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Flexible Membrane (flexible + membrane)
Selected AbstractsBioinspired Material Approaches to SensingADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Michael E. McConney Abstract Bioinspired design is an engineering approach that involves working to understand the design principles and strategies employed by biology in order to benefit the development of engineered systems. From a materials perspective, biology offers an almost limitless source of novel approaches capable of arousing innovation in every aspect of materials, including fabrication, design, and functionality. Here, recent and ongoing work on the study of bioinspired materials for sensing applications is presented. Work presented includes the study of fish flow receptor structures and the subsequent development of similar structures to improve flow sensor performance. The study of spider air-flow receptors and the development of a spider-inspired flexible hair is also discussed. Lastly, the development of flexible membrane based infrared sensors, highly influenced by the fire beetle, is presented, where a pneumatic mechanism and a thermal-expansion stress-mediated buckling-based mechanism are investigated. Other areas that are discussed include novel biological signal filtering mechanisms and reciprocal benefits offered through applying the biology lessons to engineered systems. [source] Self-Assembled Nanoparticles Based Fabrication of Gecko Foot-Hair-Inspired Polymer Nanofibers,ADVANCED FUNCTIONAL MATERIALS, Issue 13 2007S. Kustandi Abstract Wafer-scale polymer nanofabrillar structures have been fabricated using the combination of colloidal nanolithography, deep-silicon etching, and nanomolding to mimic the nanostructure of gecko foot-hairs. The artificial surface features densely packed polymeric nanofibrils with super-hydrophobic, water-repellent, and "easy-to-clean" characteristics. The lateral dimension of the nanofibrils is as small as 250,nm and an aspect-ratio as high as 10:1 has been achieved without lateral collapse between neighboring fibrils. The method allows both fabrication of synthetic structures over a large area and direct integration of a flexible membrane to assist the array of nanofibrils in making intimate contact with uneven surfaces. A single nanofibril exhibits a mean adhesive force ranging from (0.91,±,0.34),nN to (1.35,±,0.37),nN. In the macroscopic scale, the nanostructured surface can adhere firmly to a smooth glass substrate and inherits the in-use, self-cleaning property of the setal nanostructures found in gecko lamellae. [source] THE EXTRAORDINARY TRILOBITE FENESTRASPIS (DALMANITIDAE, SYNPHORIINAE) FROM THE LOWER DEVONIAN OF BOLIVIAPALAEONTOLOGY, Issue 4 2009DAVID J. HOLLOWAY Abstract: The hitherto poorly known, monotypic trilobite genus Fenestraspis from the Lower Devonian of Bolivia is revised and its original assignment to the Synphoriinae supported. The thoracic morphology of the genus remains very poorly known. Fenestraspis is morphologically unusual because of the development of extensive fenestrae in the pleural region of the pygidium and apparently of the thorax; the presence of upwardly directed spines on the cephalon, thorax and pygidium; and the exceptionally large and highly elevated eyes with the palpebral rim projecting outwards above the visual surface. The function of the fenestrae remains uncertain. If they formed openings in the body of the trilobite in life they may have allowed circulation of oxygenated water to the limb exites so that respiration could have been maintained while the trilobite was enrolled. If they were covered with a flexible membrane, they may have been secondary respiratory structures or had a sensory function. The Synphoriinae is regarded as a subfamily of the Dalmanitidae rather than as an independent family of the Dalmanitoidea as proposed by some authors. The type species of the poorly known monotypic genus Dalmanitoides from the Lower Devonian of Argentina is illustrated photographically for the first time and compared with Fenestraspis. [source] Instationary aeroelastic computation of yacht sailsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2001Heinrich Schoop Abstract Effective schemes exist to calculate aerodynamic forces for thin bodies and structural dynamics of flexible membranes. The fluid dynamic of thin wings in a irrotational flow leads to the lifting surface theory. Neglecting the inertia of the membrane the structural dynamics are solved by the non-linear (FEM). But the interaction of flexible membranes and an irrotational flow causes