この研究は、学術振興会の助成金番号16H06037によって支持された。北海道大学の佐々木裕司博士に、HR-DSCの技術援助について心から感謝します。

1.ガラス基板上へのペルフルオロポリマーの液晶配向層の調製<ol><li> パーフルオロポリマー溶液の調製 <ol><li>ペルフルオロポリマー溶液（9重量％のポリマー）を市販の溶媒に1：2の比率で溶解することによってペルフルオロポリマー溶液1mLを調製する。これにより、厚さ0.5〜1μmの均一な膜がスピンコートされることが保証される。 注：使用する溶液および溶媒については、材料リストを参照してください。 </li></ol></li><li> 清浄なガラス基板上へのペルフルオロポリマーのコーティング <ol><li>アルカリ性洗剤で38または42 kHzで超音波処理してガラス基板（典型的なサイズ：1 cm x 1 cm）を洗浄する。蒸留水で繰り返しリンスします。典型的には、毎回5分の超音波処理で10回以上すすぎます。 </li><li>基材をUV-O 3クリーナーに10分間さらす。 </li><li>ステップ1.1からの溶液20μLを洗浄したガラス基材上に滴下するテス。直ちに溶液を3,500 rpmで室温で70秒間スピンコートする。フィルムを80℃で60分間加熱して溶剤を除去し、200℃で60分間硬化させる。 </li></ol></li></ol> LCセルの調製<ol><li>光硬化性樹脂と波長365 nm（1.1 W / cm 2 ）のLEDランプを使用して、フィルムでコーティングした2枚のガラス基板を接着します。マイクロメートルサイズのガラス粒子またはポリエチレンナフタレートフィルムを使用して、2枚の基板の間のギャップの厚さを2〜100μmの範囲内に調整する。 </li><li>等方性液体（I）よりも高い温度で毛細管力下のスパチュラを用いて、調製したLCセルにLC材料、4&#39;-ブチル-4-ヘプチル - ビシクロヘキシル-4-カルボニトリル（CCN47;0.2-10μL） 9を導入する。 - ネマチック（N）相転移温度。 注：CCN47は負の誘電率異方性を有し、相系列はCry 298.6 K SmA 301.3 KN 331.3 KI（CryおよびSmAは結晶およびスメクチックA相を表す）。フロー誘導アライメントが促進されるため、N期またはSmA期にCCN47を導入しないでください。 </li></ol>サンプルの特徴付け<ol><li> 偏光光学顕微鏡（POM）によるテクスチャ観察10 <ol><li> ±0.1Kの精度でサンプル温度を制御するホットステージと組み合わせて、4-100倍の対物レンズを備えたPOM下のLCセルを観察します。テクスチャを5フレーム以上、ケルビン毎に等間隔で記録します。 冷却と加熱の両方で291〜343 Kの範囲でデジタルカラーカメラを逐次使用してください。 </li></ol></li><li> 誘電分光法（DS） 11 <ol><li>両方の基板上に、正方形または円形の形状を持ち、商業的に購入可能なITO電極を備えたLCセルを準備する。各基板にリード線を半田付けする。 注：使用される基材の材料リストをご覧ください。 </li><li>市販のインピーダンス/利得位相アナライザを使用して、POMに使用されているのとまったく同じLCセルのキャパシタンスまたは誘電率を測定します。各測定の前にサンプルの状態が平衡になっていることを確認してください。 5分ごとに手動でLCセルの静電容量を測定することにより、LCセルの静電容量または誘電率の時間依存性を測定します。 </li><li> LCセルのキャパシタンスまたは誘電率が非時間依存性になる場合にのみ、DS測定を開始します。 </li></ol></li><li> 高分解能示差走査熱量測定（HR-DSC） 12 <ol><li> LCセルをPOM（正確にはDSCパンを使用しない）と同様に、自家製のHR-DSCに入れて検査します。 HR-DSCを設計および構築し、それを使用する方法については、参考文献12を参照してください。最小温度分解能を高めるために、0.05〜1.0K /分の走査速度で測定を実施する。 </li></ol></li><li> グレージング入射X線回折（GI-XRD） 13 <ol><li>温度コントローラーが装備されているGI-XRDサンプルステージのコーティングされた基板に、LCセル（POMまたはDSC用）またはCCN47の2〜5μL液滴を入れたサンプルを入れます。 </li><li>冷却と加熱の両方で291〜343Kの範囲の所望の温度で10分間以上試料を平衡させる。 </li><li>試料上の入射X線ビームを0.05-0.10°付近の微小入射角で使用して、分子の配向および配列/構造に関する表面情報を抽出する。回折強度が最も強い最適入射角を見つけるために、X線ビームの入射角をスイングさせる。最適な入射角で測定してください。 注記：GI-XRDを使用すると、ナノメートルスケールの界面特異性を調べることができるため、薄いlバルクからの信号を最小限に抑えます。 GI-XRD以外の通常のXRDジオメトリは、X線放射ビームの材料への侵入深さが大きいため、表面に敏感な方法ではないことに注意してください。 </li></ol></li></ol>

