Category Archives: energy

Nanocellulose films made with liquid-phase fabrication method

I always appreciate a reference to Star Trek and three-dimensional chess was one of my favourite concepts. You’ll find that and more in a May 19, 2020 news item on Nanowerk,

Researchers at The Institute of Scientific and Industrial Research at Osaka University [Japan] introduced a new liquid-phase fabrication method for producing nanocellulose films with multiple axes of alignment. Using 3D-printing methods for increased control, this work may lead to cheaper and more environmentally friendly optical and thermal devices.

Ever since appearing on the original Star Trek TV show in the 1960s, the game of “three-dimensional chess” has been used as a metaphor for sophisticated thinking. Now, researchers at Osaka University can say that they have added their own version, with potential applications in advanced optics and inexpensive smartphone displays.

It’s not exactly three-dimensional chess but this nanocellulose film was produced by 3D printing methods,

Caption: Developed multiaxis nanocellulose-oriented film. Credit: Osaka University

A May 20, 2020 Osaka University press release (also on EurekAlert but dated May 19, 2020), which originated the news item, provides more detail,

Many existing optical devices, including liquid-crystal displays (LCDs) found in older flat-screen televisions, rely on long needle-shaped molecules aligned in the same direction. However, getting fibers to line up in multiple directions on the same device is much more difficult. Having a method that can reliably and cheaply produce optical fibers would accelerate the manufacture of low-cost displays or even “paper electronics”–computers that could be printed from biodegradable materials on demand.

Cellulose, the primary component of cotton and wood, is an abundant renewable resource made of long molecules. Nanocelluloses are nanofibers made of uniaxially aligned cellulose molecular chains that have different optical and heat conduction properties along one direction compared to the another.

In newly published research from the Institute of Scientific and Industrial Research at Osaka University, nanocellulose was harvested from sea pineapples, a kind of sea squirt. They then used liquid-phase 3D-pattering, which combined the wet spinning of nanofibers with the precision of 3D-printing. A custom-made triaxial robot dispensed a nanocellulose aqueous suspension into an acetone coagulation bath.

“We developed this liquid-phase three-dimensional patterning technique to allow for nanocellulose alignment along any preferred axis,” says first author Kojiro Uetani. The direction of the patterns could be programmed so that it formed an alternating checkerboard pattern of vertically- and horizontally-aligned fibers.

To demonstrate the method, a film was sandwiched between two orthogonal polarizing films. Under the proper viewing conditions, a birefringent checkerboard pattern appeared. They also measured the thermal transfer and optical retardation properties.

“Our findings could aid in the development of next-generation optical materials and paper electronics,” says senior author Masaya Nogi. “This could be the start of bottom-up techniques for building sophisticated and energy-efficient optical and thermal materials.”

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

Checkered Films of Multiaxis Oriented Nanocelluloses by Liquid-Phase Three-Dimensional Patterning by Kojiro Uetani, Hirotaka Koga and Masaya Nogi. Nanomaterials 2020, 10(5), 958; DOI: https://doi.org/10.3390/nano10050958 Published: 18 May 2020

This is an open access paper.

Smart film lets windows switch autonomously

This work from Korean research scientists gives me some hope that smart windows will one day be the norm. From a June 2, 2020 Korea Advanced Institute of Science and Technology (KAIST) press release (also on EurekAlert),

Researchers have developed a new easy-to-use smart optical film technology that allows smart window devices to autonomously switch between transparent and opaque states in response to the surrounding light conditions.

The proposed 3D hybrid nanocomposite film with a highly periodic network structure has empirically demonstrated its high speed and performance, enabling the smart window to quantify and self-regulate its high-contrast optical transmittance. As a proof of concept, a mobile-app-enabled smart window device for Internet of Things (IoT) applications has been realized using the proposed smart optical film with successful expansion to the 3-by-3-inch scale. This energy-efficient and cost-effective technology holds great promise for future use in various applications that require active optical transmission modulation.

Flexible optical transmission modulation technologies for smart applications including privacy-protection windows, zero-energy buildings, and beam projection screens have been in the spotlight in recent years. Conventional technologies that used external stimuli such as electricity, heat, or light to modulate optical transmission had only limited applications due to their slow response speeds, unnecessary color switching, and low durability, stability, and safety.

The optical transmission modulation contrast achieved by controlling the light scattering interfaces on non-periodic 2D surface structures that often have low optical density such as cracks, wrinkles, and pillars is also generally low. In addition, since the light scattering interfaces are exposed and not subject to any passivation, they can be vulnerable to external damage and may lose optical transmission modulation functions. Furthermore, in-plane scattering interfaces that randomly exist on the surface make large-area modulation with uniformity difficult.

Inspired by these limitations, a KAIST research team led by Professor Seokwoo Jeon from the Department of Materials Science and Engineering and Professor Jung-Wuk Hong of the Civil and Environmental Engineering Department used proximity-field nanopatterning (PnP) technology that effectively produces highly periodic 3D hybrid nanostructures, and an atomic layer deposition (ALD) technique that allows the precise control of oxide deposition and the high-quality fabrication of semiconductor devices.

The team then successfully produced a large-scale smart optical film with a size of 3 by 3 inches in which ultrathin alumina nanoshells are inserted between the elastomers in a periodic 3D nanonetwork.

This “mechano-responsive” 3D hybrid nanocomposite film with a highly periodic network structure is the largest smart optical transmission modulation film that exists. The film has been shown to have state-of-the-art optical transmission modulation of up to 74% at visible wavelengths from 90% initial transmission to 16% in the scattering state under strain. Its durability and stability were proved by more than 10,000 tests of harsh mechanical deformation including stretching, releasing, bending, and being placed under high temperatures of up to 70°C. When this film was used, the transmittance of the smart window device was adjusted promptly and automatically within one second in response to the surrounding light conditions. Through these experiments, the underlying physics of optical scattering phenomena occurring in the heterogeneous interfaces were identified. Their findings were reported in the online edition of Advanced Science on April 26 [2020]. KAIST Professor Jong-Hwa Shin’s group and Professor Young-Seok Shim at Silla University also collaborated on this project.

