Storing electricity in paper

One sheet, 15 centimetres in diameter and a few tenths of a millimetre thick can store as much as 1 F, which is similar to the supercapacitors currently on the market. The material can be recharged hundreds of times and each charge only takes a few seconds.

It’s a dream product in a world where the increased use of renewable energy requires new methods for energy storage – from summer to winter, from a windy day to a calm one, from a sunny day to one with heavy cloud cover.

”Thin films that function as capacitors have existed for some time. What we have done is to produce the material in three dimensions. We can produce thick sheets,” says Xavier Crispin, professor of organic electronics and co-author to the article just published in Advanced Science.

Other co-authors are researchers from KTH Royal Institute of Technology, Innventia, Technical University of Denmark and the University of Kentucky.

The material, power paper, looks and feels like a slightly plasticky paper and the researchers have amused themselves by using one piece to make an origami swan – which gives an indication of its strength.

The structural foundation of the material is nanocellulose, which is cellulose fibres which, using high-pressure water, are broken down into fibres as thin as 20 nm in diameter. With the cellulose fibres in a solution of water, an electrically charged polymer (PEDOT:PSS), also in a water solution, is added. The polymer then forms a thin coating around the fibres.

”The covered fibres are in tangles, where the liquid in the spaces between them functions as an electrolyte,” explains Jesper Edberg, doctoral student, who conducted the experiments together with Abdellah Malti, who recently completed his doctorate.

The new cellulose-polymer material has set a new world record in simultaneous conductivity for ions and electrons, which explains its exceptional capacity for energy storage. It also opens the door to continued development toward even higher capacity. Unlike the batteries and capacitors currently on the market, power paper is produced from simple materials – renewable cellulose and an easily available polymer. It is light in weight, it requires no dangerous chemicals or heavy metals and it is waterproof.

The Power Papers project has been financed by the Knut and Alice Wallenberg Foundation since 2012.

”They leave us to our research, without demanding lengthy reports, and they trust us. We have a lot of pressure on us to deliver, but it’s ok if it takes time, and we’re grateful for that,” says Professor Magnus Berggren, director of the Laboratory of Organic Electronics at Linköping University.

The new power paper is just like regular pulp, which has to be dehydrated when making paper. The challenge is to develop an industrial-scale process for this.

”Together with KTH, Acreo and Innventia we just received SEK 34 million from the Swedish Foundation for Strategic Research to continue our efforts to develop a rational production method, a paper machine for power paper,” says Professor Berggren.

Power paper – Four world records

Highest charge and capacitance in organic electronics, 1 C and 2 F (Coulomb and Farad).

Highest measured current in an organic conductor, 1 A (Ampere).

Highest capacity to simultaneously conduct ions and electrons.

Highest transconductance in a transistor, 1 S (Siemens)

Publication:

An Organic Mixed Ion-Electron Conductor for Power Electronics, Abdellah Malti, Jesper Edberg, Hjalmar Granberg, Zia Ullah Khan, Jens W Andreasen, Xianjie Liu, Dan Zhao, Hao Zhang, Yulong Yao, Joseph W Brill, Isak Engquist, Mats Fahlman, Lars Wågberg, Xavier Crispin and Magnus Berggren.  Advanced Science, DOI 10.1002/advs.201500305

Linköping University

New plastic solar cell minimizes loss of photon energy

A Japanese research team demonstrates an unconventional means to achieve more efficient and robust conversion of solar energy into electricity

As the world increasingly looks to alternative sources of energy, inexpensive and environmentally friendly polymer-based solar cells have attracted significant attention, but they still do not match the power harvest of their more expensive silicon-based counterparts.

Now, researchers at the RIKEN Center for Emergent Matter Science and Kyoto University's Department of Polymer Chemistry have shown that a newly developed polymer can minimize energy loss as well as silicon-based solar cells when converting photon energy from sunlight to electricity.

Solar cells work because photons from the sun strike electrons and move them into a position where they can create an electric current. Photon energy loss -- the amount of energy lost when converting photons energy from sunlight into electric power -- was greater in polymer-based solar cells than in silicon-based ones.

