Canadian Making Waves

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Making Desalinated Water Safer and Cheaper

Technion, Wageningen University and Wetsus scientists develop an effective and low-cost way to remove toxic boron from water in the process of desalination

Canadian born, Professor Matthew Suss

80% of drinking water in Israel is desalinated water, coming from the Mediterranean Sea. Now, scientists from the Technion – Israel Institute of Technology, the Wageningen University, and Wetsus (European center of excellence for sustainable water) in the Netherlands have developed a way to improve the quality of desalinated water, while reducing the costs of the process. The findings of the international team’s study were published in PNAS (Proceedings of the National Academy of Sciences of the United States of America).

Amit Shocron

Desalination is the process that removes mineral particles (salts) from saltwater, making it fit for human consumption and for irrigation. The chemical properties of some particles make them more challenging to remove than others. Boron, which is naturally found in high quantities in the Mediterranean Sea, is among the hardest to remove, as change in acidity causes it to change its properties. It is toxic in high concentrations, and it harms plant growth, which is a problem in the context of irrigation. The normal process of boron removal involves dosing the water with a base in order to facilitate removing the boron, followed by removal of the base.

Process of dissolved boron removal using a capacitive deionization cell. First, the cell dissociates boric acid to charged boron ions. The boron ions are then stored in the electrodes. )Credit: Paul Gerlach, Houten, The Netherlands(

The most commonly used method of desalination is by means of a membrane – a sort of sieve that allows water to pass through it, while blocking other particles, based on their size or charge. This membrane, however, is expensive, and needs to be replaced periodically.

Eric Guyes

Ph.D. students Amit Shocron and Eric Guyes, under the supervision of  Canadian born, Professor Matthew Suss of the Technion Faculty of Mechanical Engineering, together with their collaborators from Wageningen University and Wetsus, developed a new modeling technique to predict the behavior of boron during desalination by means of capacitive deionization. This is an emerging technique for water treatment and desalination using relatively cheap porous electrodes, as opposed to the expensive membrane. When an electric current is applied, charged particles (like boron under high pH conditions) are adsorbed by the electrodes and hence removed from the water.

Schematic demonstrating boron removal by a capacitive deionization (CDI) cell. Shown is a CDI cell with an anode placed upstream and a snapshot of the developed pH profile within the anode. Right: A snapshot of ion and charge distributions in a pore near the anode/separator interface, showing boric acid dissociation and adsorption

Amit Shocron formulated the theoretical framework that allowed this breakthrough, while Eric Guyes constructed the experimental setup. Working together, they were able to develop the novel system. They found that for optimal boron removal, the positive electrode should be placed upstream of the negative electrode – counter to the accepted wisdom in their field. They also calculated the optimal applied voltage for the system, finding that higher voltage does not necessarily improve the system’s effectiveness.

This same method the group developed could be used to solve other water treatment challenges as well, for example the removal of medicine residues and herbicides, which are difficult to remove using conventional methods.

Montreal native, Prof. Suss is an Associate Professor in the Faculty of Mechanical Engineering and the Wolfson Department of Chemical Engineering at Technion – Israel Institute of Technology and is affiliated with the Nancy and Stephen Grand Technion Energy Program and Stephen and Nancy Grand Water Research Institute at Technion.

For the article in PNAS click here

 

Dislocations in Gold as an “Autocatalytic Template” for Nanowire Growth

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Dislocations in Gold as an “Autocatalytic Template” for Nanowire Growth

Researchers at the Technion Faculty of Materials Science and Engineering have developed an innovative method for the creation of nanowires with numerous potential applications

Professor Boaz Pokroy

Technion researchers have presented an innovative method for the formation of nanowires. In it, the nanowires form within line defects that exist in metals. Such defects are known as dislocations. This is the first time that dislocation lines in a material of one kind serve as a template for the growth of a different inorganic material in the form of nanowires. The study, which was published in PNAS, was led by Professor Boaz Pokroy and Ph.D. student Lotan Portal of the Faculty of Materials Science and Engineering and the Russell Berrie Nanotechnology Institute (RBNI).

Dislocations are a significant phenomenon in materials science since they affect the material’s properties on both the macro- and microscales. For example, a high dislocation density increases a metal’s strength and hardness. The

Lotan Portal

dislocation edges on metal surfaces and the atoms in their proximity tend to be more chemically activated compared to other atoms in the material and tend to facilitate various chemical reactions, such as corrosion and catalysis.

The researchers in Prof. Pokroy’s group created nanowires of gold-cyanide complex from classic Au-Ag alloy. In professional terminology, they synthesized inorganic gold(I)-cyanide (AuCN) systems in the shape of nanowires, using an autocatalytic reaction (i.e. through the acceleration of a reaction by one of its reactants). Gold-cyanide complex is used in numerous fields including ammonia gas detection (NH3 sensors), catalysis (acceleration) of water-splitting reactions, and others.

