Tag Archives: nanoelectronics

A DNA switch for new electronic applications

I little dreamed when reading “The Double Helix : A Personal Account of the Discovery of the Structure of DNA” by James Watson that DNA (deoxyribonucleic acid) would one day become just another material for scientists to manipulate. A Feb. 20, 2017 news item on ScienceDaily describes the use of DNA as a material in electronics applications,

DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.

Much like flipping your light switch at home — only on a scale 1,000 times smaller than a human hair — an ASU [Arizona State University]-led team has now developed the first controllable DNA switch to regulate the flow of electricity within a single, atomic-sized molecule. The new study, led by ASU Biodesign Institute researcher Nongjian Tao, was published in the advanced online journal Nature Communications.

DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices. Courtesy: ASU

A Feb. 20, 2017 ASU news release (also on EurekAlert), which originated the news item, provides more detail,

“It has been established that charge transport is possible in DNA, but for a useful device, one wants to be able to turn the charge transport on and off. We achieved this goal by chemically modifying DNA,” said Tao, who directs the Biodesign Center for Bioelectronics and Biosensors and is a professor in the Fulton Schools of Engineering. “Not only that, but we can also adapt the modified DNA as a probe to measure reactions at the single-molecule level. This provides a unique way for studying important reactions implicated in disease, or photosynthesis reactions for novel renewable energy applications.”

Engineers often think of electricity like water, and the research team’s new DNA switch acts to control the flow of electrons on and off, just like water coming out of a faucet.

Previously, Tao’s research group had made several discoveries to understand and manipulate DNA to more finely tune the flow of electricity through it. They found they could make DNA behave in different ways — and could cajole electrons to flow like waves according to quantum mechanics, or “hop” like rabbits in the way electricity in a copper wire works —creating an exciting new avenue for DNA-based, nano-electronic applications.

Tao assembled a multidisciplinary team for the project, including ASU postdoctoral student Limin Xiang and Li Yueqi performing bench experiments, Julio Palma working on the theoretical framework, with further help and oversight from collaborators Vladimiro Mujica (ASU) and Mark Ratner (Northwestern University).

To accomplish their engineering feat, Tao’s group, modified just one of DNA’s iconic double helix chemical letters, abbreviated as A, C, T or G, with another chemical group, called anthraquinone (Aq). Anthraquinone is a three-ringed carbon structure that can be inserted in between DNA base pairs but contains what chemists call a redox group (short for reduction, or gaining electrons or oxidation, losing electrons).

These chemical groups are also the foundation for how our bodies’ convert chemical energy through switches that send all of the electrical pulses in our brains, our hearts and communicate signals within every cell that may be implicated in the most prevalent diseases.

The modified Aq-DNA helix could now help it perform the switch, slipping comfortably in between the rungs that make up the ladder of the DNA helix, and bestowing it with a new found ability to reversibly gain or lose electrons.

Through their studies, when they sandwiched the DNA between a pair of electrodes, they careful [sic] controlled their electrical field and measured the ability of the modified DNA to conduct electricity. This was performed using a staple of nano-electronics, a scanning tunneling microscope, which acts like the tip of an electrode to complete a connection, being repeatedly pulled in and out of contact with the DNA molecules in the solution like a finger touching a water droplet.

“We found the electron transport mechanism in the present anthraquinone-DNA system favors electron “hopping” via anthraquinone and stacked DNA bases,” said Tao. In addition, they found they could reversibly control the conductance states to make the DNA switch on (high-conductance) or switch-off (low conductance). When anthraquinone has gained the most electrons (its most-reduced state), it is far more conductive, and the team finely mapped out a 3-D picture to account for how anthraquinone controlled the electrical state of the DNA.

For their next project, they hope to extend their studies to get one step closer toward making DNA nano-devices a reality.

“We are particularly excited that the engineered DNA provides a nice tool to examine redox reaction kinetics, and thermodynamics the single molecule level,” said Tao.

Here’s a link to and a citation for the paper,

I last featured Tao’s work with DNA in an April 20, 2015 posting.