"In polymer-based plastic solar cells, larger photon energy loss causes lower voltage. This has been one of the largest limiting factors for efficiency," explains Hideo Ohkita, one of the authors of the study, which was published in the Dec. 2, 2015 issue of Nature Communications. "The new polymer has the potential to lead to a breakthrough on this issue."

The group began working with the new polymer, where oxygen rather than sulfur atoms are located at key positions, and found that the new material was able to overcome some of the key obstacles to extracting and utilizing greater energy from sunlight.

"Since this new polymer greatly reduces photon energy loss, it has allowed us to achieve a superb power conversion efficiency of nearly 9% with a very high open-circuit voltage in plastic solar cells," explains Itaru Osaka.

An efficiency of 15% is usually seen as a breakthrough level that will allow polymer-based cells to be commercialized.

"By achieving both a high short-circuit current and a high open-circuit voltage," he continues, "achieving a power conversion efficiency of 15% in single-junction cells is a realistic goal. This would have huge implications for the solar energy sector."

The paper 'High-efficiency polymer solar cells with small photon energy loss' appeared Dec. 2, 2015 in Nature Communications, with doi: 10.1038/ncomms10085

Kyoto University

UT membrane able to separate hot gases

Considerable potential energy savings for the chemical industry with hybrid gas separation membrane

Researchers at the MESA+ research institute at the University of Twente have developed a new type of membrane for separating gases in the chemical industry. What makes the hybrid unique is that it can also be used at high temperatures and high pressures. The polymer membranes that are currently used do not work at such conditions. This development potentially offers the chemical industry (which is responsible for more than a third of national energy consumption) considerable energy savings. The researchers published their research in the prestigious scientific periodical Journal of the American Chemical Society.

The chemical industry is responsible for one third of the energy consumption in the Netherlands. Approximately 40% of the energy is used for separation processes in which the products of chemical reactions are separated from each other. Researchers at the University of Twente have now developed a new type of membrane that allows to separate gases from each other in an energy-saving way, even under extreme conditions.

RESISTANT TO HIGH TEMPERATURES AND PRESSURE

Currently, gases are separated via processes such as of cryogenic distillation, during which gases are liquefied by intensive cooling, or through absorption processes. The disadvantage of these methods is that they often require a large amount of energy.

Using membranes that selectively allow one gas through but retain another allows energy-efficient separation. However, up until now there were no suitable organic membranes available that also performed at high temperatures and high pressures. Conventional, organic membranes are made of polymers and are not stable enough at high temperatures. The membrane developed by researchers at the University of Twente, which comprises of both organic and inorganic components, remains effective at high temperatures (of up to 300 degrees Celsius) and high pressures. This offers advantages for gas separation in the chemical industry, as many processes involve high temperature and high pressure conditions. The researchers have applied for a patent for their invention. 

100 NANOMETERS

The membrane is approximately 100 nanometers thick (10,000 times thinner than a millimeter) and consist of ceramic nanoparticles that are bound to each other at multiple points by long-chain organic molecules. These then form a sort of three dimensional web (with the nanoparticles as the junctions) and this web allows certain gases to pass through and retains others. As it is possible to choose the length of the organic molecules used (and therefore how fine the web is), it is easy to design suitable membranes for all kinds of applications. An added advantage is that the hybrid membranes are relatively easy to produce on a large scale, as the techniques used are compatible with those for producing the conventional membranes often used in water purification.

RESEARCH

Researchers from the Inorganic Membranes and Materials Science and Technology of Polymers departments at the MESA+ research institute at the University of Twente carried out the research as part of the UT's Green Energy Initiative. Researchers cooperated with Aachen University on this project. The research is part of the CARENA project funded by the European Union. 

Source: http://www.utwente.nl/en/newsevents/2014/2/286244/ut-membrane-able-to-separate-hot-gases

Discovery of a New Method for Creating mesoporous Materials from Industrial Polymers

NIMS researchers in the Polymer Materials Unit, Advanced Key Technologies Division, developed a high-performance oil absorbent with the function to purify oil-contaminated water (e.g. water discharged upon oil production) at a low cost. This new oil absorbent will provide an energy-efficient and low-cost water purification system at the site of resource development.



