Tag Archives: Japan

A tangle of silver nanowires for brain-like action

I’ve been meaning to get to this news item from late 2019 as it features work from a team that I’ve been following for a number of years now. First mentioned here in an October 17, 2011 posting, James Gimzewski has been working with researchers at the University of California at Los Angeles (UCLA) and researchers at Japan’s National Institute for Materials Science (NIMS) on neuromorphic computing.

This particular research had a protracted rollout with the paper being published in October 2019 and the last news item about it being published in mid-December 2019.

A December 17, 2029 news item on Nanowerk was the first to alert me to this new work (Note: A link has been removed),

UCLA scientists James Gimzewski and Adam Stieg are part of an international research team that has taken a significant stride toward the goal of creating thinking machines.

Led by researchers at Japan’s National Institute for Materials Science, the team created an experimental device that exhibited characteristics analogous to certain behaviors of the brain — learning, memorization, forgetting, wakefulness and sleep. The paper, published in Scientific Reports (“Emergent dynamics of neuromorphic nanowire networks”), describes a network in a state of continuous flux.

A December 16, 2019 UCLA news release, which originated the news item, offers more detail (Note: A link has been removed),

“This is a system between order and chaos, on the edge of chaos,” said Gimzewski, a UCLA distinguished professor of chemistry and biochemistry, a member of the California NanoSystems Institute at UCLA and a co-author of the study. “The way that the device constantly evolves and shifts mimics the human brain. It can come up with different types of behavior patterns that don’t repeat themselves.”

The research is one early step along a path that could eventually lead to computers that physically and functionally resemble the brain — machines that may be capable of solving problems that contemporary computers struggle with, and that may require much less power than today’s computers do.

The device the researchers studied is made of a tangle of silver nanowires — with an average diameter of just 360 nanometers. (A nanometer is one-billionth of a meter.) The nanowires were coated in an insulating polymer about 1 nanometer thick. Overall, the device itself measured about 10 square millimeters — so small that it would take 25 of them to cover a dime.

Allowed to randomly self-assemble on a silicon wafer, the nanowires formed highly interconnected structures that are remarkably similar to those that form the neocortex, the part of the brain involved with higher functions such as language, perception and cognition.

One trait that differentiates the nanowire network from conventional electronic circuits is that electrons flowing through them cause the physical configuration of the network to change. In the study, electrical current caused silver atoms to migrate from within the polymer coating and form connections where two nanowires overlap. The system had about 10 million of these junctions, which are analogous to the synapses where brain cells connect and communicate.

The researchers attached two electrodes to the brain-like mesh to profile how the network performed. They observed “emergent behavior,” meaning that the network displayed characteristics as a whole that could not be attributed to the individual parts that make it up. This is another trait that makes the network resemble the brain and sets it apart from conventional computers.

After current flowed through the network, the connections between nanowires persisted for as much as one minute in some cases, which resembled the process of learning and memorization in the brain. Other times, the connections shut down abruptly after the charge ended, mimicking the brain’s process of forgetting.

In other experiments, the research team found that with less power flowing in, the device exhibited behavior that corresponds to what neuroscientists see when they use functional MRI scanning to take images of the brain of a sleeping person. With more power, the nanowire network’s behavior corresponded to that of the wakeful brain.

The paper is the latest in a series of publications examining nanowire networks as a brain-inspired system, an area of research that Gimzewski helped pioneer along with Stieg, a UCLA research scientist and an associate director of CNSI.

“Our approach may be useful for generating new types of hardware that are both energy-efficient and capable of processing complex datasets that challenge the limits of modern computers,” said Stieg, a co-author of the study.

The borderline-chaotic activity of the nanowire network resembles not only signaling within the brain but also other natural systems such as weather patterns. That could mean that, with further development, future versions of the device could help model such complex systems.

In other experiments, Gimzewski and Stieg already have coaxed a silver nanowire device to successfully predict statistical trends in Los Angeles traffic patterns based on previous years’ traffic data.

Because of their similarities to the inner workings of the brain, future devices based on nanowire technology could also demonstrate energy efficiency like the brain’s own processing. The human brain operates on power roughly equivalent to what’s used by a 20-watt incandescent bulb. By contrast, computer servers where work-intensive tasks take place — from training for machine learning to executing internet searches — can use the equivalent of many households’ worth of energy, with the attendant carbon footprint.

“In our studies, we have a broader mission than just reprogramming existing computers,” Gimzewski said. “Our vision is a system that will eventually be able to handle tasks that are closer to the way the human being operates.”

The study’s first author, Adrian Diaz-Alvarez, is from the International Center for Material Nanoarchitectonics at Japan’s National Institute for Materials Science. Co-authors include Tomonobu Nakayama and Rintaro Higuchi, also of NIMS; and Zdenka Kuncic at the University of Sydney in Australia.

Caption: (a) Micrograph of the neuromorphic network fabricated by this research team. The network contains of numerous junctions between nanowires, which operate as synaptic elements. When voltage is applied to the network (between the green probes), current pathways (orange) are formed in the network. (b) A Human brain and one of its neuronal networks. The brain is known to have a complex network structure and to operate by means of electrical signal propagation across the network. Credit: NIMS

A November 11, 2019 National Institute for Materials Science (Japan) press release (also on EurekAlert but dated December 25, 2019) first announced the news,

An international joint research team led by NIMS succeeded in fabricating a neuromorphic network composed of numerous metallic nanowires. Using this network, the team was able to generate electrical characteristics similar to those associated with higher order brain functions unique to humans, such as memorization, learning, forgetting, becoming alert and returning to calm. The team then clarified the mechanisms that induced these electrical characteristics.

