Ting Xu

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  www.azom.com/news.asp?newsID=15710 - [Cached Version]
  Published on: 2/19/2009    Last Visited: 2/22/2009  

  Russell conceived of this new approach with co-lead investigator Ting Xu, a UC Berkeley assistant professor with joint appointments in the Department of Material Sciences and Engineering and the Department of Chemistry.
  ...
  "The density achievable with the technology we've developed could potentially enable the contents of 250 DVDs to fit onto a surface the size of a quarter," said Xu, who is also a faculty scientist at Lawrence Berkeley National Laboratory.
  
  Xu explained that the molecules in the thin film of block copolymers - two or more chemically dissimilar polymer chains linked together - will self-assemble into an extremely precise, equidistant pattern when spread out on a surface, much like a regiment of disciplined soldiers lining up in formation.For more than a decade, researchers have been trying to exploit this characteristic for use in semiconductor manufacturing, but they have been constrained because the order starts to break down as the size of the area increases.
  
  Once the formation breaks down, the individual domains cannot be read or written to, rendering them useless as a form of data storage.
  
  To overcome this size constraint, Russell and Xu conceived of the elegantly simple solution of layering the film of block copolymers onto the surface of a commercially available sapphire crystal.
  ...
  "It's one thing to get dozens of soldiers to stand in perfect formation in an area the size of a classroom, each person equidistant from the other, but quite another to get tens of trillions of individuals to do so on the field in a football stadium," Xu added.
  ...
  "The challenge with photolithography is that it is rapidly approaching the resolution limits of light," said Xu."In our approach, we shifted away from this 'top down' method of producing smaller features and instead utilized advantages of a 'bottom up' approach.The beauty of the method we developed is that it takes from processes already in use in industry, so it will be very easy to incorporate into the production line with little cost."
  
  An added benefit, said Xu, is that "our technique is more environmentally friendly than photolithography, which requires the use of harsh chemicals and acids."
  
  Posted February 19th, 2009

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  www.technologyreview.com/computing/22209/ - [Cached Version]
  Published on: 2/20/2009    Last Visited: 2/24/2009  

  The catch is that the cylinders don't arrange themselves straight, says Ting Xu, a materials-science and engineering professor at the University of California, Berkeley, and one of the researchers on the new work. "They're randomly oriented with respect to the surface," she says.

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  www.eurekalert.org/pub_releases/2009-02/uoc--nmo021309. - [Cached Version]
  Published on: 2/19/2009    Last Visited: 2/19/2009  

  Russell conceived of this new approach with co-lead investigator Ting Xu, a UC Berkeley assistant professor with joint appointments in the Department of Material Sciences and Engineering and the Department of Chemistry.
  ...
  "The density achievable with the technology we've developed could potentially enable the contents of 250 DVDs to fit onto a surface the size of a quarter," said Xu, who is also a faculty scientist at Lawrence Berkeley National Laboratory.
  
  Xu explained that the molecules in the thin film of block copolymers - two or more chemically dissimilar polymer chains linked together - will self-assemble into an extremely precise, equidistant pattern when spread out on a surface, much like a regiment of disciplined soldiers lining up in formation. For more than a decade, researchers have been trying to exploit this characteristic for use in semiconductor manufacturing, but they have been constrained because the order starts to break down as the size of the area increases.
  
  Once the formation breaks down, the individual domains cannot be read or written to, rendering them useless as a form of data storage.
  
  To overcome this size constraint, Russell and Xu conceived of the elegantly simple solution of layering the film of block copolymers onto the surface of a commercially available sapphire crystal.
  ...
  "It's one thing to get dozens of soldiers to stand in perfect formation in an area the size of a classroom, each person equidistant from the other, but quite another to get tens of trillions of individuals to do so on the field in a football stadium," Xu added.
  ...
  "The challenge with photolithography is that it is rapidly approaching the resolution limits of light," said Xu. "In our approach, we shifted away from this 'top down' method of producing smaller features and instead utilized advantages of a 'bottom up' approach. The beauty of the method we developed is that it takes from processes already in use in industry, so it will be very easy to incorporate into the production line with little cost."
  
