Colorless High Dielectric Compounds for Low Voltage Liquid Crystal Application

1999 ◽  
Vol 559 ◽  
Author(s):  
Shin-Tson Wu ◽  
Robert N. Schwartz ◽  
Qing T. Zhang ◽  
Seth Marder ◽  
Chain-Shu Hsu
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Absorption Spectra ◽  
Phase Transition Temperature ◽  
Low Voltage ◽  
Dielectric Anisotropy ◽  
Elastic Coefficient ◽  
High Dielectric

ABSTRACTSeveral colorless compounds with dielectric anisotropy in the 10-50 range were studied. The absorption spectra, phase transition temperature, birefringence, dielectric anisotropy and visco-elastic coefficient of these compounds were measured.

A Hexagonal Pillar Array of Thermo-responsive Soft Actuators Prepared by Nanoimprinting

2011 ◽  
Vol 1312 ◽  
Author(s):  
Ching-Mao Wu ◽  
Szu-Yin Lin ◽  
Kuo-Tung Huang
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Polymer Network ◽  
Isotropic Phase ◽  
Hexagonal Array ◽  
Soft Actuators ◽  
Response To Temperature ◽  
Thermomechanical Effects

ABSTRACTThermo-responsive actuation (thermomechanical effects) based on nematic liquid crystal elastomers (LCEs) have become a research priority in the preparation of soft actuators. Nematic LCEs combine the anisotropic features of liquid crystal phases with the rubber elasticity of polymer network. When heated at nematic to isotropic phase transition temperature (N-to-I temp.), a uniaxial thermomechanical deformation of LCEs will undergo at nearly constant volume due to a change of LC director order. Recently, an array of the micro-sized LCE pillars related to such thermomechanical effects have been successfully constructed through a soft lithography technology (i.e., replica molding). The prepared LCE pillars are mono-dispersive and micro-sized. They also possess N-to-I temp. higher than 100°C, largely limiting the available application. By contrast, the present study will report a hexagonal array of nano-sized thermo-responsive pillar actuators that are able to contract and expand in response to temperature changes around a lower N-to-I temp. is manufactured via using reactive rod-like liquid crystal and ultraviolet nanoimprinting technology. According to atomic force microscope (AFM) observation, a hexagonal array of pillars can be easily constructed by nanoimprinting and a responsive surface with a thermo-stimuli-driven roughness change is achieved. The room-temperature AFM scans quantitatively represent the single pillar shows a diameter of ca. 270 nm and 140 nm in depth, and the pitch meaning the averaged inter-pillar distance is measured as ca. 425 nm, thus lying in a nano-sized range. Furthermore, temperature-variable AFM is also utilized to demonstrate the pillar behaves as a thermally-stimulated nano-sized actuator. In our case, when heated above N-to-I phase transition temperature (ca. 65°C), it is clearly observed that the pillar diameter is expanded in the order of over 12-15 % and then reversibly contracted in response to temperature drop.

Thermally enhanced optical nonlinearity in nematic liquid crystal close to phase transition temperature

2010 ◽  
Vol 283 (18) ◽  
pp. 3516-3519 ◽  
Author(s):  
Chia-Chi Shih ◽  
Yu-Jen Chen ◽  
Wen-Chi Hung ◽  
I-Min Jiang ◽  
Ming-Shan Tsai
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Nematic Liquid Crystal ◽  
Optical Nonlinearity

Reversible Actuation of Origami Inspired Composites Using Liquid Crystal Elastomers

2017 ◽  
Author(s):  
A. Minori ◽  
S. Jadhav ◽  
Q. He ◽  
S. Cai ◽  
M. T. Tolley
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Shape Memory ◽  
Phase Transition Temperature ◽  
Smart Materials ◽  
Electrical Heating ◽  
Functional Composites ◽  
Rigid Layer ◽  
Liquid Crystal Elastomers

Recent work has used self-folding origami inspired composites to produce complex, scalable, affordable, and lightweight morphing structures [1]. These characteristics are of interest for engineering applications, in fields including aerospace [2] and medical devices [3]. Due to these advantages, research on self-folding smart composites has grown, with a particular focus on the use of laminate manufacturing techniques that stack layers of heterogeneous materials to generate functional composites. Previous work used this approach to manufacture self-folding origami inspired robots [1]. A simple shape memory composite design consists of a smart material (e.g. a one-way shape memory polymer, or SMP) sandwiched between patterned rigid layers. These SMPs change their shape in response to an external stimulus (e.g. temperature). Upon heating above the phase transition temperature of the polymer (Tt), the SMP contracts, causing the laminate to fold. The SMPs used in self-folding laminate composites are unidirectional and thus the laminate is unable to recover its original state without application of external force. In this work, we study the use of thermal responsive liquid crystal elastomers (LCE) for reversible self-folding and actuation of origami inspired composites using laminate manufacturing. LCEs are smart materials that exhibit reversible deformation, good strain recoverability, and tailorable properties (i.e. phase transition temperature, strain, and orientation of deformation) [4–6]. We explore two composite hinge designs using laminate manufacturing process [1, 7] with a Joule heating layer to enable self-folding: one where the LCE acts as a tensile actuator connected only on the edges of the rigid layer, which we call a tensional hinge, and a second where the LCE is attached along the patterned rigid layer hinge, which we call a flexural hinge. The angular displacements of these two hinge designs are estimated using geometric models that account for the contraction of the LCE upon heating, and compared against experimental measurements. The maximum blocked torque of the composite hinges is also measured experimentally. To demonstrate the use of LCE as an active layer for origami inspired composites, we also present a laminate crawler robot. The crawling locomotion is controlled with an electrical heating layer laminated on the LCE. These results demonstrate the possibility of using LCE to achieve rapid, reversible folding and to generate similar torques, as compared to previous work in origami inspired self-folding composite.

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