A team of researchers in the Separation Functional Materials Group of the Polymer Materials Unit (Unit Director: Izumi Ichinose), Advanced Key Technologies Division, National Institute for Materials Science (NIMS; President: Sukekatsu Ushioda), succeeded in developing a high-performance oil absorbent by creating a mesoporous material with pores of approximately 10 nm in diameter, using engineering plastics that are widely used as industrial materials.

At the site of oil or natural gas development, a large quantity of oil-contaminated water is generated. In order to prevent such water from polluting the environment, a low-cost and efficient water treatment system has been desired. In this respect, the technology for creating a mesoporous material from a general-purpose polymer was expected to provide a method for producing a high-performance oil absorbent. However, the conventional technology was unable to form a nano-scale morphology of a porous polymer in a controlled manner, and this posed an obstacle to the production of a high-performance absorbent using a polymer.

In the process of producing an industrial porous polymer, phase separation of a polymer solution had been widely used. Taking note of this phenomenon, that is, cryogenic separation of a polymer solution into a polymer and a solvent, the NIMS researchers succeeded in causing the solvent to form nanocrystals within engineering plastics. Then, by removing these nanocrystals by a unique method, they arrived at creating a mesoporous polymer in which nano-scale pores are connected in sequence. This mesoporous polymer can take the form of a sheet, pellet, or fiber. Under special conditions, the researchers were further able to create a polymer with pores of 1.9 nm in radius.

The newly developed mesoporous polymer, with its large surface area exceeding 300m2 per gram, can efficiently absorb oil that is contained in water. In the test regarding the degree of absorption of cresol contained in oil-contaminated water, the researchers observed that this new absorbent can absorb more than 260mg of cresol per gram. Moreover, the new absorbent desorbs oil at a high temperature, which will make it possible to use the absorbent repeatedly. It is also excellent in absorbing gases, such as carbon dioxide, and therefore is expected to be applied as a gas separating agent.

The research results were published in the online version of a UK science magazine,Nature Communications, on October 22, 2013, 18:00 JST (October 22, 10:00 LT) (S. Samitsu*, R. Zhang, X. Peng, M. R. Krishnan, Y. Fujii, I. Ichinose,* “Flash Freezing Route to Mesoporous Polymer Nanofibre Networks,” Nature Communications 4:2653 | DOI: 10.1038/ncomms3653).

A schematic view of a mesoporous polymer. Polymer assemblies in nanofiber form with pores of 10 to 20 nm in 

diameter are branched in a sophisticated fashion to create a minute three-dimensional network structure. The 

yellow lines represent assemblies of polymer chains that form nanofibers.




Source: http://www.nims.go.jp/eng/news/press/2013/12/p201310220.html

UCSD scientists invent MRSA 'nanosponge' vaccine

The glowing yellow specks in the image show uptake
of the nanosponge vaccine by a mouse dendritic cell --
an immune-system cell. The MRSA toxins were labeled with
a fluorescent dye which glows yellow. The nanosponge vaccine
with detained toxins and can be seen glowing yellow
after uptake by the dendritic cell. The cell is membrane
stained red and the nuclei stained blue.
— UC San Diego Department of NanoEngineering

UCSD scientists have created a vaccine for the deadly MRSA infection, using 'nanosponge' technology they previously used to soak up MRSA toxins and other poisons and venoms. The vaccine is effective in mice, they showed in a study; and their goal is to get it into human clinical trials.

The nanosponges are built on a polymer core wrapped with membranes from red blood cells that seize the toxins. They were first loaded with the MRSA toxins and injected into mice. The mouse immune system recognized the toxins and developed antibodies. The vaccinated mice were then able to survive an otherwise lethal dose of the toxins.

The study was published Sunday in Nature Nanotechnology. Liangfang Zhang, a nanoengineering professor at UC San Diego Jacobs School of Engineering, was senior author on the paper.

MRSA, or methicillin-resistant Staphylococcus aureus, has become one of the "superbugs" plaguing hospitals, and even some locations outside hospitals, because it has evolved potent resistance to antibiotics. The prospect of antibiotics becoming useless has become a nightmare scenario for modern health care. Without effective antibiotics, infections that were once easily treatable could once again become fatal, as they often were in the days before antibiotics were discovered.

But MRSA's lethality is mainly indirect, through a toxin called alpha-haemolysin. The toxin kills cells by punching holes in them. If that toxin were to be neutralized, the bacterium would be much less dangerous.

