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Dip-Pen Lithography Applied to Graphene Devices

Whenever I consider the possibilities of dip-pen nanolithography (DPN), I always think of that Xerox commercial from the 1970s in which after toiling for incalculable hours of transcribing a text a monk presents his work to the chief monk who is impressed but asks for 500 more copies. 

Let’s face it, taking the tip of an Atomic Force Microscope (AFM) and dipping it into a sort of molecular ink and then drawing patterns on a substrate may be exact but it’s not exactly a fast process.

That understood, I was intrigued by recent work researchers at Stanford University were doing with DPN in creating graphene devices. To date, electron-beam lithography (EBL) has been used for constructing such devices.

The research, which was originally published in the journal ACS Nano, showed that an AFM could be used for creating graphene devices thereby replacing EBL techniques and eliminating some of the inherent problems of working with EBL such as exposing the graphene to electron irradiation.

"DPN has several advantages over EBL, such as no damage from electron irradiation and the ability to pattern nanostructures and image them using one system operating under ambient conditions," Maria Wang, the first author of the research, told Nanowerk. "We have demonstrated that dip-pen nanolithography can be used to create arbitrarily shaped graphene devices for nanoelectronics and identified the process steps that may affect their electrical characterization."

To address issues of scalability, which I facetiously referred to with Xerox commercial, Wang also points out that the DPN process could be done with multipen arrays, establishing a kind of parallel fabrication.

"Parallel fabrication of individual graphene devices using DPN could potentially result in higher yield and faster processing times than serial fabrication using EBL,” suggests Wang. “This increase in fabrication efficiency could potentially accelerate graphene research."

Public Engagement for National Nanotechnology Strategies Continues its Upswing

Over this past year I have become intrigued by the growing practice of the US government of opening up its strategy for nanotechnology development to public input.

In my most recent blog on this subject, the National Nanotechnology Initiative (NNI) used the month of November to collect suggestions from the public on its then current draft of its strategy.

One week now into December and I am not sure what input the NNI collected, but we do know that they have announced a new public engagement scheme this time focused on getting input on its Environmental, Health and Safety (EHS) Research Strategy.

It will be possible to contribute thoughts on the current draft of the EHS strategy from December 6th to January 6th. At least one noted expert on EHS on nanotech will be taking full advantage of this one-month window.

I think this most recent public engagement move by the NNI has changed my attitude about these initiatives from mere intrigue to begrudging respect. I mean you are not going to find a more contentious issue (and one with fewer easy solutions, if any) than determining the course of EHS research and the NNI has just said, “Let us have it.”

And have it they no doubt will. As Andrew Maynard has already pointed out in his 20/20 Science blog the NNI has already come under sharp criticism in the past for its EHS research strategy from one of its own government cousins, the National Academy of Sciences. 

Frankly, it’s pretty easy pickings to criticize the NNI, and anyone else you choose to target, for their less than coherent strategy on how to address EHS of nanomaterials.

You are essentially asking researchers—before they pick up their first microscope in anger—to develop a theoretical framework by which they can reinvent the periodic table. 

And then as soon as they pick up that microscope, they discover that they have few to no microscopy tools at their disposal to enable the research. 

But at least now we have one month of input from the public to sort this all out.

How to Make Graphene at Home for Fun

I came across the video below from the blog Frogheart and considering the recent Nobel Prize for Physics and the near daily reports on graphene within the pages of Spectrum alone, I thought it worth posting here.

The video provides a demonstration in a very rough way for how one could manage to isolate a single layer of graphite to create graphene.

The presenter, Dr. Jonathan Hare, manages to bring up the issue of the speed at which electrons travel through graphene to discuss relativistic quantum mechanics and Dirac particles and still manages to make it accessible for a general audience.

Nice piece of work and will lead me to check out the video’s producers Vega Science Trust for more material. 

Revealing Impact of Nanotechnology Funding through the Literature

In the December 2nd edition of Nature (subscription required) there is an article written by Philip Shapira & Jue Wang in which an attempt is made to gauge the impact of the last 10 years of nanotechnology funding by using data mining on the literature.

I suppose this is as useful as any other method, such as counting patents or making up lists of commercial products that might somehow be affiliated with nanotechnology. But quantitative analysis of what is more or less a qualitative phenomenon is always a tricky business.

Nonetheless, since the article makes some critical points that I have made, I find myself in unequivocal agreement with some of their conclusions, such as: “We find that despite the initial focus on national initiatives, patterns of nanotechnology funding and collaboration transcend country boundaries.”

So try as you might to make your geographical region the next nanotechnology hub, you might be somewhat disappointed in the result. Not only is nanotechnology research interdisciplinary, but also is international and depends on cross-border cooperation to succeed as this article points out.

Shapira and Wang were able to build much of their research by using the recent practice by the Thomson Reuters bibliographic and citation database of including funding-acknowledgement data with research projects. In the period of 2008-2009, 67% of nanotechnology publications provided that data.

With this data set, the two researchers reached a number of conclusions, including the noteworthy, but not surprising, idea that “China is close to the United States in number of publications, but still lags behind the United States and Europe in publication quality.”