Donghwi Cho, a PhD candidate in materials science and engineering at KAIST and co-lead author of the study, said, “Our smart optical film technology can better control high-contrast optical transmittance by relatively simple operating principles and with low energy consumption and costs.”

“When this technology is applied by simply attaching the film to a conventional smart window glass surface without replacing the existing window system, fast switching and uniform tinting are possible while also securing durability, stability, and safety. In addition, its wide range of applications for stretchable or rollable devices such as wall-type displays for a beam projection screen will also fulfill aesthetic needs,” he added.

Here’s an image illustrating how the composite scatters light (I think),

Caption: Design concept of and fabrication procedures for the 3D scatterer. Credit: KAIST

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

High‐Contrast Optical Modulation from Strain‐Induced Nanogaps at 3D Heterogeneous Interfaces by Donghwi Cho, Prof. Young‐Seok Shim, Dr. Jae‐Wook Jung, Sang‐Hyeon Nam, Seokhwan Min, Dr. Sang‐Eon Lee, Youngjin Ham, Prof. Kwangjae Lee, Prof. Junyong Park, Prof. Jonghwa Shin, Prof. Jung‐Wuk Hong, and Prof. Seokwoo Jeon. Advanced Science DOI: https://doi.org/10.1002/advs.201903708 First published: 26 April 2020

This paper is open access.

Neuromorphic computing with voltage usage comparable to human brains

Part of neuromorphic computing’s appeal is the promise of using less energy because, as it turns out, the human brain uses small amounts of energy very efficiently. A team of researchers at the University of Massachusetts at Amherst have developed function in the same range of voltages as the human brain. From an April 20, 2020 news item on ScienceDaily,

Only 10 years ago, scientists working on what they hoped would open a new frontier of neuromorphic computing could only dream of a device using miniature tools called memristors that would function/operate like real brain synapses.

But now a team at the University of Massachusetts Amherst has discovered, while on their way to better understanding protein nanowires, how to use these biological, electricity conducting filaments to make a neuromorphic memristor, or “memory transistor,” device. It runs extremely efficiently on very low power, as brains do, to carry signals between neurons. Details are in Nature Communications.

An April 20, 2020 University of Massachusetts at Amherst news release (also on EurekAlert), which originated the news items, dives into detail about how these researchers were able to achieve bio-voltages,

As first author Tianda Fu, a Ph.D. candidate in electrical and computer engineering, explains, one of the biggest hurdles to neuromorphic computing, and one that made it seem unreachable, is that most conventional computers operate at over 1 volt, while the brain sends signals called action potentials between neurons at around 80 millivolts – many times lower. Today, a decade after early experiments, memristor voltage has been achieved in the range similar to conventional computer, but getting below that seemed improbable, he adds.

Fu reports that using protein nanowires developed at UMass Amherst from the bacterium Geobacter by microbiologist and co-author Derek Lovely, he has now conducted experiments where memristors have reached neurological voltages. Those tests were carried out in the lab of electrical and computer engineering researcher and co-author Jun Yao.

Yao says, “This is the first time that a device can function at the same voltage level as the brain. People probably didn’t even dare to hope that we could create a device that is as power-efficient as the biological counterparts in a brain, but now we have realistic evidence of ultra-low power computing capabilities. It’s a concept breakthrough and we think it’s going to cause a lot of exploration in electronics that work in the biological voltage regime.”

Lovely points out that Geobacter’s electrically conductive protein nanowires offer many advantages over expensive silicon nanowires, which require toxic chemicals and high-energy processes to produce. Protein nanowires also are more stable in water or bodily fluids, an important feature for biomedical applications. For this work, the researchers shear nanowires off the bacteria so only the conductive protein is used, he adds.

Fu says that he and Yao had set out to put the purified nanowires through their paces, to see what they are capable of at different voltages, for example. They experimented with a pulsing on-off pattern of positive-negative charge sent through a tiny metal thread in a memristor, which creates an electrical switch.

They used a metal thread because protein nanowires facilitate metal reduction, changing metal ion reactivity and electron transfer properties. Lovely says this microbial ability is not surprising, because wild bacterial nanowires breathe and chemically reduce metals to get their energy the way we breathe oxygen.

As the on-off pulses create changes in the metal filaments, new branching and connections are created in the tiny device, which is 100 times smaller than the diameter of a human hair, Yao explains. It creates an effect similar to learning – new connections – in a real brain. He adds, “You can modulate the conductivity, or the plasticity of the nanowire-memristor synapse so it can emulate biological components for brain-inspired computing. Compared to a conventional computer, this device has a learning capability that is not software-based.”

Fu recalls, “In the first experiments we did, the nanowire performance was not satisfying, but it was enough for us to keep going.” Over two years, he saw improvement until one fateful day when his and Yao’s eyes were riveted by voltage measurements appearing on a computer screen.

“I remember the day we saw this great performance. We watched the computer as current voltage sweep was being measured. It kept doing down and down and we said to each other, ‘Wow, it’s working.’ It was very surprising and very encouraging.”

Fu, Yao, Lovely and colleagues plan to follow up this discovery with more research on mechanisms, and to “fully explore the chemistry, biology and electronics” of protein nanowires in memristors, Fu says, plus possible applications, which might include a device to monitor heart rate, for example. Yao adds, “This offers hope in the feasibility that one day this device can talk to actual neurons in biological systems.”

That last comment has me wondering about why you would want to have your device talk to actual neurons. For neuroprosthetics perhaps?

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

Bioinspired bio-voltage memristors by Tianda Fu, Xiaomeng Liu, Hongyan Gao, Joy E. Ward, Xiaorong Liu, Bing Yin, Zhongrui Wang, Ye Zhuo, David J. F. Walker, J. Joshua Yang, Jianhan Chen, Derek R. Lovley & Jun Yao. Nature Communications volume 11, Article number: 1861 (2020) DOI: https://doi.org/10.1038/s41467-020-15759-y Published: 20 April 2020

This paper is open access.