"With our toxoid vaccine, we don't have to worry about antibiotic resistance. We directly target the alpha-haemolysin toxin," Zhang said in a UCSD news release.

The nanosponge vaccine solves a tricky problem in vaccinating against MRSA, Zhang said. The toxin from MRSA is too dangerous to be given unaltered. So it is heated or chemically treated to weaken it for vaccine development.. But the altered toxin is less effective in provoking an effective antibody response than the unaltered toxin.

Immune cells called dendritic cells seek out the toxin-laden vaccine and process it, leading to antibody production by other immune cells. Free toxin kills dendritic cells, but trapping it in the vaccine's membrane reduces its dangerous without altering the toxin itself.

"The researchers found that their nanosponge vaccine was safe and more effective than toxoid vaccines made from heat-treated staph toxin," the news release stated. "After one injection, just 10 percent of staph-infected mice treated with the heated version survived, compared to 50 percent for those who received the nanosponge vaccine. With two more booster shots, survival rates with the nanosponge vaccine were up to 100 percent, compared to 90 percent with the heat-treated toxin."

Previously, "there was no way you could deliver a native toxin to the immune cells without damaging the cells," Zhang said in the release. "But this technology allows us to do this."

In April, Zhang and colleagues published a paper in Nature Nanotechnology showing how the nanosponges could increase survival of mice injected with toxins from MRSA and other sources.

The nanosponges soaked up the toxins, which adhered to the red blood cell membranes. By reducing the amount of freely circulating toxins, the nanosponges increased survival.

Liangfang Zhang, a nanoengineer at UC San Diego, is coating drug-filled particles with the skin of red blood cells in hopes that something natural will disguise something fake from the immune system, which flushes out invaders. — Eduardo Contreras

Zhang and colleagues originally developed the nanosponges as a delivery vehicle for cancer drugs. The goal was to keep the drugs active in the body for longer periods of time, by guarding them against detection and destruction by the immune system.

Source: http://www.utsandiego.com/news/2013/dec/01/vaccine-nanoparticles-ucsd-efficient/

Scientists Invent Self-healing Battery Electrode

An electron micrograph shows cracks left in a self-healing polymer
coating due to swelling of its silicon electrode during charging. Right:
Five hours later, the smaller cracks have healed.
(C. Wang et al, Nature Chemistry)

Researchers have made the first battery electrode that heals itself, opening a new and potentially commercially viable path for making the next generation of lithium ion batteries for electric cars, cell phones and other devices. 

The secret is a stretchy polymer that coats the electrode, binds it together and spontaneously heals tiny cracks that develop during battery operation, said the team from Stanford University and the Department of Energy’s (DOE) SLAC National Accelerator Laboratory.

They report the advance in the Nov. 19 issue of Nature Chemistry.

“Self-healing is very important for the survival and long lifetimes of animals and plants,” said Chao Wang, a postdoctoral researcher at Stanford and one of two principal authors of the paper. “We want to incorporate this feature into lithium ion batteries so they will have a long lifetime as well.”

Chao developed the self-healing polymer in the lab of Stanford Professor Zhenan Bao, whose group has been working on flexible electronic skin for use in robots, sensors, prosthetic limbs and other applications. For the battery project he added tiny nanoparticles of carbon to the polymer so it would conduct electricity.

”We found that silicon electrodes lasted 10 times longer when coated with the self-healing polymer, which repaired any cracks within just a few hours,” Bao said.

“Their capacity for storing energy is in the practical range now, but we would certainly like to push that,” said Yi Cui, an associate professor at SLAC and Stanford who led the research with Bao. The electrodes worked for about 100 charge-discharge cycles without significantly losing their energy storage capacity. “That’s still quite a way from the goal of about 500 cycles for cell phones and 3,000 cycles for an electric vehicle,” Cui said, “but the promise is there, and from all our data it looks like it’s working.”

Researchers worldwide are racing to find ways to store more energy in the negative electrodes of lithium ion batteries to achieve higher performance while reducing weight. One of the most promising electrode materials is silicon; it has a high capacity for soaking up lithium ions from the battery fluid during charging and then releasing them when the battery is put to work.

