Category Archives: electronics

Human-machine interfaces and ultra-small nanoprobes

We’re back on the cyborg trail or what I sometimes refer to as machine/flesh. A July 3, 2019 news item on ScienceDaily describes the latest attempts to join machine with flesh,

Machine enhanced humans — or cyborgs as they are known in science fiction — could be one step closer to becoming a reality, thanks to new research Lieber Group at Harvard University, as well as scientists from University of Surrey and Yonsei University.

Researchers have conquered the monumental task of manufacturing scalable nanoprobe arrays small enough to record the inner workings of human cardiac cells and primary neurons.

The ability to read electrical activities from cells is the foundation of many biomedical procedures, such as brain activity mapping and neural prosthetics. Developing new tools for intracellular electrophysiology (the electric current running within cells) that push the limits of what is physically possible (spatiotemporal resolution) while reducing invasiveness could provide a deeper understanding of electrogenic cells and their networks in tissues, as well as new directions for human-machine interfaces.

The Lieber Group at Harvard University provided this image illustrating the work,

U-shaped nanowires can record electrical chatter inside a brain or heart cell without causing any damage. The devices are 100 times smaller than their biggest competitors, which kill a cell after recording. Courtesy: University of Surrey

A July 3, 2019 University of Surrey press release (also on EurekAlert), which originated the news item, provides more details about this UK/US/China collaboration,

In a paper published by Nature Nanotechnology, scientists from Surrey’s Advanced Technology Institute (ATI) and Harvard University detail how they produced an array of the ultra-small U-shaped nanowire field-effect transistor probes for intracellular recording. This incredibly small structure was used to record, with great clarity, the inner activity of primary neurons and other electrogenic cells, and the device has the capacity for multi-channel recordings.

Dr Yunlong Zhao from the ATI at the University of Surrey said: “If our medical professionals are to continue to understand our physical condition better and help us live longer, it is important that we continue to push the boundaries of modern science in order to give them the best possible tools to do their jobs. For this to be possible, an intersection between humans and machines is inevitable.

“Our ultra-small, flexible, nanowire probes could be a very powerful tool as they can measure intracellular signals with amplitudes comparable with those measured with patch clamp techniques; with the advantage of the device being scalable, it causes less discomfort and no fatal damage to the cell (cytosol dilation). Through this work, we found clear evidence for how both size and curvature affect device internalisation and intracellular recording signal.”

Professor Charles Lieber from the Department of Chemistry and Chemical Biology at Harvard University said: “This work represents a major step towards tackling the general problem of integrating ‘synthesised’ nanoscale building blocks into chip and wafer scale arrays, and thereby allowing us to address the long-standing challenge of scalable intracellular recording.

“The beauty of science to many, ourselves included, is having such challenges to drive hypotheses and future work. In the longer term, we see these probe developments adding to our capabilities that ultimately drive advanced high-resolution brain-machine interfaces and perhaps eventually bringing cyborgs to reality.”

Professor Ravi Silva, Director of the ATI at the University of Surrey, said: “This incredibly exciting and ambitious piece of work illustrates the value of academic collaboration. Along with the possibility of upgrading the tools we use to monitor cells, this work has laid the foundations for machine and human interfaces that could improve lives across the world.”

Dr Yunlong Zhao and his team are currently working on novel energy storage devices, electrochemical probing, bioelectronic devices, sensors and 3D soft electronic systems. Undergraduate, graduate and postdoc students with backgrounds in energy storage, electrochemistry, nanofabrication, bioelectronics, tissue engineering are very welcome to contact Dr Zhao to explore the opportunities further.

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

Scalable ultrasmall three-dimensional nanowire transistor probes for intracellular recording by Yunlong Zhao, Siheng Sean You, Anqi Zhang, Jae-Hyun Lee, Jinlin Huang & Charles M. Lieber. Nature Nanotechnology (2019) DOI: Published 01 July 2019

The link I’ve provided leads to a paywall. However, I found a freely accessible version of the paper (this may not be the final published version) here.

Bacteria and graphene oxide as a basis for producing computers

A July 10, 2019 news item on ScienceDaily announces a more environmentally friendly way to produce graphene leading to more environmentally friendly devices such as computers,

In order to create new and more efficient computers, medical devices, and other advanced technologies, researchers are turning to nanomaterials: materials manipulated on the scale of atoms or molecules that exhibit unique properties.

Graphene — a flake of carbon as thin as a single later of atoms — is a revolutionary nanomaterial due to its ability to easily conduct electricity, as well as its extraordinary mechanical strength and flexibility. However, a major hurdle in adopting it for everyday applications is producing graphene at a large scale, while still retaining its amazing properties.