The development of artificial intelligence (AI) techniques has been rapidly advancing in recent years and has begun impacting our lives in various ways. Although AI processes information in a manner similar to the human brain, the mechanisms by which human brains operate are still largely unknown. Fundamental brain components, such as neurons and the junctions between them (synapses), have been studied in detail. However, many questions concerning the brain as a collective whole need to be answered. For example, we still do not fully understand how the brain performs such functions as memorization, learning and forgetting, and how the brain becomes alert and returns to calm. In addition, live brains are difficult to manipulate in experimental research. For these reasons, the brain remains a “mysterious organ.” A different approach to brain research?in which materials and systems capable of performing brain-like functions are created and their mechanisms are investigated?may be effective in identifying new applications of brain-like information processing and advancing brain science.

The joint research team recently built a complex brain-like network by integrating numerous silver (Ag) nanowires coated with a polymer (PVP) insulating layer approximately 1 nanometer in thickness. A junction between two nanowires forms a variable resistive element (i.e., a synaptic element) that behaves like a neuronal synapse. This nanowire network, which contains a large number of intricately interacting synaptic elements, forms a “neuromorphic network”. When a voltage was applied to the neuromorphic network, it appeared to “struggle” to find optimal current pathways (i.e., the most electrically efficient pathways). The research team measured the processes of current pathway formation, retention and deactivation while electric current was flowing through the network and found that these processes always fluctuate as they progress, similar to the human brain’s memorization, learning, and forgetting processes. The observed temporal fluctuations also resemble the processes by which the brain becomes alert or returns to calm. Brain-like functions simulated by the neuromorphic network were found to occur as the huge number of synaptic elements in the network collectively work to optimize current transport, in the other words, as a result of self-organized and emerging dynamic processes..

The research team is currently developing a brain-like memory device using the neuromorphic network material. The team intends to design the memory device to operate using fundamentally different principles than those used in current computers. For example, while computers are currently designed to spend as much time and electricity as necessary in pursuit of absolutely optimum solutions, the new memory device is intended to make a quick decision within particular limits even though the solution generated may not be absolutely optimum. The team also hopes that this research will facilitate understanding of the brain’s information processing mechanisms.

This project was carried out by an international joint research team led by Tomonobu Nakayama (Deputy Director, International Center for Materials Nanoarchitectonics (WPI-MANA), NIMS), Adrian Diaz Alvarez (Postdoctoral Researcher, WPI-MANA, NIMS), Zdenka Kuncic (Professor, School of Physics, University of Sydney, Australia) and James K. Gimzewski (Professor, California NanoSystems Institute, University of California Los Angeles, USA).

Here at last is a link to and a citation for the paper,

Emergent dynamics of neuromorphic nanowire networks by Adrian Diaz-Alvarez, Rintaro Higuchi, Paula Sanz-Leon, Ido Marcus, Yoshitaka Shingaya, Adam Z. Stieg, James K. Gimzewski, Zdenka Kuncic & Tomonobu Nakayama. Scientific Reports volume 9, Article number: 14920 (2019) DOI: https://doi.org/10.1038/s41598-019-51330-6 Published: 17 October 2019

This paper is open access.

Purifying carbon nanotubes with dietary fiber

This work comes out of Japan according to a November 2, 2019 news item on Nanowerk,

A new, cheaper method easily and effectively separates two types of carbon nanotubes. The process, developed by Nagoya University researchers in Japan, could be up-scaled for manufacturing purified batches of single-wall carbon nanotubes that can be used in high-performance electronic devices.

Single-wall carbon nanotubes (SWCNTs) have excellent electronic and mechanical properties, making them ideal candidates for use in a wide range of electronic devices, including the thin-film transistors found in LCD displays. A problem is that only two-thirds of manufactured SWCNTs are suitable for use in electronic devices. The useful semiconducting SWCNTs must be separated from the unwanted metallic ones. But the most powerful purification process, known as aqueous two-phase extraction, currently involves the use of a costly polysaccharide, called dextran.

Caption: The unwanted metallic SWCNTs deposited at the bottom of the solution, while the wanted semiconducting ones floated to the top. Credit: Haruka Omachi

An October 29, 2019 Nagoya University press release (also on EurekAlert but dated Nov. 2, 2019), which originated the news item, describes how dextran could be replaced with something much cheaper in the SWCNT purification process,

Organic chemist Haruka Omachi and colleagues at Nagoya University hypothesized that dextran’s effectiveness in separating semiconducting from metallic SWCNTs lies in the linkages connecting its glucose units. Instead of using dextran to separate the two types of SWCNTs, the team tried the significantly cheaper isomaltodextran, which has many more of these linkages.

A batch of SWCNTs was left for 15 minutes in a solution containing polyethylene glycol and isomaltodextrin and then centrifuged for five minutes. Three different types of isomaltodextrin were tried, each with a different number of linkages and a different molecular weight. The team found that metallic SWCNTs separated to the bottom isomaltodextrin part of the solution, while the semiconducting SWCNTs floated to the top polyethylene glycol part.

The type of isomaltodextrin with high molecular weight and the most linkages was the most (99%) effective in separating the two types of SWCNTs. The team also found that another polysaccharide, called pullulan, whose glucose units are connected with different kinds of linkages, was ineffective in separating the two types of SWCNTs. The researchers suggest that the number and type of linkages present in isomaltodextrin play an important role in their ability to effectively separate the carbon nanotubes.

The team also found that a thin-film transistor made with their purified semiconducting SWCNTs performed very well.

Isomaltodextrin is a cheap and widely available polysaccharide produced from starch that is used as a dietary fibre. This makes it a cost-effective alternative for the SWCNT extraction process. Omachi and his colleagues are currently in discussions with companies to commercialize their approach. They are also working on improving the performance of thin-film transistors using semiconducting SWCNTs in flexible displays and sensor devices.

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

Aqueous two-phase extraction of semiconducting single-wall carbon nanotubes with isomaltodextrin and thin-film transistor applications by Haruka Omachi, Tomohiko Komuro, Kaisei Matsumoto, Minako Nakajima, Hikaru Watanabe, Jun Hirotani, Yutaka Ohno, and Hisanori Shinohara. Applied Physics Express, Volume 12, Number 9 DOI: https://doi.org/10.7567/1882-0786/ab369 Published 14 August 2019 • © 2019 The Japan Society of Applied Physics

This paper is open access.

