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Game-Changer in Future Solar Technology: New Perovskite Solar Modules With Greater Size, Power and Stability

Perovskite Solar Modules

The researchers created solar modules that were 5×5 cm2 and 10×10 cm2 – much larger than the 1.5 x 1.5 cm2 ones traditionally made in a lab, but smaller than commercial solar panels. Credit: OIST

  • Perovskites are projected to be a game-changer in future solar technology but currently suffer from a short operational lifespan and drops in efficiency when scaled up to a larger size
  • Scientists have improved the stability and efficiency of solar cell modules by mixing the precursor materials with ammonium chloride during fabrication
  • The perovskite active layer in the improved solar modules are thicker and have larger grains, with fewer defects
  • Both 5 x 5 cm2 and 10 x 10 cm2 perovskite modules maintained high efficiencies for over 1000 hours

Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have created perovskite solar modules with improved stability and efficiency by using a new fabrication technique that reduced defects. Their findings were published on the 25th of January 2021, in Advanced Energy Materials.

Perovskites are one of the most promising materials for the next-generation of solar technology, soaring from efficiencies of 3.8% to 25.5% in slightly over a decade. Perovskite solar cells are cheap to produce and have the potential to be flexible, increasing their versatility. But two obstacles still block the way to commercialization: their lack of long-term stability and difficulties with upscaling.

“Perovskite material is fragile and prone to decomposition, which means the solar cells struggle to maintain high efficiency over a long time,” said first author Dr. Guoqing Tong, a postdoctoral scholar in the OIST Energy Materials and Surface Sciences Unit, led by Professor Yabing Qi. “And although small-sized perovskite solar cells have a high efficiency and perform almost as well as their silicon counterparts, once scaled up to larger solar modules, the efficiency drops.”

In a functional solar device, the perovskite layer lies in the center, sandwiched between two transport layers and two electrodes. As the active perovskite layer absorbs sunlight, it generates charge carriers which then flow to the electrodes via the transport layers and produce a current.

However, pinholes in the perovskite layer and defects at the boundaries between individual perovskite grains can disrupt the flow of charge carriers from the perovskite layer to the transport layers, reducing efficiency. Humidity and oxygen can also start to degrade the perovskite layer at these defect sites, shortening the lifespan of the device.

Perovskite Solar Module and Surface of Active Layer

Perovskite solar cell devices require multiple layers to function. The active perovskite layer absorbs sunlight and generates charge carriers. The transport layers transport the charge carriers to the electrodes, releasing a current. The active perovskite layer is formed from many crystal grains. The boundaries between these grains, and other defects in the perovskite film, such as pinholes, lower the efficiency and lifespan of the solar devices. Credit: OIST

“Scaling up is challenging because as the modules increase in size, it’s harder to produce a uniform layer of perovskite, and these defects become more pronounced,” explained Dr. Tong. “We wanted to find a way of fabricating large modules that addressed these problems.”

Currently, most solar cells produced have a thin perovskite layer – only 500 nanometers in thickness. In theory, a thin perovskite layer improves efficiency, as the charge carriers have less distance to travel to reach the transport layers above and below. But when fabricating larger modules, the researchers found that a thin film often developed more defects and pinholes.

The researchers therefore opted to make 5 x 5 cm2 and 10 x 10 cm2 solar modules that contained perovskite films with double the thickness.

Scientists from the OIST Energy Materials and Surface Sciences Unit show off the perovskite solar modules in action, powering a fan and toy car. Credit: OIST

However, making thicker perovskite films came with its own set of challenges. Perovskites are a class of materials that are usually formed by reacting many compounds together as a solution and then allowing them to crystallize.

However, the scientists struggled to dissolve a high enough concentration of lead iodine – one of the precursor materials used to form perovskite – that was needed for the thicker films. They also found that the crystallization step was fast and uncontrollable, so the thick films contained many small grains, with more grain boundaries.

The researchers therefore added ammonium chloride to increase the solubility of lead iodine. This also allowed lead iodine to be more evenly dissolved in the organic solvent, resulting in a more uniform perovskite film with much larger grains and fewer defects. Ammonia was later removed from the perovskite solution, lowering the level of impurities within the perovskite film.

Surface of the Perovskite Active Layer

By adding ammonium chloride, the resultant perovskite film had fewer grains of a much larger size, reducing the number of grain boundaries. Credit: OIST

Overall, the solar modules sized 5 x 5 cm2 showed an efficiency of 14.55%, up from 13.06% in modules made without ammonium chloride, and were able to work for 1600 hours – over two months – at more than 80% of this efficiency.

The larger 10 x 10 cm2 modules had an efficiency of 10.25% and remained at high levels of efficiency for over 1100 hours, or almost 46 days.

“This is the first time that a lifespan measurement has been reported for perovskite solar modules of this size, which is really exciting,” said Dr. Tong.

This work was supported by the OIST Technology Development and Innovation Center’s Proof-of-Concept Program. These results are a promising step forward in the quest to produce commercial-sized solar modules with efficiency and stability to match their silicon counterparts.