But this high capacity comes at a price: Silicon electrodes swell to three times normal size and shrink back down again each time the battery charges and discharges, and the brittle material soon cracks and falls apart, degrading battery performance. This is a problem for all electrodes in high-capacity batteries, said Hui Wu, a former Stanford postdoc who is now a faculty member at Tsinghua University in Beijing, the other principal author of the paper.

To make the self-healing coating, scientists deliberately weakened some of the chemical bonds within polymers – long, chain-like molecules with many identical units. The resulting material breaks easily, but the broken ends are chemically drawn to each other and quickly link up again, mimicking the process that allows biological molecules such as DNA to assemble, rearrange and break down.

To show how flexible their self-healing polymer is, researchers coated a balloon with it and then inflated and deflated the balloon repeatedly, mimicking the swelling and shrinking of a silicon electrode during battery operation. The polymer stretches but does not crack. (Brad Plummer/SLAC)

Researchers in Cui’s lab and elsewhere have tested a number of ways to keep silicon electrodes intact and improve their performance. Some are being explored for commercial uses, but many involve exotic materials and fabrication techniques that are challenging to scale up for production.

The self-healing electrode, which is made from silicon microparticles that are widely used in the semiconductor and solar cell industries, is the first solution that seems to offer a practical road forward, Cui said. The researchers said they think this approach could work for other electrode materials as well, and they will continue to refine the technique to improve the silicon electrode’s performance and longevity.

The research team also included Zheng Chen and Matthew T. McDowell of Stanford. Cui and Bao are members of the Stanford Institute for Materials and Energy Sciences, a joint SLAC/Stanford institute. The research was funded by DOE through SLAC’s Laboratory Directed Research and Development program and by the Precourt Institute for Energy at Stanford University.

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. To learn more, please visitwww.slac.stanford.edu.

The Stanford Institute for Materials and Energy Sciences (SIMES) is a joint institute of SLAC National Accelerator Laboratory and Stanford University. SIMES studies the nature, properties and synthesis of complex and novel materials in the effort to create clean, renewable energy technologies. For more information, please visit simes.slac.stanford.edu.

Source: https://www6.slac.stanford.edu/news/2013-11-17-scientists-invent-self-healing-battery.aspx

Building ‘nanomachines’ in biological outer space

New research reveals how bacteria construct tiny flagella ‘nanomachines’ outside the cell

Cambridge scientists have uncovered the mechanism by which bacteria build their surface propellers (flagella) – the long extensions that allow them to swim towards food and away from danger. The results, published this week in the journal Nature, demonstrate how the mechanism is powered by the subunits themselves as they link in a chain that is pulled to the flagellum tip.

Previously, scientists thought that the building blocks for flagella were either pushed or diffused from the flagellum base through a central channel in the structure to assemble at the flagellum tip, which is located far outside the cell. However, these theories are incompatible with recent research showing that flagella grow at a constant rate. The completely new and unexpected chain mechanism, in which subunits linked in a chain ‘pull themselves’ through the flagellum, transforms understanding of how flagellum assembly is energised.

The research was led by Dr Gillian Fraser and Professor Colin Hughes in the University’s Department of Pathology and was funded by the Wellcome Trust.

Dr Lewis Evans, who carried out the research, remarked: “It’s exciting how economical bacteria are, able to harness the thermal free energy from unfolded subunits and convert it into a coherent directed transport. More broadly, it’s fascinating to imagine the implications for how heat energy (normally considered as ‘lost’) might be harnessed to drive processes even outside living cells.”

As each flagellum ‘nanomachine’ is assembled, thousands of subunit ‘building blocks’ are made in the cell and are then unfolded and exported across the cell membrane. Like other processes inside cells, this initial export phase consumes chemical energy. However, when subunits pass out of the cell into the narrow channel at the center of the growing flagellum, there is no conventional energy source and they must somehow find the energy to reach the tip.

The team has shown that at the base of the flagellum, subunits connect by head-to-tail linkage into a long chain. Together with Professor Eugene Terentjev, at the Cavendish Laboratory, they showed that the chain is pulled through the entire length of the flagellum channel by the entropic force of the unfolded subunits themselves. This produces tension in the subunit chain, which increases as each subunit refolds and incorporates into the tip of the growing structure. This pulling force automatically adjusts with increasing flagellum length, providing a constant rate of subunit delivery to the assembly site at the tip.