In a paper published in the journal ChemOpen, Anne S. Meyer, an associate professor of biology at the University of Rochester [New York state, US], and her colleagues at Delft University of Technology in the Netherlands, describe a way to overcome this barrier. The researchers outline their method to produce graphene materials using a novel technique: mixing oxidized graphite with bacteria. Their method is a more cost-efficient, time-saving, and environmentally friendly way of producing graphene materials versus those produced chemically, and could lead to the creation of innovative computer technologies and medical equipment.

A July 10, 2019 University of Rochester news release (also on EurekAlert), which originated the news item, provides details as to how this new technique for extracting graphene differs from the technique currently used,

Graphene is extracted from graphite, the material found in an ordinary pencil. At exactly one atom thick, graphene is the thinnest–yet strongest–two-dimensional material known to researchers. Scientists from the University of Manchester in the United Kingdom were awarded the 2010 Nobel Prize in Physics for their discovery of graphene; however, their method of using sticky tape to make graphene yielded only small amounts of the material.

“For real applications you need large amounts,” Meyer says. “Producing these bulk amounts is challenging and typically results in graphene that is thicker and less pure. This is where our work came in.”

In order to produce larger quantities of graphene materials, Meyer and her colleagues started with a vial of graphite. They exfoliated the graphite–shedding the layers of material–to produce graphene oxide (GO), which they then mixed with the bacteria Shewanella. They let the beaker of bacteria and precursor materials sit overnight, during which time the bacteria reduced the GO to a graphene material.

“Graphene oxide is easy to produce, but it is not very conductive due to all of the oxygen groups in it,” Meyer says. “The bacteria remove most of the oxygen groups, which turns it into a conductive material.”

While the bacterially-produced graphene material created in Meyer’s lab is conductive, it is also thinner and more stable than graphene produced chemically. It can additionally be stored for longer periods of time, making it well suited for a variety of applications, including field-effect transistor (FET) biosensors and conducting ink. FET biosensors are devices that detect biological molecules and could be used to perform, for example, real-time glucose monitoring for diabetics.

“When biological molecules bind to the device, they change the conductance of the surface, sending a signal that the molecule is present,” Meyer says. “To make a good FET biosensor you want a material that is highly conductive but can also be modified to bind to specific molecules.” Graphene oxide that has been reduced is an ideal material because it is lightweight and very conductive, but it typically retains a small number of oxygen groups that can be used to bind to the molecules of interest.

The bacterially produced graphene material could also be the basis for conductive inks, which could, in turn, be used to make faster and more efficient computer keyboards, circuit boards, or small wires such as those used to defrost car windshields. Using conductive inks is an “easier, more economical way to produce electrical circuits, compared to traditional techniques,” Meyer says. Conductive inks could also be used to produce electrical circuits on top of nontraditional materials like fabric or paper.

“Our bacterially produced graphene material will lead to far better suitability for product development,” Meyer says. “We were even able to develop a technique of ‘bacterial lithography’ to create graphene materials that were only conductive on one side, which can lead to the development of new, advanced nanocomposite materials.”

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

Creation of Conductive Graphene Materials by Bacterial Reduction Using Shewanella Oneidensis by Benjamin A. E. Lehner, Vera A. E. C. Janssen, Dr. Ewa M. Spiesz, Dominik Benz, Dr. Stan J. J. Brouns, Dr. Anne S. Meyer, Prof. Dr. Herre S. J. van der Zant. ChemistryOpen Volume 8, Issue 7 July 2019 Pages 888-895 DOI:
First published: 04 July 2019

As you would expect given the journal’s title, this paper is open access.

Turning wasted energy back into electricity

This work comes from the King Abdullah University of Science and Technology (KAUST; Saudi Arabia). From a June 27, 2019 news item on Nanowerk (Note: A link has been removed),

Some of the vast amount of wasted energy that machines and devices emit as heat could be recaptured using an inexpensive nanomaterial developed at KAUST. This thermoelectric nanomaterial could capture the heat lost by devices, ranging from mobile phones to vehicle engines, and turn it directly back into useful electricity (Advanced Energy Materials, “Low-temperature-processed colloidal quantum dots as building blocks for thermoelectrics”).

A June 27, 2019 KAUST press release, which originated the news item, provides more detail,

The nanomaterial is made using a low-temperature solution-based production process, making it suitable for coating on flexible plastics for use almost anywhere.

