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Artificial Materials (artificial + material)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Antibacterial Nitric Oxide-Releasing Polyester for the Coating of Blood-Contacting Artificial Materials

ARTIFICIAL ORGANS, Issue 7 2010
Amedea B. Seabra
Abstract The emergence of multidrug-resistant bacteria associated with blood-contacting artificial materials is a growing health problem, which demands new approaches in the field of biomaterials research. In this study, a poly(sulfhydrylated polyester) (PSPE) was synthesized by the polyesterification reaction of mercaptosuccinic acid with 3-mercapto-1,2-propanediol and blended with poly(methyl methacrylate) (PMMA) from solution, leading to solid PSPE/PMMA films, with three different PSPE : PMMMA mass ratios. These films were subsequently S-nitrosated through the immersion in acidified nitrite solution, yielding poly(nitrosated)polyester/PMMA (PNPE/PMMA) films. A polyurethane intravascular catheter coated with PNPE/PMMA was shown to release nitric oxide (NO) in phosphate buffered saline solution (pH 7.4) at 37°C at rates of 4.6 nmol/cm2/h in the first 6 h and 0.8 nmol/cm2/h in the next 12 h. When used to coat the bottom of culture plates, NO released from these films exerted a potent dose- and time-dependent antimicrobial activity against Staphylococcus aureus and a multidrug-resistant Pseudomonas aeruginosa strains. This antibacterial effect of PSPE/PMMA films opens a new perspective for the coating of blood-contacting artificial materials, for avoiding their colonization with highly resistant bacteria. [source]

Novel Multifunctional Properties Induced by Interface Effects in Perovskite Oxide Heterostructures

ADVANCED MATERIALS, Issue 45 2009
Kui-juan Jin
Abstract Multilayer structures have emerged as a leading research topic and researchers expect that multilayers may lead to interesting artificial materials with novel properties. In this Research News we show that the introduction of interfaces into perovskite oxides can induce a series of novel properties including an unusual positive magnetoresistance, great enhancement of lateral photovoltage in La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3, and an electrical modulation of the magnetoresistance in multi-p-n heterostructures of SrTiO3,,/La0.9Sr0.1MnO3/SrTiO3,,/La0.9Sr0.1MnO3/Si. This novel positive magnetoresistance is attributed to the creation of a space charge region at the interface where the spin of the carriers is anti-parallel to that of the carriers in the region far from the interface of manganese oxide in the heterostructures. [source]

Formation of Network and Cellular Structures by Viscoelastic Phase Separation

ADVANCED MATERIALS, Issue 18 2009
Hajime Tanaka
Abstract Network (sponge) and cellular structures are often seen in various types of materials. Materials with such structures are generally characterized by light weight and high mechanical strength. The usefulness of such materials is highlighted, for example, by the remarkable material properties of bone tissue, which often has a highly porous structure. In artificial materials, plastic and metallic foams and breads have such structures. Here, we describe a physical principle for producing network and cellular structures using phase separation, and its potential applications to the morphological control of materials spanning from soft to hard matter. [source]

Fabrication of Artificial Petal Sculptures by Replication of Sub-micron Surface Wrinkles,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010
Alexandra Schweikart
Abstract In this contribution, we discuss wrinkling as a process resulting in well-defined periodic micron-sized structures, as known from the interface of several plant cells. We show possible pathways to transfer this principle to artificial materials such as epoxy resins or polymers. While topographical structuring of surfaces by wrinkling is meanwhile well established for elastomers like poly (dimethyl siloxane), so far the step towards other classes of materials has not been taken. This puts several limitations to potential applications of artificial wrinkled structures, as elastomers show poor dimensional stability, low optical quality, and tend to swell in organic solvents. As well, artificial structures formed by wrinkling are not tension-free on the microscopic level, which makes them metastable. Residual mechanical tensions can affect dimensional stability on long timescales. We introduce two processes, micro thermoforming and molding, as means to overcome these restrictions and to pattern non-elastomeric materials by using wrinkled elastomers as templates. The two approaches allow the formation of negative and positive replicas and allow the transfer of sub-micron features with high fidelity. [source]

Integrated inductors on porous silicon

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007
H. Contopanagos
The cover picture illustrates the effective use of a thick porous silicon layer as an integrated micro-plate for RF isolation on a silicon substrate, proposed by Harry Contopanagos and Androula Nassiopoulou in their Original Paper [1] in the current issue. What is plotted is the magnitude of the current distribution (colour coded from blue (low) to high (red) values) on the metallization and on a screen 50 µm underneath the bottom oxide layer of a 2-metal integrated CMOS-compatible inductor on bulk silicon (lower right) and on a 50 µm thick porous silicon layer (upper left) for a frequency of 2.5 GHz. Inductors were designed in a standard 0.13 µm CMOS technology. Efficient RF isolation is produced by the porous Si layer, as evidenced by the virtual elimination of surface currents relative to the case of standard CMOS, indicating virtually complete substrate shielding by a 50 µm thick porous Si layer for the relevant size scale. The quality factor of the inductor with the use of the porous Si layer is increased by 100%, reaching a maximum value of 33 for the design shown. The first author of the article is a visiting senior researcher at the Institute of Microelectronics (IMEL), National Center for Scientific Research "Demokritos" (Athens, Greece). His research focuses on electromagnetics and microwave engineering, artificial materials and photonic crystals, wireless front ends, antennas and high-frequency analog integrated circuits. [source]

Contribution of polymer chemistry to dentistry: development of an impermeable interpenetrating polymer network to protect teeth from acid demineralization

POLYMER INTERNATIONAL, Issue 2 2008
Nobuo Nakabayashi
The purpose of this review article is to show how polymer science can contribute to the further improvement of modern dentistry. It has long been believed that the development of strong dental materials is essential to improve dentistry, and polymeric materials might not be reliable compared to metals and ceramics. It was hypothesized that the bonding of restoration materials to the tooth structure is required in order to inhibit the detachment of prostheses. However, bonding of artificial materials to natural tissues is difficult. It has been found that a polymer network interpenetrated with dental hard tissues resolves this problem, that formal bonding is not required and that protection of prepared dentin against lactic acid demineralization with an impermeable barrier is a requisite for prevention of caries. Copyright © 2007 Society of Chemical Industry [source]