Scanning electron microscope image of a lateral section of a sample that contains a gold-cyanide nanowire created from Au-Ag (to a depth of 2 microns from the surface of the sample).

In the process developed by the researchers, nanowires crystallize at the dislocation ends on the surface of the original gold-silver (Au-Ag) alloy, and the final structure obtained is classic nanoporous (sponge-like) gold, with a layer of nanowires emerging from it. Formation of the nanowires occurs during the classic selective dealloying process that separates the silver from the system and forms the nanoporous gold and is achieved only when the dislocation density exceeds a critical value, as presented in the kinetic model developed and demonstrated in the article.

A schematic drawing depicting 1D nucleation and growth of a gold-cyanide nanowire along a dislocation in the original alloy during the classic selective dealloying process.

The model provides a possible route for growing one-dimensional inorganic complexes while controlling the growth direction, shape, and morphology of a crystal according to the original alloy’s slip system. As mentioned, this scientific and technological achievement has numerous potential applications.

The research was sponsored by a European Research Council (ERC) Proof of Concept Grant (“np-Gold” project) as part of the Horizon 2020 Program.

For the article in PNAS click here

 

Revving Up-Formula Racing

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 Revving Up

 Israel’s Formula student teams – absent from international competitions for two years because of COVID-19 – have established their own Formula Race for students

This year’s Technion team is its largest ever

This month, three universities will participate in the inaugural Israeli Formula SAE Race: The Technion – Israel Institute of Technology, Tel Aviv University, and Ben-Gurion University of the Negev.

The Technion team with the 2021 model

The Technion Formula Student Team has been led by the Faculty of Mechanical Engineering since 2013. Academic guidance is provided by Prof. Leonid Tartakovsky, who replaced Prof. Reuven Katz, the project supervisor from 2013 to 2019.

Headed by Muans Omari, a master’s student in the Faculty of Mechanical Engineering, this year’s Technion team is its largest ever, made up of more than 60 students from various faculties. This is Omari’s third year participating in the project; he started out as a volunteer and driver, subsequently progressed to head of the engine crew, and since 2021, has served as the Technion’s project lead. As a driver, he won first place driving on the figure-8 Skidpad circuit in the Czech Republic in the summer of 2019, just before the global COVID-19 outbreak. During that race, the Technion unveiled the lightest car in the history of the competition, which weighed in at just 132 kg of advanced technology, after “Technion Formula” shed 120 kg in just three years.

The Formula cars from the Technion – Israel Institute of Technology, Tel Aviv University, and Ben-Gurion University of the Negev

“After two years in which we were prevented from participating in races in Europe because of the pandemic, we decided to bring the race to Israel,” said Omari, “and the three universities that will be competing in October – the Technion, Tel Aviv University, and Ben Gurion University – are fully on board. This is a unique, adrenaline-intensive motorsport event that combines engineering theory and technological applications. We believe it will have a direct impact on the vehicle industry in Israel and encourage investors and local firms to develop vehicles and other relevant products.”

The opening event in August 2021 was attended by experts from the Ministry of Transportation, who advised the teams on adapting the car to comply with licensing requirements in Israel.

The Racing Teams

The race will take place October 20-October 21 at the MotorCity – Motor Park Racing Circuit in Beersheba, Israel.

Formula Student is a series of international competitions in which university teams compete to design, manufacture, and race the best performing racecars.

Tiny Lasers Acting Together as One: Topological Vertical Cavity Laser Arrays

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Tiny Lasers Acting Together as One: Topological Vertical Cavity Laser Arrays

International research team uses topological platform to demonstrate coherent array of vertical lasers

HAIFA, ISRAEL, AND WÜRZBURG, GERMANY, September 26, 2021 – Israeli and German researchers have developed a way to force an array of vertical cavity lasers to act together as a single laser – a highly effective laser network the size of a grain of sand. The findings are presented in a new joint research paper that was published online by Science on Friday, September 24.

Cell phones, car sensors, or data transmission in fiber optic networks all use so called Vertical-Cavity Surface-Emitting Lasers (VCSELs) – semiconductor lasers that are firmly anchored in our everyday technology. Though widely used, the VCSEL device has miniscule size of only a few microns, which sets a stringent limit on the output power it can generate. For years, scientists have sought to enhance the power emitted by such devices through combining many tiny VCSELs and forcing them to act as a single coherent laser, but with limited success. The current breakthrough uses a different scheme: it employs a unique geometrical arrangement of VCSELs on the chip that forces the flight to flow in a specific path – a photonic topological insulator platform.