  An added benefit, said Xu, is that "our technique is more environmentally friendly than photolithography, which requires the use of harsh chemicals and acids."

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  news.zdnet.co.uk/emergingtech/0,1000000183,39617670,00. - [Cached Version]
  Published on: 5/7/2009    Last Visited: 5/7/2009  

  According to one of the researchers, Ting Xu of the University of California at Berkeley, the density achievable with the technology "could potentially enable the contents of 250 DVDs to fit onto a surface the size of a quarter" - about the size of a UK 10p coin.

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  technews.acm.org/archives.cfm?fo=2009-02-feb/feb-20-200 - [Cached Version]
  Published on: 2/20/2009    Last Visited: 4/5/2009  

  Russell created the new approach with UC Berkeley professor Ting Xu.
  ...
  Xu says the density achievable with the new technology could potentially allow the contents of 250 DVDs to be stored on a surface the size of a quarter. Russell and Xu discovered a new way to create block copolymers, chemically dissimilar polymer chains that join together by themselves.
  ...
  Xu says the molecules in block copolymers self-assemble into an extremely exact, equidistant pattern when spread on the surface. For over a decade, researchers have been trying to exploit this characteristic for semiconductor manufacturing, but have been limited because the order starts to break down as the size increases. Russell and Xu overcame this problem by laying the film of block copolymers onto the surface of a commercially available sapphire crystal, which, when cut at an angle and heated to 1,300 to 1,500 degrees Centigrade for 24 hours, reorganizes its surface into a highly ordered pattern that can be used to guide the self-assembly of block polymers.
  ...
  Russell and Xu were able to achieve defect-free arrays of nanoscopic elements with features as small as 3 nanometers, creating a density of 10 terabits per square inch.

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  www.firststopit.com/newsletters/2009/FSITMarch09Newslet - [Cached Version]
  Published on: 1/1/2009    Last Visited: 10/26/2009  

  Working with co-lead investigator Thomas Russell of UMass Amherst, Ting Xu of the University of California at Berkeley was able to create defect-free arrays with cell sizes as small as three nanometers.

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  www.azonano.com/news.asp?NewsID=14282 - [Cached Version]
  Published on: 10/22/2009    Last Visited: 10/31/2009  

  This electron micrograph shows a self-assembled composite in which nanoparticles of lead sulfide have arranged themselves in a hexagonal grid. Credit: Ting Xu, Lawrence Berkeley National Laboratory- UC Berkeley
  
  This electron micrograph shows a self-assembled composite in which nanoparticles of lead sulfide have arranged themselves in a hexagonal grid. Credit: Ting Xu, Lawrence Berkeley National Laboratory- UC Berkeley
  
  By adding specific types of small molecules to mixtures of nanoparticles and polymers, the researchers are able to direct the self-assembly of the nanoparticles into arrays of one, two and even three dimensions with no chemical modification of either the nanoparticles or the block copolymers. In addition, the application of external stimuli, such as light and/or heat, can be used to further direct the assemblies of nanoparticles for even finer and more complex structural details.
  
  "We've demonstrated a simple yet versatile approach to precisely controlling the spatial distribution of readily available nanoparticles over multiple length scales, ranging from the nano to the macro," says Ting Xu, a polymer scientist who led this project and who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California, Berkeley's Departments of Materials Sciences and Engineering, and Chemistry. "Our technique can be used on a wide variety of nanoparticle and should open new routes to the fabrication of nanoparticle-based devices including highly efficient systems for the generation and storage of solar energy."
  
  Xu is the corresponding author on a paper describing this work that has been published by the journal Nature Materials.
  ...
  "Precise control of the spatial organization of nanoparticles and other nanoscopic building blocks over multiple length scales has been a bottleneck in the bottom-up generation of technologically important materials," says Xu. "Most of the approaches that have been used so far have involved surface modifications."
  
  Small as they are, nanoparticles are essentially all surface so any process that modifies the surface of a nanoparticle can profoundly change the properties of that particle. Precisely arranging these nanoparticles is critical to tailoring the macroscopic properties during nanoparticle assembly. Although DNA has been used to induce self-assembly of nanoparticles with a high degree of precision, this approach only works well for organized arrays that are limited in size; it is impractical for large-scale fabrication. Xu believes a better approach is to use block copolymers - long sequences or "blocks" of one type of monomer molecule bound to blocks of another type of monomer molecule.
  
