The demand for antimicrobial coatings is growing at a fast pace. In the U.S. alone, the market for these products is expected to grow from $175 million in 2005 to over $550 million in 2012. This market is not only driven by the urgent need of hospitals to reduce infections, although it would appear that they need it most: the U.S. Centers for Disease Control and Prevention (CDC) estimates that the infections acquired in hospitals alone affect approximately 2 million persons annually. In the U.S., between 44,000 and 98,000 people die every year from infections they picked up in hospitals. With a growing concern about the role of contaminated surfaces in the spread of infections such as SARS and MRSA, antimicrobial surfaces have become popular in such areas as consumer products, public spaces such as schools and offices, and public transportation. While many conventional antibacterial coatings release their antimicrobials over time (either controlled or uncontrolled) and thereby lose their antimicrobial efficiency, researchers have now developed a unique multifunctional biomimetic material comprised of carbon nanotubes, DNA, and lysozyme that has robust mechanical properties and exhibits excellent long-term antimicrobial activity.
The addition of carbon nanotubes (CNTs), both single-walled and multi-walled, to various polymer matrices has produced significant improvements in strength and stiffness. Reinforcing materials based on CNTs could be used to fabricate more complex nanostructures by making them tougher and stronger. As is the case so often, and covered quite extensively here at Nanowerk nature has served as an inspiring source of various morphologies and composite materials for nanotechnology techniques. New work by Spanish scientists demonstrates the fabrication of novel nanostructures that resemble magnificent sea anemones (heteractis magnifica), aiming at increasing the rigidity and the available surface of magnetic and reinforced CNTs-based hollow capsules.
Since its discovery in 2004, graphene has created quite a buzz among scientists. The reason they are so excited is that two-dimensional crystals (it's called 2D because it extends in only two dimensions - length and width; as the material is only one atom thick, the third dimension, height, is considered to be zero) open up a whole new class of materials with novel electronic, optical and mechanical properties. For instance, the ultimate size limit for a nano-electromechanical system would be a nanoscale resonator that is only one atom thick, but this puts severe constraints on the material; as a single layer of atoms, it should be robust, stiff, and stable. Graphene, the simplest of the 2D conjugated carbon nanomaterials, could fit that bill. One hurdle for researchers is that current methods for the synthesis of two-dimensional, carbon-rich networks have many limitations including lack of molecular-level control and poor diversity. In a step to overcome these obstacles, researchers have now developed new synthetic strategies for forming monolayer films of conjugated carbon, in various configurations ranging from flat 2D sheets, to balloons, tubes and pleated sheets.
The controlled patterning of surfaces with biomolecules is of great importance for future generations of micro and nano biodevices (e.g. biochips, BioMEMS, lab-on-a-chip) and biomaterials. Even with current state-of-the-art technology, this patterning requirement, i.e. the immobilization and controlled and precise placement of biomolecules, often is a limiting step in the fabrication process. Commonly applied substrate materials for such biodevice applications are inexpensive polymers; but polymer surfaces are complex to chemically pattern in larger numbers. By combining two known techniques, micro-contact printing and injection molding in a new, innovative way, researchers in Denmark have now demonstrated a surprisingly successful methodology for transferring micro- and nanoscopic patterns of functionally active proteins to polymer surfaces during injection molding of hot polymer melt.
Nanotechnology researchers have appropriated the name of Janus - the Roman god of gates and doorways, usually depicted with two heads looking in opposite directions - to name a class of amphiphilic (i.e. containing both hydrophobic and hydrophilic portions) nanoparticles composed of two fused hemispheres, each made from a different substance. Their particular structure makes Janus particles an intriguing subject for exploring novel anti-cancer therapies where they, for instance, carry two different and complementary medicines. In a novel use of Janus particles, researchers have now isolated a means of using them to make 're-sealable' pores in lipid bilayer membranes. Described in another way, the localization of the nanoparticles in the pore can be thought of as the placement of a zipper, which allows a specific slit to be opened or closed at will.
As far as test tubes go, it doesn't get any smaller than a single-walled carbon nanotube (SWCNT). Among the wide range of interesting properties exhibited by SWCNTs is their capacity to encapsulate molecules within their quasi one-dimensional cavity. The confinement offered by the nanotube could serve as a nanoscale test tube to constrain a chemical reaction. This was demonstrated in principle back in 1998, when the coalescence of adjacent fullerenes was observed by transmission electron microscopy. In the following years, scientists have extensively experimented with filling nanotubes with other fullerenes, atoms, molecules and, very recently, with organic molecules. Owing to their large variety with diverse chemical properties, the incorporated organic molecules can tune the properties of the SWCNTs. Scientists are intrigued by the possibilities that SWCNTs' use as a reaction tube offers for chemistry at the nanoscale. Nanochemistry - a key to control self-assembly processes prerequisite for nanotechnology - in essence would produce stable chemical reactions inside a confined nanoscale space. Encapsulated inside this nanoscale space, molecules are isolated from the outside environment, which allows one to identify and control the source and incidence of chemical reactions. Recent work has demonstrated this new chemistry by using SWCNTs as a nanometer-scale reaction furnace.
In the past, random defects caused by particle contamination were the dominant reason for yield loss in the semiconductor industry - defects occur in the patterning process (so-called process defects) when contaminants become lodged in or on the wafer surface. Trying to prevent such fabrication defects, chip manufacturers have spent much effort and money to improve the fabrication process, for instance by installing ultra-clean fabrication facilities. With the semiconductor industry's move to advanced nanometer nodes, and feature sizes approaches the limitation of the fabrication method used, particles are no longer the only problem for chip manufacturers. In a nanoscale feature-size fabrication environment, systematic variations, such as metal width and thickness variations or mask misalignment, are also major contributors to yield loss. Rather than perfecting a nanostructure by improving its original fabrication method, researchers at Princeton University have demonstrated a new method, known as self-perfection by liquefaction (SPEL), which removes nanostructure fabrication defects and improves nanostructures after fabrication.
Future nanomanufacturing processes will rely on two basic principles: a combination of chemical synthesis and self-assembly on one hand and robotic nanofabrication on the other. While the former is a controlled 'natural' process relying on chemistry and self-organization principles of nature, the latter will be an industrial process similar in concept to today's automated manufacturing assembly lines. Robotic assembly lines in modern factories have come a long way since the early 20th century when Henry Ford first used an assembly line on an industrial scale for his Model T automobile. Nevertheless, the principle is the same. Rather than having a single craftsman or team of craftsmen create each part of a product individually and assemble them together into a single item, an assembly line is a (often completely automated) manufacturing process in which interchangeable parts are added to a product in a sequential manner to create a finished product. While sporadic automation of certain tasks has already begun (for instance, automated microrobotic injection of foreign materials into biological cells), nanotechnology techniques today are pretty much where the industrial world was before Ford's assembly line - a domain of highly skilled artisans and not of automated mass production. It has long been a dream for nanotechnologists that robots could one day be used in an assembly line type of process to manufacture nanodevices. Researchers are beginning to develop the first rudimentary nanomanipulation devices that could lead to future automated manufacturing systems. Now, a team of scientists in Canada have reported the first demonstration of closed-loop force-controlled grasping at the nanonewton level.