From topological insulators to topological lasers
Topological insulators are revolutionary quantum materials that insulate on the inside but conduct electricity on their surface, without loss. Several years ago, the Technion group led by Distinguished Professor Mordechai (Moti) Segev introduced these innovative ideas into photonics, and demonstrated the first Photonic Topological Insulator, where light travels around the edges of a two-dimensional array of waveguides without being affected by defects or disorder. This opened a new field, now known as “Topological Photonics,” where hundreds of groups currently have active research. In 2018, the Technion group also found a way to use the properties of photonic topological insulators to force many micro-ring lasers to lock together and act as a single laser. But that system still had a major bottleneck: the light was circulating in the photonic chip confined to the same plane used for extracting the light. That meant that the whole system was again subject to a power limit, imposed by the device used to get the light out, similar to having a single socket for a whole power plant. The current breakthrough uses a different scheme: the lasers are forced to lock within the planar chip, but the light is now emitted through the surface of the chip from each tiny laser and can be easily collected.

Circumstances and participants
This German-Israeli research project originated primarily during the Corona pandemic. Without the enormous commitment of the researchers involved, this scientific milestone would not have been possible. The research was conducted by PhD student Alex Dikopoltsev from the team of Distinguished Professor Mordechai (Moti) Segev of Technion’s Physics and Electrical & Computer Engineering Faculties, the Solid State Institute and the Russell Berrie Nanotechnology Institute at the Technion – Israel Institute of Technology, and Ph.D. student Tristan H. Harder from the team of Professor Sebastian Klembt and Professor Sven Höfling at the Chair of Applied Physics at the University of Würzburg, and the Cluster of Excellence ct.qmat – Complexity and Topology in Quantum Materials, in collaboration with researchers from Jena and Oldenburg. The device fabrication took advantage of the excellent clean room facilities at the University of Würzburg.

A single coherent light beam (pink) is emitted by an array of 30 individual lasers. Credit: SimplySci Animations

The long road to new topological lasers
“It is fascinating to see how science evolves,” said Distinguished Prof. Moti Segev, the Dr. Robert J. Shillman Distinguished Professor of Physics and Electrical & Computer Engineering at the Technion. “We went from fundamental physics concepts to foundational changes therein, and now to real technology that is now being pursued by companies. Back in 2015, when we started to work on topological insulator lasers, nobody believed it was possible, because the topological concepts known at that time were limited to systems that do not, in fact, cannot, have gain. But all lasers require gain. So topological insulator lasers stood against everything known at that time. We were like a bunch of lunatics searching for something that was considered impossible. And now we have made a large step towards real technology that has many applications.”

The Israeli and German team utilized the concepts of topological photonics with VCSELs that emit the light vertically, while the topological process responsible for the mutual coherence and locking of the VCSELs occurs in the plane of the chip. The end result is a powerful but very compact and efficient laser, not limited by a number of VCSEL emitters, and undisturbed by defects or altering temperatures.

“The topological principle of this laser can generally work for all wavelengths and thus a range of materials,” explains German project leader Prof. Sebastian Klembt of the University of Würzburg, who is working on light-matter interaction and topological photonics within the ct.qmat cluster of excellence. “Exactly how many microlasers need to be arranged and connected would always depend entirely on the application. We can expand the size of the laser network to a very large size, and in principle it will remain coherent also for large numbers. It is great to see that topology, originally a branch of mathematics, has emerged as a revolutionary new toolbox for controlling, steering and improving laser properties.”

The groundbreaking research has demonstrated that it is in fact theoretically and experimentally possible to combine VCSELs to achieve a more robust and highly efficient laser. As such, the results of the study pave the way towards applications of numerous future technologies such as medical devices, communications, and a variety of real-world applications.

Click here for the paper in Science

Hydrogen On the Way

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Hydrogen On the Way
Researchers in the Schulich Faculty of Chemistry at the Technion have developed a new system for producing hydrogen from water with a low energy investment and using available and inexpensive materials

Water electrolysis is an easy way to produce hydrogen gas. While hydrogen is considered a clean and renewable fuel, efficient electrolysis today requires high electric potential, high pH and in most cases, catalysts based on ruthenium and other expensive metals. Due to the inherent promise of hydrogen, many research groups are striving to develop electrolysis technologies that will make it possible to produce hydrogen fuel at a low electric potential, at a pH between 7-9 and with catalysts based on available and inexpensive metals such as copper, manganese, and cobalt.

Professor Galia Maayan

The Journal of the American Chemical Society  recently reported on a unique solution for this issue developed at the Technion – Israel Institute of Technology. It is the fastest system of its kind reported so far that operates with available metal (copper) catalysts. The research was led by Professor Galia Maayan, head of the Biomimetic Chemistry Laboratory in the Schulich Faculty of Chemistry, and doctoral student Guilin Ruan.

