High-contrast thin-film polarizers by photo-crosslinking of smectic guest-host systems

\u3cp\u3eThe preparation of high-contrast thin-film polarizers by photo-crosslinking of smectic guest-hosts systems for use in liquid crystal displays (LCDs) is presented. Thin-film polarizers has the advantages of significant reduction in display and weight, and the positioning of the polarizers inside the cell eliminates all parallax-related issues and is beneficial to the robustness of the display. One possible approach to obtaining thin, coatable polarizers based on the use of lyotropic liquid-crystalline dyes that form a crystalline polarizer with sub-micrometer film thickness after coating and evaporation of the solvent. The low viscosity of the reactive liquid crystals facilitates easy alignment, while the in setu photopolymerization provides freedom in choosing the photopolymerization temperature and conditions enabling the selection of the optimum phase and molecular order. This thin-film technology could be an alternative to traditional sheet polarizers in LCD.\u3c/p\u3

Mechanical and failure properties of single attached cells under compression

Eukaryotic cells are continuously subjected to mechanical forces under normal physiological conditions. These forces and associated cellular deformations induce a variety of biological processes. The degree of deformation depends on the mechanical properties of the cell. As most cells are anchorage dependent for normal functioning, it is important to study the mechanical properties of cells in their attached configuration. The goal of the present study was to obtain the mechanical and failure properties of attached cells. Individual, attached C2C12 mouse myoblasts were subjected to unconfined compression experiments using a recently developed loading device. The device allows global compression of the cell until cell rupture and simultaneously measures the associated forces. Cell bursting was characterized by a typical reduction in the force, referred to as the bursting force. Mean bursting forces were calculated as at an axial strain of 72±4%. Visualization of the cell using confocal microscopy revealed that cell bursting was preceded by the formation of bulges at the cell membrane, which eventually led to rupturing of the cell membrane. Finite element calculations were performed to simulate the obtained force–deformation curves. A finite element mesh was built for each cell to account for its specific geometrical features. Using an axisymmetric approximation of the cell geometry, and a Neo–Hookean constitutive model, excellent agreement between predicted and measured force–deformation curves was obtained, yielding an average Young's modulus of

Control over the morphology of porous polymeric membranes for flow through biosensors

\u3cp\u3ePorous membranes have been developed by photo-polymerisation-induced phase separation of a monomer/solvent mixture. Characterised by a large open surface area reaching up to about 50 m\u3csup\u3e2\u3c/sup\u3e/g, these membranes are suitable for flow through biosensor applications in the field of molecular diagnostics. The effects of the polymerisation conditions and the phase separation on the resulting structures are discussed. SEM analysis and BET surface area measurements revealed that morphology can be well controlled by adjusting monomer concentration and UV intensity. Membranes functionalised with epoxy and amine groups show high coupling efficiency of oligo-DNA and large hybridisation efficiency.\u3c/p\u3

Stimuli responsive delivery vehicles for cardiac microtissue transplantation

\u3cp\u3eCell transplantation has emerged as the most promising therapy for restoring the scarred myocardium in the treatment of heart failure. However, clinical efficacy of (stem) cell therapies is still limited by poor retention rate and survival of injected cells in the ischemic tissue. Here we present a new strategy to deliver microtissues in the treatment of heart dysfunction in order to improve the retention, survival, and integration of the delivered cells. For this purpose, we developed stimuli responsive biodegradable polymer constructs consisting of a thin film of thermosensitive hydrogel coupled to a thin film of non-responsive polymer. Due to the temperature responsive swelling behavior of the hydrogel layer, the bilayer polymer constructs can roll or unroll at will. Therefore they can potentially be used for efficient encapsulation and protection of cell clusters during delivery, while under physiological conditions, the constructs, named cell wraps, can unroll and expose the delivered microtissue to the ischemic tissue.\u3c/p\u3

Formation of optical films by photo-polymerisation of liquid crystalline acrylates and application of these films in liquid crystal display technology

\u3cp\u3ePhoto-polymerisation of liquid crystalline di-acrylates is a very versatile method to produce homogeneously aligned polymer films. The orientation of the liquid crystals and hence the anisotropic optical properties of the films are frozen in by the photo-polymerisation process. Homogeneously aligned nematic liquid crystals form birefringent films that find application as retarders, while splayed nematic liquid crystalline mixtures form, angle dependent birefringent films that find application as wide viewing angle foils. In addition, cholesteric liquid crystals form reflecting films that can be used as colour filters or polarisers and smectic liquid crystals form highly ordered films that find application as polarisers. Moreover, modulating the light during the manufacturing process either in lateral or in-depth direction of the film can create complex structures not attainable with liquid crystalline polymers. All these films are mechanically, thermally and chemically stable and therefore very suitable to be processed in liquid crystal display manufacturing as additional films or as in-cell optical components.\u3c/p\u3