(July 14, 2010) — Rice University scientists have found the ultimate solvent for all kinds of carbon nanotubes (CNTs), a breakthrough that brings the creation of a highly conductive quantum nanowire closer.
Nanotubes have the frustrating habit of bundling, making them less useful than when they’re separated in a solution. Rice scientists led by Matteo Pasquali, a professor in chemical and biomolecular engineering and in chemistry, have been trying to untangle them for years as they look for scalable methods to make exceptionally strong, ultralight, highly conductive materials that could revolutionize power distribution, such as the armchair quantum wire.
The armchair quantum wire — a macroscopic cable of well-aligned metallic nanotubes — was envisioned by the late Richard Smalley, a Rice chemist who shared the Nobel Prize for his part in discovering the the family of molecules that includes the carbon nanotube. Rice is celebrating the 25th anniversary of that discovery this year.
Pasquali, primary author Nicholas Parra-Vasquez and their colleagues reported this month in the online journal ACS Nano that chlorosulfonic acid can dissolve half-millimeter-long nanotubes in solution, a critical step in spinning fibers from ultralong nanotubes.
Current methods to dissolve carbon nanotubes, which include surrounding the tubes with soap-like surfactants, doping them with alkali metals or attaching small chemical groups to the sidewalls, disperse nanotubes at relatively low concentrations. These techniques are not ideal for fiber spinning because they damage the properties of the nanotubes, either by attaching small molecules to their surfaces or by shortening them.
A few years ago, the Rice researchers discovered that chlorosulfonic acid, a "superacid," adds positive charges to the surface of the nanotubes without damaging them. This causes the nanotubes to spontaneously separate from each other in their natural bundled form.
This method is ideal for making nanotube solutions for fiber spinning because it produces fluid dopes that closely resemble those used in industrial spinning of high-performance fibers. Until recently, the researchers thought this dissolution method would be effective only for short single-walled nanotubes.
In the new paper, the Rice team reported that the acid dissolution method also works with any type of carbon nanotube, irrespective of length and type, as long as the nanotubes are relatively free of defects.
Parra-Vasquez described the process as "very easy."
"Just adding the nanotubes to chlorosulfonic acid results in dissolution, without even mixing," he said.
While earlier research had focused on single-walled carbon nanotubes, the team discovered chlorosulfonic acid is also adept at dissolving multiwalled nanotubes (MWNTs). "There are many processes that make multiwalled nanotubes at a cheaper cost, and there’s a lot of research with them," said Parra-Vasquez, who earned his Rice doctorate last year. "We hope this will open up new areas of research."
They also observed for the first time that long SWNTs dispersed by superacid form liquid crystals. "We already knew that with shorter nanotubes, the liquid-crystalline phase is very different from traditional liquid crystals, so liquid crystals formed from ultralong nanotubes should be interesting to study," he said.
Parra-Vasquez, now a postdoctoral researcher at Centre de Physique Moleculaire Optique et Hertzienne, Université de Bordeaux, Talence, France, came to Rice in 2002 for graduate studies with Pasquali and Smalley.
Study co-author Micah Green, assistant professor of chemical engineering at Texas Tech and a former postdoctoral fellow in Pasquali’s research group, said working with long nanotubes is key to attaining exceptional properties in fibers because both the mechanical and electrical properties depend on the length of the constituent nanotubes. Pasquali said that using long nanotubes in the fibers should improve their properties on the order of one to two magnitudes, and that similar enhanced properties are also expected in thin films of carbon nanotubes being investigated for flexible electronics applications.
An immediate goal for researchers, Parra-Vasquez said, will be to find "large quantities of ultralong single-walled nanotubes with low defects — and then making that fiber we have been dreaming of making since I arrived at Rice, a dream that Rick Smalley had and that we have all shared since."
Co-authors of the paper are graduate students Natnael Behabtu, Colin Young, Anubha Goyal and Cary Pint; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry, and Robert Hauge, a distinguished faculty fellow in chemistry, all at Rice; and Judith Schmidt, Ellina Kesselman, Yachin Cohen and Yeshayahu Talmon of the Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
The Air Force Office of Scientific Research, the Air Force Research Laboratory, the National Science Foundation Division of Materials Research, the Robert A. Welch Foundation, the United States-Israel Binational Science Foundation and the Evans-Attwell Welch Postdoctoral Fellowship funded the research.