The Technion researchers designed and developed a homogeneous electrolysis system, or in other words, a system in which the catalyst is soluble in water, so that all components of the system are in the same medium. The innovative and original system is based on (1) copper ions; (2) a peptide-like oligomer (small molecule) that binds the copper and maintains its stability; and (3) a compound called borate whose function is to maintain the pH in a limited range. The main discovery in this study is the unique mechanism that the researchers discovered and demonstrated: the borate compound helps stabilize the metallic center and participates in the process so that it helps catalyze it.

Doctoral student Guilin Ruan

In previous studies, the research group demonstrated the efficacy of using peptide-like oligomers to stabilize metal ions exposed to oxygen – exposure that may oxidize them in the absence of the oligomer and break down the catalyst. Now, the researchers are reporting on the success in creating a very efficient and fast electrolysis system. The stable system oxidizes the water into hydrogen and oxygen under the same desired conditions: low electric potential, pH close to 9 and inexpensive catalysts. According to Prof. Maayan, the system was inspired by enzymes (biological catalysts) that use the protein’s peptide chain to stabilize the metallic center and by natural energetic processes such as photosynthesis, which are driven by units that use solar energy to transport electrons and protons.

Copper complex, consisting of two molecules of a peptide-like oligomer that binds two copper ions, reacts under electrolysis conditions with a molecule of the borate compound; the product of the reaction is the catalyst that allows the water to oxidize and create oxygen and hydrogen efficiently and quickly.

The research was supported by the Israel Science Foundation (ISF) and the Nancy and Stephen Grand Technion Energy Program.

Click here for the paper in The Journal of the American Chemical Society

This E-Skin Knows What Movement You Make

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This E-Skin Knows What Movement You Make

Technion scientists created a wearable motion sensor capable of identifying bending and twisting

The new device

 

Professor Hossam Haick

Technion scientists have produced a highly stretchable electronic material and created a wearable sensor capable of precisely identifying bending and twisting motion. It is essentially an electronic skin capable of recognizing the range of movement human joints normally make, with up to half a degree precision. This breakthrough is the result of collaborative work between researchers from different fields in the Laboratory for Nanomaterial-Based Devices, headed by Professor Hossam Haick from the Wolfson Faculty of Chemical Engineering. It was recently published in Advanced Materials and was featured on the journal’s cover.

Yehu David Horev

Prof. Haick’s lab is focused on wearable devices for various uses. Currently existing wearable motion sensors can recognize bending movement, but not twisting. Existing twisting sensors, on the other hand, are large and cumbersome. This problem was overcome by Ph.D. candidate Yehu David Horev and postdoctoral fellow Dr. Arnab Maity. Mr. Horev found a way to form a composite material that was both conductive (and thus, usable as a sensor) and flexible, stretchable, breathable, and biocompatible, and that did not change its electrical properties when stretched. Dr. Maity then solved the mathematics of analyzing the received signal, creating an algorithm capable of mapping bending and twisting motion – the nature of the movement, its speed, and its angle. The novel sensor is breathable, durable, and lightweight, allowing it to be worn on the human body for prolonged periods.

“This sensor has many possible applications,” Prof. Haick stated. “It can be used in early disease diagnosis, alerting of breathing alterations, and motor system disorders such as Parkinson’s disease. It can be used to assist patients’ motor recovery and be integrated into prosthetic limbs. In robotics, the feedback it provides is crucial for precise motion. In industrial uses, such sensors are necessary in monitoring systems, putting them at the core of the fourth industrial revolution.”

“Electrically conductive polymers are usually quite brittle,” explained Mr. Yehu about the challenge the group had overcome. “To solve this, we created a composite material that is a little like fabric: the individual polymer ‘threads’ cannot withstand the strain on the material, but their movement relative to each other lets it stretch without breaking. It is not too different from what lends stretch to t-shirts. This allows the conductive polymer withstand extreme mechanical conditions without losing its electrical properties.”

What makes this achievement more important is that the materials the group used are very cheap, resulting in an inexpensive sensor. “If we make a device that is very expensive, only a small number of institutions in the Western World can afford to use it. We want the technological advances we achieve to benefit everyone, regardless of their geographic location and socio-economic status,” said Prof. Haick. True to his word, among the laboratory’s other projects is a tuberculosis-diagnosing sticker patch, sorely needed in developing countries.

Dr. Arnab Maity

The scientists who contributed to this study are Yehu David Horev, Dr. Arnab Maity, Dr. Youbin Zheng, Yana Milyutin, Dr. Muhammad Khatib, Dr. Ning Tang, and Prof. Hossam Haick from the Department of Chemical Engineering and Russell Berrie Nanotechnology Institute at the Technion-Israel Institute of Technology; Miaomiao Yuan from the Eighth Affiliated Hospital, Sun Yat-sen University, China; Dr. Ran Yosef Suckeveriene from the Department of Water Industry Engineering at the Kinneret Academic College; and Prof. Weiwei Wu from the School of Advanced Materials and Nanotechnology at Xidian University, China.

