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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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-directing+chiral+liquid+crystal+nanostructures:+from+1D+to+3D.">Light-directing chiral liquid crystal nanostructures: from 1D to 3D.</a> Accounts of Chemical Research. 47 (10), 3184-3195 (2014).</li><li>van Delden, R. A., Koumura, N., Harada, N., Feringa, B. 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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. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+monitoring+of+gases+with+cholesteric+liquid+crystals.">Optical monitoring of gases with cholesteric liquid crystals.</a> Journal of the American Chemical Society. 132 (9), 2961-2967 (2010).</li><li>Kelly, J. 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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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. 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We have nothing to disclose.

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>
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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 ...

Cholesteric liquid crystals are known to have bright reaction colors, and the fast color modulation is important for the development of next generation of reflective displays. Our method enables the fastest color modulation with the lowest operation voltage ever reported for cholesteric liquid crystals. The key is FcD.A chiral dopant with redox responsive helical twisting power. Demonstrating the procedure will be Shoichi Tokunaga, a postdoc, and Mengyan Zeng, a graduate student from our laboratory. To begin preparing the cholesteric liquid crystal mixture, place 84.6 milligrams of 5OCB and 5.922 milligrams of FcD in a 10 milliliter glass vial.In a separate vial, dissolve 12.9 milligrams of EMIm-OTf in 10 milliliters of dichloromethane. Transfer 2.1 milliliters of the EMIm-OTf solution to the liquid crystal mixture, and mix the components well by gently shaking the vial. Then, cover the vial with aluminum foil, and punch several holes in the foil with a needle.Heat the solution at 80 degrees celsius for one hour to evaporate most of the DCM. Put the vial under vacuum, and continue heating it for another hour to remove the remaining DCM to obtain a clear, orange liquid crystal mixture. Next, to begin preparing the ITO glass, cut a 10 by 10 millimeter piece of glass patterned with ITO in the desired shape, and a 10 by 12 millimeter piece of standard ITO glass.Place both pieces of ITO glass in the diluted surfactant without letting them touch. Combine 60 milliliters of an alkaline surfactant solution, and 240 milliliters of ultra pure water in a 500 milliliter glass container. Sonicate the plates in dilute alkaline surfactant for 30 minutes.Then, decant the surfactant, and rinse the plates with 200 milliliter portions of ultra pure water. Perform this rinsing procedure three times in total. Refill the container with 300 milliliters of ultra pure water.Sonicate the plates for 20 minutes. And decant the water. Wash the plates in ultra pure water in this way three times in total.Finally, dry the clean plates with a stream of nitrogen gas and store them in clean, disposable petri dishes. Keep the dishes in a clean desiccator. To begin preparing the cell, sonicate a 0.7 percent by weigh dispersion of PEDOT in nitromethane for 60 minutes to ensure that the polymer is well dispersed.Then, fix the clean standard ITO glass on a spin coater, and remove dust from the ITO coated surface with a nitrogen blow gun. Carefully apply 50 microliters of freshly sonicated PEDOT dispersion to the ITO surface and spin coat the plate at 1000 RPM for 60 seconds. Let the coated plate sit in ambient air for one hour afterwards.Next, fix the patterned ITO plate in a rubbing machine equipped with a rayon cloth. Thoroughly rub the ITO patterned surface under a stream of nitrogen gas. Then, in a dust-free area, mix a drop of optical adhesive with a similarly sized quantity of 5 micrometer borosilicate glass beads.Lay the PEDOT coated plate face up on the work space. Apply about 0.2 cubic millimeters of the adhesive mixture to each corner of one narrow side of the plate. Apply two more portions of adhesive eight millimeters away from that side to form an eight by 10 millimeter rectangle on the plate.Place the patterned ITO plate face down on the adhesive with one edge aligned with the drops partway along the PEDOT coated plate so that the plates are offset by about two millimeters. Gently press down the corners of the cell to achieve a uniform gap between the plates as indicated by the disappearance of the fringe pattern in the cell. Eradiate the cell with 365 