Metals Tech

Smart Energy International’s Errol Bryce was at Chinese Utility Week and met with Phil Beecher, chairman of global communications protocol Wi-SUN Alliance, which supports critical infrastructure networks.

Wi-SUN attended the event to promote its technology after a large amount of interest from Chinese utilities, smart meter vendors and technology providers.

The protocol offers an open-standard, ubiquitous communications platform that differs from others in that it supports peer-to-peer communications for technologies like edge-computing, and distributed control.

An example of this is renewables injection, or distributed energy resources, where Wi-SUN is enjoying its role in contributing to the future of the smart grid, smart cities, and other emerging technologies.

The smallest pixels yet created—a million times smaller than those in smartphones, made by trapping particles of light under tiny rocks of gold—could be used for new types of large-scale flexible displays, big enough to cover entire buildings.

The colour pixels, developed by a team of scientists led by the University of Cambridge, are compatible with roll-to-roll fabrication on flexible plastic films, dramatically reducing their production cost. The results are reported in the journal Science Advances.

It has been a long-held dream to mimic the colour-changing skin of octopus or squid, allowing people or objects to disappear into the natural background, but making large-area flexible display screens is still prohibitively expensive because they are constructed from highly precise multiple layers.

At the centre of the pixels developed by the Cambridge scientists is a tiny particle of gold a few billionths of a metre across. The grain sits on top of a reflective surface, trapping light in the gap in between. Surrounding each grain is a thin sticky coating which changes chemically when electrically switched, causing the pixel to change colour across the spectrum.

The team of scientists, from different disciplines including physics, chemistry and manufacturing, made the pixels by coating vats of golden grains with an active polymer called polyaniline and then spraying them onto flexible mirror-coated plastic, to dramatically drive down production cost.

The pixels are the smallest yet created, a million times smaller than typical smartphone pixels. They can be seen in bright sunlight and because they do not need constant power to keep their set colour, have an energy performance that make large areas feasible and sustainable. “We started by washing them over aluminized food packets, but then found aerosol spraying is faster,” said co-lead author Hyeon-Ho Jeong from Cambridge’s Cavendish Laboratory.

“These are not the normal tools of nanotechnology, but this sort of radical approach is needed to make sustainable technologies feasible,” said Professor Jeremy J Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research. “The strange physics of light on the nanoscale allows it to be switched, even if less than a tenth of the film is coated with our active pixels. That’s because the apparent size of each pixel for light is many times larger than their physical area when using these resonant gold architectures.”

The pixels could enable a host of new application possibilities such as building-sized display screens, architecture which can switch off solar heat load, active camouflage clothing and coatings, as well as tiny indicators for coming internet-of-things devices.

The team are currently working at improving the colour range and are looking for partners to develop the technology further.

Majorana particles are very peculiar members of the family of elementary particles. First predicted in 1937 by the Italian physicist Ettore Majorana, these particles belong to the group of so-called fermions, a group that also includes electrons, neutrons and protons. Majorana fermions are electrically neutral and also their own anti-particles. These exotic particles can, for example, emerge as quasi-particles in topological superconductors and represent ideal building blocks for topological quantum computers.

Going to two dimensions

On the road to such topological quantum computers based on Majorana quasi-particles, physicists from the University of Würzburg together with colleagues from Harvard University (USA) have made an important step: Whereas previous experiments in this field have mostly focused on one-dimensional systems, the teams from Würzburg and Harvard have succeeded in going to two-dimensional systems.

In this collaboration, the groups of Ewelina Hankiewicz (Theoretische Physik IV) and Laurens Molenkamp (Experimentelle Physik III) from the University of Würzburg teamed up with the groups of Amir Yacoby and Bertrand Halperin from Harvard University. Their findings are presented in the current issue of the scientific journal Nature.

Two superconductors can simplify matters

“Realizing Majorana fermions is one of the most intensely studied topics in condensed matter physics,” Ewelina Hankiewicz says. According to her, previous realizations have usually focused on one-dimensional systems such as nanowires. She explains that a manipulation of Majorana fermions is very difficult in these setups. It would therefore require significant efforts to make Majorana fermions in these setups eventually applicable for quantum computing.

In order to avoid some of these difficulties, the researchers have studied Majorana fermions in a two-dimensional system with strong spin-orbit coupling. “The system we investigate is a so-called phase-controlled Josephson junction, that is, two superconductors that are separated by a normal region,” Laurens Molenkamp explains. The superconducting phase difference between the two superconductors provides an additional knob, which makes an intricate fine-tuning of the other system parameters at least partially unnecessary.

Important step towards an improved control

In the material studied, a mercury telluride quantum well coupled to superconducting thin-film aluminium, the physicists observed for the first time a topological phase transition which implies the appearance of Majorana fermions in phase-controlled Josephson junctions.