In the next stage of their research, the team plans to optimize their technique further by fabricating the perovskite solar modules using vapor-based methods, rather than by using solution, and are now trying to scale up to 15 x 15 cm2 modules.

“Going from lab-sized solar cells to 5 x 5 cm2 solar modules was hard. Jumping up to solar modules that were 10 x 10 cm2 was even harder. And going to 15 x 15 cm2 solar modules will be harder still,” said Dr. Tong. “But the team is looking forward to the challenge.”

Reference: “Scalable Fabrication of >90 cm2 Perovskite Solar Modules with >1000 h Operational Stability Based on the Intermediate Phase Strategy” by Guoqing Tong, Dae‐Yong Son, Luis K. Ono, Yuqiang Liu, Yanqiang Hu, Hui Zhang, Afshan Jamshaid, Longbin Qiu, Zonghao Liu and Yabing Qi, 25 January 2021, Advanced Energy Materials.
DOI: 10.1002/aenm.202003712

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New “Fast Forward” Algorithm Could Unleash the Power of Quantum Computers

Quantum Computer Code Concept

Fast-forwarding quantum calculations skips past the time limits imposed by decoherence, which plagues today’s machines.

A new algorithm that fast forwards simulations could bring greater use ability to current and near-term quantum computers, opening the way for applications to run past strict time limits that hamper many quantum calculations.

“Quantum computers have a limited time to perform calculations before their useful quantum nature, which we call coherence, breaks down,” said Andrew Sornborger of the Computer, Computational, and Statistical Sciences division at Los Alamos National Laboratory, and senior author on a paper announcing the research. “With a new algorithm we have developed and tested, we will be able to fast forward quantum simulations to solve problems that were previously out of reach.”

Computers built of quantum components, known as qubits, can potentially solve extremely difficult problems that exceed the capabilities of even the most powerful modern supercomputers. Applications include faster analysis of large data sets, drug development, and unraveling the mysteries of superconductivity, to name a few of the possibilities that could lead to major technological and scientific breakthroughs in the near future.

Recent experiments have demonstrated the potential for quantum computers to solve problems in seconds that would take the best conventional computer millennia to complete. The challenge remains, however, to ensure a quantum computer can run meaningful simulations before quantum coherence breaks down.

“We use machine learning to create a quantum circuit that can approximate a large number of quantum simulation operations all at once,” said Sornborger. “The result is a quantum simulator that replaces a sequence of calculations with a single, rapid operation that can complete before quantum coherence breaks down.”

The Variational Fast Forwarding (VFF) algorithm that the Los Alamos researchers developed is a hybrid combining aspects of classical and quantum computing. Although well-established theorems exclude the potential of general fast forwarding with absolute fidelity for arbitrary quantum simulations, the researchers get around the problem by tolerating small calculation errors for intermediate times in order to provide useful, if slightly imperfect, predictions.

In principle, the approach allows scientists to quantum-mechanically simulate a system for as long as they like. Practically speaking, the errors that build up as simulation times increase limits potential calculations. Still, the algorithm allows simulations far beyond the time scales that quantum computers can achieve without the VFF algorithm.

One quirk of the process is that it takes twice as many qubits to fast forward a calculation than would make up the quantum computer being fast forwarded. In the newly published paper, for example, the research group confirmed their approach by implementing a VFF algorithm on a two qubit computer to fast forward the calculations that would be performed in a one qubit quantum simulation.

In future work, the Los Alamos researchers plan to explore the limits of the VFF algorithm by increasing the number of qubits they fast forward, and checking the extent to which they can fast forward systems. The research was published September 18, 2020 in the journal npj Quantum Information.

Reference: “Variational Fast Forwarding for Quantum Simulation Beyond the Coherence Time” by Cristina Cîrstoiu, Zoë Holmes, Joseph Iosue, Lukasz Cincio, Patrick J. Coles and Andrew Sornborger, 18 September 2020, npj Quantum Information.
DOI: 10.1038/s41534-020-00302-0

The research was supported with funding from the Los Alamos National Laboratory Information Science & Technology Institute, Department of Energy Advanced Scientific Computing Beyond Moore’s Law program, and the Los Alamos National Laboratory Directed Research and Development program.

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Kevlar-Inspired Molecular Nanofibers Constructed That Are Stronger Than Steel


Kevlar Inspired Nanoribbons

MIT researchers have designed small molecules that spontaneously form nanoribbons when water is added. These molecules include a Kevlar-inspired “aramid” domain in their design, in green, which fixes each molecule in place and leads to nanoribbons that are stronger than steel. Parts of the molecules attracted to or repulsed from water, shown in purple and blue respectively, orient and guide the molecules to form a nanostructure. This image depicts three Kevlar-inspired “aramid amphiphile” nanoribbons. Credit: Peter Allen

Self-assembly of Kevlar-inspired molecules leads to structures with robust properties, offering new materials for solid-state applications.