problems due to the different nature of the mathematical equations. On the one hand, there is a partial differential equation for the structural dynamics and on the other hand, there is a singular integral equation for the aerodynamics. The numerical discretization scheme has to fit these different types of equation. Our work introduces a new interaction scheme to couple the singular integral equation of the lifting surface theory with the non-linear FEM of the membrane static. The fundamental examinations, showed by Schoop et al. (International Journal for Numerical Methods in Engineering 1998; 41: 217,219), are applied to realistic sail geometries and the aerodynamics is extended to instationary flow conditions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis and characterization of sulfonated poly(benzoxazole ether ketone)s by direct copolymerization as novel polymers for proton-exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007Jinhuan Li Abstract A new series of sulfonated poly(benzoxazole ether ketone)s (SPAEKBO-X) were prepared by the aromatic nucleophilic polycondensation of 4,4,-(hexafluoroisopropylidene)-diphenol with 2,2,-bis[2-(4-fluorophenyl)benzoxazol-6-yl]hexafluoropropane and sodium 5,5,-carbonylbis-2-fluorobenzenesulfonate in various ratios. Fourier transform infrared and 1H NMR were used to characterize the structures and sulfonic acid contents of the copolymers. The copolymers were soluble in N -methyl-2-pyrrolidinone, N,N -dimethylacetamide, and N,N -dimethylformamide and could form tough and flexible membranes. The protonated membranes were thermally stable up to 320 °C in air. The water uptake, hydrolytic and oxidative stability, and mechanical properties were evaluated. At 30,90 °C and 95% relative humidity, the proton conductivities of the membranes increased with the sulfonic acid content and temperature and almost reached that of Nafion 112. At 90,130 °C, without external humidification, the conductivities increased with the temperature and benzoxazole content and reached above 10,2 S/cm. The SPAEKBO-X membranes, especially those with high benzoxazole compositions, possessed a large amount of strongly bound water (>50%). The experimental results indicate that SPAEKBO-X copolymers are promising for proton-exchange membranes in fuel cells, and their properties might be tailored by the adjustment of the copolymer composition for low temperatures and high humidity or for high temperatures and low humidity; they are especially promising for high-temperature applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2273,2286, 2007 [source] Mechanical strain increases cytokine and chemokine production in bronchial fibroblasts from asthmatic patientsALLERGY, Issue 1 2009F. Le Bellego Background:, Mechanical strain and cytokine stimulation are two important mechanisms leading to airway remodeling in asthma. The effect of mechanical strain on cytokine secretion in airway fibroblasts is not known. The aim of this study was to determine whether bronchial and nasal fibroblasts differentially alter cytokine secretion in response to mechanical strain. Methods:, We measured secretion of the pro-fibrotic cytokine, interleukin-6 (IL-6), and the pro-inflammatory cytokines, IL-8 and monocyte chemotactic protein 1, before and after mechanical strain in bronchial fibroblasts obtained from asthmatic patients [asthmatic bronchial fibroblasts (BAF)] and normal volunteers [normal bronchial fibroblasts (BNF)], and in nasal fibroblasts (NF) obtained from nasal polyps. Cells were grown on flexible membranes and a mechanical strain of 30% amplitude, 1 Hz frequency was applied for 3, 6 and 24 h. Control cells were unstrained. IL-6, IL-8 and monocyte chemotactic protein 1 was measured after 24 h strain using enzyme-linked immunoassay; mRNA was measured by real time polymerase chain reaction. We also measured mRNA for versican, a matrix proteoglycan, known to be upregulated in the asthmatic airway wall. Results:, In unstrained conditions, no differences in cytokine secretion were observed. After 24 h strain, BAF secreted more IL-6 than BNF. Mechanical strain increased IL-8 mRNA in BAF, BNF and NF; and IL-6 and versican mRNA, in BAF, only. Conclusions:, Cytokine responses to mechanical strain varied in different airway fibroblast populations, and depended on the site of origin, and the underlying inflammatory state. Strain resulted in IL-6 upregulation and increased message for extracellular matrix protein in bronchial fibroblasts from asthmatic patients only, and may reflect these patients' propensity for airway remodeling. [source] | ||||||||||