Tag Archives: Zheng Ma

Artificial synapse courtesy of nanowires

It looks like a popsicle to me,

Caption: Image captured by an electron microscope of a single nanowire memristor (highlighted in colour to distinguish it from other nanowires in the background image). Blue: silver electrode, orange: nanowire, yellow: platinum electrode. Blue bubbles are dispersed over the nanowire. They are made up of silver ions and form a bridge between the electrodes which increases the resistance. Credit: Forschungszentrum Jülich

Not a popsicle but a representation of a device (memristor) scientists claim mimics a biological nerve cell according to a December 5, 2018 news item on ScienceDaily,

Scientists from Jülich [Germany] together with colleagues from Aachen [Germany] and Turin [Italy] have produced a memristive element made from nanowires that functions in much the same way as a biological nerve cell. The component is able to both save and process information, as well as receive numerous signals in parallel. The resistive switching cell made from oxide crystal nanowires is thus proving to be the ideal candidate for use in building bioinspired “neuromorphic” processors, able to take over the diverse functions of biological synapses and neurons.

A Dec. 5, 2018 Forschungszentrum Jülich press release (also on EurekAlert), which originated the news item, provides more details,

Computers have learned a lot in recent years. Thanks to rapid progress in artificial intelligence they are now able to drive cars, translate texts, defeat world champions at chess, and much more besides. In doing so, one of the greatest challenges lies in the attempt to artificially reproduce the signal processing in the human brain. In neural networks, data are stored and processed to a high degree in parallel. Traditional computers on the other hand rapidly work through tasks in succession and clearly distinguish between the storing and processing of information. As a rule, neural networks can only be simulated in a very cumbersome and inefficient way using conventional hardware.

Systems with neuromorphic chips that imitate the way the human brain works offer significant advantages. Experts in the field describe this type of bioinspired computer as being able to work in a decentralised way, having at its disposal a multitude of processors, which, like neurons in the brain, are connected to each other by networks. If a processor breaks down, another can take over its function. What is more, just like in the brain, where practice leads to improved signal transfer, a bioinspired processor should have the capacity to learn.

“With today’s semiconductor technology, these functions are to some extent already achievable. These systems are however suitable for particular applications and require a lot of space and energy,” says Dr. Ilia Valov from Forschungszentrum Jülich. “Our nanowire devices made from zinc oxide crystals can inherently process and even store information, as well as being extremely small and energy efficient,” explains the researcher from Jülich’s Peter Grünberg Institute.

For years memristive cells have been ascribed the best chances of being capable of taking over the function of neurons and synapses in bioinspired computers. They alter their electrical resistance depending on the intensity and direction of the electric current flowing through them. In contrast to conventional transistors, their last resistance value remains intact even when the electric current is switched off. Memristors are thus fundamentally capable of learning.

In order to create these properties, scientists at Forschungszentrum Jülich and RWTH Aachen University used a single zinc oxide nanowire, produced by their colleagues from the polytechnic university in Turin. Measuring approximately one ten-thousandth of a millimeter in size, this type of nanowire is over a thousand times thinner than a human hair. The resulting memristive component not only takes up a tiny amount of space, but also is able to switch much faster than flash memory.

Nanowires offer promising novel physical properties compared to other solids and are used among other things in the development of new types of solar cells, sensors, batteries and computer chips. Their manufacture is comparatively simple. Nanowires result from the evaporation deposition of specified materials onto a suitable substrate, where they practically grow of their own accord.

In order to create a functioning cell, both ends of the nanowire must be attached to suitable metals, in this case platinum and silver. The metals function as electrodes, and in addition, release ions triggered by an appropriate electric current. The metal ions are able to spread over the surface of the wire and build a bridge to alter its conductivity.

Components made from single nanowires are, however, still too isolated to be of practical use in chips. Consequently, the next step being planned by the Jülich and Turin researchers is to produce and study a memristive element, composed of a larger, relatively easy to generate group of several hundred nanowires offering more exciting functionalities.

The Italians have also written about the work in a December 4, 2018 news item for the Polytecnico di Torino’s inhouse magazine, PoliFlash’. I like the image they’ve used better as it offers a bit more detail and looks less like a popsicle. First, the image,

Courtesy: Polytecnico di Torino

Now, the news item, which includes some historical information about the memristor (Note: There is some repetition and links have been removed),

Emulating and understanding the human brain is one of the most important challenges for modern technology: on the one hand, the ability to artificially reproduce the processing of brain signals is one of the cornerstones for the development of artificial intelligence, while on the other the understanding of the cognitive processes at the base of the human mind is still far away.