Winter jacket made with ‘brewed protein’ and enabled by synthetic biology

It’s called a ‘Moon Parka’,

[downloaded from https://sp.spiber.jp/en/tnfsp/mp/]

Adele Peters in her October 31, 2019 article for Fast Company describes the technology used to make this jacket,

A typical waterproof winter jacket is made with nylon—a material that, like other plastics, is made from petroleum. But a new limited-edition jacket from The North Face Japan uses something called “brewed protein” instead. It’s a material inspired by spider silk that is fermented in giant vats, the same way that breweries make beer.

It’s one of the first uses of a material produced by the Japanese startup Spiber, a company that has spent more than a decade developing a new process to make high-performance textiles and other products that don’t rely on fossil fuels, animals, or natural fibers like cotton, all of which have environmental issues. …

The company designs genes that code for a specific protein—the first was an exact replica of natural spider silk, known for its extreme strength—and then introduces the genes into microorganisms that can produce the protein efficiently. Inside giant tanks, the microorganisms are fed sugar, grow and multiply, and produce the protein through fermentation. …

Spiber first started collaborating with Goldwin, a Japanese outdoor brand that owns the Japanese rights to The North Face, in 2015, and created an early prototype of a jacket then. But it quickly realized that an exact replica of spider silk wouldn’t work well for the application; the material sucks up water, and the jacket needed to be waterproof.

“We spent the last four years going back to the drawing board, redesigning our protein molecule—the very order of the amino acids in the molecule,” says Meyer [Daniel Meyer, Spiber’s head of corporate global marketing]. “And we created our own hydrophobic [water repellent] version of spider silk. It’s inspired by natural spider silk, but we have made our own design changes such that it would be more hydrophobic and meet the performance requirements of The North Face Japan.”

The jacket is available for purchase but only by a lottery, which has now closed. According to Peters, a large, commercial production facility is being built in Thailand so that at some point a Moon Parka will be affordable. For reference, the lottery jackets were priced at ¥150,000 (about $1,377 US).

You can find Spiber here in mid-March [2020] according to the homepage.

Quantum processor woven from light

Weaving a quantum processor from light is a jaw-dropping event (as far as I’m concerned). An October 17, 2019 news item on phys.org makes the announcement,

An international team of scientists from Australia, Japan and the United States has produced a prototype of a large-scale quantum processor made of laser light.

Based on a design ten years in the making, the processor has built-in scalability that allows the number of quantum components—made out of light—to scale to extreme numbers. The research was published in Science today [October 18, 2019; Note: I cannot explain the discrepancy between the dates]].

Quantum computers promise fast solutions to hard problems, but to do this they require a large number of quantum components and must be relatively error free. Current quantum processors are still small and prone to errors. This new design provides an alternative solution, using light, to reach the scale required to eventually outperform classical computers on important problems.

Caption: The entanglement structure of a large-scale quantum processor made of light. Credit: Shota Yokoyama 2019

An October 18, 2019 RMIT University (Australia) press release (also on EurekAlert but published October 17, 2019), which originated the news time, expands on the theme,

“While today’s quantum processors are impressive, it isn’t clear if the current designs can be scaled up to extremely large sizes,” notes Dr Nicolas Menicucci, Chief Investigator at the Centre for Quantum Computation and Communication Technology (CQC2T) at RMIT University in Melbourne, Australia.

“Our approach starts with extreme scalability – built in from the very beginning – because the processor, called a cluster state, is made out of light.”

Using light as a quantum processor

A cluster state is a large collection of entangled quantum components that performs quantum computations when measured in a particular way.

“To be useful for real-world problems, a cluster state must be both large enough and have the right entanglement structure. In the two decades since they were proposed, all previous demonstrations of cluster states have failed on one or both of these counts,” says Dr Menicucci. “Ours is the first ever to succeed at both.”

To make the cluster state, specially designed crystals convert ordinary laser light into a type of quantum light called squeezed light, which is then weaved into a cluster state by a network of mirrors, beamsplitters and optical fibres.

The team’s design allows for a relatively small experiment to generate an immense two-dimensional cluster state with scalability built in. Although the levels of squeezing – a measure of quality – are currently too low for solving practical problems, the design is compatible with approaches to achieve state-of-the-art squeezing levels.

The team says their achievement opens up new possibilities for quantum computing with light.

“In this work, for the first time in any system, we have made a large-scale cluster state whose structure enables universal quantum computation.” Says Dr Hidehiro Yonezawa, Chief Investigator, CQC2T at UNSW Canberra. “Our experiment demonstrates that this design is feasible – and scalable.”

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The experiment was an international effort, with the design developed through collaboration by Dr Menicucci at RMIT, Dr Rafael Alexander from the University of New Mexico and UNSW Canberra researchers Dr Hidehiro Yonezawa and Dr Shota Yokoyama. A team of experimentalists at the University of Tokyo, led by Professor Akira Furusawa, performed the ground-breaking experiment.

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

Generation of time-domain-multiplexed two-dimensional cluster state by Warit Asavanant, Yu Shiozawa, Shota Yokoyama, Baramee Charoensombutamon, Hiroki Emura, Rafael N. Alexander, Shuntaro Takeda, Jun-ichi Yoshikawa, Nicolas C. Menicucci, Hidehiro Yonezawa, Akira Furusawa. Science 18 Oct 2019: Vol. 366, Issue 6463, pp. 373-376 DOI: 10.1126/science.aay2645

This paper is behind a paywall.

Gold glue?

If you’re hoping for gold flecks in your glue, this is not going to satisfy you, given that it’s all at the nanoscale. An August 7, 2019 news item on Nanowerk briefly describes this gold glue (Note: A link has been removed),

It has long been known that gold can be used to do things that philosophers have never even dreamed of. The Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow has confirmed the existence of ‘gold glue’: bonds involving gold atoms, capable of permanently bonding protein rings. Skilfully used by an international team of scientists, the bonds have made it possible to construct molecular nanocages with a structure so far unparalleled in nature or even in mathematics (Nature, “An ultra-stable gold-coordinated protein cage displaying reversible assembly”).