Professor Terentjev noted that this breakthrough can be applied to other fields. “Understanding how polymers move through channels is a fundamental physical problem. Gaining insight into this has potential applications in other disciplines, for instance in nanotechnology, specifically the building of new nanomaterials.”

This research has far-reaching implications, according to Fraser. “By understanding the base-level, fundamental biology of medically important bacteria and their construction of flagella and related toxin-injecting molecular syringes,” she commented, “we can start to develop new ways to counteract them.”

Dr Gillian Fraser is at Queens' College; Professor Colin Hughes is at Trinity College; Professor Eugene Terentjev is at Queens' College

Source: http://www.cam.ac.uk/research/news/building-nanomachines-in-biological-outer-space

New microfluidic approach for the directed assembly of functional materials

University of Illinois researchers have developed a new approach with applications in materials development for energy capture and storage and for optoelectronic materials.

According to Charles Schroeder, an assistant professor in the Department of Chemical and Biomolecular Engineering, the results show that peptide precursor materials can be aligned and oriented during their assembly into polypeptides using tailored flows in microfluidic devices.

The research was a collaboration between the labs of Schroeder andWilliam Wilson, a research professor inmaterials science and engineering and the Frederick Seitz Materials Research Laboratory at Illinois. Their findings were recently published in a paper entitled, “Fluidic-directed assembly of aligned oligopeptides with pi-conjugated cores” inAdvanced Materials.

“A grand challenge in the field of materials science is the ability to direct the assembly of advanced materials for desired functionality,” says Amanda Marciel, a graduate student in Schroeder’s research group. “However, design of new materials is often hindered by our inability to control the structural complexity of synthetic polymers.”

“To address the need for controlled processing of functional materials, we developed a microfluidic-based platform to drive the assembly of synthetic oligopeptides,” Marciel explained. “Using a microfluidic device, we assembled DFAA and DFAG into one dimensional nanostructures using a planar extensional flow generated in a cross-slot geometry.”

The dynamics of the assembly process can be followed in real-time using fluorescence microscopy and spectroscopy.

“The assembled nanostructure is spectrally distinct from the synthetic oligopeptide monomer, which can be used to monitor the dynamics of nanostructure formation,” Marciel added. “Using precise hydrodynamic control of the microfluidic platform, the researchers demonstrated the formation of multiple parallel-aligned synthetic oligopeptide nanostructures and their subsequent disassembly. By modulating volumetric flow rates in the device they were able to manipulate the position of the fluid-fluid interface at the microchannel junction.

Reversible assembly and disassembly of synthetic oligopeptide nanostructures.

 

During this process, nanostructures initially formed at the reactive laminar interface are submerged into the advancing acidic stream, thereby preserving the integrity of the preformed nanostructures while initiating formation of an aligned nanostructure at the new interface position.

Marciel says this research shows that is possible to use microfluidic-based flows to direct the structural assembly of polymers into functional materials.

“Our approach has the potential to enable reproducible and reliable fabrication of advanced materials.” Marciel said. “Achieving nanoscale ordering in assembled materials has become the primary focus of recent efforts in the field. These approaches will ultimately lead to desired morphology in functional materials, which will enhance their ability to capture and store energy.”

“Our research team is quite interdisciplinary and has a unique range of skills to study materials assembly,” Schroeder said. “Our group has extensive experience in the design and fabrication of microfluidic devices and fluorescence imaging of soft materials." The team’s ultimate goal is to assemble the organic equivalent of typical semiconducting materials.

“This would open the door to developments of materials with application to photovoltaic devices, solid-state lighting, energy harvesting, and catalytic processes,” she said.

In addition to Marciel, Schroeder, and Wilson, the paper's authors included, Melikhan Tanyeri, Brian D. Wall, and John D. Tovar. The team used spectroscopic and analytical tools at the Frederick Seitz Materials Research Lab to conduct its research. 

Source: http://engineering.illinois.edu/news/2013/10/07/new-microfluidic-approach-directed-assembly-functional-materials

Invention jet prints nanostructures with self-assembling material

A multi-institutional team of engineers has developed a new approach to the fabrication of nanostructures for the semiconductor and magnetic storage industries. This approach combines top-down advanced ink-jet printing technology with a bottom-up approach that involves self-assembling block copolymers, a type of material that can spontaneously form ultrafine structures.