And the research published in the prestigious journal Nature Communications by Gianluca Milano and Carlo Ricciardi, PhD student and professor, respectively, of the Applied Science and Technology Department of the Politecnico di Torino, represents a step forward in these directions. In fact, the study entitled “Self-limited single nanowire systems combining all-in-one memristive and neuromorphic functionalities” shows how it is possible to artificially emulate the activity of synapses, i.e. the connections between neurons that regulate the learning processes in our brain, in a single “nanowire” with a diameter thousands of times smaller than that of a hair.

It is a crystalline nanowire that takes the “memristor”, the electronic device able to artificially reproduce the functions of biological synapses, to a more performing level. Thanks to the use of nanotechnologies, which allow the manipulation of matter at the atomic level, it was for the first time possible to combine into one single device the synaptic functions that were individually emulated through specific devices. For this reason, the nanowire allows an extreme miniaturisation of the “memristor”, significantly reducing the complexity and energy consumption of the electronic circuits necessary for the implementation of learning algorithms.

Starting from the theorisation of the “memristor” in 1971 by Prof. Leon Chua – now visiting professor at the Politecnico di Torino, who was conferred an honorary degree by the University in 2015 – this new technology will not only allow smaller and more performing devices to be created for the implementation of increasingly “intelligent” computers, but is also a significant step forward for the emulation and understanding of the functioning of the brain.

“The nanowire memristor – said Carlo Ricciardirepresents a model system for the study of physical and electrochemical phenomena that govern biological synapses at the nanoscale. The work is the result of the collaboration between our research team and the RWTH University of Aachen in Germany, supported by INRiM, the National Institute of Metrological Research, and IIT, the Italian Institute of Technology.”

h.t for the Italian info. to Nanowerk’s Dec. 10, 2018 news item.

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

Self-limited single nanowire systems combining all-in-one memristive and neuromorphic functionalities by Gianluca Milano, Michael Luebben, Zheng Ma, Rafal Dunin-Borkowski, Luca Boarino, Candido F. Pirri, Rainer Waser, Carlo Ricciardi, & Ilia Valov. Nature Communicationsvolume 9, Article number: 5151 (2018) DOI: https://doi.org/10.1038/s41467-018-07330-7 Published: 04 December 2018

This paper is open access.

Just use the search term “memristor” in the blog search engine if you’re curious about the multitudinous number of postings on the topic here.

Nature imitates art at Northeastern University (US)

It’s an intriguing mental exercise trying to flip the tables on nature as an inspiration for art to start discussing ‘artmimetics’ as they seem to be doing at Northeastern University (Boston, Massachusetts, US), according to a Dec. 11, 2013 news item on Azonano,

There are exam­ples of art imi­tating nature all around us—whether it’s Monet’s pastel Water Lilies or Chihuly’s glass­blown Seaforms, the human con­cep­tion of nat­ural phe­nomena daz­zles but does not often surprise.

Yet when asso­ciate pro­fessor of physics Latika Menon peered under the elec­tron micro­scope last fall, she dis­cov­ered the exact oppo­site. Instead of art imi­tating nature, she found nature imi­tating art.

The Dec. 10, 2013 Northeastern University news release by Angela Herring, which ‘inspired’ the news item, describes how Menon and her colleagues came to reverse the inspirational direction,

Menon grew up in the eastern region of India and was vaguely familiar with a cul­tural dance from the western state of Rajasthan known as the Bhavai pot dance. Nimble dancers sway their hips as a tall stack of wide-​​bellied pots bal­ances gin­gerly atop their heads. Back in the lab at North­eastern, Menon’s team recently cre­ated  gal­lium nitride nanowires, which bore a striking resem­blance to that stack of pots.

What’s more, a post­doc­toral research asso­ciate in Menon’s lab, Eugen Panaitescu, jumped on the band­wagon with a cul­tural art ref­er­ence of his own. Panaitescu, who hails from Romania, also saw his country’s famous End­less Column reflected in the nanowires. Ded­i­cated to the fallen Romanian heroes of World War I, Con­stantin Brancusi’s 96-​​foot-​​tall mono­lith is con­structed of 17 three-​​dimensional rhom­buses, peri­od­i­cally wavering from a wider cir­cum­fer­ence to a nar­rower one.

