High-fidelity spherical cholesteric liquid crystal Bragg reflectors generating unclonable patterns for secure authentication

Abstract

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.

Structural Color Materials for Optical Anticounterfeiting

“…In addition, the stability of the structural color and the robustness of the structural color anticounterfeiting materials can benefit from further development of self‐reinforced structural color systems, [ 19 ] and optical/mechanical self‐healable systems. [ 158–160 ] On the other hand, despite some previous works that referred to unclonable patterns based on structural color materials, [ 38,71,157,161 ] it is still a great challenge to achieve a cost‐effective structural color tag generated through a stochastic process. Such highly secure anticounterfeiting systems can essentially make counterfeiting impossible.…”

Формирование Гидрогелевых Частиц Из Полиакриламида И PEGDA В Микрофлюидном Генераторе Эмульсий С Фокусировкой Потока

“…В связи с возможностью фор-мировать капли-микрореакторы с частотой до несколь-ких kHz, этот подход находит широкое применение при скрининге перспективных лекарственных препаратов [8], проведении генетических исследований методом цифро-вой капельной ПЦР [9], а также синтезе полимерных микрочастиц [10]. Также в настоящее время изучается потенциал " капельной микрофлюидики" для изготовле-ния новых " умных" материалов [11], оптических си-стем [12] и идентификационных меток [13].…”

Novel universality classes in ferroelectric liquid crystals

“…Such mapping to established universality classes is unlikely to be restricted to only one or two specific cases, which is why there has been an upsurge in interest in stochastic modeling from the perspective of analyzing some dynamical propagation fronts and related crossovers and/or phase transitions in liquid crystalline systems [9][10][11][12][13][14]. Such phase transitions range from geometric phases [15] to isotropic-nematic-columnar phases [16,17].…”