Gate-controlled conductance switching in DNA by Limin Xiang, Julio L. Palma, Yueqi Li, Vladimiro Mujica, Mark A. Ratner, & Nongjian Tao.  Nature Communications 8, Article number: 14471 (2017)  doi:10.1038/ncomms14471 Published online: 20 February 2017

This paper is open access.

Carbyne: 40x stiffer than diamond

A material that’s tougher than diamond is the object of interest for researchers at the US Department of Energy’s Lawrence Livermore National Laboratory (LLNL) according to a Sept. 18, 2015 news item by Beth Ellison on Azonano (Note: A link has been removed),

Researchers at Lawrence Livermore National Laboratory (LLNL) have explored a method that uses laser-melted graphite to develop linear chains of carbon atoms.

This material, referred to as carbyne, could possess numerous unique properties, such as modification of the quantity of electrical current passing through a circuit according to the needs of a user. This research could probably lead to the creation of tiny electronics capable of turning on and off at an atomic scale.

A Sept. 17, 2015 LLNL news release (also on EurekAlert) details the research (Note: A link has been removed),

Carbyne is the subject of intense research because of its presence in astrophysical bodies, as well as its potential use in nanoelectronic devices and superhard materials. Its linear shape gives it unique electrical properties that are sensitive to stretching and bending, and it is 40 times stiffer than diamond. It also was found in the Murchison and Allende meteorites and could be an ingredient of interstellar dust.

Using computer simulations, LLNL scientist Nir Goldman and colleague Christopher Cannella, an undergraduate summer researcher from Caltech, initially intended to study the properties of liquid carbon as it evaporates, after being formed by shining a laser beam on the surface of graphite. The laser can heat the graphite surface to a few thousands of degrees, which then forms a fairly volatile droplet. To their surprise, as the liquid droplet evaporated and cooled in their simulations, it formed bundles of linear chains of carbon atoms.

“There’s been a lot of speculation about how to make carbyne and how stable it is,” Goldman said. “We showed that laser melting of graphite is one viable avenue for its synthesis. If you regulate carbyne synthesis in a controlled way, it could have applications as a new material for a number of different research areas, including as a tunable semiconductor or even for hydrogen storage.

“Our method shows that carbyne can be formed easily in the laboratory or otherwise. The process also could occur in astrophysical bodies or in the interstellar medium, where carbon-containing material can be exposed to relatively high temperatures and carbon can liquefy.”

Goldman’s study and computational models allow for direct comparison with experiments and can help determine parameters for synthesis of carbon-based materials with potentially exotic properties.

“Our simulations indicate a possible mechanism for carbyne fiber synthesis that confirms previous experimental observation of its formation,” Goldman said. “These results help determine one set of thermodynamic conditions for its synthesis and could account for its detection in meteorites resulting from high-pressure conditions due to impact.”

Here’s a link to and a citation for the paper,

Carbyne Fiber Synthesis within Evaporating Metallic Liquid Carbon by Christopher B. Cannella and Nir Goldman. J. Phys. Chem. C, 2015, 119 (37), pp 21605–21611 DOI: 10.1021/acs.jpcc.5b03781 Publication Date (Web): July 9, 2015 (print): Sept. 17, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Dexter Johnson in a Sept. 18, 2015 posting about the latest carbyne developments on his Nanoclast blog (on the IEEE [Institute for Electrical and Electronics Engineers] website) provides a little history (Note: Links have been removed),

A couple of years ago, a material dubbed carbyne—which is a chain of carbon atoms held together by either double or alternating single and triple atomic bonds—was awarded the title of the world’s strongest material. Later, scientists also demonstrated that it has the unusual property of being able to change from being a conductor to an insulator when it’s stretched by as little as 3 percent.

