Search results for "Liquid Crystal"
showing 10 items of 492 documents
A modular approach towards functional supramolecular aggregates - subtle structural differences inducing liquid crystallinity.
2016
Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic behaviour and fast photo-response of the liquid crystals based on phloroglucinol. The presented results prove the benefits of a modular methodology towards highly responsive materials with tailor-made properties.
Distributed feedback lasing in cellulose films
2013
Cellulose derivatives, because of their molecular structure and chirality, can self-assemble to form spatially periodic cholesteric liquid crystal phases. We have synthesized and produced solid cross-linked cholesteric cellulose based films optimized to provide high reflectivity. Since these films are self-assembled photonic bandgap materials, they may be expected to show distributed feedback lasing. By doping samples with fluorescent dyes and optically pumping thin films of these materials, we were able to demonstrate, to the best of our knowledge, for the first time, mirrorless band-edge lasing in cellulose derivatives.
SPECTRAL AND TEMPORAL CHARACTERISTICS OF LIQUID CRYSTAL GOGGLES FOR VISION RESEARCH
2008
ABSTRACT Spectral and switching characteristics of two manufacturer liquid crystal goggles are tested. Experimentally the human stereovision acuity and threshold were studied for the case, when one eye random dot stereo stimulus simulated on the display is continuously blurred or the stimulus contrast is decreased. In order to determine the artefacts of two eye channel crosstalk on the stereostimuli separation the contrast ratio limits for the computer display phosphors wavelengths are determined.
Imidazolium-based liquid crystals: a modular platform for versatile new materials with finely tuneable properties and behaviour
2011
Ionic liquid Crystals constitute highly versatile materials that have drawn much interest these past few years in the fields of academic research and industrial development. In this respect, the present article is intended as an update of K. Binnemans review published in 2005, but focusing exclusively on the imidazolium cation - the most widely studied. Herein, imidazolium-containing thermotropic liquid crystalline materials will be sorted by molecular structure (mono-, bis-, poly-imidazolium compounds, with symmetrical and non-symmetrical structures) and discussed. Their physico-chemical properties will be exposed in order to adduce the relevancy and potential of the imidazolium platform i…
Rigid Rod Polymers Having Flexible Side Chains. 3. Structural Investigations on a Novel Layered Mesophase Formed by Thermotropic Poly(1,4-phenylene-2…
1987
A series of thermotropic poly(1,4-phenylene-2,5-di-n-alkoxy terephthalate)s with the length of the n-alkoxy side chains being varied between n = 2 and n = 18 carbon atoms has been examined by optic...
Muscular MEMS—the engineering of liquid crystal elastomer actuators
2016
A new class of soft-matter actuator, the liquid crystal elastomer (LCE), shows promise for application in a wide variety of mechanical microsystems. Frequently referred to as an 'artificial muscle', this family of materials exhibits large actuation stroke and generates considerable force, in a compact form which may easily be combined with the structures and devices commonly used in microsystems and MEMS. We show here how standard microfabrication techniques may be used to integrate LCEs into mechanical microsystems and present an in-depth analysis of their mechanical and actuation properties. Using an example from micro-optics and optical MEMS, we demonstrate that their performance and fle…
MEMS analogous micro-patterning of thermotropic nematic liquid crystalline elastomer films using a fluorinated photoresist and a hard mask process
2017
In this work, we present a method to pattern liquid crystal elastomers (LCEs) in the micrometer range without using any mechanical processing steps to prepare micron sized LCE actuators compatible with microelectromechanical system (MEMS) technology. Multi-layer spin-coating processes are developed to synthesise and structure 300–3500 nm thick LCE films. A water soluble sacrificial layer, a photoalignment layer and a LCE formulation, which is polymerised and crosslinked in its liquid crystal phase, are spin-coated successively onto a substrate. A fluorinated photoresist layer is used to structure LCE films with thicknesses up to 700 nm in a photolithographic and etching process. For thicker…
Towards micrometer sized core-shell actuators from liquid crystalline elastomers by a continuous flow synthesis
2012
We present here the successful preparation of liquid crystalline core-shell elastomers via a microfluidic double-emulsion process. The customized set-up allows for a temperature-controlled fabrication of the core-shell particles from a thermoresponsive mesogenic monomer. The nematic liquid crystalline shell is filled with a non-mesogenic core of silicone oil. To verify the core-shell structure with optical microscopy, we prepared particles with a colored core using a red dye. We were also able to micro-manipulate the particles and penetrate them with a small glass capillary to extract the liquid core.
Liquid crystal lens array for 3D microscopy and endoscope application
2016
In this paper, we demonstrate two liquid crystal (LC) lens array devices for 3D microscope and 3D endoscope applications respectively. Compared with the previous 3D biomedical system, the proposed LC lens arrays are not only switchable between 2D and 3D modes, but also are able to adjust focus in both modes. The multi-function liquid crystal lens (MFLC-lens) array with dual layer electrode has diameter 1.42 mm, which is much smaller than the conventional 3D endoscope with double fixed lenses. The hexagonal liquid crystal micro-lens array (HLC-MLA) instead of fixed micro-lens array in 3D light field microscope can extend the effective depth of field from 60 um to 780 um. To achieve the LC le…
Microscope system with on axis programmable Fourier transform filtering
2017
Abstract We propose an on-axis microscope optical system to implement programmable optical Fourier transform image processing operations, taking advantage of phase and polarization modulation of a liquid crystal on silicon (LCOS) display. We use a Hamamatsu spatial light modulator (SLM), free of flickering, which therefore can be tuned to fully eliminate the zero order component of the encoded diffractive filter. This allows the realization of filtering operation on axis (as opposed to other systems in the literature that require operating off axis), therefore making use of the full space bandwidth provided by the SLM. The system is first demonstrated by implementing different optical proce…