There is an illustration of the work

Caption: A graphic depiction of protein nanowires (green) harvested from microbe Geobacter (orange) facilitate the electronic memristor device (silver) to function with biological voltages, emulating the neuronal components (blue junctions) in a brain. Credit: UMass Amherst/Yao lab

Plants as a source of usable electricity

A friend sent me a link to this interview with Iftach Yacoby of Tel Aviv University talking about some new research into plants and electricity. From a June 8, 2020 article by Omer Kabir for Calcalist (CTech) on the Algemeiner website,

For years, scientists have been trying to understand the evolutionary capabilities of plants to produce energy and have had only partial success. But a recent Tel Aviv University [TAU] study seems to make the impossible possible, proving that any plant can be transformed into an electrical source, producing a variety of materials that can revolutionize the global economy — from using hydrogen as fuel to clean ammonia to replace the pollutants in the agriculture industry.

“People are unaware that their plant pots have an electric current for everything,” Iftach Yacoby, head of the Laboratory of Renewable Energy Studies at Tel Aviv University’s Faculty of Life Sciences said in a recent interview with Calcalist.

“Our study opens the door to a new field of agriculture, equivalent to wheat or corn production for food security — generating energy,” he said. However, Yacoby makes it clear that it will take at least a decade before the research findings can be transferred to the commercial level.

At the heart of the research is the understanding that plants have particularly efficient capacities when it comes to electricity generation. “Anything green that is not dollars, but rather leaves, grass, and seaweed for example, contains solar panels that are completely identical to the panels the entire country is now building,” Yacoby explained. “They know how to take in solar radiation and make electrons flow out of it. That’s the essence of photosynthesis. Most people think of oxygen and food production, but the most basic phase of photosynthesis is the same as silicon panels in the Negev and on rooftops — taking in sunlight and generating electric current.”

… “At home, an electric current can be wired to many devices. Just plug the device into a power outlet. But when you want to do it in plants, it’s about the order of nanometers. We have no idea where to plug the plugs. That’s what we did in this study. In plant cells, we found they can be used as a socket for anything, at just a nanometer size. We have an enzyme, which is equivalent to a biological machine that can produce hydrogen. We took this enzyme, put it together so that it sits in the socket in the plant cell, which was previously only hypothetical. When he started to produce hydrogen, we proved that we had a socket for everything, though nanotermically-sized. Now we can take any plant or kelp and engineer it so that their electrical outlet can be used for production purposes,” Yacoby explained.

“If you attach an enzyme that produces hydrogen you get hydrogen, it’s the cleanest fuel that can be,” he said. “There are already electric cars and bicycles with a range of 150 km that travel on hydrogen. There are many types of enzymes in nature that produce valuable substances, such as ammonia needed for the fertilizer industry and today is still produced by a very toxic and harmful method that consumes a lot of energy. We can provide a plant-based alternative for the production of materials that are made in chemical manufacturing facilities. It’s an electric platform inside a living plant cell.”

You might find it helpful to read Kabir’s article in its entirety before moving on to the news release about the work. The work was conducted with researchers from Arizona State University (ASU;US) and a researcher from Yogi Vemana University (India), as well as, Yacoby. There’s a May 7, 2020 ASU news release (also on EurekAlert but published on May 6, 2020) detailing the work,

Hydrogen is an essential commodity with over 60 million tons produced globally every year. However over 95 percent of it is made by steam reformation of fossil fuels, a process that is energy intensive and produces carbon dioxide. If we could replace even a part of that with algal biohydrogen that is made via light and water, it would have a substantial impact.

This is essentially what has just been achieved in the lab of Kevin Redding, professor in the School of Molecular Sciences and director of the Center for Bioenergy and Photosynthesis. Their research, entitled Rewiring photosynthesis: a Photosystem I -hydrogenase chimera that makes hydrogen in vivo was published very recently in the high impact journal Energy and Environmental Science.

“What we have done is to show that it is possible to intercept the high energy electrons from photosynthesis and use them to drive alternate chemistry, in a living cell” explained Redding. “We have used hydrogen production here as an example.”

“Kevin Redding and his group have made a true breakthrough in re-engineering the Photosystem I complex,” explained Ian Gould, interim director of the School of Molecular Sciences, which is part of The College of Liberal Arts and Sciences. “They didn’t just find a way to redirect a complex protein structure that nature designed for one purpose to perform a different, but equally critical process, but they found the best way to do it at the molecular level.”

It is common knowledge that plants and algae, as well as cyanobacteria, use photosynthesis to produce oxygen and “fuels,” the latter being oxidizable substances like carbohydrates and hydrogen. There are two pigment-protein complexes that orchestrate the primary reactions of light in oxygenic photosynthesis: Photosystem I (PSI) and Photosystem II (PSII).

Algae (in this work the single-celled green alga Chlamydomonas reinhardtii, or ‘Chlamy’ for short) possess an enzyme called hydrogenase that uses electrons it gets from the protein ferredoxin, which is normally used to ferry electrons from PSI to various destinations. A problem is that the algal hydrogenase is rapidly and irreversibly inactivated by oxygen that is constantly produced by PSII.

In this study, doctoral student and first author Andrey Kanygin has created a genetic chimera of PSI and the hydrogenase such that they co-assemble and are active in vivo. This new assembly redirects electrons away from carbon dioxide fixation to the production of biohydrogen.

“We thought that some radically different approaches needed to be taken — thus, our crazy idea of hooking up the hydrogenase enzyme directly to Photosystem I in order to divert a large fraction of the electrons from water splitting (by Photosystem II) to make molecular hydrogen,” explained Redding.

Cells expressing the new photosystem (PSI-hydrogenase) make hydrogen at high rates in a light dependent fashion, for several days.

This important result will also be featured in an upcoming article in Chemistry World – a monthly chemistry news magazine published by the Royal Society of Chemistry. The magazine addresses current developments in the world of chemistry including research, international business news and government policy as it affects the chemical science community.

The NSF grant funding this research is part of the U.S.-Israel Binational Science Foundation (BSF). In this arrangement, a U.S. scientist and Israeli scientist join forces to form a joint project. The U.S. partner submits a grant on the joint project to the NSF, and the Israeli partner submits the same grant to the ISF (Israel Science Foundation). Both agencies must agree to fund the project in order to obtain the BSF funding. Professor Iftach Yacoby of Tel Aviv University, Redding’s partner on the BSF project, is a young scientist who first started at TAU about eight years ago and has focused on different ways to increase algal biohydrogen production.

