A5050295192- Liquid Crystal Research Advancements
- Advanced Materials and Mechanics
- Advanced Sensor and Energy Harvesting Materials
- Structural Analysis and Optimization
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Adhesion, Friction, and Surface Interactions
- Material Dynamics and Properties
- Hydrogels: synthesis, properties, applications
- solar cell performance optimization
- Photonic Crystals and Applications
- Nuclear Physics and Applications
- Micro and Nano Robotics
- History and Developments in Astronomy
- Solar Radiation and Photovoltaics
- Nonlinear Dynamics and Pattern Formation
- Cellular Mechanics and Interactions
- Polymer Nanocomposites and Properties
- Theoretical and Computational Physics
- Modular Robots and Swarm Intelligence
- Interactive and Immersive Displays
- Advanced Thermodynamics and Statistical Mechanics
- Surfactants and Colloidal Systems
- Molecular spectroscopy and chirality
- Pickering emulsions and particle stabilization
University of Cambridge
2014-2023
National Solar Observatory
2006-2022
Applied Photonics (United Kingdom)
2019
Cavendish Hospital
1998-2014
Rutherford Appleton Laboratory
1981-2014
Oregon State University
2013
MacDiarmid Institute for Advanced Materials and Nanotechnology
2009
Victoria University of Wellington
2009
Philips (United Kingdom)
2008
Eindhoven University of Technology
2008
We propose that large, reversible shape changes in solids, of between $10%--400%$, can be induced optically by photoisomerizing monodomain nematic elastomers. Empirical and molecular analysis change its relation to thermal effects is given along with a simple model the dynamics response. Our experiments demonstrate these for first time theory compared qualitatively our results.
Abstract We present an overview of the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides highest-resolution observations Sun ever achieved. large combined with state-of-the-art instrumentation provide sensitivity to measure vector magnetic field in chromosphere faint corona, i.e. for first time we will be able study most important free-energy source outer solar atmosphere – coronal field. Over...
Using classical elasticity theory, the rise in free energy upon crosslinking nematogenic polymers into a network is calculated for isotropic and nematic phases. Spontaneous strains are allowed network. The consequence of formation nematic–isotropic equilibria by adding these elastic contributions to conventional Landau theory. Memory conditions yields quartic quadratic additions standard We find that state lowers phase transition temperature compared with unlinked case application suitable...
Solid nematic liquids, formed by cross-linking polymer liquid crystals into elastomers, are shown to display novel and complex elasticity. The internal (nematic) direction suffers a barrier its rotation this couples standard By considering imposed strains we illuminate elasticity also demonstrate an entirely new phase transition. At critical strain there is discontinuity of director rotation.
Liquid crystalline photoactuators typically bend toward the light source, driven by isomerization of azobenzene. In samples with a relatively large thickness and high azobenzene loading such as LC photoactuators, intense optical beams are seen to be absorbed in spatially nonexponential ways. Here we show that dynamics related mechanical behavior is also strongly nonlinear, where actuator reaches maximum before unbending again its equilibrium deformed state. The effect amplified when combined...
We discuss methods of reversibly inducing non-developable surfaces from flat sheets material at the micro-scale all way to macroscopic objects. analyse elastic ground states a nematic glass in membrane approximation as function temperature for disclination defects topological charge +1. An aim is show that by writing an appropriate director field into such solid, one could create surface with Gaussian curvature, dynamically switchable while avoiding stretch energy. In addition prospect...
Abstract Synthetic approaches to prepare designer materials that localize deformation, by combining rigidity and compliance in a single material, have been widely sought. Bottom-up approaches, such as the self-organization of liquid crystals, offer potential advantages over top–down patterning methods photolithographic control crosslink density, relating ease preparation fidelity resolution. Here, we report on directed self-assembly with spatial hierarchical variation mechanical anisotropy....
Photoresponsive solids such as nematic photoelastomers can undergo large deformations induced by light absorbed into rodlike molecules which bend and disrupt liquid crystal order. Significant variation of photoabsorption through the solid leads to nonuniform elastic bending beams plates pitting layers. Such effects are also found in presence inhomogeneous thermal or swelling fields gels. We analyze small deflection limit these problems show that made materials have two elastically neutral...
