References of "Drevensek-Olenik, Irena"
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See detailCorrelation between structural properties and iridescent colors of cellulose nanocrystalline films
Licen, M. V.; Majaron, B.; Noh, Junghyun UL et al

in Cellulose (2016)

We investigate the effect of shear flow applied during the drying of aqueous suspension of cellulose nanocrystals on optical reflective properties and structural characteristics of the resulting ... [more ▼]

We investigate the effect of shear flow applied during the drying of aqueous suspension of cellulose nanocrystals on optical reflective properties and structural characteristics of the resulting solidified films. Shear flow can significantly improve internal structural homogeneity of the films, while its effect on optical reflective properties is relatively minor. The measured width of the selective reflection peak is an order of magnitude larger than expected for an ideal helically modulated structure, which reflects a distribution of pitch values and possibly also of regimes of distorted helical modulation. We attribute these imperfections to the broad size distribution of the cellulose nanocrystals. [less ▲]

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See detailHigh-fidelity spherical cholesteric liquid crystal Bragg reflectors generating unclonable patterns for secure authentication
Geng, Yong UL; Noh, Junghyun UL; Drevensek-Olenik, Irena et al

in Scientific Reports (2016), 6(26840), 1-8

Monodisperse cholesteric liquid crystal microspheres exhibit spherically symmetric Bragg reflection, generating, via photonic cross communication, dynamically tuneable multi-coloured patterns. These ... [more ▼]

Monodisperse cholesteric liquid crystal microspheres exhibit spherically symmetric Bragg reflection, generating, via photonic cross communication, dynamically tuneable multi-coloured patterns. These patterns, uniquely defined by the particular sphere arrangement, could render cholesteric microspheres very useful in countless security applications, as tags to identify and authenticate their carriers, mainly physical objects or persons. However, the optical quality of the cholesteric droplets studied so far is unsatisfactory, especially after polymerisation, a step required for obtaining durable samples that can be used for object identification. We show that a transition from droplets to shells solves all key problems, giving rise to sharp patterns and excellent optical quality even after polymerisation, the polymerised shells sustaining considerable mechanical deformation. Moreover, we demonstrate that, counter to prior expectation, cross communication takes place even between non-identical shells. This opens additional communication channels that add significantly to the complexity and unique character of the generated patterns. [less ▲]

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See detailDynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets
Noh, Junghyun UL; Drevensek-Olenik, Irena; Yamamoto, Jun et al

in Proceedings of the SPIE (2015), 9384

Drops or shells of a planar-aligned short-pitch cholesteric liquid crystal exhibit unique optical properties due to the combination of Bragg reflection in the cholesteric helix and a radial orientation of ... [more ▼]

Drops or shells of a planar-aligned short-pitch cholesteric liquid crystal exhibit unique optical properties due to the combination of Bragg reflection in the cholesteric helix and a radial orientation of the helix axis. If such a droplet is illuminated from above, light is reflected into a continuous set of cones, the opening angles of which depend on where on the droplet the light hits its surface. For the wavelength that fulfills the Bragg condition the reflection is dramatically enhanced, yielding the light cones colored. A photonic cross communication scheme arises for certain angles, reflecting light back to the observer from a different droplet than the one originally illuminated. This gives rise to an intricate pattern of colored and circularly polarized spots. A number of interesting applications may be developed based on this pattern, e.g. in identification and authentication devices. We have carried out a detailed spectrophotometric analysis of the patterns, localized to individual spot maxima. A quantitative comparison between the measured spectra and the reflection wavelength expected from a model for the pattern generation allows us to conclude that the droplets are in fact not spherical but slightly ellipsoidal. [less ▲]

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See detailTuneable Multicoloured Patterns From Photonic Cross Communication Between Cholesteric Liquid Crystal Droplets
Noh, Junghyun UL; Liang, Hsin-Ling; Drevensek-Olenik, Irena et al

in Journal of Materials Chemistry C (2014), 2(5), 806-810

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N ... [more ▼]

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications. [less ▲]

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