Read the abstract at http://pubs.acs.org/doi/abs/10.1021/nn100864v
Category Archives: Flexible Displays
(July 8, 2010) — The FlexTech Alliance awarded a contract to the Western Michigan University (WMU) to create a user-friendly database for accessing technical information on functional materials for electronic display and flexible printed electronics.
The registry targets more timely, efficient, and accurate selection of the most appropriate material sets for flexible, printed electronics industry product developments, and serve all manufacturing platforms. The project is being funded in response to an identified critical industry need for more reliable performance and applications data on the variety of materials used in flexible, printed and organic (FPO) electronics applications. FlexTech’s quarterly workshops provided the forum to bring together industry experts to formulate and outline the initial needs behind this project.
Benefits to new materials developers and suppliers for contributing to the registry include:
- increased access to technical product information,
- greater visibility within the flexible electronics supply chain,
- a broadened customer base,
- and the listing of company products along with emerging competitor products in the industry.
Open access to this information will enable industrial and university communities to propagate the use of printed electronic technology. The Center for the Advancement of Printed Electronics (CAPE) at WMU is positioned to create this registry because of its dedication to developing printing as a low cost means for manufacturing electronic devices.
“Western Michigan University is honored to take on the task of creating this much needed registry of materials for the constituents of the printed electronics industry,” said Erika Hrehorova, Assistant Professor at WMU’s CAPE. “The supply chain is expanding for this developing industry and there are already a significant number of materials suppliers ranging from small start-ups to large corporations offering products to service the industry. With this project, we will consolidate available information about functional materials into a searchable database to assist technology developers and manufacturers to commercialize and grow their technologies.”
"FlexTech is pleased to award WMU a contract for the materials registry," stated Michael Ciesinski, chief executive officer for the FlexTech Alliance. "The creation of a searchable, web-accessible materials and process registry, segmented by functional types (e.g., conductors, semiconductors, dielectrics, substrates, barrier materials) and by manufacturing platforms (e.g., roll-to-roll, gravure, inkjet) will become an essential industry tool."
Entries to the database will include relevant non-proprietary information about the material itself (e.g., viscosity, electrical and optical properties, particle loading levels, formulation), information on processing (by manufacturing platform), information on curing conditions, and any special information that might be relevant for a given end application. Each entry will also specify the analytical methods used for data collection of the material’s properties.
“Michigan has long been a leader in manufacturing technologies, and this FlexTech grant to WMU’s Center for the Advancement of Printed Electronics will help bring additional cutting edge research to our state,” said Senator Carl Levin (D-MI). “This is a fine example of how Michigan’s higher education institutions are contributing to the nation’s research and development needs.”
The FlexTech Alliance program is a collaborative effort of private industry and the U.S. Army Research Laboratory, located in Adelphi, MD. It is devoted to fostering the growth, profitability and success of the electronic display and the flexible, printed electronics supply chain. For more information, visit www.flextech.org.
Center for the Advancement of Printed Electronics (CAPE) was formed to meet the multidisciplinary challenges of printed electronics. A team of 13 researchers from the Departments of Paper Engineering, Chemical Engineering and Imaging, Electrical and Computer Engineering, Manufacturing Engineering, Mechanical Engineering, Chemistry and Physics, Western Michigan University are currently working together on research funded through federal and state agencies, industry partners and a recently formed an Electronic Device Consortium. CAPE focuses on printing as a low cost means for manufacturing electronic devices. The emphasis is on technologies that can be used on a printing press, thus taking full advantage of the benefits printing can bring to electronics manufacture.
Read more about printed electronics:
Printed, flexible integrated circuits in real-world applications
September 25, 2009 – Several weeks ago researchers from the National Institute of Standards and Technology (NIST) and the U. of Maryland touted a method to overcome an obstacle in creating molecular switches: sandwiching organic molecules between silicon and metal. The work was published in the Journal of the American Chemical Society.
While the general concept of molecular switches isn’t new, the NIST/UMaryland work managed to achieve a molecular junction of a densely packed monolayer, chemically bonded to silicon and metal, using a nanoprinting method to help overcome the fragility and susceptibility of organic molecules to semiconductor manufacturing process steps — particularly the high temperatures of metal deposition for attaching to electrical contacts.