“Among the many renewable energy sources, waste heat has not been widely considered,” says Mohamad Nugraha, a postdoctoral researcher in Derya Baran’s lab. Waste heat emitted by machines and devices could be recaptured by thermoelectric materials. These substances have a property that means that when one side of the material is hot and the other is cold, an electric charge builds up along the temperature gradient.

Until now, thermoelectric materials have been made using expensive and energy-intensive processes. Baran, Nugraha and their colleagues have developed a new thermoelectric material made by spin coating a liquid solution of nanomaterials called quantum dots.

The team spin coated a thin layer of lead-sulphide quantum dots on a surface and then added a solution of short linker ligands that crosslink the quantum dots together to enhance the material’s electronic properties.

After repeating the spin-coating process layer by layer to form a 200-nanometer-thick film, gentle thermal annealing dried the film and completed fabrication. “Thermoelectric research has focused on materials processed at very high temperatures, above 400 degrees Celsius,” Nugraha says. The quantum-dot-based thermoelectric material is only heated up to 175 degrees Celsius. This lower processing temperature could cut production costs and means that thermoelectric devices could be formed on a broad range of surfaces, including cheap flexible plastics.

The team’s material showed promising thermoelectric properties. One important parameter of a good thermoelectric is the Seebeck coefficient, which corresponds to the voltage generated when a temperature gradient is applied. “We found some key factors leading to the enhanced Seebeck coefficient in our materials,” Nugraha says.

The team was also able to show that an effect called the quantum confinement, which alters a material’s electronic properties when it is shrunk to the nanoscale, was important for enhancing the Seebeck coefficient. The discovery is a step toward practical high-performance, low-temperature, solution-processed thermoelectric generators, Nugraha says.

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

Low‐Temperature‐Processed Colloidal Quantum Dots as Building Blocks for Thermoelectrics by Mohamad I. Nugraha, Hyunho Kim, Bin Sun, Md Azimul Haque, Francisco Pelayo Garcia de Arquer, Diego Rosas Villalva, Abdulrahman El‐Labban, Edward H. Sargent, Husam N. Alshareef, Derya Baran. Advanced Energy Materials Volume 9, Issue 13 1803049 April 4, 2019 DOI: First published [online]: 14 February 2019

This paper is behind a paywall.

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); Published Online: 12 April 2019

This paper is behind a paywall.

Graphene from gum trees

Caption: Eucalyptus bark extract has never been used to synthesise graphene sheets before. Courtesy: RMIT University

It’s been quite educational reading a June 24, 2019 news item on Nanowerk about deriving graphene from Eucalyptus bark (Note: Links have been removed),

Graphene is the thinnest and strongest material known to humans. It’s also flexible, transparent and conducts heat and electricity 10 times better than copper, making it ideal for anything from flexible nanoelectronics to better fuel cells.

The new approach by researchers from RMIT University (Australia) and the National Institute of Technology, Warangal (India), uses Eucalyptus bark extract and is cheaper and more sustainable than current synthesis methods (ACS Sustainable Chemistry & Engineering, “Novel and Highly Efficient Strategy for the Green Synthesis of Soluble Graphene by Aqueous Polyphenol Extracts of Eucalyptus Bark and Its Applications in High-Performance Supercapacitors”).

A June 24, 2019 RMIT University news release (also on EurekAlert), which originated the news item, provides a little more detail,

RMIT lead researcher, Distinguished Professor Suresh Bhargava, said the new method could reduce the cost of production from $USD100 per gram to a staggering $USD0.5 per gram.

“Eucalyptus bark extract has never been used to synthesise graphene sheets before and we are thrilled to find that it not only works, it’s in fact a superior method, both in terms of safety and overall cost,” said Bhargava.

“Our approach could bring down the cost of making graphene from around $USD100 per gram to just 50 cents, increasing it availability to industries globally and enabling the development of an array of vital new technologies.”

Graphene’s distinctive features make it a transformative material that could be used in the development of flexible electronics, more powerful computer chips and better solar panels, water filters and bio-sensors.

Professor Vishnu Shanker from the National Institute of Technology, Warangal, said the ‘green’ chemistry avoided the use of toxic reagents, potentially opening the door to the application of graphene not only for electronic devices but also biocompatible materials.

“Working collaboratively with RMIT’s Centre for Advanced Materials and Industrial Chemistry we’re harnessing the power of collective intelligence to make these discoveries,” he said.

A novel approach to graphene synthesis:

Chemical reduction is the most common method for synthesising graphene oxide as it allows for the production of graphene at a low cost in bulk quantities.

This method however relies on reducing agents that are dangerous to both people and the environment.

