Nanoclast

When we get down to the nanoscale the world of macroscale physical phenomena we are familiar with is replaced in large part by a new set of phenomena. Among the key forces in this strange new world are Brownian motion and van der Waal forces. One of the great challenges of working on the nanoscale is finding ways to engineer things (move them around and generally get things to do what we want) with atomic forces such as these governing the nanoscale universe.

In a recent article here on the pages of Spectrum online the work of researchers Professor Robert Carpick at the University of Pennsylvania and Professor James Hone at Columbia University, in New York City has given us some better insight into how friction occurs at the atomic scale and how to engineer around atomic forces like the van der Waal force.

According to the Spectrum article, the researchers, who did much of their research with graphene, discovered that the thinner the sheets of the material the greater the friction.

The researchers observed that the atomic forces such as van der Waal forces would cause the sheets of graphene to be attracted to the tip of the atomic-force microscope as it drew closer thus bending the graphene and creating a “puckering effect” on the surface of the graphene. This puckering is what caused the friction.

To overcome this puckering effect the researchers also observed that the thicker the sheets the less they would bend when subjected to the atomic forces. 

By gaining a better understanding of the surface phenomenon at the atomic level, the researchers believe this will help in the engineering for microelectromechanical systems (MEMS) devices and ultimately nanoelectromechanical systems (NEMS) devices. Meanwhile the researchers note that other work is going on now to figure out the best number of sheets of a material to combat this type of friction.

Researchers at the University of California Santa Barbara have reported that they have developed a glue that can be activated and deactivated by magnetism, a sort of on/off switch for the material’s adhesiveness, that mimics the adhesive characteristics of a gecko’s foot.

The research is being heralded because of its interdisciplinary nature, combining “biology, material science, physics, surface chemistry, nanoscience and mechanical engineering”. Also, the article cited above provides a laundry list of possible applications for the technology ranging from improved handling of microchips in semiconductor fabs to greater transport capabilities of robots in pipeline inspection.

But clearly both the researchers and the reporter of the article neglected to see the most obvious potential application for this technology: Making possible the  ability to scamper around urban canyons like Spiderman.

Kidding aside, researchers have been looking at the gecko’s foot for some time as an example of how nanoscale hairs can be used as an adhesive force. While other research in this area focused on just the adhesive qualities, the UCSB researchers are the first to look at turning that adhesive on and off.

This is significant because there is a great deal of super strong adhesives out there already. However, currently there is no adhesive that can be turned on and off. Translation: Commercial opportunity.

A few years back, I noted that the concept of materials by design had fallen out of the lexicon of nanotechnology proponents and suggested that this was due, at least in part, to how difficult it would be to achieve.

I received some pointed criticism for my view, which was characterized as being so conservative as to be radical.

When I saw recent news that researcher Ronald Zuckermann and his colleagues at Lawrence Berkeley National Laboratory had manufactured a large sheet, just two molecules thick, made of a polymer that mimics the precise structures seen in proteins and crystal structures, this “material by design” debate occurred to me once again.

I was struck by a quote that Zuckerman provides in the Wired article cited above in which he states, “It was a real thrill to figure out how to really order material in a precise way at the atomic level.” Then the articles author adds: “His team knows exactly where each atom is located in the structure, so it’s possible to chemically engineer the material to serve specific functions.”

While this possibility hints at the potential of material by design, earlier in the article the more accurate description of how this material came to be designed indicates that it followed a far more an iterative process than a deliberate one: “Zuckermann’s team made the discovery by stumbling upon a particular sequence of repeating units that formed perfectly aligned two-dimensional crystals.” (Emphasis added).

This question of material by design aside, the perfectly aligned two-dimensional crystals made into such a large structure is a remarkable achievement. It has been described as the “plywood” for building the electronic devices of the future.

Suggested applications are numerous ranging from tissue engineering and drug delivery to batteries and fuel cells. Clearly applications in which flat electrical components are needed such as in photovoltaics are a likely area for initial applied research.

Preliminary research performed by Angela Belcher and her team at the Massachusetts Institute of Technology (MIT) has demonstrated a new way for breaking water down into hydrogen and oxygen—a sort of artificial photosynthesis—that departs from other methods by borrowing the methods plants use rather than their components. 

Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering at MIT, and her team used a man-made virus to serve as a scaffold that attracts molecules of the catalyst iridium oxide and a biological pigment (zinc porphyrins). The viruses then become “wire-like” and are able to split the water molecules into hydrogen and oxygen by having just the right spacing to induce the reaction.

While other artificial photosynthesis methods have attempted to used the photosynthetic parts of plants, Belcher and the lead author of the paper in Nature Nanotechnology, Yoon Sung Nam, followed the method plants use of having a natural pigment attract the sunlight and then using a catalyst to split the water into hydrogen and oxygen.

