이 작품은 학술 연구원 교부금 번호 16H06037에 의해 지원되었다. 홋카이도 대학의 사사키 유지 사장에게 HR-DSC에 대한 기술 지원에 진심으로 감사드립니다.

1. 유리 기판 상에 퍼플 루오로 중합체의 액정 배향 층의 제조 <ol><li> 퍼플 루오로 중합체 용액의 제조 <ol><li> 퍼플 루오로 중합체 용액 (9 중량 % 중합체)을 1 : 2의 비율로 시판용 용매에 용해시켜 퍼플 루오로 중합체 용액 1 mL를 제조하고; 0.5-1μm 두께의 균일 한 막이 스핀 코팅 될 수 있습니다. 참고 : 사용 된 용액 및 솔벤트의 재료 목록을 참조하십시오. </li></ol></li><li> 깨끗한 유리 기판에 퍼플 루오로 중합체 코팅 <ol><li> 알칼리성 세제로 38 또는 42 kHz에서 초음파 처리하여 유리 기판 (일반적인 크기 : 1 cm x 1 cm)을 씻으십시오. 증류수로 반복해서 헹구십시오. 일반적으로, 매회 5 번 초음파 세척으로 10 회 이상 헹구십시오. </li><li> UV-O 3 세정제로 10 분간 기판을 채 웁니다. </li><li> 단계 1.1의 용액 20 μL를 세척 된 유리 기질에 흘려 라.테. 즉시 용액을 3,500 rpm으로 실온에서 70 초 동안 스핀 코트하십시오. 80 ° C에서 60 분 동안 필름을 베이킹하여 용제를 제거하고 200 ° C에서 60 분 동안 경화시킵니다. </li></ol></li></ol> 2. 액정 셀 준비 <ol><li> 광경 화성 수지와 파장 365 nm (1.1 W / cm 2 )의 LED 램프를 사용하여 필름으로 코팅 된 두 개의 유리 기판을 접착하십시오. 마이크로 미터 크기의 유리 입자 또는 폴리에틸렌 나 프탈레이트 필름을 사용하여 두 기판 사이의 간격을 2 ~ 100 μm 범위 내로 조정하십시오. </li><li> 등방성 액체 (I)보다 높은 온도의 모세관 력으로 주걱을 사용하여 준비된 LC 셀에 LC 물질, 4&#39;- 부틸 -4- 헵틸 - 비 시클로 헥실 -4- 카보 니트릴 (CCN47; 0.2-10 μL) - 네마 틱 (N) 상 전이 온도. 참고 : CCN47은 음의 유전율 이방성을 가지며 위상 시퀀스는 Cry 298.6 K SmA 301.3 KN 331.3 KI, 여기서 Cry 및 SmA는 결정 및 스 멕틱 A 상을 나타낸다. flow-induced alignment가 촉진되기 때문에 CCN47을 N 기 또는 SmA기에 도입하지 마십시오. </li></ol> 3. 샘플 특성화 <ol><li> 편광 광학 현미경 (POM)에 의한 조직 관찰 10 <ol><li> ± 0.1-K 정확도로 샘플 온도를 제어하는 ​​핫 스테이지와 함께 4-100X 대물 렌즈로 POM에서 LC 셀을 관측하십시오. 켈빈 당 균등 한 간격으로 5 프레임 이상의 텍스처를 기록하십시오. 냉각 및 가열시 291-343 K의 범위에서 순차적 으로 디지털 컬러 카메라를 사용하십시오. </li></ol></li><li> 유전체 분광학 (DS) 11 <ol><li> 두 기판에서 ITO 전극 (정사각형 또는 원형 모양을 가질 수 있고 상업적으로 구입할 수 있음)을 사용하여 LC 셀을 준비합니다. 리드선을 각 기판에 납땜하십시오. 참고 : 사용 된 인쇄물의 재료 목록을 참조하십시오. </li><li> 상용 임피던스 / 이득 위상 분석기를 사용하여 POM에 사용 된 것과 똑같은 LC 셀의 커패시턴스 또는 유전 상수를 측정하십시오. 각 측정 전에 시료의 상태가 평형인지 확인하십시오. 매 5 분마다 LC 셀의 정전 용량을 수동으로 측정하여 LC 셀의 정전 용량 또는 유전 상수의 시간 의존성을 측정합니다. </li><li> LC 셀의 커패시턴스 또는 유전 상수가 비 시간 종속적 인 경우에만 DS 측정을 시작하십시오. </li></ol></li><li> 고해상도 시차 주사 열량계 (HR-DSC) 12 <ol><li> LC 셀을 집에서 만든 HR-DSC에 넣고 정확하게 POM (DSC 팬을 사용 하지 마십시오) 에서처럼 검사합니다. HR-DSC를 설계 및 구축하고 사용 방법을 배우려면 참조 12를 참조하십시오. 최소 온도 분해능을 높이기 위해 0.05-0.10 K / min의 스캔 속도로 측정을 수행하십시오.어. </li></ol></li><li> 방목 입사 X 선 회절 (GI-XRD) 13 <ol><li> 온도 컨트롤러가 장착 된 GI-XRD 샘플 스테이지의 코팅 된 기판 위에 CCN47의 2 ~ 5 μL 액 적이 들어있는 샘플 또는 LC 셀 (POM 또는 DSC에 사용됨)을 넣으십시오. </li><li> 냉각 및 가열시 291-343 K 범위의 원하는 온도에서 10 분 이상 샘플을 평형시킵니다. </li><li> 분자 방향 및 배열 / 구조에 대한 표면 정보를 추출하기 위해 0.05-0.10 ° 정도의 작은 입사각으로 샘플에 입사 X- 선 빔을 사용하십시오. 회절 강도가 가장 강한 최적의 입사각을 찾기 위해 X 선 광선의 입사각을 스윙합니다. 최적의 입사각으로 측정하십시오. 참고 : GI-XRD를 사용하면 나노 미터 스케일에서 계면 특이성을 조사 할 수 있으므로 얇은 층에서 신호를 최대화 할 수 있습니다벌크에서 신호를 최소화하면서. GI-XRD 이외의 일반 XRD 구조는 X 선 방사 빔이 재료에 대한 깊이가 매우 깊기 때문에 표면에 민감하지 않습니다. </li></ol></li></ol>