In summary, re-engineering the fundamental processes of photosynthetic microorganisms offers a cheap and renewable platform for creating bio-factories capable of driving difficult electron reactions, powered only by the sun and using water as the electron source.

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

Rewiring photosynthesis: a photosystem I-hydrogenase chimera that makes H2in vivo by Andrey Kanygin, Yuval Milrad, Chandrasekhar Thummala, Kiera Reifschneider, Patricia Baker, Pini Marco, Iftach Yacoby and Kevin E. Redding. Energy Environ. Sci., 2020, Advance DOI: https://doi.org/10.1039/C9EE03859K First published: 17 Apr 2020

In order to gain access to the paper, you must have or sign up for a free account.

This image was used to illustrate the research,

A model of Photosystem 1 core subunits Courtesy: ASU

Nanoparticles make home refrigeration more accessible

Periodically, academic institutions recycle news about their research. I think it happens when, for one reason or another, a piece of news (somebody was exciting) slips past with little notice. I’m glad this June 1, 2020 news item on phys.org brought this research from South Africa to my attention,

Power consumption of a home refrigerator can be cut by 29% while improving cooling capacity. Researchers replaced widely used but environmentally unfriendly R134a refrigerant with the more energy-efficient R600a dosed with multi-walled carbon nanotube nanoparticles (MWCNT). This drop-in refrigerant replacement can be deployed in the field by trained technicians, says an engineer from the University of Johannesburg.

A May 30, 2020 University of Johannesburg press release on EurekAlert, which originated the news item, provides more details about the research,

This test of nanoparticle-dosed refrigerants is a first of its kind and recently published in Energy Reports, an open-access journal. The results can help make home refrigeration more accessible for low-income families.

R134a is one of the most widely-used refrigerants in domestic and industrial refrigerators. It is safe for many applications because it is not flammable. However, it has high global warming potential, contributing to climate change. It also causes fridges, freezers and air-conditioning equipment to consume a lot of electrical energy. The energy consumption contributes even more to climate change.

Meanwhile, a more energy-efficient refrigerant can result in much lower electricity bills. For vulnerable households, energy security can be improved as a result. Improved energy economy and demand-side management can also benefit planners at power utilities, as cooling accounts for about 40% of energy demand.

Nanoparticles enhance power reduction

Nano eco-friendly refrigerants have been made with water and ethylene glycol. Previous studies showed reduced energy use in nano-refrigeration, where refrigerants were dosed with multi-walled carbon nanotube (MWCNT) nanoparticles. The nanoparticles also resulted in reduced friction and wear on appliance vapour compressors.

But previous research did not test the effects of MWCNT’s on hydro-carbon refrigerants such as R600a.

In a recent study, researchers at the University of Johannesburg tested the drop-in replacement of environmentally-unfriendly refrigerant R134a, in a home refrigerator manufactured to work with 100g R134a.

They replaced R134a with the more energy-efficient refrigerant R600a, dosed with MWCNT nanoparticles.

Reduces electricity use by more than a quarter

The researchers removed the R134a refrigerant and its compressor oil from a household fridge. They used a new refrigerant, R600a, and dosed it with multi-walled carbon nanotubes (MWCNTs). Mineral oil was used as a lubricant. The new mix was fed into the fridge and performance tests were conducted.

They found that the R600a-MWCNT refrigerant resulted in much better performance and cooling capacity for the fridge.

“The fridge cooled faster and had a much lower evaporation temperature of -11 degrees Celsius after 150 minutes. This was lower than the -8 degrees Celsius for R134a. It also exceeded the ISO 8187 standard, which requires -3 degrees Celsius at 180 minutes,” says Dr Daniel Madyira.

Dr Madyira is from the Department of Mechanical Engineering Science at the University of Johannesburg.

“Electricity usage decreased by 29% compared to using R134a. This is a significant energy efficiency gain for refrigerator users, especially for low income earners,” he adds.

To gain these advantages, the choice of MWCNT nanoparticles is critical, he says.

“The MWCNT’s need to have nanometer-scale particle size, which is extremely small. The particles also need to reduce friction and wear, prevent corrosion and clogging, and exhibit very good thermal conductivity,” says Dr Madyira.

Managing flammability

The new refrigerant mix introduces a potential risk though. Unlike R134a, R600a is flammable. On the other hand, it is more energy efficient, and it has a low Global Warming potential. Some refrigerator manufacturers have already adopted production with R600a and these appliances are available in the market.

“To do a safe drop-in replacement, no more than 150g of R600a should be used in a domestic fridge,” says Dr Madyira. “Before the replacement, the fridge used 100g of R134a gas. We replaced that with 50g to 70g of R600a, to stay within safety parameters.”

An untrained person should not attempt this drop-in replacement, says Dr Madyira. Rather, a trained refrigeration technician or technologist should do it.

Replacement procedure

“Mineral oil is used as the compressor oil. This should be mixed with the recommended concentration. A magnetic stirrer and ultrasonicator are needed to agitate and homogenize the ingredients in the mixture. The mixture can then be introduced into the compressor. After that, R600a can be charged into the refrigerator compressor, while taking care to not use more than 150g of the gas,” says Dr Madyira.

A woman’s fridge is her castle [Haven’t seen that kind of reference in many years]

A far more energy-efficient refrigerant, such as the R600a-MWCNT mix, can save consumers a lot of money. Vulnerable households in hot climates in developing countries can benefit even more.

Low income earners in many countries are dependent on home fridges and freezers to safely store bulk food supplies. This greatly reduces the risk of wasting food due to spoilage, or food poisoning due to improperly stored food. These appliances are no longer a luxury but a necessity, says Dr Madyira.

Without fridges, people may be forced to buy food daily in small quantities and at much higher prices. Because daily buying may not be required anymore, travel time and costs for buying food can be much lower as well.

Refrigeration also makes it possible to safely store more diverse food supplies, such as fresh fruit and vegetables. Medicines that require cooling can be stored at home. This can make more balanced diets and nutrition, and better physical health, more accessible for a low-income household.

Grid power still rules for low-income refrigeration

From a sustainability point of view, it can look preferable to run most home fridges and freezers from solar power.

