From 2-D blueprint, material assembles into novel 3-D nanostructuresJanuary 30, 2006An international team of scientists affiliated with the University of Wisconsin-Madison Nanoscale Science and Engineering Center has coaxed a self-assembling material into forming never-before-seen, three-dimensional nanoscale structures, with potential applications ranging from catalysis and chemical separation to semiconductor manufacturing. Led by UW-Madison chemical and biological engineering professors Paul Nealey and Juan de Pablo and colleagues at Georg-August University in Germany and the Paul Scherrer Institute in Switzerland, the team has discovered that materials known as block copolymers will spontaneously assemble into intricate 3-D shapes when deposited onto particular 2-D surface patterns created with photolithography. The result, published in the Jan. 27 issue of Physical Review Letters, demonstrates a promising strategy for building complex, 3-D nanostructures by using standard tools of the semiconductor industry, says Nealey. Those tools, particularly lithography, already allow the making of devices with dimensions substantially smaller than 100 nanometers, or a hundred-thousandth of a centimeter. But photolithography is also limited, he says, because as practiced today it is essentially a two-dimensional process. "What we've done by using self-assembling block copolymers is to extend photolithography to three dimensions," says Nealey. "And the structures we've fabricated are completely different from the same block copolymer materials in the bulk." Also important to manufacturing, the new 3-D nanostructures are stable, well defined and nearly defect-free over large areas. They also align perfectly with the underlying lithographic pattern-a key requirement for any device or application based on them. "This research shows that lithography combined with block copolymers is more versatile and powerful than we thought. We can now create completely new structures that will no doubt have new properties and new applications," says de Pablo. "Exactly what those structures will be is anybody's guess; here we demonstrate a complicated one. But the important thing is they open up a new field of exploration, both for these materials and this technology." The specific structures the team produced were composed of two tightly interwoven, yet completely independent, networks of channels and passages-all at the scale of atoms. "What we have are two interpenetrating meshes, both of which are completely continuous. And yet you could travel through one from end to end without ever entering the other," says de Pablo. The networks are also in perfect register with the photolithographic pattern underneath, which tells scientists exactly where each channel ends and gives them ready access to channel openings. A gas, for example, might be introduced through the openings to react with a catalyst deposited on the walls of the network. Nanoscale materials have massive surface areas compared to their volumes; thus, catalysis would be extremely efficient. Another use would be chemical separation of substances of different sizes. "This process gives us exquisite control over the dimensions of pores," says de Pablo. "So, we could easily make membranes that are permeable to substances smaller than the length scale of the material." The researchers study specific block copolymers consisting of long chains of two different types of molecules, which alternate with each other in blocks. At high temperature, block copolymers are molten and randomly mixed. But when cooled down, the material spontaneously assembles into alternating layers of molecules. University of Wisconsin-Madison |
|||||||||||||||||||||
| Related Nanostructures Current Events and Nanostructures News Articles Understanding mechanical properties of silicon nanowires paves way for nanodevices Silicon nanowires are attracting significant attention from the electronics industry due to the drive for ever-smaller electronic devices, from cell phones to computers. Engineers image nanostructure of a solid acid catalyst and boost its catalytic activity The catalytic processes that facilitate the production of many chemicals and fuels could become much more environmentally friendly thanks to a breakthrough achieved by researchers from Lehigh and Rice Universities. LANL Roadrunner simulates nanoscale material failure Very tiny wires, called nanowires, made from such metals as silver and gold, may play a crucial role as electrical or mechanical switches in the development of future-generation ultrasmall nanodevices. Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise. Berkeley Researchers Find New Route to Nano Self-Assembly If the promise of nanotechnology is to be fulfilled, nanoparticles will have to be able to make something of themselves. An important advance towards this goal has been achieved by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) who have found a simple and yet powerfully robust way to induce nanoparticles to assemble themselves into complex arrays. Caltech scientists solve decade-long mystery of nanopillar formations Scientists at the California Institute of Technology (Caltech) have uncovered the physical mechanism by which arrays of nanoscale (billionths-of-a-meter) pillars can be grown on polymer films with very high precision, in potentially limitless patterns. Harvard scientists bend nanowires into 2-D and 3-D structures Taking nanomaterials to a new level of structural complexity, scientists have determined how to introduce kinks into arrow-straight nanowires, transforming them into zigzagging two- and three-dimensional structures with correspondingly advanced functions. Smallest Nanoantennas for High-speed Data Networks More than 120 years after the discovery of the electromagnetic character of radio waves by Heinrich Hertz, wireless data transmission dominates information technology. Penn team uses self-assembly to make molecule-sized particles with patches of charge Physicists, chemists and engineers at the University of Pennsylvania have demonstrated a novel method for the controlled formation of patchy particles, using charged, self-assembling molecules that may one day serve as drug-delivery vehicles to combat disease and perhaps be used in small batteries that store and release charge. 'NanoPen' may write new chapter in nanotechnology manufacturing Researchers in California are reporting development of a so-called "NanoPen" that could provide a quick, convenient way of laying down patterns of nanoparticles - from wires to circuits - for making futuristic electronic devices, medical diagnostic tests, and other much-anticipated nanotech applications. More Nanostructures Current Events and Nanostructures News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||