Here’s an image illustrating the process,

A carbyne strand forms in laser-melted graphite. Carbyne is found in astrophysical bodies and has the potential to be used in nanoelectronic devices and superhard materials. Image by Liam Krauss/LLNL

A carbyne strand forms in laser-melted graphite. Carbyne is found in astrophysical bodies and has the potential to be used in nanoelectronic devices and superhard materials. Image by Liam Krauss/LLNL

Christmas-tree shaped ‘4-D’ nanowires

This Dec. 5, 2012 news item on Nanowerk features a seasonal approach to a study about ‘4-D’ nanowires,

A new type of transistor shaped like a Christmas tree has arrived just in time for the holidays, but the prototype won’t be nestled under the tree along with the other gifts.

“It’s a preview of things to come in the semiconductor industry,” said Peide “Peter” Ye, a professor of electrical and computer engineering at Purdue University.

Researchers from Purdue and Harvard universities created the transistor, which is made from a material that could replace silicon within a decade. Each transistor contains three tiny nanowires made not of silicon, like conventional transistors, but from a material called indium-gallium-arsenide. The three nanowires are progressively smaller, yielding a tapered cross section resembling a Christmas tree.

Sadly, Purdue University (Indiana, US) will not be releasing any images to accompany their Dec. 4, 2012 news release (which originated the news item) about the ‘4-D’ transistor  until Saturday, Dec. 8, 2012.  So here’s an image of a real Christmas tree from the National Christmas Tree Organization’s Common Tree Characteristics webpage,

Douglas Fir Christmas tree from http://www.realchristmastrees.org/dnn/AllAboutTrees/TreeCharacteristics.aspx


The Purdue University news release written by Emil Venere provides more detail about the work,

“A one-story house can hold so many people, but more floors, more people, and it’s the same thing with transistors,” Ye said. “Stacking them results in more current and much faster operation for high-speed computing. This adds a whole new dimension, so I call them 4-D.”

The work is led by Purdue doctoral student Jiangjiang Gu and Harvard postdoctoral researcher Xinwei Wang.

The newest generation of silicon computer chips, introduced this year, contain transistors having a vertical 3-D structure instead of a conventional flat design. However, because silicon has a limited “electron mobility” – how fast electrons flow – other materials will likely be needed soon to continue advancing transistors with this 3-D approach, Ye said.

Indium-gallium-arsenide is among several promising semiconductors being studied to replace silicon. Such semiconductors are called III-V materials because they combine elements from the third and fifth groups of the periodic table.

Transistors contain critical components called gates, which enable the devices to switch on and off and to direct the flow of electrical current. Smaller gates make faster operation possible. In today’s 3-D silicon transistors, the length of these gates is about 22 nanometers, or billionths of a meter.

The 3-D design is critical because gate lengths of 22 nanometers and smaller do not work well in a flat transistor architecture. Engineers are working to develop transistors that use even smaller gate lengths; 14 nanometers are expected by 2015, and 10 nanometers by 2018.

However, size reductions beyond 10 nanometers and additional performance improvements are likely not possible using silicon, meaning new materials will be needed to continue progress, Ye said.

Creating smaller transistors also will require finding a new type of insulating, or “dielectric” layer that allows the gate to switch off. As gate lengths shrink smaller than 14 nanometers, the dielectric used in conventional transistors fails to perform properly and is said to “leak” electrical charge when the transistor is turned off.

Nanowires in the new transistors are coated with a different type of composite insulator, a 4-nanometer-thick layer of lanthanum aluminate with an ultrathin, half-nanometer layer of aluminum oxide. The new ultrathin dielectric allowed researchers to create transistors made of indium-gallium- arsenide with 20-nanometer gates, which is a milestone, Ye said.

This work will be presented at the 2012 International Electron Devices (IEEE [Institute of Electrical and Electronics Engineers]) meeting in San Francisco, California, Dec. 10 – 12, 2012 (as per the information on the registration page) with the two papers written by the team will be published in the proceedings.

I have a full list of the authors, from the news release,

The authors of the research papers are Gu [Jiangjiang Gu]; Wang [Xinwei Wang]; Purdue doctoral student H. Wu; Purdue postdoctoral research associate J. Shao; Purdue doctoral student A. T. Neal; Michael J. Manfra, Purdue’s William F. and Patty J. Miller Associate Professor of Physics; Roy Gordon, Harvard’s Thomas D. Cabot Professor of Chemistry; and Ye [Peide “Peter” Ye].