However solar panels, backup batteries, and direct current (DC) fridges are still too expensive for most low-income families in areas served by power utilities.

Energy-efficient, alternating current (AC) fridges running on grid power may be more affordable for most. Further cutting power consumption with R600a-MWCNT refrigerant can bring down costs even more.

Refrigeration for all vs demand-side management

As more low-income households and small businesses switch on grid-powered fridges, freezers and air-conditioning, power demand needs be managed better

In South Africa where the study was conducted, the state-operated power utility faces huge challenges in meeting demand consistently. Long-lasting rolling blackouts, known as load-shedding, have been implemented as a demand-side power management measure.

Shaving off more than a quarter of the power consumption of fridges, freezers and air-conditioning units can free up national power supply for improved energy security.

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

Energy performance evaluation of R600a/MWCNT-nanolubricant as a drop-in replacement for R134a in household refrigerator system by T.O Babarinde, S.A Akinlabi, D.M Madyira. Energy Reports Volume 6, Supplement 2 ([proceedings] The 6th International Conference on Power and Energy Systems Engineering (CPESE 2019), 20–23 September 2019, Okinawa, Japan), February 2020, Pages 639-647 DOI: https://doi.org/10.101/j.egyr.2019.11.132

This paper is open access.

Artificial intelligence (AI) consumes a lot of energy but tree-like memory may help conserve it

A simulation of a quantum material’s properties reveals its ability to learn numbers, a test of artificial intelligence. (Purdue University image/Shakti Wadekar)

A May 7, 2020 Purdue University news release (also on EurekAlert) describes a new approach for energy-efficient hardware in support of artificial intelligence (AI) systems,

To just solve a puzzle or play a game, artificial intelligence can require software running on thousands of computers. That could be the energy that three nuclear plants produce in one hour.

A team of engineers has created hardware that can learn skills using a type of AI that currently runs on software platforms. Sharing intelligence features between hardware and software would offset the energy needed for using AI in more advanced applications such as self-driving cars or discovering drugs.

“Software is taking on most of the challenges in AI. If you could incorporate intelligence into the circuit components in addition to what is happening in software, you could do things that simply cannot be done today,” said Shriram Ramanathan, a professor of materials engineering at Purdue University.

AI hardware development is still in early research stages. Researchers have demonstrated AI in pieces of potential hardware, but haven’t yet addressed AI’s large energy demand.

As AI penetrates more of daily life, a heavy reliance on software with massive energy needs is not sustainable, Ramanathan said. If hardware and software could share intelligence features, an area of silicon might be able to achieve more with a given input of energy.

Ramanathan’s team is the first to demonstrate artificial “tree-like” memory in a piece of potential hardware at room temperature. Researchers in the past have only been able to observe this kind of memory in hardware at temperatures that are too low for electronic devices.

The results of this study are published in the journal Nature Communications.

The hardware that Ramanathan’s team developed is made of a so-called quantum material. These materials are known for having properties that cannot be explained by classical physics. Ramanathan’s lab has been working to better understand these materials and how they might be used to solve problems in electronics.

Software uses tree-like memory to organize information into various “branches,” making that information easier to retrieve when learning new skills or tasks.

The strategy is inspired by how the human brain categorizes information and makes decisions.

“Humans memorize things in a tree structure of categories. We memorize ‘apple’ under the category of ‘fruit’ and ‘elephant’ under the category of ‘animal,’ for example,” said Hai-Tian Zhang, a Lillian Gilbreth postdoctoral fellow in Purdue’s College of Engineering. “Mimicking these features in hardware is potentially interesting for brain-inspired computing.”

The team introduced a proton to a quantum material called neodymium nickel oxide. They discovered that applying an electric pulse to the material moves around the proton. Each new position of the proton creates a different resistance state, which creates an information storage site called a memory state. Multiple electric pulses create a branch made up of memory states.

“We can build up many thousands of memory states in the material by taking advantage of quantum mechanical effects. The material stays the same. We are simply shuffling around protons,” Ramanathan said.

Through simulations of the properties discovered in this material, the team showed that the material is capable of learning the numbers 0 through 9. The ability to learn numbers is a baseline test of artificial intelligence.

The demonstration of these trees at room temperature in a material is a step toward showing that hardware could offload tasks from software.

“This discovery opens up new frontiers for AI that have been largely ignored because implementing this kind of intelligence into electronic hardware didn’t exist,” Ramanathan said.

The material might also help create a way for humans to more naturally communicate with AI.

“Protons also are natural information transporters in human beings. A device enabled by proton transport may be a key component for eventually achieving direct communication with organisms, such as through a brain implant,” Zhang said.

Here’s a link to and a citation for the published study,

Perovskite neural trees by Hai-Tian Zhang, Tae Joon Park, Shriram Ramanathan. Nature Communications volume 11, Article number: 2245 (2020) DOI: https://doi.org/10.1038/s41467-020-16105-y Published: 07 May 2020

This paper is open access.

Brain-inspired electronics with organic memristors for wearable computing

I went down a rabbit hole while trying to figure out the difference between ‘organic’ memristors and standard memristors. I have put the results of my investigation at the end of this post. First, there’s the news.

An April 21, 2020 news item on ScienceDaily explains why researchers are so focused on memristors and brainlike computing,

The advent of artificial intelligence, machine learning and the internet of things is expected to change modern electronics and bring forth the fourth Industrial Revolution. The pressing question for many researchers is how to handle this technological revolution.

“It is important for us to understand that the computing platforms of today will not be able to sustain at-scale implementations of AI algorithms on massive datasets,” said Thirumalai Venkatesan, one of the authors of a paper published in Applied Physics Reviews, from AIP Publishing.

“Today’s computing is way too energy-intensive to handle big data. We need to rethink our approaches to computation on all levels: materials, devices and architecture that can enable ultralow energy computing.”

An April 21, 2020 American Institute of Physics (AIP) news release (also on EurekAlert), which originated the news item, describes the authors’ approach to the problems with organic memristors,

Brain-inspired electronics with organic memristors could offer a functionally promising and cost- effective platform, according to Venkatesan. Memristive devices are electronic devices with an inherent memory that are capable of both storing data and performing computation. Since memristors are functionally analogous to the operation of neurons, the computing units in the brain, they are optimal candidates for brain-inspired computing platforms.