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저자는 공개 할 것이 없습니다.

5μm LC 셀 ( 그림 1a 및 b )을 사용하여 촬영 한 10x POM 이미지는 벌크 LC 분자의 방향 상태가 1 차 방식으로 온도 변화에 따라 P 및 V 방향 사이에서 이동 함을 명확하게 보여줍니다. 이것은 도메인 핵 생성 및 성장 과정에 의해 표시되며 새로운 방향은 초기 방향과 90 ° 다릅니다. 냉각 및 가열시의 전이 온도는 각각 321.5 K 및 325.3 K입니다. CCN47이 ~ 0.02 9 의 복굴...

최근 몇 년 동안, 외부 자극에 반응하는 표면 분자의 동적 인 분자 구조 및 구조가 LC 상태에서 물질의 벌크 배향에 어떻게 영향을 줄 수 있는지에 대한 관심이 증가 해왔다. 한 가지 예는 LC 1 , 2 의 새로운 응용으로서 LC 바이오 센서를 사용하는 것이다. 얼마나 많은 표적 생물 종이 검출되는지를 정량화하기 위해 표적 분자와 접촉하는 계면 LC가 어떻게 변화하고 진화 하는지를 알아내는 동시에 그들이 성질을 대량으로 옮기거나 번역하는 방법을 알아내는 것이 중요합니다. 모델을 사용하여 이러한 해답을 추구하면서 표면 분자 방향 및 단거리 정렬이 열역학적으로 다른 시스템으로 시작했습니다. 이 시스템을 사용하여 표면 방향 및 정렬 순서의 변경 사항을 결과적으로 대량의 방향과 체계적으로 연관시킬 수 있습니다. 최근에 우리는 o를 나타내는 몇 가지 LC 시스템을 발견했습니다.온도에 따라 자발적인 벌크 분자 배향이 변화하는 리서치 천이. 원칙적으로 방향 전환은 준 2 차 3 , 4 또는 준 1 차 천이 5 , 6 , 7 , 8 로 분류 할 수 있습니다. 전자는 온도 변화시 연속적인 분자 재배 향을 동반하지만, 후자는 불연속적인 재연성을 나타낸다. 이 기사에서는 P와 V 방향 상태 사이에서 준 1 차 방식으로 방향 전환을 설명합니다. 그것은 온도를 변화시킴으로써 단일 네마 틱 (N) 상으로 진행한다. 자세한 내용은 대표 결과 및 토론에서 제공됩니다. 벌크의 방향 변화는 표면 분자 방향의 변화와 짧은이 시스템이 표면 분자 배향과 단거리 정렬의 열역학적 변화가 벌크 배향에 어떻게 영향을 미치는지에 대한 통찰력을 잠재적으로 제공 할 수 있음은 자명하다. 이 기사에서는 위에서 언급 한 문제를 이해하기 위해 POM, DS, HR-DSC 및 GI-XRD와 같은 4 가지 보완 방법을 사용하여 세 가지 문제를 해결했습니다. (1) 방향 전환은 어떻게 생겼습니까? (2) 방향 전환이 열적으로 감지 가능한가? (3) 오리엔테이션 전환은 왜 그리고 어떻게 발생합니까?

