A novel approach to synthesizing nanowires (NWs) allows their direct integration with microelectronic systems for the first time, as well as their ability to act as highly sensitive biomolecule detectors that could revolutionize biological diagnostic applications, according to a report in Nature.   “We electronically plugged into the biochemical system of cells,” said senior author Mark Reed, Harold Hodgkinson Professor of Engineering & Applied Science. “These developments have profound implications both for application of nanoscience technologies and for the speed and sensitivity they bring to the future of diagnostics.”

An interdisciplinary team of engineers in the Yale Institute for Nanoscience and Quantum Engineering has overcome hurdles in NW synthesis by using a tried-and-true process of wet-etch lithography on commercially available silicon-on-insulator wafers. These NWs are structurally stable and demonstrate an unprecedented sensitivity as sensors for detection of antibodies and other biologically important molecules.  According to Reed, not only can the NWs detect extremely minute concentrations (as few as 1000 individual molecules in a cubic millimeter), they can do it without the hazard or inconvenience of any added fluorescent or radioactive detection probes.

The study demonstrated ability of the NWs to monitor antibody binding, and to sense real-time live cellular immune response using T-lymphocyte activation as a model. Within approximately 10 seconds, the NW could register T-cell activation as the release acid to the device. The basis for the sensors is the detection of hydrogen ions or acidity, within the physiological range of reactions in the body. Traditional assays for detection of immune system cells such as T cells or for antibodies usually take hours to complete.

“The ability to differentiate between immune system cells based on their function and with label-free reagents is key for rapid and reliable diagnostics as well as for advancing basic science,” said co-author Tarek Fahmy, assistant professor of biomedical engineering. “These nanosensors can replace current technology with a solid-state device and the results promise to radically change the way we assay for these cells.”

“The sensor is essentially on the size scale of the molecules it is designed to sense,” said lead author Eric Stern, a graduate student whose thesis work has focused on designing and building nanoscale chemical and biological sensors. His project was funded by the Department of Defense and placed high importance on the capability of detecting multiple molecules, including pathogens.  “You can think of the process of making the nanowires as sculpting. It can either be done by working down from the rock or up from the clay — we carved down from the rock,” said Fahmy. “Previous approaches used the equivalent of a hacksaw, we used a molecular chisel. We were able to make exactly what we wanted with the most traditional technology out there.”

According to Stern, “We not only got the high quality smooth surface we wanted, but we were also able to make them smaller than we originally defined. Using the robust ‘old fashioned’ technology of lithography gives us manufacturing uniformity. The authors say that although this study focuses on device and sensor performance, the strength of the approach lies in seamless integration with CMOS technology, and the approach “appears to have potential for extension to a fully integrated system, with wide use as sensors in molecular and cellular arrays.”

“This project is a powerful demonstration of what we are trying to achieve in the Yale Institute of Nanoscience and Quantum Engineering,” said Paul Fleury, Dean of Engineering and Director of the Institute. “It was a remarkable collaboration, of biomedical, electrical and mechanical engineering with chemistry and applied physics, that worked for all of us. And a dedicated graduate student with a focused idea made it happen.”

The Commission has called on member states to respect the precautionary principle in research on nanoscience in order to anticipate its potential environmental, health and safety impacts.  “Member states should apply the precautionary principle in order to protect not only researchers, who will be the first to be in contact with nano-objects, but also professionals, consumers, citizens and the environment in the course of N&N research activities,” states the Commission code of conduct for responsible nanosciences and nanotechnologies (N&N) research, adopted on 7 February 2008.

The Commission recommends that member states follow the general principles and guidelines for actions outlined in the code “as they formulate, adopt and implement their strategies for developing sustainable nanosciences and nanotechnologies (N&N)”. Member states are also asked to encourage the voluntary adoption of the code by relevant national authorities, research funding bodies and researchers. They are also expected to use the document to promote dialogue at all governance levels to increase understanding and involvement by the general public in the development of new technologies.