Until now, oxides have been the leading candidate as the optimum material for memristors. Different material systems have been proposed but none have been successful so far.

“Over the last 20 years, there have been several attempts to come up with organic memristors, but none of those have shown any promise,” said Sreetosh Goswami, lead author on the paper. “The primary reason behind this failure is their lack of stability, reproducibility and ambiguity in mechanistic understanding. At a device level, we are now able to solve most of these problems,”

This new generation of organic memristors is developed based on metal azo complex devices, which are the brainchild of Sreebata Goswami, a professor at the Indian Association for the Cultivation of Science in Kolkata and another author on the paper.

“In thin films, the molecules are so robust and stable that these devices can eventually be the right choice for many wearable and implantable technologies or a body net, because these could be bendable and stretchable,” said Sreebata Goswami. A body net is a series of wireless sensors that stick to the skin and track health.

The next challenge will be to produce these organic memristors at scale, said Venkatesan.

“Now we are making individual devices in the laboratory. We need to make circuits for large-scale functional implementation of these devices.”

Caption: The device structure at a molecular level. The gold nanoparticles on the bottom electrode enhance the field enabling an ultra-low energy operation of the molecular device. Credit Sreetosh Goswami, Sreebrata Goswami and Thirumalai Venky Venkatesan

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

An organic approach to low energy memory and brain inspired electronics by Sreetosh Goswami, Sreebrata Goswami, and T. Venkatesan. Applied Physics Reviews 7, 021303 (2020) DOI: https://doi.org/10.1063/1.5124155

This paper is open access.

Basics about memristors and organic memristors

This undated article on Nanowerk provides a relatively complete and technical description of memristors in general (Note: A link has been removed),

A memristor (named as a portmanteau of memory and resistor) is a non-volatile electronic memory device that was first theorized by Leon Ong Chua in 1971 as the fourth fundamental two-terminal circuit element following the resistor, the capacitor, and the inductor (IEEE Transactions on Circuit Theory, “Memristor-The missing circuit element”).

Its special property is that its resistance can be programmed (resistor function) and subsequently remains stored (memory function). Unlike other memories that exist today in modern electronics, memristors are stable and remember their state even if the device loses power.

However, it was only almost 40 years later that the first practical device was fabricated. This was in 2008, when a group led by Stanley Williams at HP Research Labs realized that switching of the resistance between a conducting and less conducting state in metal-oxide thin-film devices was showing Leon Chua’s memristor behavior. …

The article on Nanowerk includes an embedded video presentation on memristors given by Stanley Williams (also known as R. Stanley Williams).

Mention of an ‘organic’memristor can be found in an October 31, 2017 article by Ryan Whitwam,

The memristor is composed of the transition metal ruthenium complexed with “azo-aromatic ligands.” [emphasis mine] The theoretical work enabling this material was performed at Yale, and the organic molecules were synthesized at the Indian Association for the Cultivation of Sciences. …

I highlighted ‘ligands’ because that appears to be the difference. However, there is more than one type of ligand on Wikipedia.

First, there’s the Ligand (biochemistry) entry (Note: Links have been removed),

In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. …

Then, there’s the Ligand entry,

In coordination chemistry, a ligand[help 1] is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex …

Finally, there’s the Ligand (disambiguation) entry (Note: Links have been removed),

  • Ligand, an atom, ion, or functional group that donates one or more of its electrons through a coordinate covalent bond to one or more central atoms or ions
  • Ligand (biochemistry), a substance that binds to a protein
  • a ‘guest’ in host–guest chemistry

I did take a look at the paper and did not see any references to proteins or other biomolecules that I could recognize as such. I’m not sure why the researchers are describing their device as an ‘organic’ memristor but this may reflect a shortcoming in the definitions I have found or shortcomings in my reading of the paper rather than an error on their parts.

Hopefully, more research will be forthcoming and it will be possible to better understand the terminology.

Improving batteries with cellulosic nanomaterials

This is a cellulose nanocrystal (CNC) story and in this story it’s derived from trees as opposed to banana skins or carrots or … A February 19, 2020 news item on Nanowerk announces CNC research from Northeastern University (Massachusetts, US),

Nature isn’t always generous with its secrets. That’s why some researchers look into unusual places for solutions to our toughest challenges, from powerful antibiotics hiding in the guts of tiny worms, to swift robots inspired by bats.

Now, Northeastern researchers have taken to the trees to look for ways to make new sustainable materials from abundant natural resources—specifically, within the chemical structure of microfibers that make up wood.

A team led by Hongli (Julie) Zhu, an assistant professor of mechanical and industrial engineering at Northeastern, is using unique nanomaterials derived from cellulose to improve the large and expensive kind of batteries needed to store renewable energy harnessed from sources such as sunlight and the wind.

A February 18, 2020 Northeastern University news release by Roberto Molar Candanosa, which originated the news item, provides more detail (Note: Links have been removed),

Cellulose, the most abundant natural polymer on Earth, is also the most important structural component of plants. It contains important molecular structures to improve batteries, reduce plastic pollution, and power the sort of electrical grids that could support entire communities with renewable energy, Zhu says.  

“We try to use polymers from wood, from bark, from seeds, from flowers, bacteria, green tea—from these kinds of plants to replace plastic,”  Zhu says.

One of the main challenges in storing energy from the sun, wind, and other types of renewables is that variation in factors such as the weather lead to inconsistent sources of power. 

That’s where batteries with large capacity come in. But storing the large amounts of energy that sunlight and the wind are able to provide requires a special kind of device.

The most advanced batteries to do that are called flow batteries, and are made with vanadium ions dissolved in acid in two separate tanks—one with a substance of negatively charged ions, and one with positive ones. The two solutions are continuously pumped from the tank into a cell, which functions like an engine for the battery. 

These substances are always separated by a special membrane that ensures that they exchange positive hydrogen ions without flowing into each other. That selective exchange of ions is the basis for the ability of the battery to charge and discharge energy. 