<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

액정 (LC) 물리 화학에서, 표면 근처의 분자는 벌크 배향을 제어하는데 큰 역할을한다. 지금까지, 주로 LC 디스플레이에서 원하는 분자 배향 상태를 달성하기 위해, LC의 &quot;정적&quot;표면 특성, 소위 표면 앵커링 (surface anchoring)이 집중적으로 연구되었다. 일반적으로 마찰이나 특정 배향막 처리와 같은 특정 표면 처리로 LC의 초기 배향이 &quot;고정&quot;되면 온도에 따라 거의 변하지 않습니다. 여기서, 우리는 온도 변화에 대한 방향 전환을 나타내는 시스템을 제시하는데, 이는 컨센서스와 충돌한다. 전환 직후 벌크 LC 분자는 고온에서 평면 (P) 배향과 저온에서 1 차 과도기 방식으로 수직 (V) 배향 사이에서 90 °의 방향 회전을 경험합니다. 우리는 편광 광학 현미경으로 열역학적 표면 고정 거동을 추적했다 (POM), 유전 분광법 (DS), 고분해능 시차 주사 열량계 (HR-DSC) 및 그레이 징 입사 X- 선 회절 (GI-XRD)에 대한 연구를 수행했으며, 표면 전이 습윤 시트는 벌크의 P 배향에 국부적으로 V 배향을 부과한다. 이 풍경은 많은 LC 시스템에서 평형 벌크 배향이 표면 국부 배향에 어떻게 영향을 받는지를 설명하는 일반적인 링크를 제공합니다. 우리의 특성화에서, POM과 DS는 LC 분자의 방향의 공간적 분포에 대한 정보를 제공함으로써 유리하다. HR-DSC는 변환에 대한 정확한 열역학적 정보에 대한 정보를 제공합니다.이 정보는 제한된 분해능으로 인해 기존 DSC 장비로 해결할 수 없습니다. GI-XRD는 표면 특유의 분자 배향 및 단거리 정렬에 대한 정보를 제공합니다. 이 논문의 목적은 transi를 보여주는 샘플을 준비하기위한 프로토콜을 제시하는 것이다.벌크와 표면 모두에서 열역학적 구조 변화가 위에서 언급 한 방법을 통해 어떻게 분석 될 수 있는지를 보여줄 수있다.

POM 이미지, DS 데이터, HR-DSC 데이터 및 GI-XRD 패턴은 온도 변화 동안, 특히 냉각 및 가열시의 방향 전환 부근에서 수집되었습니다. 그림 1 은 냉각 (가열) 중에 P (V) 방향에서 V (P) 방향 상태로의 방향 전환의 POM 관측 중에 POM 및 DS 측정에 의해 만들어진 텍스처의 진화를 나타냅니다. POM 관측 ( <strong class="xfig"...

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

여기서는 온도에 따라 액정의 방향 전환을 트리거하는 프로토콜을 제시합니다. 전이 과정과 상세한 이행 진화를 관찰하기 위해 표본을 준비하는 방법론을 설명합니다.

계면 습윤지의 열역학적 성장에 의해 촉발 된 액정의 방향 전환

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

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

7.1K 조회수.  RIKEN Center for Emergent Matter Science (CEMS).  여기서는 온도에 따라 액정의 방향 전환을 트리거하는 프로토콜을 제시합니다. 전이 과정과 상세한 이행 진화를 관찰하기 위해 표본을 준비하는 방법론을 설명합니다. 

비디오: 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.

탄소 나노 튜브 배열의 으러 속성을 조정을위한 트리트먼트 소둔 건식 산화, 진공

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

연구

공학

Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator

Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via stereotactic radiotherapy where positioning accuracy allows delivering very high doses per fraction in a small volume of the patient. Dosimetric measurements on medical accelerators are conventionally realized using air-filled ionization chambers. However, in small beams these are subject to nonnegligible perturbation effects. This study focuses on liquid ionization chambers, which offer advantages in terms of spatial resolution and low fluence perturbation. Ion recombination effects are investigated for the microLion detector (PTW) used with the Cyberknife system (Accuray). The method consists of performing a series of water tank measurements at different source-surface distances, and applying corrections to the liquid detector readings based on simultaneous gaseous detector measurements. This approach facilitates isolating the recombination effects arising from the high density of the liquid sensitive medium and obtaining correction factors to apply to the detector readings. The main difficulty resides in achieving a sufficient level of accuracy in the setup to be able to detect small changes in the chamber response.

A growing number of radiation therapy devices offer the advantage of delivering the dose through very small beams to the tumor, allowing for increased conformity and higher doses per fraction. Many different detectors can be used for the dosimetry of these small fields. In the present study, the effect of ion recombination is investigated for a liquid ionization chamber using a stereotactic radiation therapy system.

액체 이온화 챔버의 재조합 효과의 특성은 Radiosurgical 가속기의 선량 측정에 사용

Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via ...

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.

단계도 특성 액체 캐리어로 자기 구슬을 사용하여

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.

합성 및 디스코 틱 지르코늄 인산염의 각질 제거는 콜로이드 액체 크리스탈을 구하는

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

화학

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.

빛에 의해 유도 된 거시적인 진동 모션 액정 네트워크의 준비

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.

Photoresponsive 액정의 구조 역학을 관찰을 위한 새로운 기술

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.

액체 결정 탄성 액츄에이터의 미세 준비

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.

액정에 자석으로 조정 Ferroelectric 편광 측정

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.

모노 도메인 액정 탄성체 및 액정 엘라스토머 나노 복합 재료의 제조

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

생체공학

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.

트위스트 벤드 네매틱 액정의 고대비 및 빠른 광역학 스위칭

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