The code of conduct recommends that all N&N research activities be conducted in respect of a set of seven principles. According to these, all activities should:
* Respect fundamental rights and be conducted in the interest of the well-being of individuals and society;
* be safe for people and the environment;
* be ethical and contribute to sustainable development;
* be conducted in accordance with the precautionary principle;
* be guided by the principles of openness to all stakeholders, transparency and respect for the legitimate right of access to information;
* meet the best scientific standards, including integrity of research and good laboratory practices, and;
* encourage maximum creativity and flexibility for innovation and growth.

In addition, the code suggests that “researchers and research organisations should remain accountable for the social, environmental and human health impacts of their work”.

Stakeholder adoption of the code will be monitored annually. The code will be reviewed every two years “to take into account developments in N&N worldwide and their integration into European society”.  The code is a regulation and thus not legally binding. Therefore, member states can decide to grant a wider or narrower measure of protection regarding nanotech research than recommended in the code.

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Background:
With nanotech products already under mass production in areas such as food, electronics and cosmetics, the political debate on regulating nanotechnologies has only just begun. A lack of scientific knowledge and the absence of evidence of the health and safety hazards of nanotechnology, however, make regulation impossible.  No government in the world has, to date, developed a specific nanotech regulation but all stakeholders agree that more research on the health and environmental risks posed by nanoparticles is needed to ensure that asbestos-like scandals do not come back to haunt nanotech companies in the future.

The Commission organised, in summer 2007, a consultationPdf external on a code of conduct for responsible nanosciences and nanotechnology research, seeking input for a specific Recommendation on the issue. Drafting the code is also part of the Commission’s ambition “to promote a balanced diffusion of information on nanotechnology and foster an open dialogue”. The code was announced in the EU’s nanosciences and nanotechnology

Delft Technology University (TU Delft) in the Netherlands, has decided to create a new bionanoscience department in a clear indication of what it feels is one of the key up and coming scientific fields. Over the next decade, TU Delft will invest €10m derived from its assets in the new department, which will form part of the university’s Kavli Institute of Nanoscience. The Kavli Foundation will also donate $5m (€3.4m).

The university has said that it believes this research field has a bright future and clearly it wants in on the act now to enhance its own profile.

Bionanoscience is the discipline where biology and nanoscience meet, where scientists examine the molecular building blocks of living cells and nanotech that can precisely depict, study and control those molecules in order to gain new insight in the workings of cells. The new department will explore the full spectrum from nanoscience to cell biology to synthetic biology to create gene regulation systems, artificial biomolecules and nanoparticles that can be deployed within the cell.

“Cell biology is becoming increasingly an engineering discipline: the traditional approach of the biologist is rapidly changing into that of the engineer,” TU Delft said in a statement. The new department will work closely with the Nanoscience and Biotechnology departments and will ultimately be the same size as the existing departments in the Faculty of Applied Sciences. To this end, the “next few years” will see an intensive recruitment drive to attract around 15 top scientists to the department, according to the university.

Initial steps have already been taken towards creating structural European cooperation: the prestigious European Molecular Biology Laboratory (EMBL) in Heidelberg has told the university it is happy to work together with researchers in the new department. “EMBL is a major potential partner, in particular in view of the EMBL’s expertise in the field of molecular cell biology,” it said. Further discussions on cooperation will be held with representatives from EMBL during a Kavli-EMBL workshop in Delft on 12 and 13 February.

TU Delft is following in the footsteps of the University of Bristol in the UK, the University of Leeds, which both have their own bionanoscience departments. Scientists at the University of Manchester, also in the UK, are studying bionanoscience in its Interdisciplinary Biocentre. The Lawrence Livermore National Laboratory in the US also has several bionanoscientists on its books. The bi-annual Journal of Bionanoscience celebrated its inaugural issue in June 2007.

The Naughton Institute, a €100 million state-of-the-art new science facility at Trinity College Dublin which will house Ireland’s first purpose-built nanoscience research institute, the Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and the world’s first Science Gallery was officially opened by the Taoiseach, Bertie Ahern TD, at 4pm, January 23, 2008. CRANN has received substantial government investment, €74 million of which has come in research grants through Science Foundation Ireland (SFI).