<ol>
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著者は何も開示することはない。

5μmのLCセル（ 図1aおよびb ）を用いて得られた10倍のPOM画像は、バルクLC分子の配向状態が、一次様式で温度変化時にP配向とV配向との間を遷移することをはっきりと示している。これは、ドメインの核形成および成長プロセスによって特徴付けられ、新しい配向は初期配向と90°異なる。冷却および加熱時の転移温度は、それぞれ321.5Kおよび325.3Kである。 CCN47は〜0.02 ...

近年、外部刺激に応答する表面分子の動的な分子の特徴および構造が、LC状態における材料のバルク配向にどのように影響するかを知ることへの関心が高まっている。 1つの例は、LCバイオセンサーをLC1,2の新しい用途として使用することである。検出される標的生物種の数を定量化するには、付着している標的分子に接触する界面LCがどのように変化し、進化するかを検出し、それらの特性をバルクに移す/翻訳する方法を知ることが重要です。 モデルを使用してこれらの答えを追求することで、表面分子配向と短距離秩序が熱力学的に変化するシステムから始めました。これらのシステムは、体系的な方法で、表面の向きと順序の変化を結果のバルクの向きと相関させることができます。最近、我々は、温度に伴って自発的なバルク分子配向が変化する。原理的には、配向転移は、準2次3,4次または準一次遷移5,6,7,8のいずれかに分類することができる。前者は、温度の変化に伴って連続的なバルク分子再配向を伴い、後者は不連続なものを示す。この記事では、PとVの方向性状態の間の準一次的な向きの遷移を説明します。これは、温度を変化させることによって単一のネマチック（N）相で進行する。詳細は代表結果とディスカッションに記載されています。 バルクにおける配向の変化は、表面の分子配向の変化によって制御されるべきであり、このシステムは、表面分子配向および短距離秩序における熱力学的変動がバルク配向にどのように影響するかについての潜在的な洞察を潜在的に提供することができることは明らかである。この記事では、上記の問題を理解する目的で、 POM、DS、HR-DSC、GI-XRDの4つの補完的な方法を用いて3つの問題に取り組んでいます。（1） （2）配向転移は熱的に検出可能か？ （3）なぜ方向転換が起こるのか？

<table><tbody><tr><td>CYTOP</td><td>Asahi Glass Co. Ltd.</td><td>CTX-809A</td><td></td></tr><tr><td>Solvent for CYTOP</td><td>Asahi Glass Co. Ltd.</td><td>CT-180 Sol.</td><td></td></tr><tr><td>Alkaline detergent</td><td>Merck KGaA</td><td>Extran MA01</td><td></td></tr><tr><td>NOA61</td><td>Norland Products, Inc.</td><td>#37-322</td><td>Purchasable from Edmund Optics</td></tr><tr><td>AL1254</td><td>JSR Corporation</td><td></td><td>Planar alignment material in self-made cells</td></tr><tr><td>4&amp;rsquo;-butyl-4-heptyl-bicyclohexyl-4-carbonitrile</td><td>Nematel GmbH &amp;amp; Co. KG</td><td></td><td>Custom-made</td></tr><tr><td>UV-O&lt;sub&gt;3&lt;/sub&gt; cleaner</td><td>Technovision Inc.</td><td>UV-208</td><td></td></tr><tr><td>Hot-stage system</td><td>Mettler Toledo</td><td>HS82</td><td></td></tr><tr><td>High-Definition Color Camera Head</td><td>Nikon</td><td>DS-Fi1</td><td></td></tr><tr><td>Impedance/gain-phase analyzer</td><td>Solartron Analytical</td><td>1260</td><td></td></tr><tr><td>Indium Tin Oxide (ITO)-coated substrate</td><td>GEOMATEC Co. Ltd.</td><td></td><td>Custom-made</td></tr></tbody></table>

orientational transition in a liquid crystal triggered by the thermodynamic growth of interfacial wetting sheets