But the idea that seems to resonate the most with the two authors is that international partnering and cooperation is key to successful nanotechnology research.

When they pose themselves the question of how countries like the US, Germany and Japan should stimulate their research when it is likely that funding will remain flat, they offer: “One way would be to foster more high-quality international collaborations, perhaps by opening funding competitions to international researchers and by offering travel and mobility awards for domestic researchers to increase alliances with colleagues in other countries.”

Sorry politicos, science just doesn’t understand national boundaries.

Where Do We Stand with Molecular Electronics?

Last week I highlighted some recent research in the UK that successfully built 3D molecular structures on a surface using buckyballs and the process of self assembly. 

As exciting as this work is, I felt obliged to caution that this work is not going to usher in the era of molecular electronics anytime soon as was implied by some exuberant reports I had read on Twitter feeds.

But the prospect of building electronic devices with molecules is an appealing concept that remains the ultimate aim of many researchers investigations into nanostructured materials.

Over at Nanowerk they have a nice reexamination of molecular electronics and highlights recent work being done in Germany that has “demonstrated that rigidly wired molecules can emit light under voltage bias.”

The researchers from the Electronic and Optical Properties of Molecular Nanostructures group at Karlsruhe Institute of Technology (KIT) have reported their findings in the November 28th issue of Nature Nanotechnology.

This, of course, is not the first time that electroluminescence has been observed in molecule. However, in those previous instances it came as a result of being in contact with the tip of a scanning tunneling microscope or in nanocrystals or nanoclusters.

As Ralph Krupke, who heads the KIT research group, told Nanowerk, "In our recent work, our motivation was to form a rigid light-emitting device based on single molecules."

The design they developed with the assistance of Marcel Mayor from the University of Basel in Switzerland involved the placing of “a rod-like molecule between two metallic single-walled carbon nanotube electrodes forming a rigid solid-state device.” 

“The major challenge was to integrate a bottom-up object (molecule) into a top-down structure (electrodes) and to have control over the critical dimensions,” explained Krupke to Nanowerk. “Moreover the electronic and optical properties of the molecule and the carbon nanotube electrodes had to be tailored such that electron transport and light emission is possible."

Molecular Self Assembly on a Surface Moves from 2D to 3D

In what is being described as the first demonstration of building a 3D molecular structure on a surface, researchers at the University of Nottingham have introduced Buckyballs (C60 molecule) to a surface and found that molecules would self-assemble around the spherical shaped molecule into a 3D structure.

The research, which was initially published in the journal Nature Chemistry, took the work that has been done thus far in having molecules attract other molecules into 2D planar formations and moved it a step beyond by using a non-planar molecule like C60 to promote the growth of the host molecule into self-assembled formations that are both above and parallel to the surface, i.e. in three dimensions.

One of the authors of the research, Professor Neil Champness, had some colorful quotes to describe both the nature of self-assembly and how these 3D structures differ from their 2D precursors.

"It is the molecular equivalent of throwing a pile of bricks up into the air and then as they come down again they spontaneously build a house,’ Champness said in describing the process of self assembly.

"Until now this has only been achievable in 2-D, so to continue the analogy the molecular 'bricks' would only form a path or a patio but our breakthrough now means that we can start to build in the third dimension. It's a significant step forward to nanotechnology," Champness added.

I like to add a caveat to these stories. As innovative as this research is we shouldn’t be expecting molecular electronics in the near future.

Carbon Nanotube Production Gets a Little Greener

No sooner do the Friends of Earth highlight how the production of nanomaterials probably consumes more energy than it saves, than research at MIT has demonstrated a method for producing carbon nanotubes that reduces emissions of harmful byproducts at least ten-fold and up to a factor of 100 and cuts the amount of energy used in half.

The research, which was initially published in the American Chemical Society’s journal ACS Nano, has provided a relatively simple way of reducing the byproducts that come from the catalytic chemical vapor disposition (CCVD) method for making multi-walled nanotubes.

Multi-walled carbon nanotubes (MWNTs) have undergone a huge expansion in capacity over the last three years with one producer, Bayer Material Science, having added nearly 600% more capacity this year from its 2007 levels. Bayer was not alone. Nanocyl and Arkema have been in a capacity race along with Bayer over these last three years, matching nearly every capacity increase.

This may drop the price of MWNTs considerably (by some estimates as much as half over the last five years), but it also is not very eco-friendly. CCVD is estimated to release 97% of its initial feedstock into the air as unreacted compounds, and we’re talking real harmful stuff like benzene.

In coverage of this research over at the AIChE blog, one of the lead authors of the MIT research, Desiree Plata, explains how they replaced the process of heating carbon-based gases and instead added key reactive ingredients into the process to eliminate many of the harmful byproducts.

Now it may take some time for this get into the industrial processes of the large MWNT producers, but it could and likely eventually will. What this ultimately will result in is the production of MWNTs that is less energy intensive and better for the environment so that MWNTs can enable things like lighter wind turbines and blades and result in a net energy gain rather than loss.