Click here for the paper in Advanced Materials

 

Most Innovative Student Projects in Biomedical Engineering

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From fighting COVID-19 to detecting heart disease, these are some of the Technion’s most innovative student projects in biomedical engineering

From detecting cardiovascular disease, to fighting coronavirus, Faculty of Biomedical Engineering students recently presented an array of innovative projects that integrated everything they had learned.
During project development, the students had to go through all the stages needed to bring an idea to fruition. Starting with a medical problem which they had to tackle, they had to combine and implement medical know-how with engineering skills and scientific knowledge in order to provide a real-world solution. This hands-on experience exposes and prepares Technion graduates to the high-tech and biomed industries, and to biomedical research in a way that encourages multidisciplinary work. Therefore, such projects are vital for their future career and entrepreneurial skills.

Here’s a glimpse into some of the most intriguing (and often lifesaving) student projects in biomedical engineering.

 

Early detection of cardiovascular disease  – Sivan Barash and Shachar Zigron took first place in the student project competition, presenting a novel way of labelling macrophage cells, making them detectable by MRI. Macrophages are cells involved in the detection and destruction of bacteria. Cardiovascular disease is strongly associated in the public mind with fat storage in the body, but recent studies have shown significant involvement of inflammation in the process. Since macrophage cells have a major role in inflammation, being able to observe their movement within the body would facilitate scientists’ exploration of the connection between inflammation and cardiovascular disease. The duo’s project has lain the groundwork for in-vivo studies soon to be conducted in the laboratory of Prof. Katrien Vandoorne.

AI-based decision support machine for fetal monitoring  – Second place went to Amit Parizat and Rotem Shapira, who created an artificial intelligence (AI) system to analyze the output of the fetal monitor during labor and serve as a decision support machine. Complications during labor develop rapidly and can harm mother and child. The fetal monitor alerts healthcare providers of complications during labor. However, analyzing the monitor’s long signals manually is challenging and leads to obstetrics teams recommending a Caesarean “just in case” at the slightest indication, to the point that currently a third of all births in the U.S. involve a C-section, and only 20% of
C-sections are later found to have been necessary. C-sections carry risks to the mother and involve a long recovery and long-term side effects. Amit and Rotem proved the feasibility of training an AI machine to predict complications during childbirth, preventing unnecessary invasive intervention, while ensuring that intervention is performed when needed. To achieve this, the two worked with the Obstetrics and Newborn Medicine Division at the Carmel Medical Center.

Treating cancer  – Orel Shahadi and Or Levy, coming in third, developed a 3D model that simulates drug penetration into solid tumors, facilitating development of new drugs and drug combinations to treat cancer. Their innovative model features an inner cluster of cells engineered to display fluorescence, surrounded by an outer layer of cells. Change in the cells’ fluorescence served as an indicator, providing a way to measure drug penetration into the tumor with a high level of precision.

Detecting heart rhythm problems   – Yonathan Belicha and Daniel Cherniavsky, who took fourth place, explored a novel approach to diagnosing cardiac arrhythmias (heart rhythm problems), using nothing more than a few 1-minute videos of the patient – the kind of videos one might make using one’s smartphone. The natural contraction and relaxation of the heart cause minute changes in the human skin color. Yonathan and Daniel extracted those very small changes from the video, and from them – the subject’s pulse. Using this, they trained an AI system to recognize cardiac arrhythmia.

Fighting coronavirus with… ultrasound – Finally, Mor Ventura, Dekel Brav and Omri Magen, coming in fifth, tackled one of the challenges posed by the COVID-19 epidemic. Classification of the COVID-19 severity degree is usually done in hospitals using CT. However, CT machines’ availability is strained, they are expensive, and the process is further complicated by the need to transfer a patient with a highly contagious disease to and from the machine. Mor and Omri explored the possibility of using lung ultrasound instead, obtaining the necessary diagnostic information faster and more easily at the patient’s bedside, also significantly reducing the workload in healthcare facilities. To this end, they first developed an image-processing algorithm to “read” and label lung ultrasounds, identifying areas of interest and ignoring artefacts. Using the results of this algorithm, the trio then trained a neural network to classify the ultrasound videos and identify the severity of the patient’s illness. The project was conducted in collaboration with the Tel Aviv Sourasky Medical Center.

Award-winning FemTech startup – Asaf Licht and Zeinat Awwad presented the entrepreneurship project. Just finishing their bachelor’s degree, the two have already turned their project into a startup called Harmony. Their project is a FemTech initiative, developing a wearable, continuous, and non-invasive tracker to monitor women’s hormonal levels, aiming to ease the process of IVF, but also relevant for avoiding pregnancy, or alternatively for increasing the chances of getting pregnant. Currently, IVF procedures requires a blood test multiple times a week; Harmony seeks to replace that with an at-home device that provides continuous measurements while reducing discomfort. This project won first place in the EuroTech Innovation Day startup competition.