Self-assembly is ubiquitous in the natural world, serving as a route to form organized structures in every living organism. This phenomenon can be seen, for instance, when two strands of DNA — without any external prodding or guidance — join to form a double helix, or when large numbers of molecules combine to create membranes or other vital cellular structures. Everything goes to its rightful place without an unseen builder having to put all the pieces together, one at a time.

For the past couple of decades, scientists and engineers have been following nature’s lead, designing molecules that assemble themselves in water, with the goal of making nanostructures, primarily for biomedical applications such as drug delivery or tissue engineering. “These small-molecule-based materials tend to degrade rather quickly,” explains Julia Ortony, assistant professor in MIT’s Department of Materials Science and Engineering (DMSE), “and they’re chemically unstable, too. The whole structure falls apart when you remove the water, particularly when any kind of external force is applied.”

She and her team, however, have designed a new class of small molecules that spontaneously assemble into nanoribbons with unprecedented strength, retaining their structure outside of water. The results of this multi-year effort, which could inspire a broad range of applications, were described on January 21, 2021, in Nature Nanotechnology by Ortony and coauthors.

Julia Ortony and Yukio Cho

Professor Julia Ortony (left) and PhD student Yukio Cho. Ortony and her team have designed a new class of small molecules that spontaneously assemble into nanoribbons with unprecedented strength, retaining their structure outside of water. Credit: Lee Hopkins

“This seminal work — which yielded anomalous mechanical properties through highly controlled self-assembly — should have a big impact on the field,” asserts Professor Tazuko Aida, deputy director for the RIKEN Center for Emergent Matter Science and professor of chemistry and biotechnology at the University of Tokyo, who was not involved in the research.

The material the MIT group constructed — or rather, allowed to construct itself — is modeled after a cell membrane. Its outer part is “hydrophilic,” which means it likes to be in water, whereas its inner part is “hydrophobic,” meaning it tries to avoid water. This configuration, Ortony comments, “provides a driving force for self-assembly,” as the molecules orient themselves to minimize interactions between the hydrophobic regions and water, consequently taking on a nanoscale shape.

Ty Christoff-Tempesta

PhD student Ty Christoff-Tempesta works in the laboratory.
Credit: Lee Hopkins

The shape, in this case, is conferred by water, and ordinarily the whole structure would collapse when dried. But Ortony and her colleagues came up with a plan to keep that from happening. When molecules are loosely bound together, they move around quickly, analogous to a fluid; as the strength of intermolecular forces increases, motion slows and molecules assume a solid-like state. The idea, Ortony explains, “is to slow molecular motion through small modifications to the individual molecules, which can lead to a collective, and hopefully dramatic, change in the nanostructure’s properties.”

One way of slowing down molecules, notes Ty Christoff-Tempesta, a PhD student and first author of the paper, “is to have them cling to each other more strongly than in biological systems.” That can be accomplished when a dense network of strong hydrogen bonds join the molecules together. “That’s what gives a material like Kevlar — constructed of so-called ‘aramids’ — its chemical stability and strength,” states Christoff-Tempesta.

Ortony’s team incorporated that capability into their design of a molecule that has three main components: an outer portion that likes to interact with water, aramids in the middle for binding, and an inner part that has a strong aversion to water. The researchers tested dozens of molecules meeting these criteria before finding the design that led to long ribbons with nanometer-scale thickness. The authors then measured the nanoribbons’ strength and stiffness to understand the impact of including Kevlar-like interactions between molecules. They discovered that the nanoribbons were unexpectedly sturdy — stronger than steel, in fact. 

This finding led the authors to wonder if the nanoribbons could be bundled to produce stable macroscopic materials. Ortony’s group devised a strategy whereby aligned nanoribbons were pulled into long threads that could be dried and handled. Notably, Ortony’s team showed that the threads could hold 200 times their own weight and have extraordinarily high surface areas — 200 square meters per gram of material. “This high surface-to-mass ratio offers promise for miniaturizing technologies by performing more chemistry with less material,” explains Christoff-Tempesta. To this end, they have already developed nanoribbons whose surfaces are coated with molecules that can pull heavy metals, like lead or arsenic, out of contaminated water. Other efforts in the research group are aimed at using bundled nanoribbons in electronic devices and batteries.

Ortony, for her part, is still amazed that they’ve been able to achieve their original research goal of “tuning the internal state of matter to create exceptionally strong molecular nanostructures.” Things could easily have gone the other way; these materials might have proved to be disorganized, or their structures fragile, like their predecessors, only holding up in water. But, she says, “we were excited to see that our modifications to the molecular structure were indeed amplified by the collective behavior of molecules, creating nanostructures with extremely robust mechanical properties. The next step, figuring out the most important applications, will be exciting.”