Caption: The ‘impossible’ sphere, i.e. a molecular nanocage of 24 protein rings, each of which has an 11-sided structure. The rings are connected by bonds with the participation of gold atoms, here marked in yellow. Depending on their position in the structure, not all gold atoms have to be used to attach adjacent proteins (an unused gold atom is marked in red). Credit: Source: UJ, IFJ PAN

An August 6, 2019 Polish Academy of Sciences press release (also on EurekAlert but published August 7, 2019), which originated the news item, expands on the theme,

The world of science has been interested in molecular cages for years. Not without reason. Chemical molecules, including those that would under normal conditions enter into chemical reactions, can be enclosed within their empty interiors. The particles of the enclosed compound, separated by the walls of the cage from the environment, have nothing to bond with. These cages can be therefore be used, for example, to transport drugs safely into a cancer cell, only releasing the drug when they are inside it.

Molecular cages are polyhedra made up of smaller ‘bricks’, usually protein molecules. The bricks can’t be of any shape. For example, if we wanted to build a molecular polyhedron using only objects with the outline of an equilateral triangle, geometry would limit us to only three solid figures: a tetrahedron, an octahedron or an icosahedron. So far, there have been no other structural possibilities.

“Fortunately, Platonic idealism is not a dogma of the physical world. If you accept certain inaccuracies in the solid figure being constructed, you can create structures with shapes that are not found in nature, what’s more, with very interesting properties,” says Dr. Tomasz Wrobel from the Cracow Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN).

Dr. Wrobel is one of the members of an international team of researchers who have recently carried out the ‘impossible’: they built a cage similar in shape to a sphere out of eleven-walled proteins. The main authors of this spectacular success are scientists from the group of Prof. Jonathan Heddle from the Malopolska Biotechnology Centre of the Jagiellonian University in Cracow and the Japanese RIKEN Institute in Wako. The work described in Nature magazine took place with the participation of researchers from universities in Osaka and Tsukuba (Japan), Durham (Great Britain), Waterloo (Canada) and other research centres.

Each of the walls of the new nanocages was formed by a protein ring from which eleven cysteine molecules stuck out at regular intervals. It was to the sulphur atom found in each cysteine molecule that the ‘glue’, i.e. the gold atom, was planned to be attached. In the appropriate conditions, it could bind with one more sulphur atom, in the cysteine of a next ring. In this way a permanent chemical bond would be formed between the two rings. But would the gold atom under these conditions really be able to form a bond between the rings?

“In the Spectroscopic Imaging Laboratory of IFJ PAS we used Raman spectroscopy and X-ray photoelectron spectroscopy to show that in the samples provided to us with the test nanocages, the gold really did form bonds with sulphur atoms in cysteines. In other words, in a difficult, direct measurement, we proved that gold ‘glue’ for bonding protein rings in cages really does exist,” explains Dr. Wrobel.

Each gold atom can be treated as a stand-alone clip that makes it possible to attach another ring. The road to the ‘impossible’ begins when we realize that we don’t always have to use all of the clips! So, although all the rings of the new nanocages are physically the same, depending on their place in the structure they connect with their neighbours with a different number of gold atoms, and thus function as polygons with different numbers of vertices. 24 nanocage walls presented by the researchers were held together by 120 gold atoms. The outer diameter of the cages was 22 nanometres and the inner diameter was 16 nm.

Using gold atoms as a binder for nanocages is also important due to its possible applications. In earlier molecular structures, proteins were glued together using many weak chemical bonds. The complexity of the bonds and their similarity to the bonds responsible for the existence of the protein rings themselves did not allow for precise control over the decomposition of the cages. This is not the case in the new structures. On the one hand, gold-bonded nanocages are chemically and thermally stable (for example, they withstand hours of boiling in water). On the other hand, however, gold bonds are sensitive to an increase in acidity. By its increase, the nanocage can be decomposed in a controlled way and the contents can be released into the environment. Since the acidity within cells is greater than outside them, gold-bonded nanocages are ideal for biomedical applications.

The ‘impossible’ nanocage is the presentation of a qualitatively new approach to the construction of molecular cages, with gold atoms in the role of loose clips. The demonstrated flexibility of the gold bonds will make it possible in the future to create nanocages with sizes and features precisely tailored to specific needs.

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

An ultra-stable gold-coordinated protein cage displaying reversible assembly by Ali D. Malay, Naoyuki Miyazaki, Artur Biela, Soumyananda Chakraborti, Karolina Majsterkiewicz, Izabela Stupka, Craig S. Kaplan, Agnieszka Kowalczyk, Bernard M. A. G. Piette, Georg K. A. Hochberg, Di Wu, Tomasz P. Wrobel, Adam Fineberg, Manish S. Kushwah, Mitja Kelemen, Primož Vavpetič, Primož Pelicon, Philipp Kukura, Justin L. P. Benesch, Kenji Iwasaki & Jonathan G. Heddle Nature volume 569, pages438–442 (2019) Issue Date: 16 May 2019 DOI: https://doi.org/10.1038/s41586-019-1185-4 Published online: 08 May 2019

This paper is behind a paywall.

A deep look at atomic switches

A July 19, 2019 news item on phys.org describes research that may result in a substantive change for information technology,

A team of researchers from Tokyo Institute of Technology has gained unprecedented insight into the inner workings of an atomic switch. By investigating the composition of the tiny metal ‘bridge’ that forms inside the switch, their findings may spur the design of atomic switches with improved performance.

A July 22, 2019 Tokyo Institute of Technology press release (also on EurekAlert but published July 19, 2019), which originated the news item, explains how this research could have such an important impact,

Atomic switches are hailed as the tiniest of electrochemical switches that could change the face of information technology. Due to their nanoscale dimensions and low power consumption, they hold promise for integration into next-generation circuits that could drive the development of artificial intelligence (AI) and Internet of Things (IoT) devices.