液晶（LC）物理化学において、表面近くの分子はバルク配向を制御する上で大きな役割を果たす。これまで、主にLCディスプレイにおいて所望の分子配向状態を達成するために、LCの「静的」表面特性、いわゆる表面アンカーリングが集中的に研究されてきた。経験則として、LCの初期配向が、ラビングまたは特定の配向層による処理のような特定の表面処理によって「固定」されると、温度によってほとんど変化しない。ここでは、コンセンサスと矛盾する、温度変化時の向きの変化を示すシステムを提示する。転移の直後に、バルクLC分子は、高温での平面（P）配向と、低温での一次転移様式における垂直（V）配向との間で90°の配向回転を経験する。我々は、偏光光学顕微鏡（POM）、誘電分光法（DS）、高分解能示差走査熱量計（HR-DSC）、および斜入射X線回折（GI-XRD）を用いて、表面の成長湿潤シートは、バルク内のP方向に対して局所的にV配向を課す。このランドスケープは、多くのLCシステムにおいて平衡バルク配向が表面局在配向によってどのように影響を受けるかを説明する一般的なリンクを提供する。我々の特徴付けにおいて、POMおよびDSは、LC分子の配向の空間分布に関する情報を提供することによって有利である。 HR-DSCは、分解能が限られているため、従来のDSC機器では対応できない、移行に関する正確な熱力学情報に関する情報を提供します。 GI-XRDは、表面特有の分子配向および短距離秩序に関する情報を提供する。この論文の目標は、トランスジーを示すサンプルを調製するためのプロトコールを提示することであるバルクおよび表面の両方における熱力学的構造変化を上記の方法によってどのように分析することができるかを実証することを目的とする。

特にPOM画像、DSデータ、HR-DSCデータ、およびGI-XRDパターンは、温度変化の間、特に冷却および加熱の両方での配向転移の近傍で収集された。 図1は、冷却（加熱）中のP（V）配向状態からV（P）配向状態への配向転移のPOM観察中のPOMおよびDS測定によって作られたテクスチャの進化を表している。 POM観...

Watch this Scientific Journal Video about Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets at JoVE.com

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

ここでは、温度に応答して液晶の配向転移を引き起こすプロトコルを提示する。移行および詳細な移行進化を観察するために試料を調製するための方法論が記載されている。

界面湿潤シートの熱力学的成長によって引き起こされる液晶の配向転移

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

orientational-transition-liquid-crystal-triggered-thermodynamic

Research

JoVE Journal

Engineering

7.1K ビュー.  RIKEN Center for Emergent Matter Science (CEMS). ここでは、温度に応答して液晶の配向転移を引き起こすプロトコルを提示する。移行および詳細な移行進化を観察するために試料を調製するための方法論が記載されている。 

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

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5
The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

This article describes a simple method to fabricate vertically aligned carbon nanotube arrays by CVD and to subsequently tune their wetting properties by exposing them to vacuum annealing or dry oxidation treatment.

カーボンナノチューブアレイの濡れ特性をチューニングするための処置をアニーリングドライ酸化と真空

In this article, we describe a simple method to reversibly  tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays.  Here, CNT ...

工学

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using sputtering techniques. Here we describe a method for preparing epitaxial thin films of B2-ordered FeRh by sputter deposition onto single crystal MgO substrates. Deposition at a slow rate onto a heated substrate allows time for the adatoms to both settle into a lattice with a well-defined epitaxial relationship with the substrate and also to find their proper places in the Fe and Rh sublattices of the B2 structure. The structure is conveniently characterized with X-ray reflectometry and diffraction and can be visualised directly using transmission electron micrograph cross-sections. B2-ordered FeRh exhibits an unusual metamagnetic phase transition: the ground state is antiferromagnetic but the alloy transforms into a ferromagnet on heating with a typical transition temperature of about 380 K. This is accompanied by a 1% volume expansion of the unit cell: isotropic in bulk, but laterally clamped in an epilayer. The presence of the antiferromagnetic ground state and the associated first order phase transition is very sensitive to the correct equiatomic stoichiometry and proper B2 ordering, and so is a convenient means to demonstrate the quality of the layers that can be deposited with this approach. We also give some examples of the various techniques by which the change in phase can be detected.

A method to prepare epitaxial layers of ordered alloys by sputtering is described. The B2-ordered FeRh compound is used as an example, as it displays a metamagnetic transition that depends sensitively on the degree of chemical order and the exact composition of the alloy.

メタ磁性B2-命じFeRhエピ層のスパッタ成長と評価

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using ...

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.

相図の特徴付け液体担体として磁気ビーズを使用しました

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 ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

コロイド液の結晶を得ることが合成とディスコティックリン酸ジルコニウムの剥離

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

化学

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.

巨視的揺動運動の光によって誘起される液晶ネットワークの準備

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

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Here, we present the protocols of differential-detection analyses of time-resolved infrared vibrational spectroscopy and electron diffraction which enable observations of the deformations of local structures around photoexcited molecules in a columnar liquid crystal, giving an atomic perspective on the relationship between the structure and the dynamics of this photoactive material.

光応答性液晶の構造ダイナミクスを観察する手法

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

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.

液晶エラストマーのアクチュエータのマイクロの準備

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.

液晶における強誘電分極の磁場調整を測定

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

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.

モノドメイン液晶エラストマーおよび液晶エラストマーナノコンポジットの調製

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

生物工学

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.

ツイストベンドネマティック液晶の高コントラストと高速フォトレオロジースイッチング

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