Reference: “Self-assembly of aramid amphiphiles into ultra-stable nanoribbons and aligned nanoribbon threads” by Ty Christoff-Tempesta, Yukio Cho, Dae-Yoon Kim, Michela Geri, Guillaume Lamour, Andrew J. Lew, Xiaobing Zuo, William R. Lindemann and Julia H. Ortony, 18 January 2021, Nature Nanotechnology.
DOI: 10.1038/s41565-020-00840-w

The work was supported by the National Science Foundation, the Professor Amar G. Bose Research Grant Program, and the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS).

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A Benchmark for Single-Electron Quantum Circuits

Counting Statistics Error Signal

Top: Counting statistics (ptx) of an error signal (x) recorded by a single-charge detector, shown as a function of the number of repetitions (t) of the transfer operation; these repetitions were performed by the single-electron circuit. Bottom: Simulation of the underlying “random walks” (blue lines) based on this measurement signal. Here, the width of the line shows how frequently a step takes place. The red line exemplifies a single path of the error signal. Credit: Ubbelohde

A new methodology for an abstract and universal description of the fidelity of quantum circuits.

Manipulating individual electrons with the goal of employing quantum effects offers new possibilities and greater precision in electronics. However, these single-electron circuits are governed by the laws of quantum mechanics, meaning that deviations from error-free operation still occur – albeit (in the best possible scenario) only very rarely. Thus, insights into both the physical origin the and metrological aspects of this fundamental uncertainty are crucial for the further development of quantum circuitry. To this end, scientists from the Physikalisch-Technische Bundesanstalt (PTB) and the University of Latvia have collaborated to develop a statistical testing methodology. Their results have been published in the journal Nature Communications.

Single-electron circuits are already used as electric-current quantum standards and in quantum-computer prototypes. In these miniaturized quantum circuits, interactions and noise impede the investigation of the fundamental uncertainties and measuring them is a challenge, even for the metrological precision of the measurement apparatus.

In the field of quantum computers, a testing procedure also referred to as a “benchmark” is frequently used in which the operating principle and fidelity of the entire circuit are evaluated via the accumulation of errors following a sequence of operations. Based on this principle, researchers from PTB and the University of Latvia have now developed a benchmark for single-electron circuits. Here, the circuit’s fidelity is described by the random steps of an error signal recorded by an integrated sensor while the circuit repeatedly executes an operation. The statistical analysis of this “random walk” can be used to identify the rare but unavoidable errors when individual quantum particles are manipulated.

By means of this “random-walk benchmark”, the transfer of individual electrons was investigated in a circuit consisting of single-electron pumps developed at PTB as primary standards for realizing the ampere, an SI base unit. In this experiment, sensitive detectors record the error signal with single-electron resolution. The statistical analysis made possible by counting individual particles not only shows fundamental limitations of the circuit’s fidelity induced by external noise and temporal correlations but also provides a robust measure of assessing errors in applied quantum metrology.

The methodology developed within the scope of this work provides a rigorous mathematical foundation for validating quantum standards of electrical quantities and opens new paths for the development of integrated complex quantum systems.

Reference: “A random-walk benchmark for single-electron circuits” by David Reifert, Martins Kokainis, Andris Ambainis, Vyacheslavs Kashcheyevs and Niels Ubbelohde, 12 January 2021, Nature Communications.
DOI: 10.1038/s41467-020-20554-w

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New Ceramic Phosphors for High Power LED Lights Could Save 20–30% More Energy

Ceramic Phosphor

The microstructure of a composite ceramic phosphor, and the appearance of an LED device based on. Credit: Denis Kosyanov, FEFU

Materials scientists at Far Eastern Federal University (FEFU), in collaboration with an international research team, have advanced the design of composite ceramic materials (Ce3+:YAG-Al2O3), i.e. solid-state light converters (phosphors) that can be applied in-ground and aerospace technologies. The LED systems based on the developed materials can save 20-30 percent more energy compared to commercial analogs. A related article was published in the journal Materials Characterization.

Over 15% of the total global electricity production, or about $ 450 billion annually, is spent on lighting. According to the photonics development roadmap run in Russia, the development of LED technology with an efficiency of more than 150 lm/W will allow for the savings of up to 30% of electricity by 2025.

Based on the developed ceramic light converters, it is possible to produce both compact energy-efficient white light-emitting diodes (wLEDs) and high-power (high brightness) systems. The new material is in demand for many photonic applications from portable projectors and endoscopes to laser TVs with a diagonal of more than 100 inches, lighting devices for auto and aircraft construction, megastructures, etc.

“The consumption of white LEDs is more than half of the total consumption of high brightness LEDs. Some peculiarities of the technology for the production of organic phosphors for modern commercial white LEDs lead to the quick aging of the light-emitting diode that loses brightness and quality of color rendering. We get around the problem by creating completely inorganic light converters in the form of composite ceramics based on yttrium aluminum garnet, activated by cerium ions Ce3+:YAG, and a thermally stable phase of aluminum oxide Al2O3,” says Anastasia Vornovskikh, a Junior Researcher at the REC for “Advanced Ceramic Materials” of the FEFU Polytechnic Institute (school, PI).