The setup realized experimentally here constitutes a versatile platform for the creation, manipulation and control of Majorana fermions, which offers several advantages compared to previous one-dimensional platforms. According to Hankiewicz, “this is an important step towards an improved control of Majorana fermions.” The proof of concept of a topological superconductor based on a two-dimensional Josephson junction opens up new possibilities for the research on Majorana fermions in condensed matter physics. In particular, several constraints of previous realizations of Majorana fermions can be avoided.

Potential revolution in computer technology

At the same time, an improved control of Majorana fermions represents an important step towards topological quantum computers. Theoretically, such computers can be significantly more powerful than conventional computers. They thus have the potential to revolutionize computer technology.

Next, the researchers plan to improve the Josephson junctions and move towards junctions with narrower normal regions. Here, more localized Majorana fermions are expected. They further study additional possibilities of manipulating Majorana fermions, for example, by using other semiconductors.

Researchers at the University of Maryland (UMD) and US Army Research Lab (ARL) have taken a critical step on the path to high energy batteries by improving their water-in-salt battery with a new type of chemical transformation of the cathode that creates a reversible solid salt layer, a phenomenon yet unknown in the field of water-based batteries.

Building on their previous discoveries of the water-in-salt electrolytes reported in Science in 2015, the researchers added a new cathode. This new cathode material, lacking transition metal, operates at an average potential of 4.2 volts with excellent cycling stability, and delivers an unprecedented energy density comparable, or perhaps higher than, non-aqueous Li-ion batteries. The authors report their work on May 9 in the journal Nature.

“The University of Maryland and ARL research has produced the most creative new battery chemistry I have seen in at least 10 years,” said Prof. Jeffrey Dahn of Dalhousie University in Canada, an expert in the field not affiliated with the research. “However, it remains to be seen if a practical device with long lifetime can be created.”

Leveraging the reversible halogens intercalation in graphite structures, enabled by a super-concentrated aqueous electrolyte, the team generated an energy density previously thought impossible. The researchers found that the superconcentrated solution of the water-in-salt battery, combined with graphite anode’s ability to automatically build and re-form a protective layer within the battery, gave a stable and long lasting battery with high energy.

“This new cathode chemistry happens to be operating ideally in our previously-developed ‘water-in-salt’ aqueous electrolyte, which makes it even more unique—it combines high energy density of non-aqueous systems with high safety of aqueous systems,” said a co-first author of the paper, Chongyin Yang, an assistant research scientist in the UMD department of chemical & biomolecular engineering.

“This new ‘Conversion-Intercalation’ chemistry inherits the high energy of conversion-reaction and the excellent reversibility from intercalation of graphite,” said Ji Chen, co-first author of the paper and a research associate in the department of chemical & biomolecular engineering.

The team of researchers—led by Chunsheng Wang, ChBE Professor with a dual appointment in the Department of Chemistry and Biochemistry; Kang Xu, ARL Fellow; and Oleg Borodin, ARL scientist—have advanced the battery into a testable stage: the size of a small button, typically used as a test vehicle in research labs. More research is needed to scale it up into a practical, manufacturable battery.

The energy output of the water-based battery reported in this study boasts 25% increased energy density of an ordinary cell phone battery based on flammable organic liquids, but is much safer. The new cathode is able to hold 240 milliamps per gram for an hour of operation, roughly twice that of a typical cathode currently found in cell phones and laptops.

The water-in-salt battery could ultimately be used in applications involving large energies at kilowatt or megawatt levels, or where battery safety and toxicity are primary concerns, including non-flammable batteries for airplanes, naval vessels, or spaceships.

Scientists must often ask themselves, compared to what? How do the results we generate in the laboratory compare with those obtained by others? How do our theoretical calculations compare with experimental data?

Answering such questions is especially crucial for researchers and developers of lithium-ion batteries. Invented four decades ago, lithium-ion batteries now power most portable electronics like laptops and power tools. They are also being developed to meet the high energy storage demands for powering electric vehicles and electric grids. New designs with different compositions of electrode and electrolyte—the two key battery components—are constantly coming online.

Assessing whether an innovation in electrode or electrolyte material is actually an improvement requires comparing it to other test results. However, there is no “one size fits all” standard for battery testing. Methods for testing batteries can vary widely.

Argonne battery researcher Ira Bloom notes, “Industrial engineers and researchers from governmental and academic labs often devise their own procedures for characterizing lithium-ion batteries based on the battery technology’s intended application. This makes the comparison of any technological innovations extremely complicated.”

A team from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, University of Warwick, OVO Energy, Hawaii National Energy Institute, and Jaguar Land Rover has reviewed the literature on the various methods used around the world to characterize the performance of lithium-ion batteries in order to provide insight on best practices.

Typically, battery researchers use three parameters to define electrochemical performance: capacity, open-circuit voltage, and resistance. Capacity is a measure of the total charge stored in a battery. The open-circuit voltage is the voltage available from a battery with no current flow. It represents the battery’s maximum voltage. The resistance is the degree to which the component materials impede the flow of electric current, resulting in a voltage drop.

The problem is that, depending on battery application, researchers may measure these parameters under different test conditions (temperature, rate of discharge, state of charge, etc.), and thereby obtain a different battery operating life. Battery resistance, for example, can be measured with either a direct current or alternating current.