Although various designs have emerged, one intriguing question concerns the nature of the metallic filament, or bridge, that is key to the operation of the switch. The bridge forms inside a metal sulfide layer sandwiched between two electrodes [see figure below], and is controlled by applying a voltage that induces an electrochemical reaction. The formation and annihilation of this bridge determines whether the switch is on or off.

Now, a research group including Akira Aiba and Manabu Kiguchi and colleagues at Tokyo Institute of Technology’s Department of Chemistry has found a useful way to examine precisely what the bridge is composed of.

By cooling the atomic switch enough so as to be able to investigate the bridge using a low-temperature measurement technique called point contact spectroscopy (PCS) [2], their study revealed that the bridge is made up of metal atoms from both the electrode and the metal sulfide layer. This surprising finding controverts the prevailing notion that the bridge derives from the electrode only, Kiguchi explains.

The team compared atomic switches with different combinations of electrodes (Pt and Ag, or Pt and Cu) and metal sulfide layers (Cu2S and Ag2S). In both cases, they found that the bridge is mainly composed of Ag.

The reason behind the dominance of Ag in the bridge is likely due to “the higher mobility of Ag ions compared to Cu ions”, the researchers say in their paper published in ACS Applied Materials & Interfaces.

They conclude that “it would be better to use metals with low mobility” for designing atomic switches with higher stability.

Much remains to be explored in the advancement of atomic switch technologies, and the team is continuing to investigate which combination of elements would be the most effective in improving performance.

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Technical terms
[1] Atomic switch: The idea behind an atomic switch — one that can be controlled by the motion of a single atom — was introduced by Donald Eigler and colleagues at the IBM Almaden Research Center in 1991. Interest has since focused on how to realize and harness the potential of such extremely small switches for use in logic circuits and memory devices. Over the past two decades, researchers in Japan have taken a world-leading role in the development of atomic switch technologies.
[2] Point contact spectroscopy: A method of measuring the properties or excitations of single atoms at low temperature.

Caption: The ‘bridge’ that forms within the metal sulfide layer, connecting two metal electrodes, results in the atomic switch being turned on. Credit: Manabu Kiguchi

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

Investigation of Ag and Cu Filament Formation Inside the Metal Sulfide Layer of an Atomic Switch Based on Point-Contact Spectroscopy by A. Aiba, R. Koizumi, T. Tsuruoka, K. Terabe, K. Tsukagoshi, S. Kaneko, S. Fujii, T. Nishino, M. Kiguchi. ACS Appl. Mater. Interfaces 2019 XXXXXXXXXX-XXX DOI: https://doi.org/10.1021/acsami.9b05523 Publication Date:July 5, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

For anyone who might need a bit of a refresher for the chemical elements, Pt is platinum, Ag is silver, and Cu is copper. So, with regard to the metal sulfide layers Cu2S is copper sulfide and Ag2S is silver sulfide.

Achieving precise control by decorating iron nanocubes with gold

A June 17,2019 news item on phys.org describes a new technique for producing nanoparticles,

One of the major challenges in nanotechnology is the precise control of shape, size and elemental composition of every single nanoparticle. Physical methods are able to produce homogeneous nanoparticles free of surface contamination. However, they offer limited opportunity to control the shape and specific composition of the nanoobjects when they are being built up.

A recent collaboration between the University of Helsinki and the Okinawa Institute of Science and Technology (OIST) Graduate University revealed that hybrid Au/Fe nanoparticles can grow in an unprecedentedly complex structure with a single-step fabrication method. Using a computational modeling framework, the groups of Professor Flyura Djurabekova at the University of Helsinki and Prof. Sowwan at OIST succeeded in deciphering the growth mechanism by a detailed multistage model.

A June 14, 2019 University of Helsinki press release (also on EurekAlert but published June 17, 2019), which originated the news item, expands on the theme,

Elegantly combined considerations of kinetic and thermodynamic effects explained the formation of embedded gold layers and the site-specific surface gold decoration. These results open up a possibility for engineering a multitude of hybrid nanoparticles for a wide range of emerging applications. Their research was recently published in the highly ranked open access journal Advanced Science.

“When nature surprises us with an unexpectedly beautiful pattern, we must recognize it and explain. This is the way to cooperate with nature that is always ready to teach and expecting us to learn,” says Dr. Junlei Zhao, a postdoctoral researcher in the group of Prof. Djurabekova.

Nowadays, scientists are able to study nano-scale phenomena with great accuracy by using high-performance computational software and modern supercomputing infrastructures. These are of great support, not only for advancing fundamental science but also for finding promising solutions for many challenges of humanity.

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

Site‐Specific Wetting of Iron Nanocubes by Gold Atoms in Gas‐Phase Synthesis by Jerome Vernieres, Stephan Steinhauer, Junlei Zhao, Panagiotis Grammatikopoulos, Riccardo Ferrando, Kai Nordlund, Flyura Djurabekova, Mukhles Sowwan. Advanced Science Volume 6, Issue 13
1900447 uly 3, 2019 DOI: https://doi.org/10.1002/advs.201900447 First published online: 02 May 2019

This paper is open access.

The latest ‘golden’ age for electronics

I don’t know the dates for the last ‘golden’ age of electronics but I can certainly understand why these Japanese researchers are excited about their work. In any event, I think the ‘golden age’ is more of a play on words. From a June 25, 2019 news item on Nanowerk (Note: A link has been removed),

One way that heat damages electronic equipment is it makes components expand at different rates, resulting in forces that cause micro-cracking and distortion. Plastic components and circuit boards are particularly prone to damage due to changes in volume during heating and cooling cycles. But if a material could be incorporated into the components that compensates for the expansion, the stresses would be reduced and their lifetime increased.

Everybody knows one material that behaves like this: liquid water expands when it freezes and ice contracts when it melts. But liquid water and electronics don’t mix well – instead, what’s needed is a solid with “negative thermal expansion” (NTE).