The new materials are characterized by high values of thermal strength and thermal conductivity, endure high pumping power, and generate bright white light without obvious thermal quenching of the photoluminescence intensity. This makes it possible to reduce the operating temperature of the LED device down to 120-70°C, more than 2 times in comparison with commercial samples of Ce3+:YAG.

“We synthesized materials by vacuum reactive sintering of initial oxide powders of aluminum, yttrium, cerium, and gadolinium. Particular attention we paid to the identification of the quantitative relationship between the main scattering centers that are residual pores and Al2O3 crystallites and the spectroscopic properties of ceramic phosphors. Our light converters meet all the requirements for new generation wLEDs. They have a long lifespan, high luminous efficacy and color rendering index while maintaining the requirements for the environmental friendliness and material dimensions,” says project manager Denis Kosyanov, Director of the REC for “Advanced Ceramic Materials,” of the Industrial Safety Department of FEFU PI.

In the study took part researchers from Far Eastern Federal University (FEFU); Shanghai Institute of Ceramics, the Shanghai Technological Institute, the University of the Chinese Academy of Sciences; Institute of Chemistry of the Far Eastern Branch of the Russian Academy of Sciences; Institute of Solid State Chemistry and Mechanochemistry of the Siberian Branch of the Russian Academy of Sciences.

Reference: “Al2O3–Ce:YAG and Al2O3–Ce:(Y,Gd)AG composite ceramics for high brightness lighting: Effect of microstructure” by D. Yu. Kosyanov,
Xin Liu, A. A. Vornovskikh, A. A. Kosianova, A. M. Zakharenko, A. P. Zavjalov, O. O. Shichalin, V. Yu. Mayorov, V. G. Kuryavyi, Xinglu Qian, Jun Zou and Jiang Li, 6 January 2021, Materials Characterization.
DOI: 10.1016/j.matchar.2021.110883

This work was financially supported by the Russian Science Foundation (Project No. 20-73-10242).

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Robomorphic Computing: Designing Customized “Brains” for Robots

Robot Brain Concept

MIT researchers have developed an automated way to design customized hardware, or “brains,” that speeds up a robot’s operation.

A new system devises hardware architectures to hasten robots’ response time.

Contemporary robots can move quickly. “The motors are fast, and they’re powerful,” says Sabrina Neuman.

Yet in complex situations, like interactions with people, robots often don’t move quickly. “The hang up is what’s going on in the robot’s head,” she adds.

Perceiving stimuli and calculating a response takes a “boatload of computation,” which limits reaction time, says Neuman, who recently graduated with a PhD from the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL). Neuman has found a way to fight this mismatch between a robot’s “mind” and body. The method, called robomorphic computing, uses a robot’s physical layout and intended applications to generate a customized computer chip that minimizes the robot’s response time.

The advance could fuel a variety of robotics applications, including, potentially, frontline medical care of contagious patients. “It would be fantastic if we could have robots that could help reduce risk for patients and hospital workers,” says Neuman.

Neuman will present the research at this April’s International Conference on Architectural Support for Programming Languages and Operating Systems. MIT co-authors include graduate student Thomas Bourgeat and Srini Devadas, the Edwin Sibley Webster Professor of Electrical Engineering and Neuman’s PhD advisor. Other co-authors include Brian Plancher, Thierry Tambe, and Vijay Janapa Reddi, all of Harvard University. Neuman is now a postdoctoral NSF Computing Innovation Fellow at Harvard’s School of Engineering and Applied Sciences.

There are three main steps in a robot’s operation, according to Neuman. The first is perception, which includes gathering data using sensors or cameras. The second is mapping and localization: “Based on what they’ve seen, they have to construct a map of the world around them and then localize themselves within that map,” says Neuman. The third step is motion planning and control — in other words, plotting a course of action.

These steps can take time and an awful lot of computing power. “For robots to be deployed into the field and safely operate in dynamic environments around humans, they need to be able to think and react very quickly,” says Plancher. “Current algorithms cannot be run on current CPU hardware fast enough.”

Neuman adds that researchers have been investigating better algorithms, but she thinks software improvements alone aren’t the answer. “What’s relatively new is the idea that you might also explore better hardware.” That means moving beyond a standard-issue CPU processing chip that comprises a robot’s brain — with the help of hardware acceleration.

Hardware acceleration refers to the use of a specialized hardware unit to perform certain computing tasks more efficiently. A commonly used hardware accelerator is the graphics processing unit (GPU), a chip specialized for parallel processing. These devices are handy for graphics because their parallel structure allows them to simultaneously process thousands of pixels. “A GPU is not the best at everything, but it’s the best at what it’s built for,” says Neuman. “You get higher performance for a particular application.” Most robots are designed with an intended set of applications and could therefore benefit from hardware acceleration. That’s why Neuman’s team developed robomorphic computing.

