Friday, August 6, 2010

This week in nanotechnology - August 6, 2010

One Chicago skyline is dazzling enough. Now imagine 15,000 of them.
A Northwestern University research team has done just that -- drawing 15,000 identical skylines with tiny beams of light using an innovative nanofabrication technology called beam-pen lithography (BPL). The technology offers a means to rapidly and inexpensively make and prototype circuits, optoelectronics and medical diagnostics and promises many other applications in the electronics, photonics and life sciences industries.

Nanoparticle-coated pavement that cleans the air: The concentrations of toxic nitrogen oxide that are present in German cities regularly exceed the maximum permitted levels. That's now about to change, as innovative paving slabs that will help protect the environment are being introduced. Coated in titanium dioxide nanoparticles, they reduce the amount of nitrogen oxide in the air.

A newly discovered nanomaterial – silicon nanoneedles with modulated porosity – could improve healthcare devices by increasing energy storage, help realize implantable microchips or make better drugs. The nanoporous needles are flexible, semiconductors, biodegradable and have a surface one hundred times larger that of solid nanowires. These unique properties of the nanowires will provide a higher energy density when used as large surface anodes in lithium batteries, constitute the active elements of bioresorbable, flexible microchips for subcutaneous implants or protect drugs while in the body and release them in a controlled manner to improve their therapeutic effect.

atomically-thin graphene nanopores

Left: A side view of a forest of bicolor nanoneedles. A central low porosity segment is green and two siding high porosity segments are red. An ultrathin porous wire crosses the picture sideways, in yellow. Middle: Bicolor nanoneedles seen from an angle. The high porosity segment is red and low porosity segment is green. The grass-like flexibility of the nanowires allows the tips to join. Right: A forest of evenly spaced cylindrical nanoneedles. The diameter is 100nm and allows piercing of cell membrane without harming the cells.

In an innovation critical to improved DNA sequencing, a markedly slower transmission of DNA through nanopores has been achieved. Solid-state nanopores sculpted from silicon dioxide are generally straight. They are used as sensors to detect and characterize DNA, RNA and proteins. But these materials shoot through such holes so rapidly that sequencing the DNA passing through them is a problem. Researchers now report using self-assembly techniques to fabricate equally tiny but kinked nanopores which achieve a fivefold slowdown in the voltage-driven translocation speeds critically needed in DNA sequencing.

For the first time ever, scientists watch an atom's electrons moving in real time. The researchers used ultrashort flashes of laser light to directly observe the movement of an atom's outer electrons for the first time. Through a process called attosecond absorption spectroscopy, researchers were able to time the oscillations between simultaneously produced quantum states of valence electrons with great precision. These oscillations drive electron motion.

While most most polymer solar cells are manufactured through a spin-coating process – a technology very useful for fabricating very thin and homogeneous film and for controlling the film thickness – spin-coating has several drawbacks with regard to its application to mass production: scale-up is problematic and the process is not continuous; it is impossible to fabricate flexible devices; the process is not only expensive and wasteful but the cost increases exponentially as the substrate size increases. To overcome these problems, researchers have now introduced a highly efficient polymer solar cell fabrication method by a novel coating process – roller painting.