Although such materials have been known since the 1960s, a number of challenges had to be overcome before the concept would be broadly useful and commercially viable. In terms of both materials and function, these efforts have only had limited success.

The experimental materials had been produced under specialized laboratory conditions using expensive equipment; and even then, the temperature and pressure ranges in which they would exhibit NTE were well outside normal everyday conditions.

Moreover, the amount they expanded and contracted depended on the direction, which induced internal stresses that changed their structure, meaning that the NTE property would not last longer than a few heating and cooling cycles.

A research team led by Koshi Takenaka of Nagoya University has succeeded in overcoming these materials-engineering challenges (APL Materials, “Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd)”).

A June 22, 2019 Nagoya University press release (also on EurekAlert but published on June 25, 2019), which originated the news item, provides more technical detail,

Inspired by the series of work by Noriaki Sato, also of Nagoya University – whose discovery last year of superconductivity in quasicrystals was considered one of the top ten physics discoveries of the year by Physics World magazine – Professor Takenaka took the rare earth element samarium and its sulfide, samarium monosulfide (SmS), which is known to change phase from the “black phase” to the smaller-volume “golden phase”. The problem was to tune the range of temperatures at which the phase transition occurs. The team’s solution was to replace a small proportion of samarium atoms with another rare earth element, giving Sm1-xRxS, where “R” is any one of the rare earth elements cerium (Ce), neodymium (Nd), praseodymium (Pr) or yttrium (Y). The fraction x the team used was typically 0.2, except for yttrium. These materials showed “giant negative thermal expansion” of up to 8% at ordinary room pressure and a useful range of temperatures (around 150 degrees) including at room temperature and above … . Cerium is the star candidate here because it is relatively cheap.

The nature of the phase transition is such that the materials can be powdered into very small crystal sizes around a micron on a side without losing their negative expansion property. This broadens the industrial applications, particularly within electronics.

While the Nagoya University group’s engineering achievement is impressive, how the negative expansion works is fascinating from a fundamental physics viewpoint. During the black-golden transition, the crystal structure stays the same but the atoms get closer together: the unit cell size becomes smaller because (as is very likely but perhaps not yet 100% certain) the electron structure of the samarium atoms changes and makes them smaller – a process of intra-atomic charge transfer called a “valence transition” or “valence fluctuation” within the samarium atoms … . “My impression,” says Professor Takenaka, “is that the correlation between the lattice volume and the electron structure of samarium is experimentally verified for this class of sulfides.”

More specifically, in the black (lower temperature) phase, the electron configuration of the samarium atoms is (4f)6, meaning that in their outermost shell they have 6 electrons in the f orbitals (with s, p and d orbitals filled); while in the golden phase the electronic configuration is (4f)5(5d)1 -an electron has moved out of a 4f orbital into a 5d orbital. Although a “higher” shell is starting to be occupied, it turns out – through a quirk of the Pauli Exclusion Principle – that the second case gives a smaller atom size, leading to a smaller crystal size and negative expansion.

But this is only part of the fundamental picture. In the black phase, samarium sulfide and its doped offshoots are insulators – they do not conduct electricity; while in the golden phase they turn into conductors (i.e. metals). This is suggesting that during the black-golden phase transition the band structure of the whole crystal is influencing the valance transition within the samarium atoms. Although nobody has done the theoretical calculations for the doped samarium sulfides made by Professor Takenaka’s group, a previous theoretical study has indicated that when electrons leave the samarium atoms’ f orbital, they leave behind a positively charged “hole” which itself interacts repulsively with holes in the crystal’s conduction band, affecting their exchange interaction. This becomes a cooperative effect that then drives the valence transition in the samarium atoms. The exact mechanism, though, is not well understood.

Nevertheless, the Nagoya University-led group’s achievement is one of engineering, not pure physics. “What is important for many engineers is the ability to use the material to reduce device failure due to thermal expansion,” explains Professor Takenaka. “In short, in a certain temperature range – the temperature range in which the intended device operates, typically an interval of dozens of degrees or more – the volume needs to gradually decrease with a rise in temperature and increase as the temperature falls. Of course, I also know that volume expansion on cooling during a phase transition [like water freezing] is a common case for many materials. However, if the volume changes in a very narrow temperature range, there is no engineering value. The present achievement is the result of material engineering, not pure physics.”

Perhaps it even heralds a new “golden” age for electronics.

I worked in a company for a data communications company that produced hardware and network management software. From a hardware perspective, heat was an enemy which distorted your circuit boards and cost you significant money not only for replacements but also when you included fans to keep the equipment cool (or as cool as possible).

Enough with the reminiscences, here’s a link to and a citation for the paper,

Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd) by D. Asai, Y. Mizuno, H. Hasegawa, Y. Yokoyama, Y. Okamoto, N. Katayama, H. S. Suzuki, Y. Imanaka, and K. Takenaka. Applied Physics Letters > Volume 114, Issue 14 > 10.1063/1.5090546 or Appl. Phys. Lett. 114, 141902 (2019); https://doi.org/10.1063/1.5090546. Published Online: 12 April 2019

This paper is behind a paywall.

CARESSES your elders (robots for support)

Culturally sensitive robots for elder care! It’s about time. The European Union has funded the Culture Aware Robots and Environmental Sensor Systems for Elderly Support (CARESSES) project being coordinated in Italy. A December 13, 2018 news item on phys.org describes the project,

Researchers have developed revolutionary new robots that adapt to the culture and customs of the elderly people they assist.

Population ageing has implications for many sectors of society, one of which is the increased demand on a country’s health and social care resources. This burden could be greatly eased through advances in artificial intelligence. Robots have the potential to provide valuable assistance to caregivers in hospitals and care homes. They could also improve home care and help the elderly live more independently. But to do this, they will have to be able to respond to older people’s needs in a way that is more likely to be trusted and accepted.
The EU-funded project CARESSES has set out to build the first ever culturally competent robots to care for the elderly. The groundbreaking idea involved designing these robots to adapt their way of acting and speaking to match the culture and habits of the elderly person they’re assisting.