Gold unzips your DNA but not in a sexy way

The animation that the scientists from North Carolina have provided makes the gold nanoparticles look downright mean as that DNA definitely does not want to be unzipped but perhaps your mileage varies,

The June 20, 2012 news item on Nanowerk provides more detail,

New research from North Carolina State University finds that gold nanoparticles with a slight positive charge work collectively to unravel DNA’s double helix. This finding has ramifications for gene therapy research and the emerging field of DNA-based electronics.

The research team introduced gold nanoparticles, approximately 1.5 nanometers in diameter, into a solution containing double-stranded DNA. The nanoparticles were coated with organic molecules called ligands. Some of the ligands held a positive charge, while others were hydrophobic – meaning they were repelled by water.

Because the gold nanoparticles had a slight positive charge from the ligands, and DNA is always negatively charged, the DNA and nanoparticles were pulled together into complex packages.

“However, we found that the DNA was actually being unzipped by the gold nanoparticles,” Melechko [Dr. Anatoli Melechko, an associate professor of materials science and engineering at NC State and co-author of the paper] says. The positively-charged ligands on the nanoparticles attached to the DNA as predicted, but the hydrophobic ligands of the nanoparticles became tangled with each other. As this tangling pulled the nanoparticles into clusters, the nanoparticles pulled the DNA apart.

The implications for this ‘unzipping’ are,

“We think gold nanoparticles still hold promise for gene therapy,” says Dr. Yaroslava Yingling, an assistant professor of materials science and engineering at NC State and co-author of the paper. “But it’s clear that we need to tailor the ligands, charge and chemistry of these materials to ensure the DNA’s structural integrity is not compromised.”

The finding is also relevant to research on DNA-based electronics, which hopes to use DNA as a template for creating nanoelectronic circuits. Because some work in that field involves placing metal nanoparticles on DNA, this finding indicates that researchers will have to pay close attention to the characteristics of those nanoparticles – or risk undermining the structural integrity of the DNA.

My ‘Whose electric brain?’ talk on March 15, 2012

Later this week (March 15, 2012), I will be giving a talk in Vancouver,

The Canadian Academy of Independent Scholars

Notice of Meeting

Date:  Thursday, March 15, 2012

Time:  7:30 pm

Place:  Simon Fraser University, Vancouver, BC campus, 515 West Hastings Street (between Seymour and Richards Streets) in the Diamond Alumni Lounge, Room 2065 (second floor)

Speaker:  Maryse de la Giroday

Topic:  Whose electric brain?

Memristors are collapsing the boundaries between humans and machines and ushering in an age where humanistic discourse must grapple with cognitive entanglements. Perceptible only at the level of molecular electronics (nanoelectronics), the memristor was a theoretical concept until 2008. Two different researchers without knowledge of each other had postulated its probable existence respectively in the 1960s and the 1970s. Traditionally in electrical engineering there are resistors, inductors, and capacitors. The new circuit element, the memristor, was postulated to account for anomalies that had been experienced and described in the literature since the 1950s.

Conceptually, a memristor remembers how much and when current has been flowing. In 2008 when it was proved experimentally, engineering control was achieved months later in both digital and analogue formats. The more intriguing of the two formats is the analogue where a memristor is capable of an in-between state similar to certain brain states as opposed to the digital format where it’s either on or off. As some have described it, the memristor is a synapse on a chip making neural computing a reality. In other words, with post-human engineering we will have machines that can think like humans.

The memristor moves us past Jacques Derrida’s notion of undecidability (a cognitive entanglement) as largely theoretical to a world where we confront this reality on a daily basis.

A Brief Bio:

Maryse de la Giroday is a science communications consultant and writer who focuses on nanotechnology and science in Canada. Her blog (www.frogheart.ca) offers “Commentary about nanotech, science policy and communication, society, and the arts” and it currently enjoys an average of 50,000+ visits per month.