When tested in the application of a supercapacitor, the ‘green’ graphene produced using this method matched the quality and performance characteristics of traditionally-produced graphene without the toxic reagents.

Bhargava said the abundance of eucalyptus trees in Australia made it a cheap and accessible resource for producing graphene locally.

“Graphene is a remarkable material with great potential in many applications due to its chemical and physical properties and there’s a growing demand for economical and environmentally friendly large-scale production,” he said.

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

Novel and Highly Efficient Strategy for the Green Synthesis of Soluble Graphene by Aqueous Polyphenol Extracts of Eucalyptus Bark and Its Applications in High-Performance Supercapacitors by Saikumar ManchalaV. S. R. K. Tandava, Deshetti Jampaiah, Suresh K. Bhargava, Vishnu Shanker. ACS Sustainable Chem. Eng.2019XXXXXXXXXX-XXX DOI: Publication Date:June 13, 2019

Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Nanocellulose sensors: 3D printed and biocompatible

I do like to keep up with nanocellulose doings, especially when there’s some Canadian involvement, and an October 8, 2019 news item on Nanowerk alerted me to a newish application for the product,

Physiological parameters in our blood can be determined without painful punctures. Empa researchers are currently working with a Canadian team to develop flexible, biocompatible nanocellulose sensors that can be attached to the skin. The 3D-printed analytic chips made of renewable raw materials will even be biodegradable in future.

The idea of measuring parameters that are relevant for our health via the skin has already taken hold in medical diagnostics. Diabetics, for example, can painlessly determine their blood sugar level with a sensor instead of having to prick their fingers.

An October 8, 2019 Empa (Swiss Federal Laboratories for Materials Science and Technology) press release, which originated the news item, provides more detail,

A transparent foil made of wood

Nanocellulose is an inexpensive, renewable raw material, which can be obtained in form of crystals and fibers, for example from wood. However, the original appearance of a tree no longer has anything to do with the gelatinous substance, which can consist of cellulose nanocrystals and cellulose nanofibers. Other sources of the material are bacteria, algae or residues from agricultural production. Thus, nanocellulose is not only relatively easy and sustainable to obtain. Its mechanical properties also make the “super pudding” an interesting product. For instance, new composite materials based on nanocellulose can be developed that could be used as surface coatings, transparent packaging films or even to produce everyday objects like beverage bottles.

Researchers at Empa’s Cellulose & Wood Materials lab and Woo Soo Kim from the Simon Fraser University [SFU] in Burnaby, Canada, are also focusing on another feature of nanocellulose: biocompatibility. Since the material is obtained from natural resources, it is particularly suitable for biomedical research.

With the aim of producing biocompatible sensors that can measure important metabolic values, the researchers used nanocellulose as an “ink” in 3D printing processes. To make the sensors electrically conductive, the ink was mixed with silver nanowires. The researchers determined the exact ratio of nanocellulose and silver threads so that a three-dimensional network could form.

Just like spaghetti – only a wee bit smaller

It turned out that cellulose nanofibers are better suited than cellulose nanocrystals to produce a cross-linked matrix with the tiny silver wires. “Cellulose nanofibers are flexible similar to cooked spaghetti, but with a diameter of only about 20 nanometers and a length of just a few micrometers,” explains Empa researcher Gilberto Siqueira.

The team finally succeeded in developing sensors that measure medically relevant metabolic parameters such as the concentration of calcium, potassium and ammonium ions. The electrochemical skin sensor sends its results wirelessly to a computer for further data processing. The tiny biochemistry lab on the skin is only half a millimeter thin.

While the tiny biochemistry lab on the skin – which is only half a millimeter thin – is capable of determining ion concentrations specifically and reliably, the researchers are already working on an updated version. “In the future, we want to replace the silver [nano] particles with another conductive material, for example on the basis of carbon compounds,” Siqueira explains. This would make the medical nanocellulose sensor not only biocompatible, but also completely biodegradable.

I like the images from Empa better than the ones from SFU,

Using a 3D printer, the nanocellulose “ink” is applied to a carrier plate. Silver particles provide the electrical conductivity of the material. Image: Empa
Empa researcher Gilberto Siqueira demonstrates the newly printed nanocellulose circuit. After a subsequent drying, the material can be further processed. Image: Empa

SFU produced a news release about this work back in February 2019. Again, I prefer what the Swiss have done because they’re explaining/communicating the science, as well as , communicating benefits. From a February 13, 2019 SFU news release (Note: Links have been removed),

Simon Fraser University and Swiss researchers are developing an eco-friendly, 3D printable solution for producing wireless Internet-of-Things (IoT) sensors that can be used and disposed of without contaminating the environment. Their research has been published as the cover story in the February issue of the journal Advanced Electronic Materials.

