3,064 research outputs found
Liquid Crystal Coatings Switched between Flat and Corrugated Surface Texture
No full textThe topography of the surface is the local deviations of a surface from a perfectly flat plane. Topographic textures on the surface of coating materials consist of gradual or steep concave or convex steps that may vary from nanometers to a more macroscopic level of micrometers to even millimeters. The use of liquid crystal (LC) networks induces the formation of surface topographies. An additional advantage of using photopolymerized LC networks is that one can choose between varieties of alignment strategies that lead to formation of pre‐programmed surface structures. An interesting feature, already found in the LC networks, is that the thermal expansion of uniaxially oriented LC networks is highly anisotropic. The principle of photo‐activated deformation of LC network films shows resemblance to the deformation induced by heating of structured LC network films. In this case, a copolymerized azobenzene molecule disturbs the order when it transforms from its trans state to the cis state
Dynamic Tribology in Liquid Crystal Coatings
No full textThis chapter demonstrates that under UV illumination dynamic surface topographies can be used to modulate the surface friction. The modulation of friction is based on a reversible switch between a flat and a pre‐designed surface texture. The change in friction, both and dynamic, is employed by utilizing some materials. The dynamic friction behavior of the system is quantified by the kinetic friction coefficient (μk) and is measured by two coatings that are sliding against each other at a constant speed. A home‐built measuring system is designed to measure the dynamic surface friction. The static friction coefficient (μs) is measured by placing two coatings against each other and tilting them from the horizontal position to a deflection angle β. The chapter also demonstrates a method to bring a sample into motion by decreasing the static friction at two surfaces through UV light
Inkjet Printed Liquid Crystal Cilia
No full textA widely applied method to form liquid crystal networks (LCNs) is photo‐initiated polymerization of monomers that possess a LC phase. The variety in LC phases of the LC monomers provides diversity in molecular order, all self‐organizing and being preserved by photopolymerization. This chapter first explains the principles of shape deformation in LC networks using the most straightforward case of a thermal actuator. Using the thermal actuator as an example, effects of various alignments such as twisted nematic (TN), splay, and cholesteric order are shown. Next, the chapter demonstrates that LCN actuators can be made to respond to light as trigger. It further deals with an example of miniaturization of actuators for a microfluidic application, where actuators are structured using inkjet printing. For the purpose of inkjet printed cilia, two different azo dyes are used: A3MA and DR1A, a methacrylate and an acrylate, respectively, capable of copolymerizing with the other monomers in the mentioned system
Engineered complex molecular order in liquid crystals towards unusual optics and responsive mechanics
No full textDefects in liquid crystals have been studied over decades to disclose information and knowledge on the structure of LC phases. More recently, LC defects have been identified as a tool to implement new physical functions useful in optical films for polarization conversion or mechanical actuators able to adopt novel exotic shapes. In the present paper we describe a general methodology to engineer different defect patterns by combining the use of linear photopolymerizable polymers and liquid crystals
Photoresponsive polymer hydrogel coatings that change topography
No full textThis chapter provides a brief overview of the principles as well as the potential applications of photoresponsive hydrogel films, which change surface topography. It discusses the operating mechanisms that lead to topographical changes. Changes in topography can affect the wettability of a surface, which is an interesting characteristic for making self‐cleaning coatings. The chapter also discusses polymer films that are useful for the development of self‐cleaning films. It then discusses responsive materials, for cell culturing and microfluidics applications. The chapter further shows that appealing photoresponsive polymer hydrogel coatings that change topography can be fabricated, which holds great promise in a variety of fields ranging from microfluidic devices to biomedical applications. When the structures of the topography are in the micrometer size regime, they influence the wettability of the surface. Two types of wetting can be defined: Wenzel and Cassie‐Baxter
Rapporteur’s report – innovative geotechnologies for energy transition
No full textThe 9th Society for Underwater Technology (SUT) International Conference on Offshore Site Investigation and Geotechnics (OSIG) closed with a Rapporteur’s report given by the author. This paper provides a record of that report, transcribed from a video recording. The presentation slides are shown as Figures.</p
DEFRApH - Sample collection and handling procedures
Get PDFAll chemical and biogeochemical process in the sea are affected by the acidity of the water. Acidity is therefore fundamental property of seawater. The growing concern that the acidity of the oceans might be increasing has revealed weaknesses in our knowledge of this fundamental property and its variation in space and time. In 2008 the DEFRApH project (DEFRA contract ME4133) was initiated to provide this missing information in UK related waters. It required sampling for and analysis of the total inorganic carbon and total alkalinity content of samples. This reports documents the procedures sued for sampling. A companion document Hartman Dumousseaud and Roberts (NOC Internal Document No. 01) describes in detail the analytical procedures used and the calculation of the results
On maximum field components in the focal point of a lens
No full textWe determine field distributions in the pupil of a high NA lens, that give, for a given power incident on the lens, the maximum electric field amplitude in focus in a specific direction. We consider in particular the cases of maximum longitudinal and maximum transverse components. The distribution of the maximum longitudinal component in the focal plane is narrower than that of the focused Airy spot and hence can give higher resolution in imaging.Optics Research GroupApplied Science
Financing Retirement in the European Union
Get PDFThis paper explores how EU countries can address various challenges (including the aging of the population) affecting their systems of old-age income support. It presents two scenarios illustrating the most important uncertainties surrounding the major developments that affect the pension systems of the EU. To diversify these risks, EU governments should act on several fronts. In addition to the formation of human capital (especially that of children), employment (especially that of older workers) should be boosted. This calls for social insurance reform with more emphasis on individual saving schemes. Pension schemes should be more explicit about how they share demographic and other risks. Countries that currently rely heavily on public pay-as-you-go (PAYG) schemes should stimulate private pensions by gradually reducing PAYG benefits collected by high-income earners, by issuing new financial instruments, and by conducting intergenerational risk sharing through the tax system.
Author Correction:Prefrontal cortical ChAT-VIP interneurons provide local excitation by cholinergic synaptic transmission and control attention (Nature Communications, (2019), 10, 1, (5280), 10.1038/s41467-019-13244-9)
No full textThe original version of this Article contained an error in the spelling of the author Wilma D.J. van de Berg, which was incorrectly given as Wilma D.J. van den Berg. This has now been corrected in both the PDF and HTML versions of the Article.</p
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