In the MIT article cited above Thomas Mallouk, the DuPont Professor of Materials Chemistry and Physics at Pennsylvania State University, describes the work as “…an extremely clever piece of work that addresses one of the most difficult problems in artificial photosynthesis, namely, the nanoscale organization of the components in order to control electron transfer rates.”

The idea behind artificial photosynthesis is to create a method of energy conversion using sunlight. But this preliminary research is a long way from providing an alternative energy source. 

At the end of the article when Belcher is prodded to provide a timetable for a commercial product she is wisely reluctant, offering only that “within two years she expects to have a prototype device that can carry out the whole process of splitting water into oxygen and hydrogen, using a self-sustaining and durable system.”

Well done, Professor Belcher. I have noted before when discussing the potential for virus-enabled lithium-ion batteries to make it into commercial markets within a year, that often times people neglect to take into account that business sometimes much longer than science. A phenomenon with which Professor Belcher is herself aware with one of her own companies, I’m sure.

Earlier this week I offered up a headline for recent research into the memristor in which I referred to the memristor as the “Fourth Fundamental Circuit Element”.

I was quickly taken to task for this in the comments section. I used the phrase based on how I have seen it characterized in other articles. I wanted to put its discovery in what I thought was its appropriate context of importance. However, the commenter suggested that this was just marketing copy that actually was detracting from the discovery’s impact. Fair enough, if or when I have the opportunity to write about the memristor again I will not use that phrase.

I bring this all up to highlight the headline I am using for this entry and how It stands in contrast, I hope, to the headline to the story that inspired it: “Self-Powered Nanotechnology Closer to Reality”. When I first saw this headline I really had no idea what it could be, but was intrigued enough to click on the link to the article—I guess that was the point. I expected to see something along the lines of what caused my recent confusion over headlines that trumpeted “MIT researchers discover a new energy source: nanotechnology”.

And that’s what I found, more or less. What we got was the work of Professor Zhong Lin Wang, Director of the Center for Nanostructure Characterization at Georgia Tech whose work on exploiting the piezoelectric qualities of zinc oxide nanowires to power small devices through human movement I have covered on this blog.

The author of the blog relates her meeting with the charismatic Professor Wang while at a conference and discovering that his highly touted research had seemingly overcome the low voltage problems of his previous devices. He was now making devices that produced 2.4 volts, which as the author notes makes possible “integrating a charge-storage device that will make it possible to regulate the voltage going into the sensors for better control of measurements.” Wang concurs and even says that is his next bit of research.

All in all a nice bit of reporting, but I can’t help but think that the headline while intriguing is hopelessly muddled. I believe the headline here at the very least is free from any marketing copy. 

In any case, here’s a video from CNN about six months ago in which Professor Wang exhibits his devices.

My first introduction to the discovery of the fabled memristor was right here on the pages of Spectrum and I have been hooked on this story ever since.

Whenever a new bit of information comes out about the memristor, I can’t resist the urge to read that story, or watch that video:

So when I saw Frogheart, which is a new addition to my blog roll, had written something on the latest news around the fourth fundamental circuit element, I was compelled to read it. And I’m glad I did.

The article filled me in on research that took place in 2008 in Japan, which is about the same time that R. Stanley Williams and his colleagues at HP reported that they had manufactured devices that were memristors.

The Japanese researchers were working with rather humble slime mould after having been inspired by a research group at the University of California San Diego (UC San Diego). They were able to confirm that theorist Leon Chua’s intuition that biological organisms used memristive systems to learn. Frogheart was good enough to provide the link to the article from a publication called HPlus.

This year researchers at the University of Michigan led by Dr. Wei Lu have demonstrated how synapses behave like memristors, which was published in Nano Letters. 

As Frogheart says, “In the short term, scientists talk about energy savings (no need to reboot your computer when you turn it back on). In the longer term, they talk about hardware being able to learn.”

While IBM researchers were reporting one breakthrough after another in applying graphene to electronics this year (see here and here) researchers at the University of Cambridge in the UK and CNRS in Grenoble, France were busy applying the new wonder material to optoelectronic applications.

The Europe-based researchers fabricated a device that demonstrated “the most wideband saturable light absorber ever”. But not to be outdone in applying graphene to the field of optoelectronics, IBM has quickly reported on their own research of using graphene as a photodetector in an optical link fabricated on a silicon-on-insulator (SOI) substrate.

The graphene photodetector has proven itself to be effective over a wide bandwidth between 300 nanometers to 6 microns, which could make the optical link useful for applications beyond just communications “but for remote sensing, environmental monitoring and surveillance.”