To read about additional student projects recently presented at the Technion, click here

Could New Findings Explain Age-old Mystery, and Improve Use of Hematite to Split H2O Via Solar Energy?

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Could New Findings Explain Age-old Mystery, and Improve Use of Hematite to Split H2O Via Solar Energy?

(L-R) Yifat Piekner, Dr. Daniel Grave, Prof. Avner Rothschild, Dr. David Ellis

Energy & Environmental Science has reported a scientific breakthrough in the study of hematite, an important and promising material in the conversion of solar energy into hydrogen through photoelectrochemical water splitting. The research project was headed by Professor Avner Rothschild of the Faculty of Materials Science and Engineering at the Technion – Israel Institute of Technology and Yifat Piekner, a doctoral student in the Nancy and Stephen Grand Technion Energy Program (GTEP).

The importance of solar energy to our lives is obvious. The sun transmits energy to Earth continuously, and if we are able to harness it for our needs, use of fossil fuels and pollutants such as petroleum and gas will no longer be necessary. The main challenge in switching to solar energy lies in the varying availability of sunlight as the day progresses and seasons change. Every place on earth experiences sunlight for a limited period during the day, but naturally, there is no sunlight at night. Since the electrical grid needs a stable power at all hours of the day and night, use of solar energy depends on our ability to store it so that we are able to use it at night and on overcast days. The problem is that the known form of electrical energy storage – batteries – is inapplicable when it comes to the supply of electricity for a city, a neighborhood, manufacturing site, etc. Moreover, the energy stored in batteries is adequate for a few hours, but batteries cannot provide a solution for long-term storage between seasons.

 

(L-R) Dr. David Ellis, Dr. Daniel Grave, Yifat Piekner

A possible solution to the storage problem is to convert solar energy into hydrogen using photoelectrochemical solar cells. These cells are similar to photovoltaic cells, which convert solar energy into electricity, but instead of producing electricity, they produce hydrogen using the electric power (current ´ voltage) generated in them. The power is used for photoelectrochemical water splitting – the use of sunlight energy to directly dissociate water molecules into hydrogen and oxygen.

 

Dr. Daniel Grave

The advantage of hydrogen over electricity lies in the fact that it easy to store and can be used when needed to generate electricity or for other requirements, such as to power FCEVs (fuel cell electric vehicles). In such cases, the fuel cell replaces the heavy, expensive batteries in Tesla cars and similar vehicles, and could also be used for residential and industrial heating, and the production of ammonia and other raw materials. The advantage of hydrogen as fuel is that its production and consumption do not involve greenhouse gas emissions, or any other emissions, other than oxygen and water.

 

Prof. Avner Rothschild

One of the main challenges in photoelectrochemical cells is the development of efficient and stable photoelectrodes in a base or acid electrolyte, which is the chemical environment in which water can be efficiently split into hydrogen and oxygen. The photoelectrodes absorb the photons emitted by the sun, and use their energy to generate electronic charge carriers (electrons and holes, or missing electrons) that produce hydrogen and oxygen, respectively. Silicon, which is the semiconductor material used in photovoltaic cells, cannot serve as a photoelectrode of this kind, since it is unstable in an electrolyte.

 

Dr. David Ellis

This is the backdrop against which photoelectrochemical cells based on hematite photoelectrodes were developed. Hematite is an iron oxide that has a similar chemical composition to rust. Hematite is inexpensive, stable and nontoxic, and has properties that are suitable for water splitting. However, hematite also has its disadvantages, one of which is the gap between its theoretical energy yield and the yield achieved in practice in actual devices. For reasons that have not been clarified to date despite decades of research, the photon-to-hydrogen conversion efficiency in hematite-based devices is not even half of the theoretical limit for this material. By comparison, the conversion efficiency of photons in silicon solar cells is very close to the theoretical limit. In the present research, which extends and augments the findings recently published in Nature Materials, the research team headed by Prof. Rothschild puts forth an explanation for the mystery. It transpires that the photons absorbed by hematite produce localized electronic transitions that are “chained” to a specific atomic location in the hematite crystal, thus rendering them incapable of generating the electric current used for water splitting, i.e. the separation of water into its elements, hydrogen, and oxygen.

Yifat Piekner

And now for the good news: Using a new analysis method developed by Yifat Piekner with the help of her research colleagues, Dr. David Ellis of the Technion and Dr. Daniel Grave, senior lecturer at Ben-Gurion University of the Negev, the following data were measured for the first time:

  • Quantum efficiency in the generation of mobile (productive) and localized (nonproductive) electronic transitions in a material as a result of photon absorption at different wavelengths
  • Electron-hole separation efficiency
Photon activity in a 32 nanometers thick hematite layer. Only the photons in green contribute to hydrogen generation; The photons represented in the other colors do not contribute to the process, as a result of various optical and physical processes that prevent the formation of mobile charges that contribute to the photocurrent.