Taoiseach, Bertie Ahern TD, said on the occasion of the opening: “I am delighted to have been asked to officially open the Naughton Institute at Trinity College. This is a state-of-the-art facility. It will house Ireland’s first purpose-built nanoscience research institute, the Centre for Research on Adaptive Nanostructures and Nanodevices. The Government has made a substantial funding commitment to nanoscience research through Science Foundation Ireland (SFI) among others. Our overall aim is to translate the considerable National Development Plan investment in this area into a tangible return, in terms of quality jobs, knowledge output and Irish competitiveness.”

Commenting on the significance of the nanoscience research institute for Ireland, TCD Provost, Dr John Hegarty said: “Nanoscience has the potential to change our lives in unforeseeable ways in the coming decades. Imagine being able to diagnose up to 20 cancers through one finger prick of blood through ‘lab on a chip’ nanotechnology. Or powering entire cities with wind or solar energy thanks to carbon nanotube electrical conductors. Or through refined chemotherapy, targeting only cancer cells and not large sections of your body. These are all possible through nanoscience which is the study of nanoscale objects less than 100 nanometres – a nanometre is one million times smaller than a millimetre. New technologies emerging from nanoscience are set to yield the next generation of microelectronics, drug delivery systems, medical imaging techniques among many other areas”.

“Trinity’s CRANN is an internationally leading nanoscience research institute committed to delivering world-class science research at the forefront of industry and innovation. Ireland is ranked 6th globally for the impact of its nanoscience research. There is now a real opportunity for CRANN to lead Ireland’s activity and play a key role in these developments by linking world class university research with the challenges faced by industry ”.
In relation to the Science Gallery, the Provost, Dr John Hegarty, added: “Through our Creativity in the Community programme, Trinity College is committed to engaging the public and in particular young people with the activities of the university and of science. This takes a significant step forward through the delivery of the Naughton Institute and the new Science Gallery – the first phase of our Pearse Corridor Development. The Science Gallery is a flagship national initiative which will probe major scientific issues through a programme of innovative and interactive exhibitions, workshops, events and debate. As a vibrant new public science cultural centre, celebrating science, and technology, it will focus on connecting with the 15-25 age group, firing up these young people to develop a passion for science. ”
The Science Gallery will open next week (February 2) with LIGHTWAVE – a spectacular 9-day festival which will explore light in science, technology and art. Featuring among others an installation by U2’s lighting designer, Willie Williams, LIGHTWAVE will also include an exciting range of events and workshops by world renowned scientists, artists and engineers.

The Naughton Institute is a state-of-the-art facility comprising five storeys over basement. Wilson Architects, specialists in nanoscience research buildings, in conjunction with RKD designed environmentally controlled, vibration-free laboratories for the specific purpose of the study of nanoparticles. The building has been named the Naughton Institute in recognition of the generous support provided by Dr Martin Naughton, Chairman of the Glen Dimplex Group. Other funding bodies which have contributed to the building include SFI, the Department of Enterprise, Trade and Employment among others.

SFI in particular, has invested a total of €74 million which includes capital funding as part of its commitment to nanoscience research in CRANN. This includes funding for the original Centre for Science, Engineering & Technology (CSET) award and a significant number of Principal Investigator awards to researchers based in CRANN, all of whom have been assessed under the international peer review system operated by SFI.

Trinity’s researchers in CRANN are developing groundbreaking research which has the potential of enabling revolutionary development in both the information and communication technology and health care sectors. It is providing solutions which will drive the miniaturisation of existing technologies resulting in more powerful and multifunctional mobile electronics. Applied to health, nanoscience research in CRANN has the potential of radically improving patient care through the development of improved diagnostics for cancer and disease. Approximately 150 researchers, postgraduates and technicians are currently working at CRANN.

