Bioinspired, Cholesteric Liquid-Crystal Reflectors with Time-Controlled Coexisting Chiral and Achiral Structures

Abstract

The twisted structures of the chitin-based cuticle of beetles confer specific optical characteristics on them. Intrigued by the observation of Bragg gratings with a depth-dependent periodicity in the cuticle of Chrysina beetles, we determine the experimental conditions leading to their transcription into cholesteric liquid-crystal oligomers. We correlate the optical properties of reflectors thus produced with their internal morphology, as observed by transmission electron microscopy. With the use of a single parameter, thermal annealing time, the reflection color is made time-tunable. Different spectral bands and reflection colors from golden yellow to NIR are available, and the irreversibility of the final color is reached at the end. On the basis of the design concept and these properties, these hybrid chiral–achiral materials inspire the fabrication of smart reflective labels. When encapsulated in the package of a product to be kept under cold conditions, the label records the history of the product conservation. Two kinds of information based on color changes are recorded as follows: qualitative information reporting that the product was kept outside of the specified storage temperature and quantitative information giving an indication of the time elapsed since the temperature exceeded the storage temperature of the product.

Light Intensity-Selective Photopolymerization and Photoisomerization for Creating Colorful Polymer-Stabilized Cholesteric Liquid Crystal Patterns

“…It was reported that the isomerization of CA was time-dependent under UV light . Therefore, the structural colors of LC242/CA mixtures in the cholesteric phase should be also irradiation time-dependent.…”

“…It was reported that the isomerization of CA was timedependent under UV light. 37 Therefore, the structural colors of LC242/CA mixtures in the cholesteric phase should be also irradiation time-dependent. To reveal this irradiation time dependency behavior, an LC242/CA mixture at a weight ratio of 94/6 was irradiated under a low-pressure Hg lamp (80 W) at a distance of 5 cm and 80 °C.…”

“…To tune the structural color of PSCLC films, both phase separation and chemical injection techniques , were developed. It was reported that the structural color of CLCs was tunable using photoisomeriable chiral additives. − The color was controlled by the intensity and time of UV irradiation.…”

“…30 Recent results indicated that they could be used for programmable paintings, 31,32 colorful-patterned CLC materials, 33,34 and rewritable papers. 35 To tune the structural color of PSCLC films, both phase separation 36 and chemical injection techniques 37,38 were developed. It was reported that the structural color of CLCs was tunable using photoisomeriable chiral additives.…”

Design and Applications of Liquid Crystal Biophotonic Sensors for Ion Detection

“…Liquid crystals (LCs) have been the star materials in the past decades due to the subtle integration of the molecular ordering and fluidity. [1][2][3] Since the first observation of liquid crystalline behavior by Reinitzer in 1888, the research on these strange and fascinating materials has gathered wide attention. [4,5] Based on the phase-transition condition, the LCs are classified into two types including thermotropic LCs and lyotropic LCs.…”