“The idea is that robots should be capable of adapting to human culture in a broad sense, defined by a person’s belonging to a particular ethnic group. At the same time, robots must be able to adapt to an individual’s personal preferences, so in that sense, it doesn’t matter if you’re Italian or Indian,” explained researcher Alessandro Saffiotti of project partner Örebro University, Sweden, …

A December 13, 2018 (?) CORDIS press release, which originated the news item, adds more detail about the robots and their anticipated relationship to their elderly patients,

Through its communication with an elderly person, the robot will fine-tune its knowledge by adapting it to that person’s cultural identity and individual characteristics. Using this knowledge, it will be able to remind the elderly person to take their prescribed medication, encourage them to eat healthily and be active, or help them stay in touch with family and friends. The robot will also be able to make suggestions about the appropriate clothing for specific occasions and remind people of upcoming religious and other celebrations. It doesn’t replace a care home worker. Nevertheless, it will play a vital role in helping to make elderly people’s lives less lonely and reducing the need to have a caregiver nearby at all times.

Scientists are testing the first CARESSES robots in care homes in the United Kingdom and Japan. They’re being used to assist elderly people from different cultural backgrounds. The aim is to see if people feel more comfortable with robots that interact with them in a culturally sensitive manner. They’re also examining whether such robots improve the elderly’s quality of life. “The testing of robots outside of the laboratory environment and in interaction with the elderly will without a doubt be the most interesting part of our project,” added Saffiotti.

The innovative CARESSES (Culture Aware Robots and Environmental Sensor Systems for Elderly Support) robots may pave the way to more culturally sensitive services beyond the sphere of elderly care, too. “It will add value to robots intended to interact with people. Which is not to say that today’s robots are completely culture-neutral. Instead, they unintentionally reflect the culture of the humans who build and program them.”

Having had a mother who recently died in a care facility, I can testify to the importance of cultural and religious sensitivity on the part of caregivers. As for this type of robot not replacing anyone, I take that with a grain of salt. They always say that and I expect it’s true in the initial stages but once the robots are well established and working well? Why not? After all, they’re cheaper in many, many ways and with the coming tsunami of elders in many countries around the world, it seems to me that displacement by robots is an inevitability.

Chen Qiufan, garbage, and Chinese science fiction stories

Garbage has been dominating Canadian news headlines for a few weeks now. First, it was Canadian garbage in the Philippines and now it’s Canadian garbage in Malaysia. Interestingly, we’re also having problems with China, since December 2018, when we detained a top executive from Huawe, a China-based international telecommunicatons company, in accordance with an official request from the US government and, in accordance, with what Prime Minister Justin Trudeau calls the ‘rule of law’. All of this provides an interesting backdrop (for Canadians anyway) on the topic of China, garbage, and science fiction.

A May 16, 2019 article by Anjie Zheng for Fast Company explores some of the latest and greatest from China’s science fiction writing community,

Like any good millennial, I think about my smartphone, to the extent that I do at all, in terms of what it does for me. It lets me message friends, buy stuff quickly, and amass likes. I hardly ever think about what it actually is—a mass of copper wires, aluminum alloys, and lithium battery encased in glass—or where it goes when I upgrade.

Chen Qiufan wants us to think about that. His debut novel, Waste Tide, is set in a lightly fictionalized version of Guiyu, the world’s largest electronic waste disposal. First published in Chinese in 2013, the book was recently released in the U.S. with a very readable translation into English by Ken Liu.

Chen, who has been called “China’s William Gibson,” is part of a younger generation of sci-fi writers who have achieved international acclaim in recent years. Liu Cixin became the first Chinese to win the prestigious Hugo Award for his Three Body Problem in 2015. The Wandering Earth, based on a short story by Liu, became China’s first science-fiction blockbuster when it was released in 2018. It was the highest-grossing film in the fastest-growing film market in the world last year and was recently scooped up by Netflix.

Aynne Kokas in a March 13, 2019 article for the Washington Post describes how the hit film, The Wandering Earth, fits into an overall Chinese-led movie industry focused on the future and Hollywood-like, i. e. like US movie industry, domination,

“The Wandering Earth,” directed by Frant Gwo, takes place in a future where the people of Earth must flee their sun as it swells into a red giant. Thousands of engines — the first of them constructed in Hangzhou, one of China’s tech hubs — propel the entire planet toward a new solar system, while everyone takes refuge from the cold in massive underground cities. On the surface, the only visible reminders of the past are markers of China’s might. The Shanghai Tower, the Oriental Pearl Tower and a stadium for the Shanghai 2044 Olympics all thrust out of the ice, having apparently survived the journey’s tsunamis, deep freeze and cliff-collapsing earthquakes.

The movie is China’s first big-budget sci-fi epic, and its production was ambitious, involving some 7,000 workers and 10,000 specially-built props. Audience excitement was correspondingly huge: Nearly half a million people wrote reviews of the film on Chinese social network site Douban. Having earned over $600 million in domestic sales, “The Wandering Earth” marks a major achievement for the country’s film industry.

It is also a major achievement for the Chinese government.

Since opening up the country’s film market in 2001, the Chinese government has aspired to learn from Hollywood how to make commercially appealing films, as I detail in my book “Hollywood Made in China.” From initial private offerings for state media companies, to foreign investment in films, studios and theme parks, the government allowed outside capital and expertise to grow the domestic commercial film industry — but not at the expense of government oversight. This policy’s underlying aim was to expand China’s cultural clout and political influence.

Until recently, Hollywood films dominated the country’s growing box office. That finally changed in 2015, with the release of major local blockbusters “Monster Hunt” and “Lost in Hong Kong.” The proliferation of homegrown hits signaled that the Chinese box office profits no longer depend on Hollywood studio films — sending an important message to foreign trade negotiators and studios.