Trinity College’s nanoscience activities in CRANN are supported by Science Foundation Ireland and the Higher Education Authority, in partnership with Intel and Hewlett-Packard. €100m has been invested in this research area to date in programmes and infrastructure with CRANN most recently coordinating the national PRTLI4 NANOTEIRE programme, a consortium of eight Irish Higher Education Institutes involved in nanoscience.
Trinity College’s Science Gallery is supported by both public and private funding. Significant capital support was provided by the Department of Enterprise, Trade and Employment. Ulster Bank is the Gallery’s founding corporate partner and through the ‘Science Circle’ corporate support has also been provided by DELL, Google, ICON, PACCAR and Wyeth.

Nanoscience Europe (NanoSci-E+) has announced a call for proposals for nanoscience research funding in Europe.  Proposals must include organisations from at least three qualifying European countries (Austria, Finland, France, Germany, Israel, Republic of Ireland, Italy, Netherlands, Poland, Portugal, Slovakia, Spain and the United Kingdom).

A minimum of €16m will be distributed for the funding of high-quality projects, possibly complemented by an additional €8m (subject to contract with the European Commission). Projects will be funded for up to three years from 1 January 2009.  Letters of Intent must be submitted online at www.nanoscience-europe.org by 27 March 2008, and full proposals by 23 July 2008.

Proposals are limited to ground-breaking nanotechnology research projects that address the issue of interfacing functional nano-objects or nano-materials.  The aim of this Call is to enable scientists working in nanoscience in different countries in the ERA to build an effective collaboration on a common research project based on ambitious and original ideas at the frontier of knowledge.

More information is available at:
www.nanoscience-europe.org/page.php?optim=NanoSci-E–Transnational-Call
The official announcement can be downloaded as a PDF file from:
www.nanoscience-europe.org/assets/NanoSci-E+/Announcement_NanoSci-E+_v2.pdf

Nanoscience Instruments today announced the launch of a new line of Silicon-Nitride probes for Atomic Force Microscopes (AFMs). The new HYDRA series is available world-wide and fills a need in the market for AFM probes specifically designed for imaging soft materials such as biological and polymeric samples.  HYDRA series probes feature a unique, patent-pending design that combines low stress, silicon-nitride cantilevers with sharp Silicon tips (radii of less than 10nm). Offered in a variety of spring constants, they are ideal for applications ranging from highly sensitive force curve measurements to soft contact mode and gentle fluid tapping mode experiments.

HYDRA probes offer the best of both worlds with their soft Silicon-Nitride cantilevers and sharp Silicon tips that feature the same well-defined shape as the sharpest Silicon probes on the market. HYDRA probes are available with a V-shaped Si3N4 cantilever or a rectangular Si3N4 cantilever. The V-shaped model is available with either a narrow or wide cantilever and all models are offered with an optional back-side gold reflex coating. HYDRA’s industry-standard chip design ensures compatibility with all standard AFMs including those by Veeco, Asylum Research, Agilent, and others.

Biophysicists, biologists, and many other AFM users are excited about the new HYDRA line of probes since it is tailored to their specialty applications. These users prefer soft cantilevers for contact mode and fluid tapping mode imaging but don’t want to sacrifice tip sharpness.  “HYDRA probes offer the best of both worlds with their soft Silicon-Nitride cantilevers and sharp Silicon tips that feature the same well-defined shape as the sharpest Silicon probes on the market”, said Dr. Sebastian Kossek, co-founder of Nanoscience Instruments and long-time AFM user.

HYDRA AFM probes are manufactured by Applied Nanostructures, adding a key component to the AppNano line of AFM tips, and reaffirming Nanoscience Instruments’ role as the largest independent AFM probe supplier in the world. Nanoscience Instruments’ brands include AppNano, Team Nanotec, CNTek, and their exclusive Vistaprobes line.

http://www.nanowerk.com/news/newsid=4620.php

The government is planning to appropriate NT$23 billion (US$726 million) to fund the second stage of the “Taiwan National Science and Technology Program for Nanoscience and Nanotechnology” slated for 2009-2014, officials at the cabinet-level National Science Council (NSC) said Tuesday. The first stage, which began in 2003 with NT$17.8 billion in funding, will conclude by the end of this year, officials told reporters.