Flow batteries are ideal devices in which to store solar and wind energy because they can be tweaked to increase the amount of energy stored without compromising the amount of energy that can be generated. The bigger the tanks, the more energy the battery can store from non-polluting and practically inexhaustible resources.

But manufacturing them requires several moving pieces of hardware. As the membrane separating the two flowing substances decays, it can cause the vanadium ions from the solution to mix. That crossover reduces the stability of a battery, along with its capacity to store energy.

Zhu says the limited efficiency of that membrane, combined with  its high cost, are the main factors keeping flow batteries from being widely used in large-scale grids.

In a recent paper, Zhu reported that a new membrane made with cellulose nanocrystals demonstrates superior efficiency compared to other membranes used commonly in the market. The team tested different membranes made from cellulose nanocrystals to make flow batteries cheaper.

“The cost of our membrane per square meter is 147.68 US dollars, ” Zhu says, adding that her calculations do not include costs associated with marketing. “The price quote for the commercialized Nafion membrane is $1,321 per square meter.”

Their tests also showed that the membranes, made with support from the Rogers Corporation and its Innovation Center at Northeastern’s Kostas Research Institute, can offer substantially longer battery lifetimes than other membranes. 

Zhu’s naturally derived membrane is especially efficient because its cellular structure contains thousands of hydroxyl groups, which involve bonds of hydrogen and oxygen that make it easy for water to be transported in plants and trees. 

In flow batteries, that molecular makeup speeds the transport of protons as they flow through the membrane.

The membrane also consists of another polymer known as poly(vinylidene fluoride-hexafluoropropylene), which prevents the negatively and positively charged acids from mixing with each other. 

“For these materials, one of the challenges is that it is difficult to find a polymer that is proton conductive and that is also a material that is very stable in the flowing acid,” Zhu says. 

Because these materials are practically everywhere, membranes made with it can be easily put together at large scales needed for complex power grids. 

Unlike other expensive artificial materials that need to be concocted in a lab, cellulose can be extracted from natural sources including algae, solid waste, and bacteria. 

“A lot of material in nature is a composite, and if we disintegrate its components, we can use it to extract cellulose,” Zhu says. “Like waste from our yard, and a lot of solid waste that we don’t always know what to do with.” 

Here’s a link to and a citation for the paper mentioned in the news release,

Stable and Highly Ion-Selective Membrane Made from Cellulose Nanocrystals for Aqueous Redox Flow Batteries by Alolika Mukhopadhyay, Zheng Cheng, Avi Natan, Yi Ma, Yang Yang, Daxian Cao, Wei Wan, Hongli Zhu. Nano Lett. 2019, 19, 12, 8979-8989 DOI: https://doi.org/10.1021/acs.nanolett.9b03964Publication Date:November 8, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Make electricity by flowing water over nanolayers of metal

Scientists at Northwestern University (Chicago, Illinois) and the California Institute of Technology (CalTech) have developed what could be a more sustainable way to produce electricity. From a July 31, 2019 news item on Nanowerk,

Scientists from Northwestern University and Caltech have produced electricity by simply flowing water over extremely thin layers of inexpensive metals, including iron, that have oxidized. These films represent an entirely new way of generating electricity and could be used to develop new forms of sustainable power production.

A July 31, 2019 Northwester University news release (also on EurekAlert) by Megan Fellman, which originated the news item, provides details that suggest this discovery could prove beneficial in medical implants, as well as, in solar cells,

The films have a conducting metal nanolayer (10 to 20 nanometers thick) that is insulated with an oxide layer (2 nanometers thick). Current is generated when pulses of rainwater and ocean water alternate and move across the nanolayers. The difference in salinity drags the electrons along in the metal below.

“It’s the oxide layer over the nanometal that really makes this device go,” said Franz M. Geiger, the Dow Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences. “Instead of corrosion, the presence of the oxides on the right metals leads to a mechanism that shuttles electrons.”

The films are transparent, a feature that could be taken advantage of in solar cells. The researchers intend to study the method using other ionic liquids, including blood. Developments in this area could lead to use in stents and other implantable devices.

“The ease of scaling up the metal nanolayer to large areas and the ease with which plastics can be coated gets us to three-dimensional structures where large volumes of liquids can be used,” Geiger said. “Foldable designs that fit, for instance, into a backpack are a possibility as well. Given how transparent the films are, it’s exciting to think about coupling the metal nanolayers to a solar cell or coating the outside of building windows with metal nanolayers to obtain energy when it rains.”

The study, titled “Energy Conversion via Metal Nanolayers,” was published this week [on July 29, 2019] in the journal Proceedings of the National Academy of Sciences (PNAS).

Geiger is the study’s corresponding author; his Northwestern team conducted the experiments. Co-author Thomas Miller, professor of chemistry at Caltech, led a team that conducted atomistic simulations to study the device’s behavior at the atomic level.

The new method produces voltages and currents comparable to graphene-based devices reported to have efficiencies of around 30% — similar to other approaches under investigation (carbon nanotubes and graphene) but with a single-step fabrication from earth-abundant elements instead of multistep fabrication. This simplicity allows for scalability, rapid implementation and low cost. Northwestern has filed for a provisional patent.

Of the metals studied, the researchers found that iron, nickel and vanadium worked best. They tested a pure rust sample as a control experiment; it did not produce a current.

The mechanism behind the electricity generation is complex, involving ion adsorption and desorption, but it essentially works like this: The ions present in the rainwater/saltwater attract electrons in the metal beneath the oxide layer; as the water flows, so do those ions, and through that attractive force, they drag the electrons in the metal along with them, generating an electrical current.

“There are interesting prospects for a variety of energy and sustainability applications, but the real value is the new mechanism of oxide-metal electron transfer,” Geiger said. “The underlying mechanism appears to involve various oxidation states.”

The team used a process called physical vapor deposition (PVD), which turns normally solid materials into a vapor that condenses on a desired surface. PVD allowed them to deposit onto glass metal layers only 10 to 20 nanometers thick. An oxide layer then forms spontaneously in air. It grows to a thickness of 2 nanometers and then stops growing.

“Thicker films of metal don’t succeed — it’s a nano-confinement effect,” Geiger said. “We have discovered the sweet spot.”

When tested, the devices generated several tens of millivolts and several microamps per centimeter squared.

