperature. The sample wells are lidded on both sides with polymeric polyimide foil windows that allow diffraction data collection with low X-ray background. This fabrication method is undemanding and inexpensive. After the sourcing of a SU-8 master wafer, all fabrication can be completed outside of a cleanroom in a typical research lab environment. The chip design and fabrication protocol utilize capillary valving to microfluidically split an aqueous reaction into defined nanoliter sized droplets. This loading mechanism avoids the sample loss from channel dead-volume and can easily be performed manually without using pumps or other equipment for fluid actuation. We describe how isolated nanoliter sized drops of protein solution can be monitored in situ by dynamic light scattering to control protein crystal nucleation and growth. After suitable crystals are grown, complete X-ray diffraction datasets can be collected using goniometer based in situ fixed target serial X-ray crystallography at room temperature. The protocol provides custom scripts to process diffraction datasets using a suite of software tools to solve and refine the protein crystal structure. This approach avoids the artefacts possibly induced during cryo-preservation or manual crystal handling in conventional crystallography experiments. We present and compare three protein structures that were solved using small crystals with dimensions of approximately 10-20 &#181;m grown in chip. By crystallizing and diffracting in situ, handling and hence mechanical disturbances of fragile crystals is minimized. The protocol details how to fabricate a custom X-ray transparent microfluidic chip suitable for in situ serial crystallography. As almost every crystal can be used for diffraction data collection, these microfluidic chips are a very efficient crystal delivery method.

Microfluidic Chips for In Situ Crystal X-ray Diffraction and In Situ Dynamic Light Scattering for Serial Crystallography

This protocol describes in detail how to fabricate and operate microfluidic devices for X-ray diffraction data collection at room temperature. Additionally, it describes how to monitor protein crystallization by dynamic light scattering and how to process and analyze obtained diffraction data.

用于原位晶体 x 射线衍射和原位的微流控芯片系列晶体学的动态光散射

This protocol describes fabricating microfluidic devices with low X-ray background optimized for goniometer based fixed target serial crystallography. The ...

化学

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

This article describes the microfluidic process and parameters to prepare actuating particles from liquid crystalline elastomers. This process allows the preparation of actuating particles and the variation of their size and shape (from oblate to strongly prolate, core-shell, and Janus morphologies) as well as the magnitude of actuation.

液晶弹性体致动器的微流控制备

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due to their potential applications for future device technologies such as sensors and storage. However, conventional approaches, which usually utilize materials containing magnetic metal ions (or radicals), have a major problem: only a few materials have been found to show the coupling phenomena at room temperature. Recently, we proposed a new approach to achieve room-temperature magnetoelectrics. In contrast to conventional approaches, our alternative proposal focuses on a completely different material, a &#34;liquid crystal&#34;, free from magnetic metal ions. In such liquid crystals, a magnetic field can be utilized to control the orientational state of constituent molecules and the corresponding electric polarization through magnetic anisotropy of the molecules; it is an unprecedented mechanism of the magnetoelectric effect. In this context, this paper provides a protocol to measure ferroelectric properties induced by a magnetic field, that is, the direct magnetoelectric effect, in a liquid crystal. With the method detailed here, we successfully detected magnetically-tuned electric polarization in the chiral smectic C phase of a liquid crystal at room temperature. Taken together with the flexibility of constituent molecules, which directly affects the magnetoelectric responses, the introduced method will serve to allow liquid crystal cells to acquire more functions as room-temperature magnetoelectrics and associated optical materials.

In this report, we present a protocol to examine direct magnetoelectric effects, i.e., induction of ferroelectric polarization by applying magnetic fields, in liquid crystals. This protocol provides a unique approach, supported by the softness of liquid crystals, to achieve room-temperature magnetoelectrics.

液晶中磁调谐铁电极化的测量

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due ...

An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation

We demonstrate a method for fabricating a prototype reflective display device that contains cholesteric liquid crystal (LC) as an active component. The cholesteric LC is composed of a nematic LC 4&#39;-pentyloxy-4-cyanobiphenyl (5OCB), redox-responsive chiral dopant (FcD), and a supporting electrolyte 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIm-OTf). The most important component is FcD. This molecule changes its helical twisting power (HTP) value in response to redox reactions. Therefore, in situ electrochemical redox reactions in the LC mixture allow for the device to change its reflection color in response to electrical stimuli. The LC mixture was introduced, by a capillary action, into a sandwich-type ITO glass cell comprising two glass slides with patterned indium tin oxide (ITO) electrodes, one of which was coated with poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol) doped with perchlorate (PEDOT+). Upon application of +1.5 V, the reflection color of the device changed from blue (467 nm) to green (485 nm) in 0.4 s. Subsequent application of 0 V made the device recover the original blue color in 2.7 s. This device is characterized by its fastest electrical response and lowest operating voltage among any previously reported cholesteric LC device. This device could pave the way for the development of next generation reflective displays with low energy consumption rates.

A protocol for the fabrication of a reflective cholesteric liquid crystalline display device containing a redox-responsive chiral dopant allowing quick and low-voltage operation is presented.

一种用于快速和低压彩色调制的电化学胆固醇液晶器件

We demonstrate a method for fabricating a prototype reflective display device that contains cholesteric liquid crystal (LC) as an active component. The ...

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

单域液晶的弹性体和液晶橡胶纳米复合材料的制备

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

生物工程

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such as on-demand switchable adhesion technologies, actuators, molecular clutches, and nano-/microscopic mass transporters. Recently it was found that through a special solid-liquid transition, rheological properties can exhibit significant changes, thus providing suitable smart viscoelastic materials. However, designing materials with such a property is complex, and forward and backward switching times are usually long. Therefore, it is important to explore new working mechanisms to realize solid-liquid transitions, shorten the switching time, and enhance the contrast of rheological properties during switching. Here, a light-induced crystal-liquid phase transition is observed, which is characterized by means of polarizing light microscopy (POM), photorheometry, photo-differential scanning calorimetry (photo-DSC), and X-ray diffraction (XRD). The light-induced crystal-liquid phase transition presents key features such as (1) fast switching of crystal-liquid phases for both forward and backward reactions and (2) a high contrast ratio of viscoelasticity. In the characterization, POM is advantageous in offering information on the spatial distribution of LC molecule orientations, determining the type of liquid crystalline phases appearing in the material, and studying the orientation of LCs. Photorheometry allows measurement of a material&#8217;s rheological properties under light stimuli and can reveal the photorheological switching properties of materials. Photo-DSC is a technique to investigate thermodynamic information of materials in darkness and under light irradiation. Lastly, XRD allows studying of microscopic structures of materials. The goal of this article is to clearly present how to prepare and measure the discussed properties of a photorheological material.

This protocol demonstrates the preparation of a photorheological material that exhibits a solid phase, various liquid crystalline phases, and an isotropic liquid phase by increasing temperature. Presented here are methods for measuring the structure-viscoelasticity relationship of the material.

扭曲弯曲的液晶的高对比度和快速光圈开关

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such ...