Tunable backflow in chiral nematic liquid crystals via twist-bend nematogens and surface-localised <i>in-situ</i> polymer protrusions

Joshi, Vinay; Paterson, Daniel A.; Storey, John M. D.; Imrie, Corrie T.; Chien, Liang Chy

doi:10.1080/02678292.2017.1374479

Cited by 11 publications

(5 citation statements)

References 39 publications

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“…The absolute transmittance denotes the ratio of the transmittance measured at the photodetector with the cell between the crossed polarizers to the maximum intensity of the probing beam without any cell or polarizers. From the plot, it is evident that switching behavior of the cell is free from any hysteresis and this is the result of fast relaxation of CLCs from its deformed state back to the planar state, as reported earlier in polymer stabilized CLCs with long helical pitch . The driving electric field for PSCLC_7 is ≈30 V µm −1 .…”

supporting

confidence: 66%

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Joshi

Chang

Varanytsia

et al. 2018

Advanced Optical Materials

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demonstration of flexoelectro-optic effect in CLCs with helical axis in the plane of the device showed an in-plane rotation of 4° in both directions of the undeformed state. [5] Recently the flexoelectro-optical effect has received considerable attention due to the availability of high flexoelectric coefficient materials and their potential applications that can surpass the performance of existing electro-optical and photo nic device technologies. [9,[12][13][14] Being linear in the electric field, the swinging amplitude in flexoelectrically driven CLCs can be programmed using both the sign and magnitude of the electric field. TheReplicating natural phenomena using soft material actuators is a major challenge for material scientists. For example, a metronome is a device that produces an audible beat at a selected interval. In anisotropic soft materials, a flexoelectrically-driven cholesteric liquid crystal (CLC) can display a metronome-like swinging effect when an applied electric field is normal to the helices of a CLC that are aligned normal to the substrates. The amplitude and direction of swing of a flexoelectrically-driven CLC is electrically programmable. Combining a bimesogen and a CLC with an optimized helical pitch, the mixture enables a large flexoelastic ratio (e/K = 2.758 CN -1 m -1 ) and swinging amplitude of 53°. Furthermore, assisted by polymer stabilization the composite mixture offers many benefits of electro-optical characteristics including fast response time (425 µs) and high optical contrast (500:1) between the field-on and field-off states as well as wavelength-independent transmittance. The advances in the flexoelectro-optical behavior of cholesteric metronomes open new avenues for applications in information displays, sensors and photonic devices.

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confidence: 66%

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Joshi

Chang

Varanytsia

et al. 2018

Advanced Optical Materials

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“…It is possible, for example, to control the spectral response of mixtures containing twistbend nematogens by switching between light-scattering, colour reflection and transparent states, as a function of electrical fields. 16,17 The optical properties can be modulated by changing the helicoidal pitch formed by the directors, via fast polar switching 18 under the application of variable electrical fields. 19 Light can also be used as a tool with which to exert spatial control over molecular order in liquid crystals, for example, by utilising the trans-to-cis photoisomerization of an azobenzene unit.…”

Section: Cb7cbmentioning

confidence: 99%

Photo-driven effects in twist-bend nematic phases: Dynamic and memory response of liquid crystalline dimers

Zaton

Karamoula

Strachan

et al. 2021

Journal of Molecular Liquids

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“…Small value of the ratio of bend over twist elastic constants, K3/K2, enables electrically-induced oblique heliconical CLC texture (CLCOH) [9]. Bimesogenic CLCs have wide-ranging application potential in devices such as CLCOH lasers [10], active color filters, fast switching active retarders and light modulators benefiting from strong flexoelectric properties of bimesogenic LC materials [11][12][13][14][15]. The self-assembly of CLCOH structure with low K3 occurs upon reducing the electric field from a homeotropic configuration [6,7].…”

Section: Objective and Backgroundmentioning

confidence: 99%

P‐165: Effect of Polarized Light Polymerization on Reflection Band Tunability in Polymer‐Stabilized Bimesogenic Cholesteric Liquid Crystal Devices

Varanytsia

Joshi

Chien

2019

Symp Digest of Tech Papers

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This work demonstrates approach for improvement of electrooptic performance and light reflectance properties of electricallycontrolled reflective heliconical cholesteric liquid crystal (CLCOH) textures. A noticeable increase of the electric field range which supports the CLCOH texture is demonstrated by using photo polymerization with polarized UV light. Such performance improvement broadens the scope of potential applications of CLCOH materials in electro-optical devices. Author KeywordsColor smart window; polymer-stabilized; bimesogenic cholesteric liquid crystal; oblique heliconical texture.

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Tunable backflow in chiral nematic liquid crystals via twist-bend nematogens and surface-localised in-situ polymer protrusions

Cited by 11 publications

References 39 publications

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Photo-driven effects in twist-bend nematic phases: Dynamic and memory response of liquid crystalline dimers

P‐165: Effect of Polarized Light Polymerization on Reflection Band Tunability in Polymer‐Stabilized Bimesogenic Cholesteric Liquid Crystal Devices

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