If we just walk away from nanotechnology altogether, especially at this early stage, we may never get there.

Overcoming Misleading Nanotechnology Lists

There seems to be an odd fascination for some experts, journalists and other assorted types to create lists when confronted with the topic of nanotechnology.

The annually updated list that annoys me at least once a year is the Project on Emerging Nanotechnologies' Nanotech-enabled consumer product list.

As annoying as I find that list, an entirely new type of list that seems to be growing in favor is even more pointless. Their titles are usually some twist on “x number of things you should know about nanotech” or “x number of things you didn’t know about nanotech.”

My first encounter with these was in the men’s magazine Askmen.com, which got things started with “5 Things You Didn’t Know about Nanotech”. This was just the first for me in what would become a genre of nanotechnology lists that seems to me to be increasingly annoying, pointless and misleading.

Then came the far more reputable publication, at least in all things nano, Nanowerk that told us “10 things people should know”, or perhaps more appropriately 10 things you should agree with Nanowerk on when it comes to nanotech.

And now we have the publication “Discover” upping the ante by giving us "20 (that’s right twenty) Things You Didn’t Know about Nanotechnology.”

This one may be the most comical of them all, and yet still be as equally annoying as the others. What makes this list such a farce is that apparently they could only come up with 10 things so they split each one into two entries. I kid you not.

For instance the now 20-year-old event of spelling out I-B-M with xenon atoms gets two entries:

13.  In 1989, using an atomic force microscope, IBM engineer Don Eigler became the first person to move and control a single atom.

14.  Eigler and his team later used 35 xenon atoms to spell out “IBM,” thus performing the world’s smallest PR stunt.

To add insult to injury, they keep the entire misleading quality of these lists up to snuff by using artwork that depicts some “nanorobot” manipulating red blood cells.

Really, if this is the only way we have to engage people on the subject of science, and specifically nanotechnology, might we not be better off not engaging people at all?

Nano-Enabled Water Filter Brings Clean Water to Poor, Remote Regions

It seems that my criticisms of the Friends of the Earth’s (FoE) overly ideological report on nanotechnology’s role in improving our environment and enabling alternative energy are not alone. The reports continues to garner more sharp rebukes, like here  and here.

These are all well deserved criticisms in my opinion. To reinforce one of my own points that the FoE seemed to ignore, I bring you this story “Teabag filter cleans water with nanotechnology”.

Admittedly, inexpensive nano-enabled water filters are nothing new since Argonide Corporation has been around since 1994 offering more or less the same thing, but this current solution looks to be specifically targeted at providing clean drinking water to poor and remote regions of Africa.

"This project takes nanotechnology to the poorest of the poor people who live in this world, and it will make a difference in their lives," said Eugen Cloete, who in addition to inventing the filter is dean of the faculty of science at Stellenbosch University and chair of Stellenbosch University's Water Institute.

And anticipating the immediate knee-jerk reaction that this solution is probably more expensive than other methods of providing clean drinking water, Marelize Botes, who is analyzing the tea bags in her in her laboratory at the University of Stellenbosch in South Africa, said, "The filter is much cheaper than bottled water as well as any other filter on the market."

"It is simply impossible to build purification infrastructure at every polluted stream," Cloete said. "So we have to take the solution to the people. The water is cleaned right then and there when you drink from the bottle." 

Researchers from every imaginable scientific discipline looking for ways to apply nanotools and nanomaterials to every imaginable application, like clean drinking water, like clean energy, like energy conservation is not in itself a crime against the planet Earth. However, depriving the rest of us from these potential solutions may very well be.

Solution to Riddle in Fundamental Material Science Could Lead to New Age in Electronics

Researchers at Oregon State University (OSU) have reported success in creating a metal-insulator-metal (MIM) diode architecture that in the past has proven difficult to produce with high yield and top-level performance.

The research, which was initially published in the Wiley journal Advanced Materials, is being lauded as opening up a new approach to electronics.

"Researchers have been trying to do this for decades, until now without success," said Douglas Keszler, a distinguished professor of chemistry at OSU. "Diodes made previously with other approaches always had poor yield and performance.

"This is a fundamental change in the way you could produce electronic products, at high speed on a huge scale at very low cost, even less than with conventional methods," Keszler said. "It's a basic way to eliminate the current speed limitations of electrons that have to move through materials."

The OSU researchers found success in their MIM design over previous attempts through the use of an "amorphous metal contact" instead of a crystalline material.

The MIM architecture enables a quantum tunneling current flow through the insulator material, which is superior to traditional current flow that requires electrons to essentially jump across device barriers. This all translates to electronics that are faster, consume less energy and run cooler.

While this may be a diode architecture that can improve current speed of electrons that have to move through materials, it is not clear to some familiar with other MIM diode designs whether this will have much of an impact unless OSU has a working transistor (see comments).

Meanwhile the research, which was supported by National Science Foundation, the Army Research Laboratory and the Oregon Nanoscience and Microtechnologies Institute, is now seeking a patent.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
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Rachel Courtland
Associate Editor, IEEE Spectrum
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