A polyvinylsilixane sample fabricated to replicate biological attachment systems consisting of microscale pillars (about 230/mm 2 ) approximately 50 lm in diameter, 70 lm in height, and 60 lm centerto-center was characterized for surface roughness, friction force, and contact angle and compared to an unstructured sample. Macroscale coefficient of kinetic friction of the structured sample was found to be almost four times greater than the unstructured sample. This increase was determined to be a result of the structured roughness of the sample and not the random nanoroughness. The structured roughness also increased the hydrophobicity of the structured sample, which is important for self cleaning to occur.
The one-dimensional, cylindrical nature of single-walled carbon nanotubes ͑SWCNTs͒ suggests that the ideal gating geometry for nanotube field-effect transistors ͑FETs͒ is a surround gate ͑SG͒. Using vertical SWCNTs templated in porous anodic alumina, SGs are formed using top-down processes for the dielectric/metal depositions and definition of the channel length. Surround gates allow aggressive scaling of the channel to 25% of the length attainable with a bottom-gate geometry without incurring short-channel effects. The process demonstrated here for forming SGs on vertical SWCNTs is amenable for large-scale fabrication of multinanotube FETs.
Abstract-Vertical single-walled carbon nanotubes (vSWCNTs) are synthesized within highly ordered porous anodic alumina (PAA) templates supported on Si substrates. A process for obtaining thin-film PAA with long-range ordered nanopores is presented in this paper. Each nanopore contains at most one v-SWCNT that is supported by a dielectric and addressed by electrochemically formed Pd nanowire source contacts and evaporated Pd drain contacts. Characteristics of these completely vertical, two-terminal nanotube devices are presented. Control of the v-SWCNT length is demonstrated using a straightforward etching process with lengths of less than 100 nm achieved without the need for complex/expensive lithography. This effective nanoscale length control of highly ordered v-SWCNTs provides a practical basis for the realization of CNT-based nanoelectronics.Index Terms-Carbon nanotubes (CNTs), length scaling, nanotechnology, porous anodic alumina (PAA), vertical devices.
The in vitro star system used for sunscreen UVA-testing is not an absolute measure of skin protection being a ratio of the total integrated UVA/UVB absorption. The in vivo persistent-pigment-darkening method requires human volunteers. We investigated the use of the ESR-detectable DMPO protein radical-adduct in solar-simulator-irradiated skin substitutes for sunscreen testing. Sunscreens SPF rated 20+ with UVA protection, reduced this adduct by 40-65% when applied at 2 mg/cm(2). SPF 15 Organic UVA-UVB (BMDBM-OMC) and TiO(2)-UVB filters and a novel UVA-TiO(2) filter reduced it by 21, 31 and 70% respectively. Conventional broad-spectrum sunscreens do not fully protect against protein radical-damage in skin due to possible visible-light contributions to damage or UVA-filter degradation. Anisotropic spectra of DMPO-trapped oxygen-centred radicals, proposed intermediates of lipid-oxidation, were detected in irradiated sunscreen and DMPO. Sunscreen protection might be improved by the consideration of visible-light protection and the design of filters to minimise radical leakage and lipid-oxidation.
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