  "Block copolymers readily self-assemble into well-defined arrays of nanostructures over macroscopic distances," she says. "They would be an ideal platform for directing the assembly of nanoparticles except that block copolymers and nanoparticles are not particularly compatible with one another from a chemistry standpoint. A mediator is required to bring them together."
  
  Xu and her group found such a "mediator" in the form of small molecules that will join with nanoparticles and then able attach themselves and their nanoparticle partners to the surface of a block copolymer. For this study, Xu and her group used two different types of small molecules, surfactants (wetting agents) dubbed "PDP" and "OPAP. These small molecules can be stimulated by light (PDP) or heat (OPAP) to sever their connection to the surface of a block copolymer and be repositioned to another location along the polymeric chain. In this manner, the spatial distribution of the small molecule mediators and their nanoparticle partners can be precisely directed with no need to modify either the nanoparticles or the polymers.
  
  "The beauty of this technique is that it involves no sophisticated chemistry," says Xu. "It really is a plug and play technique, in which you simply mix the nanoparticles with the block copolymers and then add whatever small molecules you need."
  
  For this study, Xu and her colleagues added PDP or OPAP small molecules to various blends of nanoparticles, such as cadmium selenide and lead sulfide, mixed in with a commercial block copolymer - polystyrene-block-poly (4-vinyl pyridine). While she and her group worked with light and heat, she says other stimuli, such as pH, could also be used to reposition small molecules and their nanoparticle partners along block copolymer formations. Strategic substitutions of different types of stimulus-responsive small molecules could serve as a mechanism for structural fine-tuning or for incorporating specific functional properties into nanocomposites. Xu and her colleagues are now in the process of adding functionality to their self-assembly technique.
  
  "Bring together the right basic components - nanoparticles, polymers and small molecules - stimulate the mix with a combination of heat, light or some other factors, and these components will assemble into sophisticated structures or patterns," says Xu.

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  www.dailycollegian.com/scientists_at_umass_and_uc_berke - [Cached Version]
  Published on: 3/3/2009    Last Visited: 3/3/2009  

  Russell envisioned this new idea with co-lead investigator Ting Xu, a UC
  ...
  enable the contents of 250 DVDs to fit onto a surface the size of a quarter," said Xu.
  
  Here's how the nanotechnology works: Xu explained that the molecules in the thin film of block copolymers (two or more chemically dissimilar polymer chains linked together) self-assemble into an extremely precise, equidistant pattern when spread out on a surface.
  
  For more than a decade, researchers have been trying to exploit this characteristic for use in semiconductor manufacturing, but they have been constrained because the order starts to break down as the size of the area increases.
  
  Once the formation breaks down, the individual domains cannot be read or written to, rendering them useless as a form of data storage.
  
  To overcome this size constraint, Russell and Xu decided to layer the film of block copolymers onto the surface of a commercially available sapphire crystal.
  ...
  "It's one thing to get dozens of soldiers to stand in perfect formation in an area the size of a classroom, each person equidistant from the other, but quite another to get tens of trillions of individuals to do so on the field in a football stadium," Xu added.
  ...
  "The challenge with photolithography is that it is rapidly approaching the resolution limits of light," said Xu. "In our approach, we shifted away from this 'top-down' method of producing smaller features and instead utilized advantages of a 'bottom-up' approach. The beauty of the method we developed is that it takes from processes already in use in industry, so it will be very easy to incorporate into the production line with little cost."
  
  According to Xu, an added benefit is that "our technique is more environmentally-friendly than photolithography, which requires the use of harsh chemicals and acids."

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  2003 MRS Fall Meeting - Tutorial Program - [Cached Version]
  Published on: 2/13/2003    Last Visited: 11/25/2003  

  Ting XuUniversity of Massachusetts, Amherst

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  Gordon Research Conferences - 2009 Program... - [Cached Version]
  Published on: 7/2/2009    Last Visited: 7/2/2009  

  Discussion Leader: Ting Xu (University of California-Berkeley)

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