“It’s complicated,” observes Anup Barai, a principal investigator and senior research fellow at the University of Warwick. “The appropriateness of a test depends on what the investigator is studying. Our review provides guidance on the most appropriate test method for a given situation.” To that end, the team has produced an easy-to-use table comparing eight test methods, including the main equipment needed, the information generated, and the advantages and drawbacks for each.

“Our hope,” Bloom adds, “is that our results may one day lead to more reliably comparable methods for testing lithium-ion batteries tailored to different applications.”

The study, entitled “A comparison of methodologies for the non-invasive characterisation of commercial Li-ion cells,” recently appeared in the online version of the journal Progress in Energy and Combustion Science.

Researchers at Kanazawa University have recently developed a friction reduction system based on a lubricating effect, which could have interesting soft robotics applications. Their system, presented in a paper published in Taylor & Francis’ Advanced Robotics journal, could aid the development of robots that can efficiently manipulate objects under both dry and wet conditions.

“Our previously developed surface texture or skin for soft robotic handsprovides high friction under both dry and wet conditions,” Tetsuyou Watanabe, one of the researchers who carried out the study, told TechXplore. “However, this high friction makes several manipulation styles (including releasing and sliding) difficult. In some cases, a grasped object sticks to the surface. To overcome this problem, we developed a new friction reduction system utilizing lubricants.”

When developing their system, Watanabe and his colleagues drew inspiration from human behavior. They observed that in supermarkets people often lick their fingers to open plastic bags or containers. Similar actions are also performed when trying to pick up sheets of paper or turn the pages in a book.

The researchers found that this ‘finger licking’ behavior is particularly common in middle aged or elderly people, as aging typically leads to dryer skin. Younger people, on the other hand, often do not need to lick their fingers when trying to manipulate plastic or paper, because they can automatically control the skin’s friction via their body’s sweat mechanisms.

“Of course, the aim of licking fingers is to get high friction, and totally different from our purpose (i.e. reduction of friction),” Watanabe said. “However, normally the aim of lubricants is to reduce friction in mechanical systems. Thus, we considered the possibility of a friction reduction system that is similar to sweat control in humans.”

The researchers constructed a robotic fingertip that has slits in its surface. When lubricants (e.g. ethanol) are injected around the boundaries of these slits, they permeate throughout the surface, via a capillary action.

The fingertip before and after ethanol is injected in it. Credit: Mizushima et al.

“We utilized the thin surface area including texture, and the system works on not only rigid but also deformable bodies without loss of adaptability to an object’s shape,” Watanabe said. “Therefore, the main advantage of our system is that surface friction can be controlled while maintaining the surface deformability and adaptability. This means that the developed system can be attached on robots with soft bodies.”

In recent years, the use of soft bodies has become increasingly popular in robotics, due to their high deformability and adaptability. For instance, soft robots can move more freely in their surroundings, without presenting extensive damage when hitting walls or obstacles. In addition, soft robotic hands can adapt to an object’s shape while grasping it, which enables more advanced manipulation strategies.

“Another key advantage of our system is that it works under both dry and wet conditions,” Watanabe added. “It is hence very useful for robots that work in human environments, because housework is performed under both these conditions.”

The researchers embedded their system into a robotic fingertip and evaluated its performance in a series of experiments that involved grasping and releasing objects. Their findings suggest that the lubrication technique they developed can effectively reduce friction under both wet and dry conditions.

“As you can imagine from the human behavior of licking fingers, water can increase friction and in some cases allow the skin to stick to surfaces,” Watanabe said. “In contrast, ethanol reduces friction. The important factor for friction reduction is the spreading coefficient closely associated with capillary forces (i.e. surface tension).”

In this context, a low capillary force entails the easy diffusion of liquid throughout a surface. Using ethanol, which has a low capillary force, the researchers were able to reduce friction and easily spread the lubricant throughout the fingertip’s entire surface. A further advantage of ethanol is its high volatility, which considerably reduces tact time.

“We also observed that to facilitate the function of our system, the surface should not be completely smooth,” Watanabe added. “A surface that is a little bit rough or uneven can further improve its function.”

Robots could soon support humans in a variety of settings, for instance helping them with housework or providing nursing care. As these tasks are generally performed under both dry and wet conditions, the researchers’ friction reduction system could prove very helpful.

“Handling and manipulating objects are the main targets for our research and then the tasks including such actions are the targeted applications,” Watanabe said. “A few examples are folding clothes, cooking, washing, etc.”

In the future, the lubrication system developed by Watanabe and his colleagues could inform the development of soft robots that can manipulate objects more effectively, in both dry and wet environments. The researchers are now planning further research aimed at delineating and broadening their system’s possible applications.

“Currently, we have only combined fingertips with our system,” Watanabe said. “As a next step, we would like to apply our friction control system to a robotic hand. Moreover, the applications for the system are still unclear, so we would like to outline appropriate methodologies for real operations, such as folding or cooking.”