Photodectors that are effective within these wavelengths have typically been made from III-V semiconductor materials, such as gallium nitride. But in this new research by being able to fabricate the optical link on a conventional SOI substrate the possibility of fabricating photonic circuits with CMOS processes seems as though it may be within reach.

As the author of the EE Times article speculates on his own blog: 

“Silicon photonics is the holy grail of optical communications, enabling cheap integrated optics that handle all high-speed communications among chips and even among on-chip cores. Now IBM has demonstrated the last piece of the photonics toolkit--an optical receiver on a silicon-on-insulator substrate (SoI). Look for optical chips that integrate graphene with CMOS in five years.”

One of the most vexing problems faced in nanoscale electronics has been that the more you decrease the size of the metallic interconnects the greater their resistance. This typically leads to Joule heating of the interconnects that melts and destroys them.

Researchers at the University of Ohio are reporting that they have created a molecule chain made from organic salt that exhibits superconductivity thereby bringing its resistance down to zero.

The research was initially published in Nature Nanotechnology and describes how the researchers were able to first synthesize the molecules of organic salt ((BETS)2-GaCl4) place them on a silver substrate and then with a scanning tunneling microscope were able to observe how when formed into groups as small as just four pairs could exhibit superconductivity.

While the research looked at the smallest limit to the superconductivity with the four pairs, it also noted that the best results were found in chains of the molecule longer than 50nm in length.

Beyond the claims that the researchers have created the smallest known superconductor, this work would seem to reopen the option of using metallic interconnects at this nanometer scale.

I was reading a very professional article in the Boston Globe (I emphasize “professional” because so often these articles are not) that details the impact of nanotechnology innovation in Massachusetts when I stopped to consider why it is that people feel nanotechnology has not fulfilled their expectations.

The article starts with: “State officials and economic developers imagined new industries and jobs. Universities jockeyed for billions in research money. The news media hyped it as the next big thing. So what happened?” The answer we quickly get is “A lot, actually.”

The Globe reporter, Robert Gavin, offers some explanations for why the public has not been overwhelmed by nanotechnology’s impact that include its lack of “sexiness” and “Unlike with other technologies, there is not necessarily a consumer product at the end of the pipeline. Instead, nanotechnology often provides the components that make breakthroughs in new and existing products possible.” I couldn’t agree more. As I have said before in nanotech it’s the mundane that’s interesting.

The article goes on to share some interesting quotes from Mihail Roco, the long-time director of the National Nanotechnology Initiative (NNI), which offer up some possible timelines for nanotechnology’s development: “Nanotechnology is at about the point that IT had reached in 1975, said Roco, but has gotten there much faster. Roco estimates nanotechnology will reach IT’s 1995 stage by 2020.”

However, it neglects to address another key reason why nanotechnology has seemingly disappointed the fertile imagination of the general public. The unspoken and unanswered question seems to be: Where are the nanofactories and nanobots and the ability to make a laptop computer by pushing a button on your table-top factory?

While I have had my differences of opinion with some of the folks from the molecular manufacturing community, I do agree with them that many people believed that the nanotechnology they thought they would be getting would be more like that instead of the advanced material science and chemistry that we have today. As Philip Moriarty is quoted as saying in a recent interview “The problem with the nano- prefix is that there isn’t an area of modern condensed matter/solid state physics or chemistry that can’t be badged as nanoscience.”  

So, it seems that this is where science was in 2001 when the NNI was launched and the advanced material science of “surface reconstructions” needed funding and research and stood a far better chance of getting it if it was called “nano”. It’s worthwhile research, it will enable already existing products and even create some new ones, but maybe it’s time to say this doesn’t seem like the nanotechnology that captured our imagination because it isn’t.

I have had a fair amount of fun in the past at the expense of Nokia and Cambridge University ever since they announced in 2008 their much reported on Morph phone, which displayed the work that the two organizations were doing jointly in applying plastic electronics to mobile phones.

As I stated at the time and since then, I haven’t much interest, and I am not sure why anyone else would, in a phone that can wrap around my wrist, when what I really want is a phone with much improved battery technology.

So I was encouraged when I saw that Nokia researchers had published an entire book  on the topic of how nanotechnology could be applied to the mobile phone. Certainly in an entire book there would likely be discussion on how mobile phone batteries are being improved by nanotechnology.

The book entitled “Nanotechnologies for Future Mobile Devices” (excerpts can be read here) is supposed to detail the work that is going on at the Nokia Research Center (NRC) at Cambridge University. One of the fields of research that is detailed is battery capabilities. I don’t know what that research is since it is neither discussed in the article or in the available excerpts, but I am hoping it’s significant.

I know the “gee whiz” factor of a Dick-Tracy-like wrap around phone is high, but I still contend that a battery that could work  on any kind of smart phone for a month or a week would really get a lot of “gee whiz” press too.