Security use of the chiral photonic film made of helical liquid crystal structures

Park, Wongi; Ha, Taewoo; Jung, Taek Sun; Sim, Kyung Ik; Kim, Jae-Hoon; Wolska, Joanna M.; Pociecha, Damian; Górecka, Ewa; Kim, Teun-Teun; Yoon, Dong Ki

doi:10.1039/d0nr03743e

Cited by 16 publications

(25 citation statements)

References 30 publications

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“…The developed systems based on oblate CLC droplets are unique and could demonstrate synergetic color and shape responses. Compared to various color changing systems based on CLCs, [ 26–28,32,55–57 ] our systems have several advantages: 1) A new strategy to achieve large selective Bragg reflection in CLC droplets. CLC droplets or shells could show macroscopic color that is visible by naked eyes only when they are large enough on the scale of hundreds of micrometers.…”

Section: Figurementioning

confidence: 99%

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Yang

Ruan

et al. 2021

Advanced Materials

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Living organisms in nature have amazing control over their color, shape, and morphology in response to environmental stimuli for camouflage, communication, or reproduction. Inspired by the camouflage of the octopus via the elongation or contraction of its pigment cells, oblate cholesteric liquid crystal droplets are dispersed in a polymer matrix, serving as the role of pigment cells and showing structural color due to selective Bragg reflection by their periodic helical structure. The color of 3D‐printed biomimetic systems can be tuned by changing the helical pitch via the chiral dopant concentration or temperature. When the oblate liquid crystal droplets are heated up to isotropic, the opaque and colored biomimetic systems become transparent and colorless. Meanwhile, the isotropic liquid crystal droplets tend to become spherical, causing volume contraction along the film plane and volume dilation in the perpendicular direction. The internal strain combined with the gradient distribution of the oblate isotropic liquid crystal droplets result in corresponding shape transformations. The camouflage of a biomimetic octopus and the blossom of a biomimetic flower, both of which show synergetic color and shape responses, are demonstrated to inspire the design of functional materials and intelligent devices.

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Section: Figurementioning

confidence: 99%

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Yang

Ruan

et al. 2021

Advanced Materials

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“…TheH NF phaseh as an anoscale helical structure induced by saddlesplay deformation of smecticl ayers (Figure 1) and has potential to be applied in patterning tools based on templates for chirala ssembly [20][21][22][23] andv arious chiro-opticala pplications such as chiral sensors [24] and security codes. [25] In this study,p olymorphs of HNFp hases formed by as ingle kind of molecules were investigated.I tw as found that under differentc onditions-illumination with UV light in the bulk state or geometricaln anoconfinement( Figure 2)-either twisted ribbonso rc ylindrical ribbons are grown.F or these studies, photosensitive azobenzene derivatives and nanoporous anodic aluminumo xide (AAO) having various pore diameters D P were used for light-driven orientation and geometrical nanoconfinement, respectively.The structural analysisineach case was performed by SEM and grazing-incidence X-ray diffraction (GIXD) with synchrotron radiation.…”

Section: Introductionmentioning

confidence: 99%

Directing Polymorphism in the Helical Nanofilament Phase

Park

Yang

Park

et al. 2021

Chemistry A European J

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Herein, it is reported that the polymorphismin the helical nanofilament (HNF,B 4 )l iquid-crystallinep hase depends on the fabrication methods, that is, UV-driven formation andt emplate-assisted self-assembly in the nanoconfined geometry. As aresult, uniaxially oriented HNFs with different helical structures wereo btained, in which generation of the twisted-ribbon and cylindrical-ribbonp olymorphs showed that even the molecular lattice has ad ifferent orientation.T he detailed structures were directly observed by SEM and grazing-incidence X-ray diffractionw ith synchrotron radiation. Ther esultant polymorphs could be used in chiro-optical applicationsd ue to the capability for fine control of the helical structures.

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“…Polarization-dependent liquid crystal (LC) films have been applied in broad fields, including in LC polarizers [1][2][3][4][5], photo-luminescence films [6][7][8], and photonic crystals [9][10][11]. Among these, dye-doped LC films composed of coaligned LC polymer networks and dichroic dyes attract interest among researchers due to their novel optical property and efficient fabrication process [1][2][3][4][5][6][7][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…This conventional film could show a difference in brightness depending on the direction of the incident LPL because almost all dichroic dyes have only one absorption axis, except in special cases [20,21]. To overcome this limitation, chiral photonic crystals [11] or materials that use refractive index change [22] have been proposed, but this method requires expensive and complicated fabrication methods. In this study, we suggest the use of a bilayer dichroic dye-doped LC (BDLC) film as an anti-counterfeiting film with enhanced security.…”

Section: Introductionmentioning

confidence: 99%

Security use of bilayer dichroic films made of liquid crystal polymer networks

Park

Yoon

2021

Journal of Information Display

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We report on bilayer dichroic dye-doped liquid crystal (BDLC) films for patternable color codes, which can be used in anti-counterfeiting applications such as security codes and, unlike the conventional single-layer LC color films, show unique color changes depending on the direction of the polarization of the incident light that passes through them. This is a facile way to enhance the security level of security codes. BDLC films are fabricated by laminating two single-layer LC polymer network films with crossed optical axes. We believe that BDLC films can be used as a new platform for a securityenhanced anti-counterfeiting code that can replace complex chiral materials or expensive plasmonic particles.

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Security use of the chiral photonic film made of helical liquid crystal structures

Abstract: The color change of photonic crystal (PC) has been widely studied due to its beauty and anti-counterfeiting purpose. Here we demonstrated security codes based on chiral PCs that are not...

Cited by 16 publications

References 30 publications

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Directing Polymorphism in the Helical Nanofilament Phase

Security use of bilayer dichroic films made of liquid crystal polymer networks

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