The team, consisting of nine researchers from the University of Illinois at Urbana-Champaign, the University of Chicago and Hanyang University in Korea, was able to increase the resolution of their intricate structure fabrication from approximately 200 nanometers to approximately 15 nanometers. A nanometer is a billionth of a meter, the width of a double-stranded DNA molecule.

The ability to fabricate nanostructures out of polymers, DNA, proteins and other “soft” materials has the potential to enable new classes of electronics, diagnostic devices and chemical sensors. The challenge is that many of these materials are fundamentally incompatible with the sorts of lithographic techniques that are traditionally used in the integrated circuit industry. 

Recently developed ultrahigh resolution ink-jet printing techniques have some potential, with demonstrated resolution down to 100-200 nanometers, but there are significant challenges in achieving true nanoscale dimension. “Our work demonstrates that processes of polymer self-assembly can provide a way around this limitation,” said John Rogers, the Swanlund Chair Professor in Materials Science and Engineering at Illinois.

Rogers and his associates report their findings in the September issue of Nature Nanotechnology. Combining jet printing with self-assembling block copolymers enabled the engineers to attain the much higher resolution, as suggested by lead author Serdar Onses, a postdoctoral scientist at Illinois. Onses earned his doctorate at the University of Wisconsin under Paul Nealey, now the Brady W. Dougan Professor in Molecular Engineering at UChicago and a co-author of the Nature Nanotechnology paper. “This concept turned out to be really useful,” Rogers said.

Engineers use self-assembling materials to augment traditional photolithographic processes that generate patterns for many technological applications. They first create either a topographical or chemical pattern using traditional processes. For the Nature Nanotechnology paper, this was done at imec in Belgium, an independent nanoelectronics research center. Nealey’s laboratory pioneered this process of directed self-assembly of block copolymers using chemical nanopatterns.

NEARING THE LIMITS

The resolution of the chemical pattern nears the current limit of traditional photolithography, noted Lance Williamson, a graduate student in molecular engineering at UChicago and co-author of the Nature Nanotechnology article. “Imec has the capability to perform the photolithography at this scale over large areas with high precision,” Williamson said.

Back at the University of Illinois, engineers place a block copolymer atop this pattern. The block copolymer self-organizes, directed by the underlying template to form patterns that are at much higher resolution than the template itself.

Previous work has focused on the deposition and assembly of uniform films on each wafer or substrate, resulting in patterns with essentially only one characteristic feature size and spacing between features. But practical applications may need block copolymers of multiple dimensions patterned or spatially placed over a wafer.

“This invention, to use inkjet printing to deposit different block copolymer films with high spatial resolution over the substrate, is highly enabling in terms of device design and manufacturing in that you can realize different dimension structures all in one layer,” Nealey said. “Moreover, the different dimension patterns may actually be directed to assemble with either the same or different templates in different regions.”

BENEFITS OF E-JET PRINTING

The advanced form of ink-jet printing the engineers use to locally deposit block copolymers is called electrohydrodynamic, or e-jet printing. It operates much like the ink-jet printers office workers use for printing on paper. “The idea is flow of materials from small openings, except e-jet is a special, high-resolution version of ink-jet printers that can print features down to several hundred nanometers,” Onses said. And because e-jet can naturally handle fluid inks, it is exceptionally well-suited for patterning solution suspensions of nanotubes, nanocrystals, nanowires and other types of nanomaterials.

“The most interesting aspect of this work is the ability to combine ‘top-down’ techniques of jet printing with ‘bottom-up’ processes of self-assembly, in a way that opens up new capabilities in lithography—applicable to soft and hard materials alike,” Rogers said.

“The opportunities are in forming patterned structures of nanomaterials to enable their integration into real devices. I am optimistic about the possibilities.”

Sourc: http://news.uchicago.edu/article/2013/09/16/invention-jet-prints-nanostructures-self-assembling-material?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+UchicagoNews%2FStories%2FScienceMedicine+%28UChicago+News%3A+Stories+-+Science+%26+Medicine%29#sthash.d6bNCDC1.dpuf