This is the first time that these two properties (the first, optical in nature and the second, electrical) have been measured separately, whereas previous studies measured the combined effect of both properties together. Their separation allows for deeper understanding of the factors that influence the energy efficiency of materials for the conversion of solar energy into hydrogen or electricity.

Besides the achievement in terms of practical application, this is a scientific breakthrough that paves a new way for research into light-matter interaction in correlated electron materials.

The research study was sponsored by the Israel Science Foundation’s research center for photocatalysts and photoelectrodes for hydrogen production in the Petroleum Alternatives for Transportation Program, the Grand Technion Energy Program (GTEP) and the Russell Berrie Nanotechnology Institute (RBNI) at the Technion.

Click here for the paper in Energy & Environmental Science

 

Technion among world’s top 100 universities

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Technion among world’s top 100 universities

The Shanghai Ranking, which ranks the world’s leading academic institutions, places Technion 94th in the world

Haifa, Israel – August 16, 2021 – The Technion is 94th on a list of the world’s top 100 universities, according to a report published yesterday by Shanghai Ranking, the world’s leading index for higher education. The Technion – Israel Institute of Technology is also on the top 50 list in two fields: aerospace engineering (16th place) and automation & control (46th place). In chemistry, the Technion ranks among the top 50-75 universities in the world. The Technion has consistently made the top 100 list of the Shanghai Ranking since 2012 (with one exception in 2020).

“The Technion is one of the world’s leading universities, and we will continue to invest efforts and resources to maintain this position for years to come,” said Technion President Prof. Uri Sivan. “The Technion’s strength lies in its excellent human capital, which leads to numerous achievements and breakthroughs in research and teaching. This is the result of hard work and dedication by Technion faculty, deans, administrative staff, and management.”

Prof. Sivan added that the Technion’s listing on the Shanghai Ranking and other indices “is not a purpose on its own. Global academic competition is rapidly intensifying, and while many governments around the world are steadily increasing their investments in academia and research, Israeli universities rely almost entirely on donations, which are becoming increasingly difficult to get.”

According to Prof. Sivan, “in order for Israel to preserve its standing at the forefront of global research, and to ensure the nation’s security, as well as its academic and economic future, the government should significantly increase investment in research and teaching, as well as adopt a welcoming stance toward the absorption of foreign faculty and students.”

While Prof. Sivan is “pleased that the Technion is among the three Israeli academic institutions on the top 100 list, we must remember that without government support and globalization of our research institutions, it will be harder for us to maintain this position.”

The Shanghai Ranking, first published in 2003, categorizes academic institutions according to objective criteria, such as the number of Nobel Prize laureates and other prestigious awards; the number of scientific articles published in the leading journals Nature and Science; the number of times scientific articles published by university researchers have been quoted; and researchers who’ve been frequently quoted in academic journals, relative to their peers in the field.

The index looks at 1,800 universities, from which the top 1000 are selected. Leading the list are Harvard University, Stanford University, University of Cambridge, MIT and UC Berkeley.

Letter from Uri Sivan, President Technion – Israel Institute ofTechnology Click Here

For the full ranking, click here.

Solution to the Chaotic Three-Body Problem

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Solution to the Chaotic Three-Body Problem

Scientists find an effective solution for the centuries-old famous three-body problem in physics, and all related to a drunkard’s walk

The three-body problem is one of the oldest problems in physics: it concerns the motions of systems of three bodies – like the Sun, Earth, and the Moon – and how their orbits change and evolve due to their mutual gravity. The three-body problem has been a focus of scientific inquiry ever since Newton.

Star orbits in a three-body system

When one massive object comes close to another, their relative motion follows a trajectory dictated by their mutual gravitational attraction, but as they move along, and change their positions along their trajectories, the forces between them, which depend on their mutual positions, also change, which, in turn, affects their trajectory et cetera. For two bodies (e.g. like Earth moving around the Sun without the influence of other bodies), the orbit of the Earth would continue to follow a very specific curve, which can be accurately described mathematically (an ellipse). However, once one adds another object, the complex interactions lead to the three-body problem, namely, the system becomes chaotic and unpredictable, and one cannot simply specify the system evolution over long time-scales. Indeed, while this phenomenon has been known for over 400 years, ever since Newton and Kepler, a neat mathematical description for the three-body problem is still lacking. 