In the first phase, more than 4,000 science research papers have been generated to date, dozens of top-notch research teams were initiated, and ties between industry, university, and research institutions have been strengthened, they said.
Program Director Wu Maw-kuen, who is also the director of the Institute of Physics under Taiwan’s top research institute Academia Sinica, said the program office is now working on the outlines of the next phase by determining which items of research are worth further financial support.

Wu said the focus of the next stage will be nano- electronic and optoelectronic technology, nano-scale instruments, nanotechnology for energy and environmental applications, nano-scale biomedical research, and the various technologies’ utilization in potential and traditional industries. According to the science council, so far completed research projects under the auspices of the program include the visualization of circuits and gene expression patterns in the whole Drosophila (fruit fly) brain, the target drug for diabetes, and nano porosity materials for cell marking and gene therapy.

And those that have already been used in pilot production or mass production include various materials, equipment, machinery, components and instruments using related nanotechnologies developed by Taiwanese researchers, according to the council.
Some of the items have great commercial potential, science council officials said. They said TAK Technology Co., a local company which received the technology of LiNiCoO2 anode production from the Hsinchu-based Industrial Technology Research Institute, had generated a production value of NT$1.5 billion last year, and the estimated production value for 2009 is expected to reach NT$3 billion. (By Zep Hu)

Sometimes simpler is better. Engineering researchers at Texas A&M University have developed a new way to produce ultra-thin electricity-conducting wire that is simpler and faster than existing processes.  “Other methods used to produce nanowires use high temperatures and high pressure,” said Subrata Kundu, a post-doctoral researcher in the research group of Hong Liang, an associate professor in Texas A&M’s Department of Mechanical Engineering. “This method is much simpler and faster.”

Kundu and Liang described the process in an article in the current issue of the journal Advanced Materials.  The process developed by Kundu and Liang works by shining ultraviolet light on a mixture of strands of DNA, cadmium sulfate and thioacetamide for about six hours. UV light breaks thioacetamide to produce sulfide ions (S2-). Chemical changes produced by the UV light allow the cadmium sulfate molecules to bind to the DNA. The resulting nanowires — about 1,000 times thinner than a human hair — conduct electricity and could be used in the development of so-called nano-scale electronic devices like small chips to make tiny computer or medical devices.

Nano-scale devices range in size from the size of a molecule to about 100 nanometers. One meter is 1 billion nanometers long.

Liang and Kundu plan to continue research in this area using different metals — lead, zinc and molybdenum — to produce the nanowires. Kundu said working with the other metals will give the researchers important information about how the process works.

The UV process also allows nanowires to be built on DNA arranged in two or three dimensions, t-joints and cubes, for example. This opens the possibility of using the process to build entire nano-scale circuits.

Researchers at McMaster University, in Ontario, say that they have grown light-absorbing nanowires made of high-performance photovoltaic materials on thin but highly durable carbon-nanotube fabric. They’ve also harvested similar nanowires from reusable substrates and embedded the tiny particles in flexible polyester film. Both approaches, they argue, could lead to solar cells that are both flexible and cheaper than today’s photovoltaics.

Now the researchers’ challenge is to improve the efficiency of the cells without increasing cost. The research team, led by Ray LaPierre, a professor in the university’s engineering physics department, has been given three years to achieve its goals–backed by about $600,000 from the Ontario government and private-sector research partner Cleanfield Energy, a Toronto-area developer of wind and solar technologies.

LaPierre says that the aim is to produce flexible, affordable solar cells composed of Group III-V nanowires that, within five years, will achieve a conversion efficiency of 20 percent. Longer term, he says, it’s theoretically possible to achieve 40 percent efficiency, given the superior ability of such materials to absorb energy from sunlight and the light-trapping nature of nanowire structures. By comparison, current thin-film technologies offer efficiencies of between 6 and 9 percent.