SFU professor Woo Soo Kim is leading the research team’s discovery, which uses a wood-derived cellulose material to replace the plastics and polymeric materials currently used in electronics.

Additionally, 3D printing can give flexibility to add or embed functions onto 3D shapes or textiles, creating greater functionality.

“Our eco-friendly, 3D-printed cellulose sensors can wirelessly transmit data during their life, and then can be disposed without concern of environmental contamination,” says Kim, a professor in the School of Mechatronic Systems Engineering. The SFU research is being carried out at PowerTech Labs in Surrey, which houses several state-of-the-art 3D printers used to advance the research.

“This development will help to advance green electronics. For example, the waste from printed circuit boards is a hazardous source of contamination to the environment. If we are able to change the plastics in PCB to cellulose composite materials, recycling of metal components on the board could be collected in a much easier way.”

Kim’s research program spans two international collaborative projects, including the latest focusing on the eco-friendly cellulose material-based chemical sensors with collaborators from the Swiss Federal Laboratories for Materials Science.

He is also collaborating with a team of South Korean researchers from the Daegu Gyeongbuk Institute of Science and Technology’s (DGIST)’s department of Robotics Engineering, and PROTEM Co Inc, a technology-based company, for the development of printable conductive ink materials.

In this second project, researchers have developed a new breakthrough in the embossing process technology, one that can freely imprint fine circuit patterns on flexible polymer substrate, a necessary component of electronic products.

Embossing technology is applied for the mass imprinting of precise patterns at a low unit cost. However, Kim says it can only imprint circuit patterns that are imprinted beforehand on the pattern stamp, and the entire, costly stamp must be changed to put in different patterns.

The team succeeded in developing a precise location control system that can imprint patterns directly resulting in a new process technology. The result will have widespread implications for use in semiconductor processes, wearable devices and the display industry.

This paper was made available online back in December 2018 and then published in print in February 2019. As to why there’d be such large gaps between the paper’s publication dates and the two institution’s news/press releases, it’s a mystery to me. In any event, here’s a link to and a citation for the paper,

3D Printed Disposable Wireless Ion Sensors with Biocompatible Cellulose Composites by Taeil Kim, Chao Bao, Michael Hausmann, Gilberto Siqueira, Tanja Zimmermann, Woo Soo Kim. Advanced Electronic Materials DOI: First published online December 19, 2018. First published in print: 08 February 2019 (Adv. Electron. Mater. 2/2109) Volume 5, Issue 2 February 2019 1970007

This paper is behind a paywall.

‘Smart’ windows in Vancouver (Canada): engineering issues?

This post was going to focus on the first building in Canada to feature ‘smart’ windows. In this case, they are electrochromic windows and the company, View Dynamic Glass, was mentioned here in a September 17, 2018 posting about the windows’ use at the Dallas/Fort Worth Airport. (The posting includes a link to the View Dynamic Glass report on the windows’ use and a short video.)

However, things changed but, first, let’s start with an explanation as to what electrochromic glass ir. Chris Woodford in a December 5, 2018 article on offers a great overview which includes an explanation, a description of how they work, and more. What follows is a brief excerpt from Woodford’s overview (Note: Links have been removed),

What is electrochromic glass?

Glass is an amazing material and our buildings would be dark, dingy, cold, and damp without it. But it has its drawbacks too. It lets in light and heat even when you don’t want it to. On a blinding summer’s day, the more heat (“solar gain”) that enters your building the more you’ll need to use your air-conditioning—a horrible waste of energy that costs you money and harms the environment. That’s why most of the windows in homes and offices are fitted with curtains or blinds. If you’re into interior design and remodeling, you might think furnishings like this are neat and attractive—but in cold, practical, scientific terms they’re a nuisance. Let’s be honest about this: curtains and blinds are a technological kludge to make up for glass’s big, built-in drawback: it’s transparent (or translucent) even when you don’t want it to be.

Since the early 20th century, people have got used to the idea of buildings that are increasingly automated. We have electric clothes washing machines, dishwashers, vacuum cleaners and much more. So why not fit our homes with electric windows that can change from clear to dark automatically? Smart windows (also referred to by the names smart glass, switchable windows, and dynamic windows) do exactly that using a scientific idea called electrochromism, in which materials change color (or switch from transparent to opaque) when you apply an electrical voltage across them. Typically smart windows start off a blueish color and gradually (over a few minutes) turn transparent when the electric current passes through them.