Previous efforts, NIST materials scientist Mariona Coll Bau told Small Times in an email exchange, used nanotransfer printing (nTP) to build electrodes on top of fully formed monolayers on materials (e.g. metal, dielectric, semiconductors), but it doesn’t work with the silicon generally used in manufacturing due to the reactive nature of the semiconductor surface. What Coll Bau and colleagues did was use a commercially available nTP to create an ultrasmooth gold surface, and (utilizing gold-thiol surface chemistry properties) "create[d] a well-ordered monolayer on the ultrasmooth Au with an exposed functional group capable of bonding to silicon." The same nTP tool was then used to bring the Au-monolayer together with a chemically cleaned silicon surface to bond the reactive groups — a process they dubbed "flip-chip lamination" (FCL). The flexible substrate also enables conformal contact over a large area to make uniform molecular junctions, she added.
The flip-chip lamination method creates an ultra-smooth gold surface (top), which allows the organic molecules to form a thin yet even layer between the gold and silicon. Gold surfaces created by other methods are substantially rougher (bottom), and would result in many of the molecular switches either being smashed or not contacting the silicon. (Credit: Coll Bau, NIST)
Thus, two challenges were addressed and solved, she explained: Making top electrical contact, with a process that produces a smooth, low-temperature, and conformal electrical contact; and making a dense monolayer chemically attached to silicon. "We utilize well studied Au-thiol chemistry to make highly ordered monolayers first, then attach to Si using FCL," Coll Bau said.
The ultimate goal of their work is a metal-molecule-silicon structure, she noted. Previous work started with silicon and formed a monolayer, followed by metal evaporation — but this was tricky because the monolayers were less dense (than those on Au) and harsh evaporation forms "many shorts and degrad[es] the molecular layers." Evaporation (on molecules on Si) could be replaced with the nanolamination process, she said, but that still leaves a less dense monolayer. "The nanolamination requires a sticky group at the end. Forming monolayers with two sticky groups (one functional group to react with the metal and one for the silicon) doesn’t work well on Si because both stick really well," she said — adding that thiols still well on Au, but not on other species.
Yet another conceivable method would be to evaporate the metal on plastic, form the monolayer on the metal, "and then squish it onto Si," she said. However, this generates a very rough Au layer with grains equal to or bigger than the molecule (see figures), "making it easy to short and hard to have a molecular junction where the electrical properties of the metal-molecule-Si are determined by the molecular layer."
Ultimately, they figured out to lift off the Au to get: an extremely smooth Au surface, shown to make the most dense bifunctional monolayers, and flexible enough to be squished onto the Si wafer and create uniform contacts with the molecules bonded to both Si and metal.
And there’s a bonus to the process, she pointed out. "This fabrication technique can be extended to patterned metal, different molecular layers, different metals and bottom substrates," she said. "In addition to bioelectronics, we could do graphene electronics, nanowires, organic crystals, etc."
August 25, 2009: The Nanoscale Science and Engineering Research Center for High-rate Nanomanufacturing, a joint venture pooling efforts from Northeastern, U. of Massachusetts/Lowell, and U. of New Hampshire, has received a five-year, $12.25M renewal grant from the National Science Foundation to continue its work with commercializing nanoscale scientific process.
Work going on at the center, centered at Northeastern in Boston, MA, runs the gamut from nanobiosensors for cancer detection to flexible solar cells to nanodrug-delivery systems to batteries to flexible electronics. It also investigates the environmental, economic, regulatory, social, and ethical impacts of nanomanufacturing.
In a statement, the center cited projections from the NSF of a $1 trillion market for nanotech products by 2015 — and that getting there will require perfecting mass-production techniques of nanostructures. “The collaborative research partnership between the Center and industry is accelerating the development of nanotechnology-based products that can impact a number of industries, including healthcare and energy,” stated Ahmed Busnaina, director of the Center and prof. of mechanical and industrial engineering at Northeastern. “Our research is developing more cost-effective, safe, and highly reliable processes that can be scaled up for large-scale manufacturing.”
Established in 2004, the Center now has more than 160 researchers and staff members working on developing nanoscale processes and applications. Leadership includes deputy director Joey Mead, prof. of plastics engineering at UMass Lowell; associate director Glen Miller, prof. of chemistry and director of UNH’s materials science program; associate director Carol Barry, prof. of plastics engineering at UMass Lowell; associate director Jackie Isaacs, prof. of mechanical engineering at Northeastern; and associate director Nick McGruer, prof. of electrical and computer engineering at Northeastern.