“Most of the nanowire work to date has focused on silicon nanowires,” says LaPierre, explaining that McMaster’s approach relies on nanowires containing multiple layers of exotic Group III-V materials, such as gallium arsenide, indium gallium phosphide, aluminum gallium arsenide, and gallium arsenide phosphide. “It creates tandem or multi-junction solar cells that can absorb a greater range of the [light] spectrum, compared to what you could achieve with silicon. That’s one of the major unique aspects of our work.”

When used in conventional crystalline solar cells, Group III-V materials are known to have much higher efficiencies than silicon, but the great cost of these materials has limited their use. LaPierre says that cost becomes less of an issue with nanowires because so little material is needed. This is in part because the structure of the nanowires provides a more efficient way to absorb light and extract electrons freed by the light. In conventional solar cells, which are made of slabs of crystalline material, greater thickness means better light absorption, but it also means that it’s more difficult for electrons to escape. This forced trade-off is overcome with nanowires. Each nanowire is 10 to 100 nanometers wide and up to five microns long. Their length maximizes absorption, but their nanoscale width permits a much freer movement and collection of electrons. “The direction in which you absorb the light is essentially perpendicular to how you collect electricity,” explains LaPierre. “The dilemma is overcome.”

In addition to reducing costs by using less active material, LaPierre’s team can also cut the cost of the substrate that the nanowires are grown on. LaPierre’s team doesn’t require an expensive Group III-V substrate. It has successfully grown its nanowires on substrates made of more plentiful and relatively cheaper silicon. It’s also working on using even lower cost substrates made of glass, which would be ideal for building-integrated PV applications. Flexible substrates such as polymer films and carbon nanotube fabric could be useful for many applications, and could be manufactured with inexpensive roll-to-roll processes.

To further drive down costs, the focus on cheaper substrates will be complemented by an attempt to replace the gold catalysts used to grow the nanowires with aluminum, although more work in this area is needed to achieve the necessary nanowire densities. “We have grown nanowires from aluminum, but gold works much better,” says LaPierre.

Charles Lieber, a professor of chemistry at Harvard University who has created single light-harvesting nanowires made of silicon, says that his team is also pursuing the use of other materials for making nanowires. “But there are many challenges in going from nanowire to photovoltaic,” says Lieber. He adds that comparison of approaches is difficult without data on the energy-conversion properties of each material.

Nathan Lewis, a professor of chemistry at the California Institute of Technology and an expert on nanowire structures, says that it’s too early to say which approach and materials are best. “We know nanowires work in bulk form, but we don’t know if you can make high-purity, high-quality nanowires and control all their electrical properties,” says Lewis. “There’s no theory that one works better than the other. It’s just a question of getting any of them to work.”

It’s still early days for McMaster, which in prototypes has only achieved low efficiencies–”where silicon PV was in the 1950s,” says LaPierre. But he’s optimistic that the higher-efficiency materials and the approach chosen will get results.

Nanotechnology researchers are developing the perfect complement to the power tie: a “power shirt” able to generate electricity to power small electronic devices for soldiers in the field, hikers and others whose physical motion could be harnessed and converted to electrical energy.  The February 14 issue of the journal Nature details how pairs of textile fibers covered with zinc oxide nanowires can generate electrical current using the piezoelectric effect. Combining current flow from many fiber pairs woven into a shirt or jacket could allow the wearer’s body movement to power a range of portable electronic devices. The fibers could also be woven into curtains, tents or other structures to capture energy from wind motion, sound vibration or other mechanical energy.

“The fiber-based nanogenerator would be a simple and economical way to harvest energy from physical movement,” said Zhong Lin Wang, a Regents professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “If we can combine many of these fibers in double or triple layers in clothing, we could provide a flexible, foldable and wearable power source that, for example, would allow people to generate their own electrical current while walking.”

The research was sponsored by the National Science Foundation, the U.S. Department of Energy and the Emory-Georgia Tech Nanotechnology Center for Personalized and Predictive Oncology.

