Name: an electrochemical cholesteric liquid crystalline device for quick and low-voltage color modulation
Uploaded: 2019-02-27T14:30:00
Description: Watch this Scientific Journal Video about An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation at JoVE.com

We&#160;thank Dr. Keisuke Tajima from RIKEN Center for Emergent Matter Science for valuable discussions. A part of this work was conducted at the Advanced Characterization Nanotechnology Platform of the University of Tokyo, supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This work was financially supported by a JSPS Grant-in-Aid for Scientific Research (S) (18H05260) on &#34;Innovative Functional Materials based on Multi-Scale Interfacial Molecular Science&#34; for T.A. Y.I. is grateful for a JSPS Grant-in-Aid for Challenging Exploratory Research (16K14062). S.T. thanks the JSPS Young Scientist Fellowship.

1. Preparation of the cholesteric LC mixture
<ol>
	<li>Add 84.6 mg of 5OCB and 5.922 mg of FcD19&#160;(3.1 mol% to 5OCB) into a clean 10 mL glass vial.</li>
	<li>Add 12.9&#160;mg of EMIm-OTf and 10 mL of dichloromethane (CH2Cl2) into a new clean 10 mL glass vial and mix well. Transfer 2.1&#160;mL of the EMIm-OTf solution into the 5OCB- and FcD-containing glass vial. Gently shake the vial to let all th...

<ol>
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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tuning+the+photonic+band+gap+in+cholesteric+liquid+crystals+by+temperature-dependent+dopant+solubility.">Tuning the photonic band gap in cholesteric liquid crystals by temperature-dependent dopant solubility.</a> Optics Express. 14 (3), 1236-1242 (2006).</li><li>Hu, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetite+nanoparticles/chiral+nematic+liquid+crystal+composites+with+magnetically+addressable+and+magnetically+erasable+characteristics.">Magnetite nanoparticles/chiral nematic liquid crystal composites with magnetically addressable and magnetically erasable characteristics.</a> Liquid Crystals. 37 (5), 563-569 (2010).</li><li>Han, Y., Pacheco, K., Bastiaansen, C. W. M., Broer, D. J., Sijbesma, R. 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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Responsive+photonic+hydrogels+based+on+nanocrystalline+cellulose.">Responsive photonic hydrogels based on nanocrystalline cellulose.</a> Angewandte Chemie International Edition. 52 (34), 8912-8916 (2013).</li><li>Coles, H., Morris, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid-crystal+lasers.">Liquid-crystal lasers.</a> Nature Photonics. 4 (10), 676-685 (2010).</li><li>Xiang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+tunable+laser+based+on+oblique+heliconical+cholesteric+liquid+crystal.">Electrically tunable laser based on oblique heliconical cholesteric liquid crystal.</a> Proceedings of the National Academy of Sciences of the United States of America. 113 (46), 12925-12928 (2016).</li><li>Song, M. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+phase+retardation+on+defect-mode+lasing+in+polymeric+cholesteric+liquid+crystals.">Effect of phase retardation on defect-mode lasing in polymeric cholesteric liquid crystals.</a> Advanced Materials. 16 (9-10), 779-783 (2004).</li><li>White, T. J., McConney, M. E., Bunning, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+color+in+stimuli-responsive+cholesteric+liquid+crystals.">Dynamic color in stimuli-responsive cholesteric liquid crystals.</a> Journal of Materials Chemistry. 20 (44), 9832-9847 (2010).</li><li>Bisoyi, H. K., Bunning, T. J., Li, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimuli-driven+control+of+the+helical+axis+of+self-organized+soft+helical+superstructures.">Stimuli-driven control of the helical axis of self-organized soft helical superstructures.</a> Advanced Materials. 30 (25), 1706512 (2018).</li><li>Bisoyi, H. K., Li, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light-driven+liquid+crystalline+materials:+from+photo-induced+phase+transitions+and+property+modulations+to+applications.">Light-driven liquid crystalline materials: from photo-induced phase transitions and property modulations to applications.</a> Chemical Reviews. 116 (26), 15089-15166 (2016).</li><li>Tokunaga, S., Itoh, Y., Tanaka, H., Araoka, F., Aida, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox-responsive+chiral+dopant+for+quick+electrochemical+color+modulation+of+cholesteric+liquid+crystal.">Redox-responsive chiral dopant for quick electrochemical color modulation of cholesteric liquid crystal.</a> Journal of the American Chemical Society. 140 (35), 10946-10949 (2018).</li><li>Step&#780;nick&#780;a, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ferrocenes: Ligands, Materials and Biomolecules. , (2008).</li><li>Togni, A., Hayashi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials Science. , (1995).</li><li>Fukino, T., Yamagishi, H., Aida, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox-responsive+molecular+systems+and+materials.">Redox-responsive molecular systems and materials.</a> Advanced Materials. 29 (25), 1603888 (2017).</li><li>Goh, M., Akagi, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Powerful+helicity+inducers:+axially+chiral+binaphthyl+derivatives.">Powerful helicity inducers: axially chiral binaphthyl derivatives.</a> Liquid Crystals. 35 (8), 953-965 (2008).</li><li>Xianyu, H., Faris, S., Crawford, G. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-plane+switching+of+cholesteric+liquid+crystals+for+visible+and+near-infrared+applications.">In-plane switching of cholesteric liquid crystals for visible and near-infrared applications.</a> Applied Optics. 43 (26), 5006-5015 (2004).</li><li>Lin, T. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+controllable+laser+based+on+cholesteric+liquid+crystal+with+negative+dielectric+anisotropy.">Electrically controllable laser based on cholesteric liquid crystal with negative dielectric anisotropy.</a> Applied Physics Letters. 88 (6), 061122 (2006).</li><li>Bailey, C. 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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromechanical+tuning+of+cholesteric+liquid+crystals.">Electromechanical tuning of cholesteric liquid crystals.</a> Journal of Applied Physics. 107 (1), 013105 (2010).</li><li>Xiang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+tunable+selective+reflection+of+light+from+ultraviolet+to+visible+and+infrared+by+heliconical+cholesterics.">Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics.</a> Advanced Materials. 27 (19), 3014-3018 (2015).</li><li>Hu, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+controllable+selective+reflection+of+chiral+nematic+liquid+crystal/chiral+ionic+liquid+composites.">Electrically controllable selective reflection of chiral nematic liquid crystal/chiral ionic liquid composites.</a> Advanced Materials. 22 (4), 468-472 (2010).</li><li>Choi, S. S., Morris, S. M. M., Huck, W. T. S., Coles, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+tuneable+liquid+crystal+photonic+bandgaps.">Electrically tuneable liquid crystal photonic bandgaps.</a> Advanced Materials. 21 (38-39), 3915-3918 (2009).</li><li>Tokunaga, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+deposition+for+cholesteric+liquid-crystalline+devices+with+memory+and+modulation+of+reflection+colors.">Electrophoretic deposition for cholesteric liquid-crystalline devices with memory and modulation of reflection colors.</a> Advanced Materials. 28 (21), 4077-4083 (2016).</li><li>Sen, M. S., Brahma, P., Roy, S. K., Mukherjee, D. K., Roy, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Birefringence+and+order+parameter+of+some+alkyl+and+alkoxycyanobiphenyl+liquid+crystals.">Birefringence and order parameter of some alkyl and alkoxycyanobiphenyl liquid crystals.</a> Molecular Crystrals and Liquid Crystals. 100 (3-4), 327-340 (1983).</li><li>McConney, M. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+induced+color+changes+in+polymer-stabilized+cholesteric+liquid+crystals.">Electrically induced color changes in polymer-stabilized cholesteric liquid crystals.</a> Advanced Optical Materials. 1 (6), 417-421 (2013).</li><li>Choi, S. S., Morris, S. M., Huck, W. T. S., Coles, H. 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Upon application of +1.5 V to the top ITO electrode (Figure 1C), FcD undergoes an oxidation reaction to generate FcD+. As the helical twisting power of FcD+ (101 &#181;m-1, Figure 1B) is lower than that ...