She has a BA (honors-Communications) from SFU and an MA (Creative Writing and New Media) De Montfort University, UK.

As an independent academic, she has presented on the topic of nanotechnology at the 2009 International Symposium on Electronic Arts, the 2008 Congress of Humanities and the Social Sciences, the 2008 Cascadia Nanotechnology Symposium, and the 2007 Association of Internet Researchers.

She gratefully acknowledge the 2011 grant from the Canadian Academy of Independent Scholars which makes the publication of her latest paper, Whose electric brain? possible.

I expect to be exploring ideas about machines and humans as buttressed by the notion of the memristor. The talk will be recorded (tarted up/edited) by Sama Shodjai and posted, in the near future, here and elsewhere online.

To be or not to be the memristor?

The memristor (aka, memresistor), for anyone not familiar with it, is a contested ‘new’ circuit element. In my April 5, 2010 posting I gave a brief overview of the history as I understood it (the memristor was a new addition to the traditional circuit elements [the capacitor, the resistor, and the inductor]) and in my April 7, 2010 posting I conducted an interview with Forrest H Bennett III who presented an alternative view to the memristor as ‘new’ circuit element discussion.

Discussion has continued on and off since then but in the last few weeks it has become more topical with the publication of a paper (Memresistors and non-memristive zero-crossing hysteresis curves) by Blaise Mouttet at arXiv.org on Jan. 12, 2012.

I don’t feel competent to summarize the gist of Blaise’s paper so I’m excerpting a passage *from* Peter Clarke’s Jan. 18, 2012 article for EE (Electronic Engineering) Times,

Blaise Mouttet argues that the interpretation of the memristor as a fourth fundamental circuit element – after the resistor, capacitor and inductor – was incorrect and that the memory device under development at HP Labs is not actually a memristor but part of a broader class of variable resistance systems.

Since publishing his arXiv paper Mouttet has also been in discussion with an e-mailing list of researchers into non-volatile memory device physics.

Some e-mail correspondents have come out in favor of Mouttet’s position stating that trying to define any two-terminal device in which the resistance can be altered by the current passed through the device as a memristor, adds nothing to the understanding of a complex field in which there are many types of device.

The article and the comments that follow (quite interesting and technical) are worth reviewing if this area of nanoelectronics interests you.

HP Labs has responded to Blaise’s paper and subsequent debate, and before included an excerpt from the response, I want to include a few passages from Blaise’s paper,

The “memristor” was originally proposed in 1971by Leon Chua as a missing fourth fundamental circuit element linking magnetic flux and electric charge. In 2008 a group of scientists from HP led by Stan Williams claimed to have discovered this missing memristor . It is my position that HP’s “memristor” claim lacks any scientific merit. My position is not that the HP researchers have presented an incorrect model of a memristor or even an incorrect model of resistance memory. If this were the case it would not be so bad because an incorrect model could at least be proven incorrect and possibly corrected to produce a better model. My position is that the HP researchers have avoided presenting any scientifically testable model at all by hiding behind the reputation of Leon Chua and the mythology of the memristor. They have thus attempted to bypass the principle of the scientific method.

If the HP researchers had developed a realistic model for resistive memory (whether it is called “memristor” or by some other name) it could be vetted by other researchers, compared to experimental data, and determined to be true or false. If necessary the model could be modified or corrected and an improved version of the model could be produced.

This is not what has happened. (p. 1 PDF)

Here’s my excerpt of HP’s response (from Peter Clarke’s Jan. 20, 2012 article for EE Times),

The spokesperson said in email: “HP is proud of the research it has undertaken into memristor technology and the recognition this has received in the scientific community. In a little over three years, our papers, which were subject to rigorous peer review before being published in leading scientific journals, have been cited more than 1,000 times by other researchers in the field. We continue this research and collaboration with the electronics industry to bring this important technology to market.”