The system creates a customized hardware design to best serve a particular robot’s computing needs. The user inputs the parameters of a robot, like its limb layout and how its various joints can move. Neuman’s system translates these physical properties into mathematical matrices. These matrices are “sparse,” meaning they contain many zero values that roughly correspond to movements that are impossible given a robot’s particular anatomy. (Similarly, your arm’s movements are limited because it can only bend at certain joints — it’s not an infinitely pliable spaghetti noodle.)

The system then designs a hardware architecture specialized to run calculations only on the non-zero values in the matrices. The resulting chip design is therefore tailored to maximize efficiency for the robot’s computing needs. And that customization paid off in testing.

Hardware architecture designed using this method for a particular application outperformed off-the-shelf CPU and GPU units. While Neuman’s team didn’t fabricate a specialized chip from scratch, they programmed a customizable field-programmable gate array (FPGA) chip according to their system’s suggestions. Despite operating at a slower clock rate, that chip performed eight times faster than the CPU and 86 times faster than the GPU.

“I was thrilled with those results,” says Neuman. “Even though we were hamstrung by the lower clock speed, we made up for it by just being more efficient.”

Plancher sees widespread potential for robomorphic computing. “Ideally we can eventually fabricate a custom motion-planning chip for every robot, allowing them to quickly compute safe and efficient motions,” he says. “I wouldn’t be surprised if 20 years from now every robot had a handful of custom computer chips powering it, and this could be one of them.” Neuman adds that robomorphic computing might allow robots to relieve humans of risk in a range of settings, such as caring for covid-19 patients or manipulating heavy objects.

“This work is exciting because it shows how specialized circuit designs can be used to accelerate a core component of robot control,” says Robin Deits, a robotics engineer at Boston Dynamics who was not involved in the research. “Software performance is crucial for robotics because the real world never waits around for the robot to finish thinking.” He adds that Neuman’s advance could enable robots to think faster, “unlocking exciting behaviors that previously would be too computationally difficult.”

Neuman next plans to automate the entire system of robomorphic computing. Users will simply drag and drop their robot’s parameters, and “out the other end comes the hardware description. I think that’s the thing that’ll push it over the edge and make it really useful.”

This research was funded by the National Science Foundation, the Computing Research Agency, the CIFellows Project, and the Defense Advanced Research Projects Agency.

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An Aqueous Battery That’s Fast Charging, Safer and Less Expensive

Flow Battery Concept

New anode for aqueous batteries allows use of cheap, plentiful seawater as an electrolyte.

Lithium-ion batteries are critical for modern life, from powering our laptops and cell phones to those new holiday toys. But there is a safety risk – the batteries can catch fire.

Zinc-based aqueous batteries avoid the fire hazard by using a water-based electrolyte instead of the conventional chemical solvent. However, uncontrolled dendrite growth limits their ability to provide the high performance and long life needed for practical applications.

Now researchers have reported in Nature Communications that a new 3D zinc-manganese nano-alloy anode has overcome the limitations, resulting in a stable, high-performance, dendrite-free aqueous battery using seawater as the electrolyte.

Xiaonan Shan, co-corresponding author for the work and an assistant professor of electrical and computer engineering at the University of Houston, said the discovery offers promise for energy storage and other applications, including electric vehicles.

“It provides a low-cost, high energy density, stable battery,” he said. “It should be of use for reliable, rechargeable batteries.”

Aqueous Battery

An electric fan (top left) is powered by the proposed zinc battery; typical charge/discharge profiles of ZIBs at 0.5C (top right); in-situ microscope setup to image the zinc deposition dynamics (bottom left); and the morphology change caused by the zinc deposition (bottom right). Credit: University of Houston

Shan and UH PhD student Guangxia Feng also developed an in situ optical visualization technique, allowing them to directly observe the reaction dynamics on the anode in real time. “This platform provides us with the capability to directly image the electrode reaction dynamics in situ,” Shan said. “This important information provides direct evidence and visualization of the reaction kinetics and helps us to understand phenomena that could not be easily accessed previously.”

Testing determined that the novel 3D zinc-manganese nano alloy anode remained stable without degrading throughout 1,000 hours of charge/discharge cycling under high current density (80 mA/cm2).

The anode is the electrode that releases current from a battery, while electrolytes are the medium through which the ionic charge flows between the cathode and anode. Using seawater as the electrolyte rather than highly purified water offers another avenue for lowering battery cost.

Traditional anode materials used in aqueous batteries have been prone to dendrites, tiny growths that can cause the battery to lose power. Shan and his colleagues proposed and demonstrated a strategy to efficiently minimize and suppress dendrite formation in aqueous systems by controlling surface reaction thermodynamics with a zinc alloy and reaction kinetics by a three-dimensional structure.

Shan said researchers at UH and University of Central Florida are currently investigating other metal alloys, in addition to the zinc-manganese alloy.

