P‐151: Fast Flexoelectro‐optic Response of Bimesogen‐doped Polymer Stabilized Cholesteric Liquid Crystals in Vertical Standing Helix Mode

Joshi, Vinay; Chang, Kai-Han; Paterson, Daniel A.; Storey, John M. D.; Imrie, Corrie T.; Chien, Liang–Chy

doi:10.1002/sdtp.12051

Cited by 11 publications

(11 citation statements)

References 14 publications

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“…While the flexoelectric response in CB n CB bimesogens has received widespread attention, there is a dearth of systematic experimental demonstrations of commercial device applications due to their high temperature nematic phases which makes it difficult to operate under ambient conditions. Here, we report the experimental demonstration of a swinging phenomenon in CLCs doped with CB7CB, CB9CB, and CB11CB with helical axis normal to the surface and an in‐plane electric field at room temperature, implementing the electrode structure and configuration of CLC that were reported previously . The low frequency electro‐optical switching observed under a microscope provides a direct experimental evidence of a two‐way swinging effect, analogous to a metronome.…”

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confidence: 56%

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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: 56%

“…A sub‐millisecond response time is the main attribute of the flexoelectro‐optic behavior of a PSCLC which makes it optimal for the next‐generation electro‐optic and photonic devices . Hence, the main goal of this work is to explore the practical applications of the PSCLC cells to be operated in ambient conditions.…”

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confidence: 99%

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Joshi

Chang

Varanytsia

et al. 2018

Advanced Optical Materials

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“…They could also measure the flexoelectric parameters in the bimesogenic CLC mixture that was fabricated to exhibit optimized flexoelectric effect. Joshi et al have recently reported fast flexoelectro‐optic response in a polymer stabilized planar CLC doped with bent‐shaped bimesogen compounds . Electrooptical devices fabricated with the polymer stabilized planar texture using in‐plane switching driving scheme displayed fast response, low hysteresis, and color dispersion which renders them as potential candidates for field‐sequential color displays.…”

Section: Uniform Lying Helix Structurementioning

confidence: 99%

Stimuli‐Driven Control of the Helical Axis of Self‐Organized Soft Helical Superstructures

2018

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Supramolecular and macromolecular functional helical superstructures are ubiquitous in nature and display an impressive catalog of intriguing and elegant properties and performances. In materials science, self-organized soft helical superstructures, i.e., cholesteric liquid crystals (CLCs), serve as model systems toward the understanding of morphology- and orientation-dependent properties of supramolecular dynamic helical architectures and their potential for technological applications. Moreover, most of the fascinating device applications of CLCs are primarily determined by different orientations of the helical axis. Here, the control of the helical axis orientation of CLCs and its dynamic switching in two and three dimensions using different external stimuli are summarized. Electric-field-, magnetic-field-, and light-irradiation-driven orientation control and reorientation of the helical axis of CLCs are described and highlighted. Different techniques and strategies developed to achieve a uniform lying helix structure are explored. Helical axis control in recently developed heliconical cholesteric systems is examined. The control of the helical axis orientation in spherical geometries such as microdroplets and microshells fabricated from these enticing photonic fluids is also explored. Future challenges and opportunities in this exciting area involving anisotropic chiral liquids are then discussed.

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“…However, there is another important EO effect called flexoelectric effect in a HTN cell. Some bimesogenic [54][55][56][57]60] and bent-core [58] LC materials with strong flexoelectric effect can be doped into USH precursors as well [71,72]. We injected the USH precursors into an IPS cell, as figure 1(e) illustrates.…”

Section: Sample Preparationmentioning

confidence: 99%

Review on polymer-stabilized short-pitch cholesteric liquid crystal displays

Tan

Lee

Gou

et al. 2017

J. Phys. D: Appl. Phys.

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Submillisecond response times and low operation voltage are critical to next generation liquid crystal display and photonic devices. In this paper, we review the recent progress of three fastresponse short-pitch cholesteric liquid crystal modes: blue phase (BP), uniform standing helix (USH), and uniform lying helix (ULH). This review starts with a brief introduction of device structures and working principles, and then highlights two competing electro-optical effects: dielectric effect and flexoelectric effect. Next, we compare their electro-optical behaviors, response time, temperature dependence, and contrast ratio. Based on our established simulation model, we are able to optimize the phase compensation scheme for improving the viewing angle and gamma shift of USH and ULH modes. Finally, we analyze some major challenges, which remain to be overcome before the widespread applications of these liquid crystal devices can be realized.

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P‐151: Fast Flexoelectro‐optic Response of Bimesogen‐doped Polymer Stabilized Cholesteric Liquid Crystals in Vertical Standing Helix Mode

Cited by 11 publications

References 14 publications

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Cholesteric Metronomes with Flexoelectrically Programmable Amplitude

Stimuli‐Driven Control of the Helical Axis of Self‐Organized Soft Helical Superstructures

Review on polymer-stabilized short-pitch cholesteric liquid crystal displays

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