Under the three-year renewable agreement, Baxter will fund research-collaboration projects at Northwestern. Funding levels for each year may reach approximately $1 million, and Baxter will determine specific project funding levels on a case-by-case basis. Aligned with Baxter’s diversified business model, activities will focus on new therapeutics, biomedical and device engineering, biomaterials and drug-delivery technologies.
January 9, 2009: Using a simple chemical process, scientists at Cornell and DuPont have invented a method of preparing carbon nanotubes for suspension in a semiconducting “ink,” which can then be printed into such thin, flexible electronics as transistors and photovoltaic materials.
November 24, 2008: Hague Corp., a solar technology and quantum dot manufacturing company, has appointed Ghassen E. Jabbour to the position of chief science officer, to lead development and characterization of thin-film quantum dot solar cell products at recently acquired Solterra Renewable Technologies.
Jabbour is the director of flexible and organic electronics development at the Flexible Display Center (FDC) and has been a professor of chemical and materials engineering at Arizona State University since 2006. He is also the technical advisory board leader on Optoelectronic Materials, Devices, and Encapsulation at FDC. He has been selected to the Asahi Shimbun 100 New Leaders of the USA and has received the Presidential Award for Excellence from the Hariri Foundation in 1997. His research experience encompasses flexible-roll-to-roll-electronics and displays, smart textile, moisture and oxygen barrier technology, transparent conductors, organic light emitting devices, organic and hybrid photovoltaics, organic memory storage, organic thin film transistors, combinatorial discovery of materials, nano and macro printed devices, micro and nanofabrication, biosensors, and quantum simulations of electronic materials. He has authored and co-authored more than 300 publications and has edited several books and symposia proceedings involving organic photonics and electronics, and nanotechnology.
“We are extremely pleased to have someone as talented and accomplished as Dr. Jabbour join our team as CSO,” said Stephen Squires, president and CEO of Solterra, in a statement. “Ghassen’s deep understanding of nanotechnology and photovoltaics will drive our future product development.”
Cadmium selenide quantum dots manufactured by Solterra Renewable Technologies.
Oct. 8, 2008 – European R&D consortium IMEC says it has made first functional optical links embedded in a flexible substrate, paving the way toward optical sensing foils for use in monitoring irregular or moving surfaces.
Integrated optical interconnections are highly sensitive, but are insensitive to electromagnetic interference and are applicable in harsh environments. IMEC previously achieved embedded optical links on rigid surfaces last year. Its new work advances on this, by thinning standard GaAs photodetectors and VCSELs (vertical-cavity surface-emitting laser) down to 30μm and embedding them into a flexible foil of optical transparent material, and optically coupling them with embedded waveguides and out-of-plane micromirrors. IMEC says the resulting structure “shows good adhesion and flexible behavior.”
IMEC is looking to extend this technology into two types of sensors, array waveguide and optical fiber, both of which can be used for sensor foils. The former relies on the change in coupling between arrays of crossing waveguides. Two layers of polymer waveguides are separated by a thin layer of soft silicone;when pressure is applied to the foil the distance between the waveguides decreases and light is transmitted from one layer to the other. This is a low-cost sensor suited for high-density pressure sensors on small areas, IMEC notes.
The other type of sensor, optical sensing foils, combine integrated optical interconnections and flexible, stretchable electronics, to create a “skin-like” foil sensitive to touch, pressure, or deformation, with applications in medicine and industry. IMEC is currently working on this technology with partners in the EC’s 7th Framework project PHOSFOS (Photonic Skins For Optical Sensing) to develop photonic foils based on optical sensors.
(Source: IMEC)
June 18, 2008 — The U.S. Display Consortium (USDC), a public/private partnership chartered with developing the flat panel display (FPD) and flexible electronics industry infrastructure, today announced a significant expansion to its 8th annual Flexible Electronics and Displays Conference, which returns February 2-5, 2009. In addition to the three-day market and technical tracks, the conference now features a business investment summit and a variety of short courses.
The business investment summit, which will be held Monday, February 2, 2009, will address issues of relevance to industry innovators, manufacturers and investors in the flexible and printed electronics market. The all-day event will feature visionary and pragmatic talks from invited speakers, market research firms, investment banks and venture capital firms. Business plan presentations by public and private companies will round out the summit. “Connecting potential customers with product developers and the financial community is the theme for this inaugural business summit,” noted Dr. Kevin Cammack, USDC’s director of technical marketing and development, and organizer of the event. “The agenda is geared to stimulate discussion on near-term applications; challenges in getting products to market; and, the dynamics of constructing a profitable business model,” he added.