As for the news about its Vancouver debut, I was very excited to see this April 28, 2019 article by Kenneth Chan for,

BlueSky Properties’ 10-storey office building at 988 West Broadway [in Vancouver, Canada; emphasis mine] is home to the new Vancouver offices of Industrial Alliance Financial Group, which has leased nine stories and 93,700-sq-ft of office space.

One of the building’s unique design features is its use of View Dynamic Glass technology [emphases mine] — a glass technology that controls heat and glare, reduces overall energy consumption and costs, and improves the health and wellness of individuals working inside the building.

These smart windows optimize the amount of natural light to enhance mental and physical well-being without the need for shades or blinds. The application of the technology on this building, the first of its kind in Canada, will result in energy savings of up to 20%, [emphasis mine] with the amount of sunlight streaming through automatically tinted to block glare.

Blue Sky Properties (a Bosa Family Company), the local developer for this building, was very excited about the building and the ‘smart’ glass technology, according to its April 23, 2019 news release (here for a short version and here for the full version).

Other than being happy to see the technology being employed in Vancouver, I didn’t spend a lot of time thinking about the property. That changed on reading a May 8, 2019 article by Kenneth Chan for,

A structural engineer based in Vancouver has been stripped of his license to work in British Columbia [emphasis mine] following an investigation that determined his design for a condominium tower in Surrey fell short of the provincial building code.

According to a disciplinary notice posted by Engineers and Geoscientists British Columbia Association (EGBCA) on April 30, John Bryson, a managing partner of Bryson Markulin Zickmantel Structural Engineers (BMZSE), [emphases mine] admitted to unprofessional conduct and acted contrary to the association’s code of ethics that requires its members to “hold paramount the safety, health, and welfare of the public.”

“Mr. Bryson admitted that his structural design for the building did not comply with the 2006 BC Building Code, to which he certified it had been designed, in particular with respect to seismic and wind loads,” reads the notice. [emphases mine]

BMZSE has been involved in the design work of a number of projects across Metro Vancouver, including Station Square, Rogers Arena South Tower, Lougheed Heights, River District Parcel 17, The Jervis, Harwood, Plaza 88, Solo District, Burrard Place, Centreview Place, Trump International Hotel & Tower Vancouver, Central, Sovereign, Kings Crossing, and 988 West Broadway. [emphases mine]

You can find the ‘disciplinary notice’ (it’s an account of what Bryson failed to do and the punishment for the failure) here on the Association of Professional Engineers and Geoscientists of the Province of British Columbia (also known as Engineers and Geoscientists British Columbia) website.

Presumably, all of Bryson’s projects have been reviewed since the disciplinary action.

Bad battery, good synapse from Stanford University

A May 4, 2019 news item on ScienceDaily announces the latest advance made by Stanford University and Sandia National Laboratories in the field of neuromorphic (brainlike) computing,

The brain’s capacity for simultaneously learning and memorizing large amounts of information while requiring little energy has inspired an entire field to pursue brain-like — or neuromorphic — computers. Researchers at Stanford University and Sandia National Laboratories previously developed one portion of such a computer: a device that acts as an artificial synapse, mimicking the way neurons communicate in the brain.

In a paper published online by the journal Science on April 25 [2019], the team reports that a prototype array of nine of these devices performed even better than expected in processing speed, energy efficiency, reproducibility and durability.

Looking forward, the team members want to combine their artificial synapse with traditional electronics, which they hope could be a step toward supporting artificially intelligent learning on small devices.

“If you have a memory system that can learn with the energy efficiency and speed that we’ve presented, then you can put that in a smartphone or laptop,” said Scott Keene, co-author of the paper and a graduate student in the lab of Alberto Salleo, professor of materials science and engineering at Stanford who is co-senior author. “That would open up access to the ability to train our own networks and solve problems locally on our own devices without relying on data transfer to do so.”

An April 25, 2019 Stanford University news release (also on EurekAlert but published May 3, 2019) by Taylor Kubota, which originated the news item, expands on the theme,

A bad battery, a good synapse

The team’s artificial synapse is similar to a battery, modified so that the researchers can dial up or down the flow of electricity between the two terminals. That flow of electricity emulates how learning is wired in the brain. This is an especially efficient design because data processing and memory storage happen in one action, rather than a more traditional computer system where the data is processed first and then later moved to storage.

Seeing how these devices perform in an array is a crucial step because it allows the researchers to program several artificial synapses simultaneously. This is far less time consuming than having to program each synapse one-by-one and is comparable to how the brain actually works.