In the past, physicists – including Newton himself – have tried to solve this so-called three-body problem; in 1889, King Oscar II of Sweden even offered a prize, in commemoration of his 60th birthday, to anybody who could provide a general solution. In the end, it was the French mathematician Henri Poincaré who won the competition. He ruined any hope for a full solution by proving that such interactions are chaotic, in the sense that the final outcome is essentially random; in fact, his finding opened a new scientific field of research, termed chaos theory. 

The absence of a solution to the three-body problem means that scientists cannot predict what happens during a close interaction between a binary system (formed of two stars that orbit each other like Earth and the Sun) and a third star, except by simulating it on a computer, and following the evolution step-by-step. Such simulations show that when such an interaction occurs, it proceeds in two phases: first, a chaotic phase when all three bodies pull on each other violently, until one star is ejected far from the other two, which settle down to an ellipse. If the third star is on a bound orbit, it eventually comes back down towards the binary, whereupon the first phase ensues, once again. This triple dance ends when, in the second phase, one of the star escapes on an un-bound orbit, never to return.

Professor Hagai Perets (Left) and Ph.D. student Yonadav Barry Ginat

In a paper accepted for publication in Physical Review X this month, Ph.D. student Yonadav Barry Ginat and Professor Hagai Perets of the Technion-Israel Institute of Technology used this randomness to provide a statistical solution to the entire two-phase process. Instead of predicting the actual outcome, they calculated the probability of any given outcome of each phase-1 interaction. While chaos implies that a complete solution is impossible, its random nature allows one to calculate the probability that a triple interaction ends in one particular way, rather than another. Then, the entire series of close approaches could be modeled by using a particular type of mathematics, known as the theory of random walks, sometimes called “drunkard’s walk.” The term got its name from mathematicians thinking about a drunk would walk, essentially of taking it to be a random process – with each step the drunk doesn’t realize where they are and takes the next step in some random direction. The triple system behaves, essentially, in the same way. After each close encounter, one of the stars is ejected randomly (but with the three stars collectively still conserving the overall energy and momentum of the system). One can think of the series of close encounters as a drunkard’s walk. Like a drunk’s step, a star is ejected randomly, comes back, and another (or the same star) is ejected to a likely different random direction (similar to another step taken by the drunk) and comes back, and so forth, until a star is completely ejected to never come back (and the drunk falls into a ditch).

Another way of thinking about this is to notice the similarities with how one would describe the weather. It also exhibits the same phenomenon of chaos the Poincaré discovered, and that is why the weather is so hard to predict. Meteorologists therefore have to recourse to probabilistic predictions (think about that time when a 70% chance of rain on your favorite weather application ended up as a glorious sunshine in reality). Moreover, to predict the weather in a week from now, meteorologists have to account for the probabilities of all possible types of weather in the intervening days, and only by composing them together can they get a proper long-term forecast.

What Ginat and Perets showed in their research was how this could be done for the three-body problem: they computed the probability of each phase-2 binary-single configuration (the probability of finding different energies, for example), and then composed all of the individual phases, using the theory of random walks, to find the final probability of any possible outcome, much like one would do to find long-term weather forecasts.

“We came up with the random walk model in 2017, when I was an undergraduate student,” said Mr. Ginat, “I took a course that Prof. Perets taught, and there I had to write an essay on the three-body problem. We didn’t publish it at the time, but when I started a Ph.D., we decided to expand the essay and publish it.”

The three-body problem was studied independently by various research groups in recent years, including Nicholas Stone of the Hebrew University in Jerusalem, collaborating with Nathan Leigh, then at the American Museum of Natural History, and Barak Kol, also of the Hebrew University. Now, with the current study by Ginat and Perets, the entire, multi-stage, three-body interaction is fully solved, statistically.

“This has important implications for our understanding of gravitational systems, and in particular in cases where many encounters between three stars occur, like in dense clusters of stars,” said Prof. Perets. “In such regions many exotic systems form through three-body encounters, leading to collisions between stars and compact objects like black holes, neutron stars and white dwarves, which also produce gravitational waves that have been first directly detected only in the last few years. The statistical solution could serve as an important step in modelling and predicting the formation of such systems.”

The random walk model can also do more: so far, studies of the three-body problem treat the individual stars as idealized point particles. In reality, of course, they are not, and their internal structure might affect their motion, for example, in tides. Tides on Earth are caused by the Moon and change the former’s shape slightly. Friction between the water and the rest of our planet dissipates some of the tidal energy as heat. Energy is conserved, however, so this heat must come from the Moon’s energy, in its motion about the Earth. Similarly for the three-body problem, tides can draw orbital energy out of the three-bodies’ motion.

 
“The random walk model accounts for such phenomena naturally,” said Mr. Ginat, “all you have to do is to remove the tidal heat from the total energy in each step, and then compose all the steps. We found that we were able to compute the outcome probabilities in this case, too.” As it turns out a drunkard’s walk can sometime shed light on some of the most fundamental questions in physics. 

Click here for the paper in Physical Review X