Polymeric nematic liquid crystals crosslinked into elastomers (solid crystals) are shown to display novel and complex elasticity. The internal (nematic) direction can experience a barrier its rotation which couples standard We predict new phenomena unique anisotropic rubber - «soft elastic response»; uniaxial strain is developed without resistance below critical deformation λ * due the relaxation of related shear strains reorientation director. discuss possible experiments verify this...
We consider the elastic and orientational response of a uniform nematic elastomer subjected to an extension perpendicular its director.By allowing possibility local shear in material, we show that effect "soft elasticity" leads new regime director re- orientation, through highly non-uniform stripe domain state (in contrast earlier predictions observations discontinuous jump).The molecular theory developed here gives on two levels: general texture plus interval strains which it occurs,...
The order parameter and anisotropy (elongation) of the configurations a nematic polymer in phase are calculated. At low temperatures exponentially rapid growth chain dimensions as function inverse temperature is found. In direction eventually adopts rod-like state. thermal activation hairpins (abrupt reversals directions) causes this behaviour. However, at even lower deviation from alignment governed by gentle meandering away mean field direction. A Maier-Saupe theory nematic-isotropic...
Nematic solids respond strongly to changes in ambient heat or light, significantly differently parallel and perpendicular the director. This phenomenon is well characterized for uniform director fields, but not defect textures. We analyze elastic ground states of a nematic glass membrane approximation as function temperature some disclination defects with an eye towards reversibly inducing three-dimensional shapes from flat sheets material, at nano-scale all way macroscopic objects,...
Glassy and elastomeric nematic networks with dye molecules present can be very responsive to illumination, huge reversible strains being possible. If absorption is appreciable, strain decreases depth into a cantilever, leading bend that the basis of micro-opto-mechanical systems (MOMS). Bend actually occurs even when Beer's law suggests tiny penetration light heavily dye-doped system. We model nonlinear opto-elastic processes behind this effect. In regime cantilever thickness giving optimal...
The lattice theory of hard rods with anisotropic dispersion forces presented recently is extended to the case where are dispersed in a diluent. Two systems treated: (i) axial ratio x diluted solvent molecules having x=1, and (ii) xα mixed homologs xβ. Treatment latter system can be regarded as an extension Flory Abe for ’’athermal’’ polydisperse systems, which inconsequential. Solutions sufficiently long (x≳20) subject predicted exhibit complex phase equilibria involving re-entrant nematic...
Much recent progress has been made in the study of nematic solids, both glassy and elastomeric, particularly realm stress-free, defect-driven deformation thin sheets material. In this paper we consider a subset texture domains glasses that are simple to synthesize, explore ways these may be compatibly combined yield analogs traditional smooth disclination defect textures seen standard liquid crystals. We calculate properties constructed textures, show that, subject compatibility constraints...
Nematic elastic bodies can develop a gradient of response to heat, light and other stimuli. They then bend curvature in complex manner depending on director field distributions, whether they are monodomain or polydomain structures linear nonlinear absorptive processes. In each case, we derive the general weak where direction is treated independently that others. subsequent paper, address reverse phenomenon, strong spontaneous distortion leading suppression.
We describe shape transitions of thin, solid nematic sheets with smooth, preprogrammed, in-plane director fields patterned across the surface causing spatially inhomogeneous local deformations. A metric description deformations is used to study intrinsic geometry resulting surfaces upon exposure stimuli such as light and heat. highlight specific patterns that encode constant Gaussian curvature prescribed sign magnitude. present first experimental results for programmed solids, they...
Liquid crystal elastomers and glasses suffer huge length changes on heating, illumination, exposure to humidity, etc. A challenge is program these give a complex mechanical response for micromachines soft robotics. Also desirable can be strong response, where bend avoided in favor of stretch compression, even the slender shells that are our subject. new mechanics paradigm arises from such materials—spatially programmed anisotropy allows spatially varying metric develop upon stimulation, with...
The shape of liquid crystalline elastomers (LCEs) with spatial variation in the director orientation can be transformed by exposure to a stimulus. Here, informed previously reported analytical treatments, we prepare complex spiral patterns imprinted into LCEs and quantify resulting transformation. Quantification stimuli-induced shapes reveals good agreement between predicted experimentally observed curvatures. We conclude this communication reporting design strategy allow LCE films anchored...