Cholesteric liquid crystals (LCs) are known to exhibit bright reflection colors due to their internal helical molecular arrangements1,2,3,4. The reflection wavelength &#955; is determined by the helical pitch P and the average refractive index n of the LC (&#955; = nP). Such LCs can be generated by doping chiral compounds (chiral dopants) to nematic LCs and its helical pitch is defined by the equation P = 1/&#946;MC, where &#946;M is the helical twisting power (HTP) and C is the molar fraction of the chiral dopant. Based on this notion, various chiral dopants that can respond to a variety of stimuli such as light5,6,7,8, heat9, magnetic field10, and gas11&#160;has been developed. Such properties are potentially useful for various applications such as sensors12&#160;and lasers13,14,15&#160;among others16,17,18.
Recently, we developed the first redox-responsive chiral dopant FcD (Figure 1A)19&#160;that can change its HTP value in response to redox reactions. FcD is composed of a ferrocene unit, which can undergo reversible redox reactions20,21,22, and a binaphthyl unit, which is known to exhibit high HTP value23. The cholesteric LC doped with FcD, in the presence of a supporting electrolyte, can change its reflection color within 0.4 s and recover its original color in 2.7 s upon voltage application of +1.5 and 0 V, respectively. The high response speed and low operating voltage observed for the device is unprecedented among any other cholesteric LC device so far reported.
One of the important applications of the cholesteric LCs is in reflective displays, whose energy consumption rate is much lower than the conventional LC displays. For this purpose, cholesteric LCs should change its reflection color with electrical stimuli. However, most of the previous methodologies utilize an electrical coupling between the applied electrical stimuli and the host LC molecules, which requires high voltage over 40 V24,25,26,27,28. For the use of the electrically responsive chiral dopant, there are only few examples29,30&#160;including our previous work31, which also requires high voltage with low response speed. Considering these previous works, the performance of our FcD-doped cholesteric LC device, especially for the fast color modulation speed (0.4 s) and low operating voltage (1.5 V), is a groundbreaking achievement that can greatly contribute to the development of next generation reflective displays. In this detailed protocol, we demonstrate the fabrication processes and the operating procedures of the prototype cholesteric LC display devices.