Reference: “Stable, high-performance, dendrite-free, seawater-based aqueous batteries” by Huajun Tian, Zhao Li, Guangxia Feng, Zhenzhong Yang, David Fox, Maoyu Wang, Hua Zhou, Lei Zhai, Akihiro Kushima, Yingge Du, Zhenxing Feng, Xiaonan Shan and Yang Yang, 11 January 2021, Nature Communications.
DOI: 10.1038/s41467-020-20334-6

In addition to Shan and Feng, researchers on the project include Huajun Tian, Zhao Li, David Fox, Lei Zhai, Akihiro Kushima and co-corresponding author Yang Yang, all with the University of Central Florida; Zhenzhong Yang and Yingge Du, both with Pacific Northwest National Laboratory; Maoyu Wang and co-corresponding author Zhenxing Feng, both with Oregon State University; and Hua Zhou with Argonne National Laboratory.

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3D-Printed Nanosatellite Thruster Emits Pure Ions for Propulsion

Nanosatellite Thrusters

Nanosatellite thrusters that emit a stream of pure ions are the first of their kind to be entirely additively manufactured, using a combination of 3D printing and hydrothermal growth of zinc oxide nanowires. A stainless steel version (top) works better overall but is much more expensive to produce. MIT researchers found that a polymer version (bottom) yields comparable performance at a lower cost. Credit: Velásquez-García Group

Study is first demonstration of a fully 3D-printed thruster using pure ion emission for propulsion.

A 3D-printed thruster that emits a stream of pure ions could be a low-cost, extremely efficient propulsion source for miniature satellites.

The nanosatellite thruster created by MIT researchers is the first of its kind to be entirely additively manufactured, using a combination of 3D printing and hydrothermal growth of zinc oxide nanowires. It is also the first thruster of this type to produce pure ions from the ionic liquids used to generate propulsion.

The pure ions make the thruster more efficient than similar state-of-the-art devices, giving it more thrust per unit flow of propellant, says Luis Fernando Velásquez-García, principal research scientist at MIT’s Microsystems Technology Laboratories (MTL).

The thrust provided by the device, which is about the size of a dime, is minuscule. The force can be measured on the scale of a few tens of micronewtons, a thrust about equal to half the weight of one of the sesame seeds in a hamburger bun. But in the frictionless environment of orbit, a CubeSat or similarly small satellite could use these tiny thrusts to accelerate or maneuver with fine control.

Velásquez-García says additive manufacturing’s advantages offer new low-cost possibilities for powering satellites. “If you want to be serious about developing high-performance hardware for space, you really need to look into optimizing the shapes, the materials, everything that composes these systems. 3D printing can help with all of these things,” he says.

Velásquez-García and MTL postdoc Dulce Viridiana Melo Máximo describe the thruster in the December 2020 issue of the journal Additive Manufacturing. The work was sponsored by the MIT–Tecnológico de Monterrey Program in Nanoscience and Nanotechnology and the MIT Portugal program.

Electrospraying pure ions

The miniaturized thruster operates electrohydrodynamically, producing a fine spray of accelerated, charged particles that are emitted to produce a propulsive force. The particles come from a sort of liquid salt called ionic liquid.

In the MIT design, a 3D-printed body holds a reservoir of ionic liquid along with a miniature forest of emitter cones coated with zinc oxide nanowires hydrothermally grown on the cone surfaces. The nanowires act as wicks to transport the liquid from the reservoir to the emitter tips. By applying a voltage between the emitters and a 3D-printed extractor electrode, charged particles are ejected from the emitter tips. The researchers experimented with printing the emitters in a type of stainless steel as well as a polymer resin.

The researchers were able to detect the pure ion jet using a technique called mass spectrometry, which can identify the composition of particles based on their molecular mass. Typically, an electrospray produced from ionic liquids would contain ions plus other species made of ions mixed with neutral molecules.

The pure ion jet was a surprise, and the research team still isn’t entirely sure how it was produced, although Velásquez-García and his colleagues think the zinc oxide nanowires “are the secret sauce,” he says. “We believe it has something to do with the way the charge is injected and the way the fluid interacts with the wire material as it transports the fluid to the emission sites.”

Producing a jet of pure ions means that the thruster can utilize more efficiently the propellant on board, and propellant efficiency is key for objects in orbit because refueling satellites is rarely an option, he explains. “The hardware that you put into space, you want to get many, many years of use out of that, so I think it’s a good strategy to do it efficiently.”

Advantages of additive manufacturing

Electrospray designs can have many applications beyond space, says Velásquez-García. The technique “can emit not just ions, but also things like nanofibers and droplets. You could use the fibers to make filters, or electrodes for energy storage, or use the droplets to purify seawater by removing brine. You could also use electrospray designs in a combustor, to atomize fuel into very small and fine droplets.”

The nanosatellite thruster is a good example how additive manufacturing can produce devices that are “personalized, customized and made from finely featured, complex multi-material structures,” he adds. Instead of using expensive laser machining or clean-room technologies for specialized industrial manufacturing, he and his colleagues made the thruster mostly on commercial printers using instructions that can be distributed widely.

