Versuchsschule und Innovationswerkstatt. Das Oberstufen-Kolleg Bielefeld im Porträt

Asdonk J, Boller S, Geweke M, Kroeger H, Obst G. Versuchsschule und Innovationswerkstatt. Das Oberstufen-Kolleg Bielefeld im Porträt. Pädagogische Führung. 2010;2010(4):150-152

Fully Stable And Homogeneous Lyotropic Liquid Crystal Alignment On Anisotropic Surfaces

Lyotropic chromonic liquid crystals have great potential in both biosensing and optical devices due to their biocompatible nature and strong optical characteristics. These applications, however, demand a homogeneous and stable alignment on anisotropic surfaces, a challenge that, so far, has not been solved adequately. In this work, it is shown how to drastically increase the quality of in-plane alignment and stability of these liquid crystals on conventional rubbed polyimide substrates by the addition of a small amount of a nonionic surfactant. Samples with surfactant show excellent alignment that is stable for months, while control samples without surfactant show much poorer alignment that further deteriorates in days. Also, well-aligned dry films of chromonics can be prepared following this approach. It is demonstrated how to obtain high-quality alignment by controlling the concentration and the nature of the surfactant, in particular its molecular structure and hydrophilic/lipophilic balance (HLB value) and other critical parameters are discussed. It is believed that this approach may very well be essential for advancing the applicability of these water-based, biocompatible, and often highly dichroic materials for a wide range of uses

Anchoring Strength Measurements Of A Lyotropic Chromonic Liquid Crystal On Rubbed Polyimide Surfaces

Techniques to achieve planar anchoring of the director of a lyotropic chromonic liquid crystal (LCLC) have been developed only recently. These techniques range from the very weak anchoring achieved by simply scratching the glass with a very fine abrasive to the very strong anchoring achieved with lithographic techniques. A possible alignment technique is to use rubbed polyimide (PI) alignment layers as is routinely done to align thermotropic liquid crystals (TLCs). The anchoring strength of the LCLC disodium cromoglycate (DSCG) on different rubbed PI alignment layers is measured using a pi/2 twist cell and optical polarisation techniques. Although the anchoring strength is not as large as can be achieved with lithographic techniques, it is larger than scratched glass for one PI. Just as important, rubbed PI provides a much more uniform surface than is possible with scratched glass. Interestingly, addition of a small amount of surfactant to the LCLC, which results in improved alignment, does not increase the anchoring strength. Weak anchoring of LCLCs can also be achieved with a photo-patterned dye surface layer. Finally, atomic force microscopy measurements of the surface combined with prior theoretical work linking surface features and anchoring strength predict anchoring strengths consistent with experiment

Directing Soft Matter in Water Using Electric Fields

Directing the spatial organization of functional supramolecular and polymeric materials at larger length scales is essential for many biological and molecular optoelectronic applications. Although the application of electrical fields is one of the most powerful approaches to induce spatial control, it is rarely applied experimentally in aqueous solutions, since the low susceptibility of soft and biological materials requires the use of high fields, which leads to parasitic heating and electrochemical degradation. In this work, we demonstrate that we can apply electric fields when we use a mineral liquid crystal as a responsive template. Besides aligning and positioning functional soft matter, we show that the concentration of the liquid crystal template controls the morphology of the assembly. As our setup is very easy to operate and our approach lacks specific molecular interactions, we believe it will be applicable for a wide range of (aqueous) materials

Directing Soft Matter in Water Using Electric Fields

Directing the spatial organization of functional supramolecular and polymeric materials at larger length scales is essential for many biological and molecular optoelectronic applications. Although the application of electrical fields is one of the most powerful approaches to induce spatial control, it is rarely applied experimentally in aqueous solutions, since the low susceptibility of soft and biological materials requires the use of high fields, which leads to parasitic heating and electrochemical degradation. In this work, we demonstrate that we can apply electric fields when we use a mineral liquid crystal as a responsive template. Besides aligning and positioning functional soft matter, we show that the concentration of the liquid crystal template controls the morphology of the assembly. As our setup is very easy to operate and our approach lacks specific molecular interactions, we believe it will be applicable for a wide range of (aqueous) materials

An outbreak of endophthalmitis after extracapsular cataract surgery probably caused by endotoxin contaminated distilled water used to dissolve acetylcholine

AIM: To study possible causes of an outbreak of severe endophthalmitis after planned extracapsular cataract surgery in Medan, Indonesia. METHODS: In a 3 week period in November 2001, 17 of 43 patients developed signs of endophthalmitis after planned extracapsular cataract surgery. A search for possible causes was undertaken 4 months later. RESULTS: In autoclaved stored distilled water used to dissolve acetylcholine (used in 16 of 17 patients with endophthalmitis) a high amount of endotoxin was detected in a human blood essay, as well as a small number of non‐typeable Pseudomonas spp. CONCLUSIONS: These findings suggest that distilled water used as solvent for acetylcholine was responsible for this outbreak of endophthalmitis. As a consequence, we now rely on solvents that are regularly checked for impurities such as an intravenous infusion fluid, rather than on vials with distilled water that is presumed to be sterile and kept for some time