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Showing Spotlights 761 - 768 of 2131 in category (newest first):


Dip-pen nanolithography surface patterning with bacterial cells

dip_pen_nanolithographyDip-Pen Nanolithography (DPN) is a scanning probe lithography technique in which the tip of an atomic force microscope is used to 'write' molecules directly onto a substrate, allowing nanostructured surface patterning on scales of under 100 nm. Since the driving force of DPN for transporting materials is molecular diffusion through the sub-micrometer sized water meniscus formed between the AFM tip and the surface, large-sized ink materials are not efficiently transported through this water meniscus. For this reason, bacterial cells (1-2 micrometer or larger in length) patterning with DPN technique is often considered to be impossible. Overcoming this limitation, researchers have developed a 'stamp-on' DPN method that uses a previously developed hydrogel-coated tip and carrier agents to generate micrometer-sized bacterial cells.

Posted: Oct 11th, 2012

Doping graphene with light

Controlling the density of electron carriers - which are essential to the operation of electronic devices such as transistors - is achieved by doping conventional three-dimensional semiconductors. But graphene, a semi-metallic layer that is just one atom thick, has properties very different from traditional materials such as silicon. However, the doping of graphene is a key parameter in the development of graphene-based electronics. Researchers have investigated numerous strategies for doping graphene, including attaching organic or metallic molecules to its hexagonal lattice. Now, researchers have managed to dope graphene with light in a way that could lead to more efficient design and manufacture of electronics, as well as novel security and cryptography devices.

Posted: Oct 10th, 2012

Invisible security feature with nanotechnology QR codes

QR_codeQuick Response Codes, or QR codes for short, are two-dimensional matrix codes that can hold 100 times more data than a traditional barcode. QR codes have rapidly gained popularity and are now very commonly used in various products, because of fast readability and large storage capacity. Applying the concept of QR codes to security printing applications - think banknotes - researchers have now developed an invisible QR code made from nanoparticles. They applied upconverting inks to print QR codes on paper and transparent tape, using an aerosol jet direct writing machine. They produced QR codes with embedded security characters using blue and green upconverting inks. These codes are invisible to the naked eye but produce single- and multi-color upconversion luminescence images under near-infrared excitation which can be read and decoded with an unmodified smart phone.

Posted: Oct 8th, 2012

Researchers fabricate a virus-sized laser

bowtie_plasmonic_structuresReducing the size of photonic and electronic elements is critical for ultra-fast data processing and ultra-dense information storage. The miniaturization of a key, workhorse optical instrument - the laser - is no exception. Coherent light sources at the nanometer scale are important not only for exploring phenomena in small dimensions but also for realizing optical devices with sizes that can beat the diffraction limit of light. Researchers at Northwestern University have now found a way to manufacture single laser devices that are the size of a virus particle and that operate at room temperature. They show that subdiffraction nanoresonators based on metallic bowties, when coupled to a gain material, can generate coherent and directional light emission.

Posted: Oct 4th, 2012

The rise of graphene in microwave photonics

graphene_photonicsThe unique energy band structure in graphene allows it to actively respond to photons with ultra-wide spectrum range - from the visible to the infrared - with record strong inter-band transition efficiency. As a consequence, graphene based ultra-fast photonics has been rising fast in various aspects of ultra-fast photonics - an ultra-fast graphene photo-detector with bandwidth exceeding 500 GHz; a broadband graphene optical modulator; a broadband graphene polarizer etc, which all benefit from the material's broadband photonics property. Researchers have now experimentally demonstrated for the first time that graphene, besides its well-known optical saturable absorption, also shows microwave and terahertz saturable absorption. The results lead to the expectation that graphene may show potential applications in microwave photonics.

Posted: Oct 2nd, 2012

Making high-resolution holograms with nanoscale pixels

carbon_nanotube_forestThe size of pixels is one of the key limiting features in the state of the art of holographic displays systems. Holography is a technique that enables a light field to be recorded and later reconstructed when the original light field is no longer present, due to the absence of the original objects. The resolution and field of view in these holographic systems are dictated by the size of the pixel, i.e. the smallest light scattering element. To address the limitations of current holographic systems due to their pixel size, a research team set out to use nanostructures as the smallest possible light-scattering elements for producing holograms. They harnessed the extraordinary conductive and light scattering abilities of nanotubes and patterned an array of carbon nanotubes to produce a high resolution hologram.

Posted: Oct 1st, 2012

All-carbon solar cells

carbon_solar_cellsIt was previously thought that carbon nanotubes and other carbon nanomaterials are not well suited to make efficient solar cells. The main reason for this is that nanotubes are hard to isolate in single chiralities or in a given diameter range and only of semiconducting or metallic type, and thus it is hard to use them in a controlled way. New work has now shown that thin film solar cells made entirely out of carbon nanomaterials can achieve an efficiency similar to that of polymer solar cells at their initial research stages (a decade ago), but with much improved photostability. As a result, the use of carbon materials holds great promise towards the realization of photostable thin film solar cells.

Posted: Sep 27th, 2012

Just say no to cracks

cracksed_nanofilmOne way to use engineered nanoparticles in the real world is in thin films. Such nanoparticulate films are thin layers, sometimes only a few nanometers thick, of composite materials that contain nanoparticles. These new materials have a wide range of applications in drug delivery, nanoelectronics, magnetic storage devices, sensors, or optical coating. However, most processes used to fabricate thin nanocomposite films with high nanoparticle fillings suffer from random nanoparticle agglomeration causing formation of irregularly shaped nanostructured features within the composite. Another complication arises from cracks that develop during the fabrication of the films. Researchers have now described a simple method for fabricating thick, crack-free silica nanoparticle films by subsequent deposition of thin, crack-free silica nanoparticle multilayers.

Posted: Sep 26th, 2012