In previous tests of an earlier version of this device, the researchers found their processing and memory action requires about one-tenth as much energy as a state-of-the-art computing system needs in order to carry out specific tasks. Still, the researchers worried that the sum of all these devices working together in larger arrays could risk drawing too much power. So, they retooled each device to conduct less electrical current – making them much worse batteries but making the array even more energy efficient.

The 3-by-3 array relied on a second type of device – developed by Joshua Yang at the University of Massachusetts, Amherst, who is co-author of the paper – that acts as a switch for programming synapses within the array.

“Wiring everything up took a lot of troubleshooting and a lot of wires. We had to ensure all of the array components were working in concert,” said Armantas Melianas, a postdoctoral scholar in the Salleo lab. “But when we saw everything light up, it was like a Christmas tree. That was the most exciting moment.”

During testing, the array outperformed the researchers’ expectations. It performed with such speed that the team predicts the next version of these devices will need to be tested with special high-speed electronics. After measuring high energy efficiency in the 3-by-3 array, the researchers ran computer simulations of a larger 1024-by-1024 synapse array and estimated that it could be powered by the same batteries currently used in smartphones or small drones. The researchers were also able to switch the devices over a billion times – another testament to its speed – without seeing any degradation in its behavior.

“It turns out that polymer devices, if you treat them well, can be as resilient as traditional counterparts made of silicon. That was maybe the most surprising aspect from my point of view,” Salleo said. “For me, it changes how I think about these polymer devices in terms of reliability and how we might be able to use them.”

Room for creativity

The researchers haven’t yet submitted their array to tests that determine how well it learns but that is something they plan to study. The team also wants to see how their device weathers different conditions – such as high temperatures – and to work on integrating it with electronics. There are also many fundamental questions left to answer that could help the researchers understand exactly why their device performs so well.

“We hope that more people will start working on this type of device because there are not many groups focusing on this particular architecture, but we think it’s very promising,” Melianas said. “There’s still a lot of room for improvement and creativity. We only barely touched the surface.”

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

Parallel programming of an ionic floating-gate memory array for scalable neuromorphic computing by Elliot J. Fuller, Scott T. Keene, Armantas Melianas, Zhongrui Wang, Sapan Agarwal, Yiyang Li, Yaakov Tuchman, Conrad D. James, Matthew J. Marinella, J. Joshua Yang3, Alberto Salleo, A. Alec Talin1. Science 25 Apr 2019: eaaw5581 DOI: 10.1126/science.aaw5581

This paper is behind a paywall.

For anyone interested in more about brainlike/brain-like/neuromorphic computing/neuromorphic engineering/memristors, use any or all of those terms in this blog’s search engine.

Dessert or computer screen?

Scientists at Japan’s University of Osaka have a technique for creating higher resolution computer and smart phone screens from the main ingredient for a dessert, nata de coco. From the nata de coco Wikipedia entry (Note: Links have been removed),

Nata de coco (also marketed as “coconut gel”) is a chewy, translucent, jelly-like food produced by the fermentation of coconut water,[1] which gels through the production of microbial cellulose by ‘Komagataeibacter xylinus’. Originating in the Philippines, nata de coco is most commonly sweetened as a candy or dessert, and can accompany a variety of foods, including pickles, drinks, ice cream, puddings, and fruit cocktails.[2]

An April 18, 2018 news item on Nanowerk announces the research (Note: A link has been removed),

A team at the Institute of Scientific and Industrial Research at Osaka University has determined the optical parameters of cellulose molecules with unprecedented precision. They found that cellulose’s intrinsic birefringence, which describes how a material reacts differently to light of various orientations, is powerful enough to be used in optical displays, such as flexible screens or electronic paper (ACS Macro Letters, “Estimation of the Intrinsic Birefringence of Cellulose Using Bacterial Cellulose Nanofiber Films”

An April 18, 2019 Osaka University press release on AlphaGalileo, which originated the news release, provides some historical context for the use of cellulose along with additional detail about the research,

Cellulose is an ancient material that may be poised for a major comeback. It has been utilized for millennia as the primary component of paper books, cotton clothing, and nata de coco, a tropical dessert made from coconut water. While books made of dead trees and plain old shirts might seem passé in world increasingly filled with tablets and smartphones, researchers at Osaka University have shown that cellulose might have just what it takes to make our modern electronic screens cheaper and provide sharper, more vibrant images.

Cellulose, a naturally occurring polymer, consists of many long molecular chains. Because of its rigidity and strength, cellulose helps maintain the structural integrity of the cell walls in plants. It makes up about 99% of the nanofibers that comprise nata de coco, and helps create its unique and tasty texture.

