Showing Spotlights 1985 - 1992 of 2140 in category (newest first):
Adhesives may be broadly divided in two classes: structural and pressure sensitive. To form a permanent bond, structural adhesives harden via processes such as evaporation of solvent or water (white glue), reaction with radiation (dental adhesives), chemical reaction (two part epoxy), or cooling (hot melt). In contrast, pressure sensitive adhesives (PSAs) form a bond simply by the application of light pressure to attach the adhesive to the adherend. PSAs adhere instantly and firmly to nearly any surface under the application of light pressure, without covalent bonding or activation. Waterborne pressure-sensitive adhesives solve the problem of meeting environmental regulations that forbid the emission of volatile organic compounds in manufacturing. However, often waterborne PSAs have poor adhesive performance. Another problem, particularly relevant to display technologies, is how to make an electrically-conducting material that is also flexible and optically transparent. Indium tin oxide is commonly used as a transparent electrode in displays, but it is brittle and prone to mechanical failure or scratching. Adhesives can be made electrically conductive through the addition of metal particles, but then they lose optical transparency, and their adhesiveness is diminished. New research shows that waterborne PSAs containing single-wall carbon nanotubes (SWNTs) meet the requirements of environmental regulations while improving the adhesive performance. The resulting unprecedented combination of adhesion and conductivity properties holds enormous potential for demanding applications in displays and electronics.
Oct 24th, 2006
Nanotechnology has recently found practical applications in the conservation and restoration of the world's cultural heritage. Nanoparticles of calcium and magnesium hydroxide and carbonate have been used to restore and protect wall paints, such as Maya paintings in Mexico or 15th century Italian masterpieces. Nanoparticle applications were also used to restore old paper documents, where acidic inks have caused the cellulose fibers to break up, and to treat acidic wood from a 400-year-old shipwreck.
Oct 23rd, 2006
Sophisticated biomolecular motors have evolved in nature, where motor proteins actively control the delivery and assembly of materials within cells. In contrast, the development of synthetic nanomotors is in its infancy. Such nanomotors are currently explored for an increasing number of applications in hybrid bionanodevices. Along these lines, gliding motility assays, where reconstituted microtubule filaments are propelled over a substrate by surface-attached motor proteins, have been used to transport micro- and nanosized objects, such as small beads, quantum dots or DNA molecules. However, one prerequisite for controllable nanotransport is the reliable guiding of filament movement along predefined paths, a challenging task that has recently been achieved only via costly and labor-intensive topographical surface modifications. Researchers have now demonstrated a novel approach for the nanostructuring of surfaces with functional motor proteins. In contrast to all other current methods, their approach allows the three-dimensionally oriented deposition of proteins on surfaces, being the result of first binding them to the highly oriented and regulated structures of microtubules and then transferring them to the surface.
Oct 20th, 2006
Nucleoside analogues, which are a class of therapeutic agents, display significant anticancer or antiviral activity by interfering with DNA synthesis. They work by incorporating into the elongating DNA strands and terminating the extension process. However, they also affect normal cell growth, such as bone marrow cells, so there can be significant toxic effects. Further limitations to their use are relatively poor intracellular diffusion, rapid metabolism, poor absorption after oral use, and the induction of resistance. French and Italian researchers have now come up with a completely new approach to render anticancer and antiviral nucleoside analogues significantly more potent. By linking the nucleoside analogues to squalene, a biochemical precursor to the whole family of steroids, the researchers observed the self-organization of amphiphilic molecules in water. These nanoassemblies exhibited superior anticancer activity in vitro in human cancer cells.
Oct 19th, 2006
Paper manufacturing is one of the mainstays of economic infrastructure and paper products influence many aspects of business and personal life. Pulping, process chemistry, paper coating, and recycling are key areas that can benefit from nanotechnology methods. One such method, layer-by-layer (LbL) assembly, is of great interest of its usage in the field of nanocoating. It allows creating nanometer-sized ultrathin films both on large surfaces and on microfibers and cores with the desired composition. Researchers at Louisiana Tech University have developed a simple and cost effective technique to fabricate an electrically conductive paper by applying layer-by-layer nanoassembly coating directly on wood microfibers during paper making process. Nanocoated wood microfibers and paper may be applied to make electronic devices, such as capacitors, inductors, and transistors fabricated on cost-effective lignocellulose pulp. The use of a conductive nanocoating on wood fibers can open the door for the future development of smart paper technology, applied as sensors, communication devices, electromagnetic shields, and paper-based displays.
Oct 18th, 2006
Controlling the shape of nanostructures is one of the challenging issues presently faced by synthetic chemists and materials engineers. Various shapes of nanomaterials, such as sphere-, rod-, wire-, triangle-, cube-, and tube-outlines have been synthesized by various approaches. However, to produce nanostructures with high monodispersity is still one of the major issues to be solved. Most work in this area focused on inorganic or synthetically organic materials. Using pure biomolecules to produce nano- or micro-structures, without the assistance of inorganic materials, is rare. Biocompatible nanospheres have been and remain of intense interest for biosensor, drug delivery, and biomedical contrast imaging. A new research report coming out of China now shows that highly monodispersed nanospheres of cystine (a sulfur-containing amino acid) aggregate were successfully produced by a quite simple method without the assistance of any other inorganic materials. This work could be of great significance in the production of nanomaterials, biosensors, and drug delivery.
Oct 17th, 2006
As the semiconductor industry continues to miniaturize in following Moore's Law, there are some real challenges ahead, particularly in moving deeper and deeper into the nano length scale. In particular, sustaining the traditional logic MOSFET (metal-oxide-semiconductor field-effect transistor) structure, design, and materials composition will be especially difficult, particularly beyond the 22 nm node. Nanocables, consisting of a range of materials, offer potential solutions to these problems and may even be an alternative to today's MOSFET. A group of researchers from several European countries now reports the synthesis of a magnetically tunable nanocable array, combining separate hard and soft magnetic materials in a single nanocable structure. The combination of two or more magnetic materials in such a radial structure is seen as a very powerful tool for the future fabrication of magnetoresistive, spin-valve and ultrafast spin-injection devices with nonplanar geometries.
Oct 16th, 2006
With the advent of nanoscience and technology, a new area has developed in the area of textile finishing called "Nanofinishing". Growing awareness of health and hygiene has increased the demand for bioactive or antimicrobial and UV-protecting textiles. Coating the surface of textiles and clothing with nanoparticles is an approach to the production of highly active surfaces to have UV blocking, antimicrobial, flame retardant, water repellant and self-cleaning properties. While antimicrobial properties are exerted by nano-silver, UV blocking, self-cleaning and flame-retardant properties are imparted by nano-metal oxide coatings. Zinc oxide (ZnO) nanoparticles embedded in polymer matrices like soluble starch are a good example of functional nanostructures with potential for applications such as UV-protection ability in textiles and sunscreens, and antibacterial finishes in medical textiles and inner wears.
Oct 13th, 2006