nanometer UV light for 20 seconds to set the adhesive.Heat the cell on a hot plate at 100 degrees celsius for three hours to finish curing the adhesive. Lastly, connect conducting wires fitted with aligator clips to the exposed ITO surface on each plate by ultrasonic sautering. Use insulating tape to fix the wires of the glass cell to a microscope slide for easier handling later.Heat the ITO glass, a small spatula, and the cholesteric liquid crystal mixture at 80 degrees celsius for 10 to 15 minutes. Then, quickly transfer a small amount of the hot cholesteric liquid crystal mixture to the gap between the plates with the heated spatula. The cell will fill by capillary action in about 60 seconds.Once the cell is full, reduce the stage temperature to 37 degrees celsius and wait for the cell to stabilize at that temperature. Apply sheer force by gently pressing the center of the liquid crystal device to see the bright reflected color. Then, place the device on top of the hot stage under a digital optical microscope with the patterned side of the device facing the lens.Connect the patterned and PEDOT coated plates to the positive and negative terminals of a poteniostat respectively. Configure the poteniostat to alternate between applying 1.5 volts for four seconds, and 0 volts for eight seconds. Observe and record the color change of the liquid crystal device with the digital microscope while cycling the voltage.Next, set up a UV-vis spectrophotometer to scan transmittance from 800 to 300 nanometers. Put a small jack in the sample compartment to hold the hot stage. Place the liquid crystal device on a hot plate to keep warm and acquire a background measurement of the empty hot stage.Then, load the device back into the hot stage and place it in the spectrometer with the patterned side facing the beam. Use a dark cloth to cover gaps between the sample chamber door and the wires. Wait a few minutes for the device to stabilize at 37 degrees celsius.If necessary, adjust the position of the hot stage to maximize transmittance. Then, acquire an initial spectrum of transmittance through the device. After that, apply a 1.5 volts to the device for four seconds and immediately acquire a transmittance spectrum.When the measurement finishes, apply 0 volts to the device for eight seconds and acquire another spectrum. Finally, record percent transmittance at 510 nanometers over time while cycling the voltage between 1.5 volts for four seconds and 0 volts for eight seconds five times. The cholesteric liquid crystal doped with a chiral ferrocene binaphtol complex, appeared bright blue and had a reflection band centered at 467 nanometers.Applying 1.5 volts to an ITO electrode in contact with the liquid crystal solution, shifted the reflectance band to center on 485 nanometers. The oxidized cholesteric liquid crystal appeared bright cyan to green against the unoxidized blue surroundings. The reflectance band shifted back to 467 nanometers upon applying 0 volts to the electrode with a corresponding recovery of the blue reflection color.Transmittance decreased modestly with repeated cycles because of increasing orientational disorder, but this was repaired by applying a sheer force to the device. The color change from blue to cyan occurred in 0.4 seconds, and the return change took 2.7 seconds. Alternately applying 1.5 volts for 0.5 seconds, and 0 volts for five seconds resulted in a blinking electrode.When attempting the procedure, please take care when assembling the cell. The quality of the cell determines the quality of the display image of the device. You can identify the appropriate voltage range for operating the device using cyclic voltammetry.X-ray for the electron spectroscopy can confirm that emergence of the oxidized part in the liquid crystalline material. By precisely tuning the chemical structure of the redox responsive chirol dopant and other components, we can develop new types of reflective displays, such as full color e-paper. Further investigation of the mechanism of our chirol dopant, can deepen the fundamental science of cholesteric liquid crystals where the molecular mechanism of chirol induction is still unclear.

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Research

JoVE Journal

Chemistry

8.3K visualizações.  The University of Tokyo. Cristais líquidos choleséricos são conhecidos por ter cores de reação brilhantes, e a modulação rápida de cores é importante para o desenvolvimento da próxima geração de displays reflexivos. Nosso método permite a modulação de cores mais rápida com a menor tensão de operação já relatada para cristais líquidos cholestéricos. A chave é a FcD.Um dopant quiral com poder de torção helicoidal reertivo redox. Demonstrando o procedimento estarão Shoichi Tokunaga, um p...