The microfiber-nanowire hybrid system builds on the nanowire nanogenerator that Wang’s research team announced in the journal Science in April 2007. That system generates current from arrays of vertically-aligned zinc oxide (ZnO) nanowires that flex beneath an electrode containing conductive platinum tips. The nanowire nanogenerator was designed to harness energy from environmental sources such as ultrasonic waves, mechanical vibrations or blood flow.

The nanogenerators developed by Wang’s research group take advantage of the unique coupled piezoelectric and semiconducting properties of zinc oxide nanostructures, which produce small electrical charges when they are flexed. After a year of development, the original nanogenerators – which are two by three millimeters square – can produce up to 800 nanoamperes and 20 millivolts.

The microfiber generators rely on the same principles, but are made from soft materials and designed to capture energy from low-frequency mechanical energy. They consist of DuPont Kevlar fibers on which zinc oxide nanowires have been grown radially and embedded in a polymer at their roots, creating what appear to be microscopic baby-bottle brushes with billions of bristles. One of the fibers in each pair is also coated with gold to serve as the electrode and to deflect the nanowire tips.

“The two fibers scrub together just like two bottle brushes with their bristles touching, and the piezoelectric-semiconductor process converts the mechanical motion into electrical energy,” Wang explained. “Many of these devices could be put together to produce higher power output.”

Wang and collaborators Xudong Wang and Yong Qin have made more than 200 of the fiber nanogenerators. Each is tested on an apparatus that uses a spring and wheel to move one fiber against the other. The fibers are rubbed together for up to 30 minutes to test their durability and power production.

So far, the researchers have measured current of about four nanoamperes and output voltage of about four millivolts from a nanogenerator that included two fibers that were each one centimeter long. With a much improved design, Wang estimates that a square meter of fabric made from the special fibers could theoretically generate as much as 80 milliwatts of power.

Fabrication of the microfiber nanogenerator begins with coating a 100-nanometer seed layer of zinc oxide onto the Kevlar using magnetron sputtering. The fibers are then immersed in a reactant solution for approximately 12 hours, which causes nanowires to grow from the seed layer at a temperature of 80 degrees Celsius. The growth produces uniform coverage of the fibers, with typical lengths of about 3.5 microns and several hundred nanometers between each fiber.

To help maintain the nanowires’ connection to the Kevlar, the researchers apply two layers of tetraethoxysilane (TEOS) to the fiber. “First we coat the fiber with the polymer, then with a zinc oxide layer,” Wang explained. “Then we grow the nanowires and re-infiltrate the fiber with the polymer. This helps to avoid scrubbing off the nanowires when the fibers rub together.”

Finally, the researchers apply a 300 nanometer layer of gold to some of the nanowire-covered Kevlar. The two different fibers are then paired up and entangled to ensure that a gold-coated fiber contacts a fiber covered only with zinc oxide nanowires. The gold fibers serve as a Shottky barrier with the zinc oxide, substituting for the platinum-tipped electrode used in the original nanogenerator.

To ensure that the current they measured was produced by the piezoelectric-semiconductor effect and not just static electricity, the researchers conducted several tests. They tried rubbing gold fibers together, and zinc oxide fibers together, neither of which produced current. They also reversed the polarity of the connections, which changed the output current and voltage.  By allowing nanowire growth to take place at temperatures as low as 80 degrees Celsius, the new fabrication technique would allow the nanostructures to be grown on virtually any shape or substrate.

As a next step, the researchers want to combine multiple fiber pairs to increase the current and voltage levels. They also plan to improve conductance of their fibers.   However, one significant challenge lies head for the power shirt – washing it. Zinc oxide is sensitive to moisture, so in real shirts or jackets, the nanowires would have to be protected from the effects of the washing machine, Wang noted.

The research is supported by the NSF’s Division of Materials Research through grant 0706436. “This multi-disciplinary research grant enables materials scientists and engineers from varied backgrounds to work together toward translating basic and applied research into viable technologies,” noted Harsh Deep Chopra, NSF’s program manager.