“For perspective, plates having an area of 10 square meters each would generate a few kilowatts per hour — enough for a standard U.S. home,” Miller said. “Of course, less demanding applications, including low-power devices in remote locations, are more promising in the near term.”

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

Energy conversion via metal nanolayers by Mavis D. Boamah, Emilie H. Lozier, Jeongmin Kim, Paul E. Ohno, Catherine E. Walker, Thomas F. Miller III, and Franz M. Geiger. PNAS DOI: https://doi.org/10.1073/pnas.1906601116 First published July 29, 2019

This paper is behind a paywall.

Climate change and black gold

A July 3, 2019 news item on Nanowerk describes research coming from India and South Korea where nano gold is turned into black nanogold (Note: A link has been removed),

One of the main cause of global warming is the increase in the atmospheric CO2 level. The main source of this CO2 is from the burning of fossil fuels (electricity, vehicles, industry and many more).

Researchers at TIFR [Tata Institute of Fundamental Research] have developed the solution phase synthesis of Dendritic Plasmonic Colloidosomes (DPCs) with varying interparticle distances between the gold Nanoparticles (AU NPs) using a cycle-by-cycle growth approach by optimizing the nucleation-growth step. These DPCs absorb the entire visible and near-infrared region of solar light, due to interparticle plasmonic coupling as well as the heterogeneity in the Au NP [gold nanoparticle] sizes, which transformed golden gold material to black gold (Chemical Science, “Plasmonic colloidosomes of black gold for solar energy harvesting and hotspots directed catalysis for CO2 to fuel conversion”).

A July 3, 2019 Tata Institute of Fundamental Research (TIFR) press release on EurekAlert, which originated the news item, provides more technical detail,

Black (nano)gold was able to catalyze CO2 to methane (fuel) conversion at atmospheric pressure and temperature, using solar energy. They also observed the significant effect of the plasmonic hotspots on the performance of these DPCs for the purification of seawater to drinkable water via steam generation, temperature jump assisted protein unfolding, oxidation of cinnamyl alcohol using pure oxygen as the oxidant, and hydrosilylation of aldehydes.

This was attributed to varying interparticle distances and particle sizes in these DPCs. The results indicate the synergistic effects of EM and thermal hotspots as well as hot electrons on DPCs performance. Thus, DPCs catalysts can effectively be utilized as Vis-NIR light photo-catalysts, and the design of new plasmonic nanocatalysts for a wide range of other chemical reactions may be possible using the concept of plasmonic coupling.

Raman thermometry and SERS (Surface-enhanced Raman Spectroscopy) provided information about the thermal and electromagnetic hotspots and local temperatures which was found to be dependent on the interparticle plasmonic coupling. The spatial distribution of the localized surface plasmon modes by STEM-EELS plasmon mapping confirmed the role of the interparticle distances in the SPR (Surface Plasmon Resonance) of the material.

Thus, in this work, by using the techniques of nanotechnology, the researchers transformed golden gold to black gold, by changing the size and gaps between gold nanoparticles. Similar to the real trees, which use CO2, sunlight and water to produce food, the developed black gold acts like an artificial tree that uses CO2, sunlight and water to produce fuel, which can be used to run our cars. Notably, black gold can also be used to convert sea water into drinkable water using the heat that black gold generates after it captures sunlight.

This work is a way forward to develop “Artificial Trees” which capture and convert CO2 to fuel and useful chemicals. Although at this stage, the production rate of fuel is low, in coming years, these challenges can be resolved. We may be able to convert CO2 to fuel using sunlight at atmospheric condition, at a commercially viable scale and CO2 may then become our main source of clean energy.

Here’s an image illustrating the work

Caption: Use of black gold can get us one step closer to combat climate change. Credit: Royal Society of Chemistry, Chemical Science

A July 3, 2019 Royal Society of Chemistry Highlight features more information about the research,

A “black” gold material has been developed to harvest sunlight, and then use the energy to turn carbon dioxide (CO2) into useful chemicals and fuel.

In addition to this, the material can also be used for applications including water purification, heating – and could help further research into new, efficient catalysts.

“In this work, by using the techniques of nanotechnology, we transformed golden gold to black gold, by simply changing the size and gaps between gold nanoparticles,” said Professor Vivek Polshettiwar from Tata Institute of Fundamental Research (TIFR) in India.

Tuning the size and gaps between gold nanoparticles created thermal and electromagnetic hotspots, which allowed the material to absorb the entire visible and near-infrared region of sunlight’s wavelength – making the gold “black”.

The team of researchers, from TIFR and Seoul National University in South Korea, then demonstrated that this captured energy could be used to combat climate change.

Professor Polshettiwar said: “It not only harvests solar energy but also captures and converts CO2 to methane (fuel). Synthesis and use of black gold for CO2-to-fuel conversion, which is reported for the first time, has the potential to resolve the global CO2 challenge.

“Now, like real trees which use CO2, sunlight and water to produce food, our developed black gold acts like an artificial tree to produce fuel – which we can use to run our cars,” he added.
Although production is low at this stage, Professor Polshettiwar (who was included in the RSC’s 175 Faces of Chemistry) believes that the commercially-viable conversion of CO2 to fuel at atmospheric conditions is possible in the coming years.

He said: “It’s the only goal of my life – to develop technology to capture and convert CO2 and combat climate change, by using the concepts of nanotechnology.”

Other experiments described in the Chemical Science paper demonstrate using black gold to efficiently convert sea water into drinkable water via steam generation.

It was also used for protein unfolding, alcohol oxidation, and aldehyde hydrosilylation: and the team believe their methodology could lead to novel and efficient catalysts for a range of chemical transformations.

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

Plasmonic colloidosomes of black gold for solar energy harvesting and hotspots directed catalysis for CO2 to fuel conversion by Mahak Dhiman, Ayan Maity, Anirban Das, Rajesh Belgamwar, Bhagyashree Chalke, Yeonhee Lee, Kyunjong Sim, Jwa-Min Nam and Vivek Polshettiwar. Chem. Sci., 2019, Advance Article. DOI: 10.1039/C9SC02369K First published on July 3, 2019

This paper is freely available in the open access journal Chemical Science.