<table border="0" cellpadding="0" cellspacing="0" style="width:1295px;" width="1295">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate, 98%</td>
			<td style="width:211px;">TCI</td>
			<td style="width:163px;">E0494</td>
			<td style="width:343px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">4-Cyano-4&#39;-pentyloxybiphenyl, 98%</td>
			<td style="width:211px;">TCI</td>
			<td style="width:163px;">C1551</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Diamond tipped glass cutter</td>
			<td style="width:211px;">AS ONE</td>
			<td style="width:163px;">6-539-05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Dichloromethane, 99.5%</td>
			<td style="width:211px;">KANTO CHEMICAL</td>
			<td style="width:163px;">10158-2B</td>
			<td>HPLC grade</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Differential Scanning Calorimeter</td>
			<td style="width:211px;">METTLER TOLEDO</td>
			<td style="width:163px;">DSC 1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital microscope&#160;</td>
			<td style="width:211px;">KEYENCE</td>
			<td style="width:163px;">VHX-5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Extran MA01</td>
			<td style="width:211px;">Merck</td>
			<td style="width:163px;">107555</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Fully ITO-coated glass plate</td>
			<td style="width:211px;"></td>
			<td style="width:163px;"></td>
			<td>Costum order, Resistance: ~30&#937;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Glass beads</td>
			<td style="width:211px;">Thermo Fisher Scientific</td>
			<td style="width:163px;">9005</td>
			<td>5 &#177; 0.3 &#956;m in diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Hot stage</td>
			<td style="width:211px;">INSTEC</td>
			<td style="width:163px;">mK1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">ITO-patterned glass plate</td>
			<td style="width:211px;"></td>
			<td style="width:163px;"></td>
			<td>Costum order, Resistance: ~30&#937;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Oil rotary vacuum pump</td>
			<td style="width:211px;">SATO VAC</td>
			<td style="width:163px;">TSW-150</td>
			<td>Pressure: ~5 Pa</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Optical adhesive</td>
			<td style="width:211px;">Noland</td>
			<td style="width:163px;">NOA81</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Poly(3,4-ethylenedioxythiophene), bis-poly(ethyleneglycol), lauryl terminated</td>
			<td style="width:211px;">Sigma Aldrich</td>
			<td style="width:163px;">687316</td>
			<td>0.7 wt% (dispersion in nitromethane)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Potentiostat</td>
			<td style="width:211px;">TOHO TECHNICAL RESEARCH</td>
			<td style="width:163px;">PS-08</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rubbing machine</td>
			<td style="width:211px;">EHC</td>
			<td style="width:163px;">MRJ-100S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Spectrophotometer</td>
			<td style="width:211px;">JASCO</td>
			<td style="width:163px;">V-670 UV/VIS/NIR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Spin coater</td>
			<td style="width:211px;">MIKASA</td>
			<td style="width:163px;">1H-D7</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Ultrapure water</td>
			<td style="width:211px;">Merck&#160;</td>
			<td style="width:163px;">Milli-Q Integral 3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:579px;">Ultrasonic bath</td>
			<td style="width:211px;">AS ONE</td>
			<td style="width:163px;">ASU-2</td>
			<td>Power: 40 W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic soldering</td>
			<td style="width:211px;">KURODA TECHNO</td>
			<td style="width:163px;">SUNBONDER USM-IV</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:579px;">UV lamp</td>
			<td style="width:211px;">AS ONE</td>
			<td style="width:163px;">SLUV-4</td>
			<td>Power: 4 W</td>
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</table>

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.

Photographs, transmittance spectra, and time dependent transmittance change profiles at 510 nm are collected for the LC device containing FcD-doped (3.1 mol%) cholesteric LC in the presence of EMIm-OTf (3.0 mol%) during the voltage application cycles between 0 and +1.5 V at 37 &#176;C.
The LC mixture containing FcD (3.1 mo...

Watch this Scientific Journal Video about An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation at JoVE.com

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

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.

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

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