Multiple short courses are being planned prior to the conference opening in response to enthusiastic demand from previous short course offerings. The courses will reflect the variety of technologies being developed in flexible, printed electronics and will offer an excellent opportunity for collaboration between industry and academia. Six half-day courses, running concurrently, will be held on Monday, February 2, 2009.
Abbie Gregg of Abbie Gregg Inc. and Dan Gamota of Motorola return as the conference co-chairs. They are joined by Dieter Schroth, managing director of EMD Chemical’s new Materials Research Lab. According to Schroth, “USDC’s Flex Conference has evolved to become the leading North American event to learn about the latest developments in the emerging market in flexible and printed electronics. I’m delighted to be part of the team organizing the expanded conference.”
The 2009 Flex Conference will include three distinct tracks – a Fundamental Research Track with peer-reviewed abstracts and a full technical paper requirement (published by IEEE); a Business, Markets, Applied and Developmental Research Track with committee-reviewed abstracts; and a Student Research Poster Track with peer-reviewed abstracts, along with a competition for best poster. Conference sessions will focus on the emerging field of flexible, printed and organic electronics manufacturing, including printing processes and technologies, photovoltaics, solid-state lighting, OLEDs, RFID, sensors and flexible display applications and markets. A Call for Papers will be issued in early July 2008.
June 12, 2008 – Vitex Systems says it has achieved a “key breakthrough” in protecting flexible copper indium gallium selenide (CIGS) solar cells with its “Flexible Glass,” achieving 1100 hrs of testing in high-temperature and humidity conditions with stable efficiency.
CIGS has shown promise to achieve production efficiencies using low-cost roll-to-roll manufacturing, but like cadmium telluride (CdTe) cells they are sensitive to moisture and oxygen, and commercially-available flexible CIGS solar cells typically carry a lifetime guarantee of only a couple of years, the company notes. Encapsulating in rigid glass extends that lifetime but also adds weight and costs (production and shipping/installation) as well as less flexibility in packaging.
The CIGS cells used for the 1100hr tests at the Pacific Northwest National Laboratory were made on stainless-steel foil laminated with Vitex’s Flexible Glass 200 (thickness ~0.3mm) with a proprietary lamination process. Samples were exposed to damp heat (85°C, 85% relative humidity) for >1000 hrs. They were shown to maintain >98% of their original efficiency after 1100 hrs, exceeding requirements of the International Electrotechnical Commission’s (IEC) 61646 standard, the company noted.
Tests are continuing to determine the devices’ ultimate lifetime, though Vitex’s Chyi-Shan Suen, director of business development, notes that early internal tests have extended to >4000 hours under such conditions, maintaining ~80% of the cell’s original performance. The company is now seeking licensees to manufacture and commercialize the Flexible Glass 200 films to widen availability to more solar-cell manufacturers.
May 16, 2008 — Researchers at the National Science Foundation’s Nanoscale Science and Engineering Center for High-rate Nanomanufacturing (CHN) at Northeastern University — with partners UMass Lowell and University of New Hampshire — say they have discovered “an innovative technology that will have a tremendous impact on the nanotechnology industry.”
Under the direction of Ahmed Busnaina, Ph.D., researchers developed a technique to scale-up the directed assembly of single-walled carbon nanotube (SWNT) networks, from microns to inches, creating a viable circuit template that can be transferred from one substrate to another (say, silicon to polymer) in continuous or batch processes. According to CHN, devising methods to create nanoscale structures, and to mass-produce those them while ensuring reliability and cost-effectiveness, are top priorities for the nanotechnology industry. The center’s approach for assembling nanoelements (nanotubes, nanoparticles, etc.) into structures will lead to the production of devices such as biosensors, batteries, memory devices and flexible electronics quickly and efficiently and with minimal error, they say.
“This technology is a platform for many applications, and the fact that it is scalable makes it easier to bring to market,” said Busnaina, William Lincoln Smith Professor and Director of the CHN. “The cost of current nanomanufacturing techniques is sky high, and our product has the potential to increase productivity tremendously without sacrificing reliability.”
Concurrently, researchers at the CHN are investigating the environmental and biological implications to ensure that these devices and techniques are safe for people and for the environment.
The work will be on display at Booth #211 at the upcoming NSTI Nanotech 2008 conference in Boston, June 1-5, 2008. For more information about SWNT research at Northeastern, contact Jenny Eriksen.