News from Materials Research Society - 2009 March

Materials in Focus

Picoscale stability in a room-temperature AFM

A research team has shown how to detect and monitor the tiny amount of light reflected directly off the needle point of an atomic force microscope probe, and in so doing has demonstrated a 100-fold improvement in the stability of the instrument’s measurements under ambient conditions. The team was able to control the probe’s position in three dimensions to better than 40 picometers over 100 seconds. In imaging applications, they showed the long-term drift at room temperature was a mere 5 picometers per minute, a 100-fold improvement over the best previous results under ambient conditions.

Omnidirectional printing of silver microelectrodes for flexible electronics

Researchers show how metal can be added to components within flexible electronic devices, enabling conductivity to be maintained even after repeated deformation. They used inkjet printing to create three-dimensional (3D) metallic connections between functional components of flexible devices. Controlling the deposition of the colloidal silver ink is essential for fabricating freestanding wires that have both 2D and 3D components. The electrical connections demonstrated by the researchers include springs and structures with built-in slack to accommodate the stretching and bending of a flexible device.

Oblique angle deposition for mass production of metamaterials

Though metamaterials have generated a lot of interest in the last few years, the ones made so far have only worked over a limited range of frequencies and are difficult to produce in large quantities. Taking a different approach, researchers have turned their attention to a more established production technique known as “oblique angle deposition” (OAD) which involves depositing vapor at an angle onto a substrate held in a vacuum. The formed film thickness was 240 nm and the angle between the normal to the substrate and the tilt of the nanorods was maintained at 66 degrees. Silver nanorods were grown to about 650 nm long and 80 nm wide.

TEM images 47 picometer spacing of a Ge crystal

Hailed as the world’s most powerful transmission electron microscope, an instrument has clinched another world first - resolving matter to less than half an angstrom with high contrast. The microscope has been tweaked by researchers to resolve a 47 picometer spacing in a Germanium crystal. The TEM corrects for spherical blurring caused by “aberrations” in the lens. They also optimized the electron probe itself.

Nano Focus

Carbon nanotube aerogel forms superelastic artificial muscle

_{As light as air, yet stronger than steel and bendier than rubber. A new material made from bundles of carbon nanotubes combines all of these characteristics in a substance that twitches like a muscle when a voltage is applied. The 'artificial muscle' is an aerogel drawn into a long ribbon. It can expand about 4,000 times faster than human muscle does, and can be switched on and off up to 1,000 times a second with no deterioration.}

_{Graphene makes good microwave switch}

_{A research team has shown that graphene flakes can enable and disable the propagation of high-frequency electromagnetic fields up to 60 GHz when a DC voltage is applied. The switching time is very short at less than 1 ns, which is among the fastest ever observed in such a device. The device is a microwave NEMS switch that comprises a coplanar waveguide and an array of metallic graphene sheets suspended over it.}

_{Bio Focus}

_{Flow sensors based on hair structures of blind cavefish}

_{A blind fish that has evolved a unique technique for sensing motion may inspire a new generation of sensors that perform better than current active sonar. Although members of the fish speciesAstyanax fasciatus cannot see, they sense their environment and the movement of water around them with gel-covered hairs that extend from their bodies. Their ability to detect underwater objects and navigate through their lightless environment inspired a group of researchers to mimic the hairs of these blind cavefish in the laboratory. They conducted preliminary experiments with a simple artificial hair cell microsensor made of SU-8, a common epoxy-based polymer capable of solidifying, and built with conventional CMOS microfabrication technology.}

_{Polymer coats multi-task in drug delivery}

_{Polymer spheres with a sugar coating on the outside and a plastic coating on the inside have been developed. This gives them dual functionality to target and deliver drugs. Researchers made the spheres by dissolving glycosylated polybutadiene-poly(ethylene oxide) block copolymers in water. When dissolved, the copolymers spontaneously formed hollow colloids called vesicles with a glucose coating on the outside and a poly(ethylene oxide) coating on the inside. The polymer vesicles could be used as living cell mimics or drug delivery vessels.}

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