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PhD Student, Case Western Reserve University

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Development of programmable, stimuli-responsive, shape and color changing cholesteric LC elastomers.

Biological systems employ anisotropy to enable selectivity in motion, transport, or add functionality, like structural color. Resembling the structure-function relationships found in nature, cholesteric liquid crystals (CLCs) are inherently and selectively reflective, and shown to exhibit stimuli-induced changes in coloration particularly in compositions prepared with low-molar mass liquid crystals. Here, we report on the ability to pattern and imprint both color and shape (topography) change in monolithic elements prepared from cholesteric liquid crystalline elastomers. The materials examined here are of the main-chain subclass, synthesized via photopolymerization. The spatial anisotropy was initiated via photoalignment of dye molecules on substrate surfaces. We will elucidate subtle nuances in the fundamental nature of the mechanics that differentiate the stimuli-response of these materials from nematic liquid crystalline elastomers. The ability to simultaneously and concurrently regulate the color as well as the direction of reflected light could open up interesting applications in textiles, optics, and sensing.

6 ITEMS PINNED

Cholesteric liquid crystals in living matter.

Abstract: Liquid crystals play an important role in biology because the combination of order and mobility is a basic requirement for self-organisation and structure formation in living systems. Cholesteric liquid crystals are omnipresent in living matter under both in vivo and in vitro conditions and address the major types of molecules essential to life. In the animal and plant kingdoms, the cholesteric structure is a recurring design, suggesting a convergent evolution to an optimised left-handed helix. Herein, we review the recent advances in the cholesteric organisation of DNA, chromatin, chitin, cellulose, collagen, viruses, silk and cholesterol ester deposition in atherosclerosis. Cholesteric structures can be found in bacteriophages, archaea, eukaryotes, bacterial nucleoids, chromosomes of unicellular algae, sperm nuclei of many vertebrates, cuticles of crustaceans and insects, bone, tendon, cornea, fish scales and scutes, cuttlebone and squid pens, plant cell walls, virus suspensions, silk produced by spiders and silkworms, and arterial wall lesions. This article specifically aims at describing the consequences of the cholesteric geometry in living matter, which are far from being fully defined and understood, and discusses various perspectives. The roles and functions of biological cholesteric liquid crystals include maximisation of packing efficiency, morphogenesis, mechanical stability, optical information, radiation protection and evolution pressure.

Pub.: 08 Jun '17, Pinned: 05 Jul '17