Kokas provides some insight into how the Chinese movie industry is designed to further the Chinese government’s vision of the future. As a Canadian, I don’t see that much difference between the US and China industry’s vision. Both tout themselves as the answer to everything, both target various geographic regions for the ‘bad guys’, and both tout their national moral superiority in their films. I suppose the same can be said for most countries’ film industries but both China and the US can back themselves with economic might.

Zheng’s article delves deeper into garbage, and Chen Qiufan’s science fiction while illuminating the process of changing a ‘good guy’ into a ‘bad guy’,

Chen, 37, grew up a few miles from the real Guiyu. Mountains of scrap electronics are shipped there every year from around the world. Thousands of human workers sort through the junk for whatever can be reduced to reusable precious metals. They strip wires and disassemble circuit boards, soaking them in acid baths for bits of copper, tin, platinum, and gold. Whatever can’t be processed is burned. The water in Guiyu has been so contaminated it is undrinkable; the air is toxic. The workers, migrants from poor rural areas in China, have an abnormally high rate of respiratory diseases and cancer.

For the decades China was revving its economic engine, authorities were content to turn a blind eye to the human costs of the recycling business. It was an economic win-win. For developed countries like the U.S., it’s cheaper to ship waste to places like China than trying to recycle it themselves. And these shipments create jobs and profits for the Chinese.

In recent years, however, steps have been taken to protect workers and the environment in China. …

Waste Tide highlights the danger of “throw-away culture,” says Chen, also known in English as Stanley Chan. When our personal electronics stop serving us, whether because they break or our lust for the newest specs get the better of us, we toss them. Hopefully we’re conscientious enough to bring them to local recyclers that claim they’ll dispose of them properly. But that’s likely the end of our engagement with the trash. Out of sight, out of mind.

Fiction, and science fiction in particular, is an apt medium for Chen to probe the consequences of this arrangement. “It’s not journalism,” he says. Instead, the story is an imaginative, action-packed tale of power imbalances, and the individual characters that think they’re doing good. Waste Tide culminates, expectedly, in an insurgency of the workers against their exploitative overlords.

Guiyu has been fictionalized in Waste Tide as “Silicon Isle.” (A homophone of the Chinese character “gui” translates to “Silicon,” and “yu” is an island). The waste hell is ruled by three ruthless family clans, dominated by the Luo clan. They treat workers as slaves and derisively call them “waste people.”

Technology in the near-future has literally become extensions of selves and only exacerbates class inequality. Prosthetic inner ears improve balance; prosthetic limbs respond to mental directives; helmets heighten natural senses. The rich “switch body parts as easily as people used to switch phones.” Those with fewer means hack discarded prosthetics to get the same kick. When they’re no longer needed, synthetic body parts contaminated with blood and bodily fluids are added to the detritus.

At the center of the story is Mimi, a migrant worker who dreams of earning enough money to return home and live a quiet life. She strikes up a relationship with Kaizong, a Chinese-American college graduate trying to rediscover his roots. But the good times are short-lived. The boss of the Luo clan becomes convinced that Mimi holds the key to rousing his son from his coma and soon kidnaps the hapless girl.

For all the advanced science, there is a backwards superstition that animates Silicon Isle. [emphasis mine] The clan bosses subscribe to “a simple form of animism.” They pray to the wind and sea for ample supplies of waste. They sacrifice animals (and some humans) to bring them luck, and use local witches to exorcise evil spirits. Boss Luo has Mimi kidnapped and tortured in an effort to appease the gods in the hopes of waking up his comatose son. The torture of Mimi infects her with a mysterious disease that splits her consciousness. The waste people are enraged by her violation, which eventually sparks a war against the ruling clans. [emphasis mine]

A parallel narrative involves an American, Scott Brandle, who works for an environmental company. While in town trying to set up a recycling facility, he stumbles onto the truth about the virus that may have infected Mimi: a chemical weapon developed and used by the U.S. [emphasis mine] years earlier. Invented by a Japanese researcher [emphasis mine] working in the U.S., the drug is capable of causing mass hallucinations and terror. When Brandle learns that Mimi may have been infected with this virus, he wants a piece of her [emphasis mine] too, so that scientists back home can study its effects.

Despite portraying the future of China in a less-than-positive light, [emphasis mine] Waste Tide has not been banned–a common result for works that displease Beijing; instead, the book won China’s prestigious Nebula award for science fiction, and is about to be reprinted on the mainland. …

An interview with Chen (it’s worthwhile to read his take on what he’s doing) follows the plot description in this intriguing and what seems to be a sometimes disingenuous article.

The animism and the war against the ruling class? It reminds me a little of the tales told about old Chine and Mao’s campaign to overthrow the ruling classes who had kept control of the proletariat, in part, by encouraging ‘superstitious religious belief’.

As far as I’m concerned the interpretation can go either or both ways: a critique of the current government’s policies and where they might lead in the future and/or a reference back to the glorious rising of China’s communist government. Good fiction always contains ambiguity; it’s what fuels courses in literature.

Also, the bad guys are from the US and Japan, countries which have long been allied with each other and with which China has some serious conflicts.

Interesting, non? And, it’s not that different from what you’ll see in US (or any other country’s for that matter) science fiction wiring and movies, except that the heroes are Chinese.

Getting back to the garbage in the Philippines, there are 69 containers on their way back to Canada as of May 30, 2019. As for why all this furor about Canadian garbage in the Philippines and Malaysia, it’s hard to believe that Canada is the only sinner. Of course, we are in China’s bad books due to the Huawei executive’s detention here (she is living in her home in Vancouver and goes out and about as she wishes, albeit under surveillance).

Anyway, I can’t help but wonder if indirect pressure is being exerted by China or if the Philippines and Malaysia have been incentivized in some way by China. The timing has certainly been interesting.

Political speculation aside, it’s probably a good thing that countries are refusing to take our garbage. As I’m sure more than one environmentalist would be happy to point out, it’s about time we took care of our own mess.