Thickness measurement of ultrathin films on metal substrates using ATR

Next generation covered stents made from nanocomposite materials: A complete assessment of uniformity, integrity and biomechanical properties

Covered stents are stents wrapped with a thin polymeric membrane, and are typically used to treat vessel aneurysms and seal perforated arteries. Current covered stents suffer from restenosis due to limitations in material and fabrication methods which leaves metallic struts directly exposed to blood. We have developed a biocompatible and haemocompatible nanocomposite polymer, polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU). We devised a novel combination of ultrasonic spray atomisation system and dip-coating process to produce small calibre covered stents with metal struts fully embedded within the membrane, which also yields greater coating uniformity. Stent-polymer bonding was enhanced via silanisation and coating of reactive pre-polymer. Platelet studies supported the non-thrombogenicity of POSS-PCU. Biomechanical performances including diametrical compliance, bending strength, radial strength and recoil were evaluated and optimised. This proof-of-principle manufacturing technique could lead to the development of next-generation small calibre adult and paediatric covered stents. These stents are currently undergoing preclinical trial. From the Clinical Editor: The use of stents to treat vascular diseases is now the standard of care in the clinical setting. Nonetheless, a major problem of the current stents is the risk of restenosis and thrombosis. The authors developed a nanocomposite material using polyhedral oligomeric silsesquioxane and poly(carbonate-urea) urethane (POSS-PCU) and incorporated into metallic stents. Preliminary data have already shown promising results. It is envisaged that this would further lead to better stent technology in the future.

Accelerometer design based on attenuated total reflection

It is shown that the effect of attenuated total internal reflection might be suitable for acceleration measurements. A prototype design and preliminary measurements are presented. The performance limitations of the device are discussed.

Optimum conditions in the attenuated total reflection technique

In this paper the optimum condition for using the attenuated total reflection (ATR) technique is studied. In optimum conditions, the energy of an incident plane wave can be totally absorbed. The optimum condition can be realized by fabricating a localized thickness variation in the gap between a prism and a sample substrate with a point contact pressure. In the ATR technique, for example, the complex refractive index and the foil thickness of a thin metal foil, and the gap thickness are unknown parameters. To determine these unknown parameters, we prepared three prism coupling systems with different refractive indices. By this technique, we measured the complex refractive indices and the foil thicknesses of thin gold foils sputtered onto glass substrates, and the refractive index and the film thickness of a silica film sputtered onto a metal substrate.