Director distribution in field-induced undulated structures of cholesteric liquid crystals

Shtykov, N. M.; Palto, S. P.; Rybakov, D. O.; Simdyankin, I. V.

doi:10.1080/02678292.2018.1441460

Cited by 7 publications

(3 citation statements)

References 13 publications

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“…As a result the layers undergo some periodic sinusoidal deformations, called undulations, that strongly depend on the cell thickness/cholesteric pitch ratio. [ 29 ] In an oblate ellipsoid type of confinement, the dielectric torque and the planar alignment could cause a 3D formation of undulations that could lead to this peculiar fingerprint‐like texture. [ 30 ] In general, for droplets with diameters between 40 µm and 70 µm, both distortion and fingerprint texture are observed at about the same voltages.…”

Section: Resultsmentioning

confidence: 99%

Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

Bruno,

Fuoco,

Petriashvili

et al. 2023

Adv Materials Technologies

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In this study, a method is presented to fabricate optical fingerprint‐like patterns. The method relies on the use of commercially available chiral nematic liquid crystals (CNLCs) confined in microspheres. The peculiar optical texture is obtained by applying a high‐frequency voltage to the micrometric objects able to distort the molecular director orientation. The texture can be stabilized by doping the CNLC with photosensitive materials. Each microsphere shows a different fingerprint‐like pattern that is generated in a completely random manner making this procedure suitable to create physical unclonable functions (PUFs) keys. The optical patterns can be stored to create an artificial fingerprints database or they can be used to fabricate electroluminescent labels to be exploited as complex anti‐counterfeiting devices. An authentication software is developed and used to test the robustness of the proposed anti‐counterfeiting system.

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Section: Resultsmentioning

confidence: 99%

Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

Bruno,

Fuoco,

Petriashvili

et al. 2023

Adv Materials Technologies

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“…Passing through the golden age of the liquid crystal display (LCD) industry, nanotechnology based on liquid crystals (LCs) started gradually fading away from the prime line in industries once organic light-emitting diodes (OLEDs) and quantum dot technology appeared in display applications. Albeit not the most exciting material anymore, LCs are still indispensable due to their intrinsic physical properties that are easily switchable under various external stimuli, including light [1][2][3][4][5][6][7][8], temperature [9][10][11], and electric [12][13][14][15][16][17][18] and magnetic sources [19][20][21]. As the current era demands novel materials with tunable physical properties in an on/off but dynamic manner, LCs can still be one of the most appropriate media to satisfy the demand.…”

Section: Introductionmentioning

confidence: 99%

Role of Stimuli on Liquid Crystalline Defects: From Defect Engineering to Switchable Functional Materials

Shin

Yoon

2020

Materials

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Achieving tunable physical properties is currently one of the most exciting research topics. In order to realize this goal, a medium that is responsive to external stimuli and can undergo a change in its physical property is required. Liquid crystal (LC) is a prominent candidate, as its physical and optical properties can be easily manipulated with various stimuli, such as surface anchoring, rubbing, geometric confinement, and external fields. Having broken away from the past devotion to obtaining a uniform domain of LCs, people are now putting significant efforts toward forming and manipulating ordered and oriented defect structures with a unique arrangement within. The complicated molecular order with tunability would benefit the interdisciplinary research fields of optics, physics, photonics, and materials science. In this review, the recent progress toward defect engineering in the nematic and smectic phases by controlling the surface environment and electric field and their combinational methods is introduced. We close the review with a discussion of the possible applications enabled using LC defect structures as switchable materials.

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“…It is also known that destabilization of the helical structure may alternatively occur through the Helfrich-Hurault mechanism [44][45][46][47] giving rise to undulated patterns with in-plane electrically dependent periodicity. These patterns also known as striped textures or Helfrich distortions have aroused considerable interest as switchable CLC diffraction gratings [48][49][50][51][52][53].…”

Section: Introductionmentioning

confidence: 99%

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

Tenishchev¹,

Kiselev²,

Ivanov³

et al. 2019

Phys. Rev. E

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We apply the minimum energy paths (MEPs) approach to study the helix unwinding transition in chiral nematic liquid crystals. A mechanism of the transition is determined by a MEP passing through a first order saddle point on the free energy surface. The energy difference between the saddle point and the initial state gives the energy barrier of the transition. Two starting approximations for the paths are used to find the MEPs representing different transition scenarios: (a) the director slippage approximation with in-plane helical structures; and (b) the anchoring breaking approximation that involves the structures with profound out-of-plane director deviations. It is shown that, at sufficiently low voltages, the unwinding transition is solely governed by the director slippage mechanism with the planar saddle point structures. When the applied voltage exceeds its critical value below the threshold of the Fréedericksz transition, the additional scenario through the anchoring breaking transitions is found to come into play. For these transitions, the saddle point structure is characterized by out-of-plane deformations localized near the bounding surface. The energy barriers for different paths of transitions are computed as a function of the voltage and the anchoring energy strengths. * tenischev.

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Director distribution in field-induced undulated structures of cholesteric liquid crystals

Cited by 7 publications

References 13 publications

Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

Cholesteric Liquid Crystals Based Micro‐Fingerprints Generator for Anti‐Counterfeiting Labels

Role of Stimuli on Liquid Crystalline Defects: From Defect Engineering to Switchable Functional Materials

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

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