The news release goes on to explain more about applications using gallium nitride and why Menon’s insight may prove useful in developing new uses for gallium nitride nanowires,

… Gal­lium nitride is used across a range of tech­nolo­gies, including most ubiq­ui­tously in light emit­ting diodes. The mate­rial also holds great poten­tial for solar cell arrays, mag­netic semi­con­duc­tors, high-​​frequency com­mu­ni­ca­tion devices, and many other things. But these advanced appli­ca­tions are restricted by our lim­ited ability to con­trol the material’s growth on the nanoscale.

The very thing that makes Menon’s nanowires beau­tiful rep­re­sents a break­through in her ability to process them for these novel uses. She deposited onto a sil­icon sub­strate small droplets of liquid gold metal, which act as cat­a­lysts to grab gaseous gal­lium nitride from the atmos­phere of the exper­i­mental system. The net forces between the tiny gold droplet, the solid sub­strate, and the gas cause the nanowire to grow in a par­tic­ular direc­tion, she explained. Depending on the size of the gold cat­a­lyst, she can create wires that exhibit peri­odic serrations.

“It first tries to grow out­ward, but that gives the gold a larger sur­face area,” she said. “So now the wire gets pulled in the inward direc­tion, and then the gold gets a smaller sur­face area, so it grows out­ward again.” This inward and out­ward growth repeated itself again and again to create a peri­odic struc­ture nearly 6 mil­lion times smaller than the end­less column and is sig­nif­i­cantly more promising for its use in advanced devices.

“That there is very little imple­men­ta­tion of nanowire tech­nology in elec­tronics or optical devices is due to the fact that it’s very hard to con­trol their shape and dimen­sions,” said Menon. But now that she has a very simple way of con­trol­ling growth, the next step is to con­trol the size of the cat­alytic droplet with which she starts.

Another advan­tage of Menon’s approach is using what Panaitescu called “macro­scopic tech­niques” to create nanoscale mate­rials, thus making it scal­able and inex­pen­sive. “We just con­trol a few para­me­ters and then leave it, let it do it’s nat­ural thing,” explained Menon.

Here’s an image the researchers have supplied to illustrate their insights and their work,

Depending on the size of the gold cat­a­lyst used to make them, Latika Menon’s nanowires will exhibit peri­odic grooves that resemble common motifs in art. Images cour­tesy of Latika Menon. - See more at: http://www.northeastern.edu/news/2013/12/menon-nanowires/#sthash.LkgJU4es.dpuf

Depending on the size of the gold cat­a­lyst used to make them, Latika Menon’s nanowires will exhibit peri­odic grooves that resemble common motifs in art. Images cour­tesy of Latika Menon. – See more at: http://www.northeastern.edu/news/2013/12/menon-nanowires/#sthash.LkgJU4es.dpuf

I’m not sure I can connect the  imagery in this pot dance video (it does show some pretty astonishing feats of balance) with any of the images from Menon’s lab but sometimes the source of an inspiration is not readily accessible to those who are not amongst the inspired or perhaps there other versions of the dance that make it more obvious to an untrained eye,

Here’s an image of the other artistic inspiration, Constantin Brancusi’s Endless Column found on Dr. Cătălina Köpetz’s (University of Maryland) webpage featuring Brancusi’s work along with this quote from him “Create like a god, comand like a king, work like a slave.”

The Endless Column, Târgu Jiu, România  [downlaoded from http://terpconnect.umd.edu/~ckopetz/brancusi.htm]

The Endless Column,
Târgu Jiu, România [downlaoded from http://terpconnect.umd.edu/~ckopetz/brancusi.htm]

Interestingly, Dr. Köpetz is a social psychologist working in the university’s Center for Addictions, Personality, and Emotion Research.

For anyone who’d like to read more about Menon’s work, here’s a link to a webpage featuring a PDF selection of her papers and a citation for her latest paper on the work described in the news release,

Vapor–liquid–solid growth of serrated GaN nanowires: shape selection driven by kinetic frustration by Zheng Ma, Dillon McDowell, Eugen Panaitescu, Albert V. Davydov, Moneesh Upmanyu and Latika Menon, Physics Faculty Publications (2013)

Compound semiconducting nanowires are promising building blocks for several nanoelectronic devices yet the inability to…

The paper is open access although you will have to click a few times to retrieve it.