Deciding what something is and how fits into our understanding of how the world operates, in this case, a new circuit element, or not, has consequences beyond the actual discussion. If science is the process of posing questions, we need to test the assumptions we make (in this case, whether or not the memristor is a fourth circuit element or part of a larger system of variable resistance systems) as they can define the questions we’ll ask in the future.

As I noted earlier, I’m not competent to draw any conclusions as to which party may have the right approach but I am glad to see the discussion taking place.

*’from’ added on Sept. 27, 2016.

Science communication in Canada (part 4b); NanoArt 2009; future nanoelectronics

Most science public relations (pr) and marketing efforts (including public engagement) in Canada are made by government agencies.  There is a communications officer (actually, it’s usually a team of communications officers) in every government-funded science-oriented agency (e.g. National Research Council, the National of Institute of Nanotechnology, Natural Sciences and Engineering Research Council, Canadian Institutes of Health Research, etc.)

In part 3 of this series (Sept. 21, 2009), I mentioned the impact a gag order placed on Environment Canada scientists in January 2008 has had on Canadian science journalism. It’s fair to assume that the gag order also has had an impact on people whose government agency job is science pr.

My guess is that an already cautious science pr and marketing community has become more controlling and more worried.  Take for example the nanomaterials inventory (mentioned in earlier postings) that was announced not by Environment Canada but, in February 2009, by the Project on Emerging Nanotechnologies based in Washington, DC. It’s somewhat disconcerting to have a Canadian government initiative announced in the US first. It’s possible that there’s no connection to the gag order but I cannot recall any Canadian government initiative being announced in another country first.

I have another example of a science pr oddity but it’s based on memory because I didn’t think to save the article and I can’t find it online. As memory serves, months after the 2008 federal election there was an article in a paper that I read stating that an important Canadian science advance done in conjunction with (US) NASA had been suppressed during the election campaign. The information was announced later in the US (again). The article noted this was the first time that information about an advance attributable to Canadian scientists was suppressed during an election campaign, apparently, due to concerns that the announcement would be prejudicial.

In what universe does someone read about a scientific advance and immediately praise or condemn (depending on how you view the advance) a political party? I cannot recall the last time a local candidate got a boost or fell  in the polls when the government announced a scientific advance. Even a biotechnology advance (with biotech being one of the most contentious science sectors in terms of public perception) would not be likely to have that kind of impact. Note that I said unlikely not impossible and that is where the problem lies. There are risks associated with science pr and marketing.

Whether it’s a government, a business, or a non-for-profit agency, there’s always the risk of embarrassment (your data is incorrect), the risk that popular opinion will rise against you, and/or the risk that someone more persuasive will slant your data to prove the case against you. These risks don’t pertain to science alone but there is a specific problem associated with science. Most of us are intimidated by it and, if you’re not, it’s hard to get information that is slanted for an adult who doesn’t have a science background. (Tomorrow’s installment will feature some current science pr initiatives and it will  be last of this series.)

Now for a couple of quick announcements. Chris Orfescu’s NanoArt 2009 competition  is calling for submissions (from the Azonano news item),

The artists can participate with up to 5 images (artworks). All submitted works will be exhibited on the nanoart21.org site until March 31, 2010, together with artist’s name, a short description of the artistic process, and artist’s web site and e-mail. The top 10 artists will be exhibited on nanoart21.org site for one full year and will be invited to exhibit at the 3rd edition of The International Festival of NanoArt. The previous editions of the festival were held in Finland and Germany.

There are more details on the Azonano website.

Michael Berger (Nanowerk Spotlight) has an article on future nanoelectronics which contradicts much that you may have learned about electricity and electronics in high school. From the article on Nanowerk,

Nanotechnology-enabled electronics of the future will be invisible, i.e. transparent (see “Invisible electronics made with carbon nanotubes”), or flexible, or both. One of the areas [John Rogers’ group at the University of Illlinois] focus on is creating materials and processes that will allow high-performance electronics that are flexible and stretchable (see our previous Spotlight “Gutenberg + nanotechnology = printable electronics”)

That’s it.