The team at Osaka University achieved better results using unidirectionally-aligned cellulose nanofiber films created by stretching hydrogels from nata de coco at various rates. Nata de coco nanofibers allow the cellulose chains to be straight on the molecular level, and this is helpful for the precise determination of the intrinsic birefringence–that is, the maximum birefringence of fully extended polymer chains. The researchers were also able to measure the birefringence more accurately through improvements in method. “Using high quality samples and methods, we were able to reliably determine the inherent birefringence of cellulose, for which very different values had been previously estimated,” says senior author Masaya Nogi.

The main application the researchers envision is as light compensation films for liquid crystal displays (LCDs), since they operate by controlling the brightness of pixels with filters that allow only one orientation of light to pass through. Potentially, any smartphone, computer, or television that has an LCD screen could see improved contrast, along with reduced color unevenness and light leakage with the addition of cellulose nanofiber films.

“Cellulose nanofibers are promising light compensation materials for optoelectronics, such as flexible displays and electronic paper, since they simultaneously have good transparency, flexibility, dimensional stability, and thermal conductivity,” says lead author Kojiro Uetani. “So look for this ancient material in your future high-tech devices.”

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

Estimation of the Intrinsic Birefringence of Cellulose Using Bacterial Cellulose Nanofiber Films by Kojiro Uetani, Hirotaka Koga, and Masaya Nogi. ACS Macro Lett., 2019, 8 (3), pp 250–254 DOI: 10.1021/acsmacrolett.9b00024 Publication Date (Web): February 22, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Brainlike computing with spintronic devices

Adding to the body of ‘memristor’ research I have here, there’s an April 17, 2019 news item on Nanowerk announcing the development of ‘memristor’ hardware by Japanese researchers (Note: A link has been removed),

A research group from Tohoku University has developed spintronics devices which are promising for future energy-efficient and adoptive computing systems, as they behave like neurons and synapses in the human brain (Advanced Materials, “Artificial Neuron and Synapse Realized in an Antiferromagnet/Ferromagnet Heterostructure Using Dynamics of Spin–Orbit Torque Switching”).

Just because this ‘synapse’ is pretty,

Courtesy: Tohoku University

An April 16, 2019 Tohoku University press release, which originated the news item, expands on the theme,

Today’s information society is built on digital computers that have evolved drastically for half a century and are capable of executing complicated tasks reliably. The human brain, by contrast, operates under very limited power and is capable of executing complex tasks efficiently using an architecture that is vastly different from that of digital computers.

So the development of computing schemes or hardware inspired by the processing of information in the brain is of broad interest to scientists in fields ranging from physics, chemistry, material science and mathematics, to electronics and computer science.

In computing, there are various ways to implement the processing of information by a brain. Spiking neural network is a kind of implementation method which closely mimics the brain’s architecture and temporal information processing. Successful implementation of spiking neural network requires dedicated hardware with artificial neurons and synapses that are designed to exhibit the dynamics of biological neurons and synapses.

Here, the artificial neuron and synapse would ideally be made of the same material system and operated under the same working principle. However, this has been a challenging issue due to the fundamentally different nature of the neuron and synapse in biological neural networks.

The research group – which includes Professor Hideo Ohno (currently the university president), Associate Professor Shunsuke Fukami, Dr. Aleksandr Kurenkov and Professor Yoshihiko Horio – created an artificial neuron and synapse by using spintronics technology. Spintronics is an academic field that aims to simultaneously use an electron’s electric (charge) and magnetic (spin) properties.

The research group had previously developed a functional material system consisting of antiferromagnetic and ferromagnetic materials. This time, they prepared artificial neuronal and synaptic devices microfabricated from the material system, which demonstrated fundamental behavior of biological neuron and synapse – leaky integrate-and-fire and spike-timing-dependent plasticity, respectively – based on the same concept of spintronics.

The spiking neural network is known to be advantageous over today’s artificial intelligence for the processing and prediction of temporal information. Expansion of the developed technology to unit-circuit, block and system levels is expected to lead to computers that can process time-varying information such as voice and video with a small amount of power or edge devices that have the an ability to adopt users and the environment through usage.

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

Artificial Neuron and Synapse Realized in an Antiferromagnet/Ferromagnet Heterostructure Using Dynamics of Spin–Orbit Torque Switching by Aleksandr Kurenkov, Samik DuttaGupta, Chaoliang Zhang, Shunsuke Fukami, Yoshihiko Horio, Hideo Ohno. Advanced Materials First published: 16 April 2019

This paper is behind a paywall.