And since the techniques are relatively inexpensive, fast, and easy to use, Velásquez-García says designs can be “exquisitely iterated” to improve features and explore surprising effects, such as the pure ion emission in the case of the new thruster.

The advantages of 3D printing microsystems include lower costs and shorter times for prototyping and development, along with the ease of assembling multimaterial structures, says Tomasz Grzebyk, a microsystems professor at Wroclaw University of Science and Technology, who was not involved with the study.

“All these advantages can be seen also in the ion thrusters developed at MIT,” Grzebyk says. “And what more, since there has been a great progress in 3D printing in last few years, the parameters of devices fabricated using this method are becoming similar to these obtained by much more complex, expensive and restricted to specialized laboratories microengineering techniques.”

“3D printing technology is also constantly improving, potentially making it possible to implement in the near future even better systems that have smaller features and are made of better materials,” he says. “We are on track to producing the best possible hardware that a lot more people can afford.”

Reference: “Additively manufactured electrohydrodynamic ionic liquid pure-ion sources for nanosatellite propulsion” by Dulce Viridiana Melo Máximo and Luis Fernando Velásquez-García, 21 November 2020, Additive Manufacturing.
DOI: 10.1016/j.addma.2020.101719

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Infrastructure Improvements to Get More Electric Cars on the Road


More Electric Cars on the Road

MIT researchers have found that installing charging stations on residential streets and along highways could lead to wider adoption of clean vehicles. Credit: Courtesy of Trancik Lab

Study measures which kinds of infrastructure improvements could lead to wider adoption of clean vehicles.

A new study from researchers at MIT uncovers the kinds of infrastructure improvements that would make the biggest difference in increasing the number of electric cars on the road, a key step toward reducing greenhouse gas emissions from transportation.

The researchers found that installing charging stations on residential streets, rather than just in central locations such as shopping malls, could have an outsized benefit. They also found that adding on high-speed charging stations along highways and making supplementary vehicles more easily available to people who need to travel beyond the single-charge range of their electric vehicles could greatly increase the vehicle electrification potential.

The findings are reported in the journal Nature Energy, in a paper by MIT associate professor of energy studies Jessika Trancik, graduate student Wei Wei, postdoc Sankaran Ramakrishnan, and former doctoral student Zachary Needell SM ’15, PhD ’18.

The researchers developed a new methodology to identify charging solutions that would conveniently fit into people’s daily activities. They used data collected from GPS tracking devices in cars, as well as survey results about people’s daily driving habits and needs, including detailed data from the Seattle area and more general data from the U.S. as a whole. Greatly increasing the penetration of electric cars into the personal vehicle fleet is a central feature of climate mitigation policies at local, state, and federal levels, Trancik says. A goal of this study was “to better understand how to make these plans for rapid vehicle electrification a reality,” she adds.

In deciding how to prioritize different kinds of improvements in vehicle charging infrastructure, she says, “the approach that we took methodologically was to emphasize building a better understanding of people’s detailed energy consuming behavior, throughout the day and year.”

To do that, “we examine how different people are moving from location to location throughout the day, and where they are stopping,” she says. “And from there we’re able to look at when and where they would be able to charge without interrupting their daily travel activities.”

The team looked at both regular daily activities and the variations that occur over the course of a year. “The longitudinal view is important for capturing the different kinds of trips that a driver makes over time, so that we can determine the kinds of charging infrastructure needed to support vehicle electrification,” Wei says.

While the vast majority of people’s daily driving needs can be met by the range provided by existing lower-cost electric cars, as Trancik and her colleagues have reported, there are typically a few times when people need to drive much farther. Or, they may need to make more short trips than usual in a day, with little time to stop and recharge. These “high-energy days,” as the researchers call them, when drivers are consuming more than the usual amount of energy for their transportation needs, may only happen a handful of times per year, but they can be the deciding factor in people’s decision making about whether to go electric.

Even though battery technology is steadily improving and extending the maximum range of electric cars, that alone will not be enough to meet all drivers’ needs and achieve rapid emissions reductions. So, addressing the range issue through infrastructure is essential, Trancik says. The highest-capacity batteries tend to be the most expensive, and are not affordable to many, she points out, so getting infrastructure right is also important from an equity perspective.

Being strategic in placing infrastructure where it can be most convenient and effective — and making drivers aware of it so they can easily envision where and when they will charge — could make a huge difference, Trancik says.

“There are various ways to incentivize the expansion of such charging infrastructures,” she says. “There’s a role for policymakers at the federal level, for example, for incentives to encourage private sector competition in this space, and demonstration sites for testing out, through public-private partnerships, the rapid expansion of the charging infrastructure.” State and local governments can also play an important part in driving innovation by businesses, she says, and a number of them have already signaled their support for vehicle electrification.

Providing easy access to alternative transportation for those high-energy days could also play a role, the study found. Vehicle companies may even find it advantageous to provide or partner with convenient rental services to help drive their electric car sales.

In their analysis of driving habits in Seattle, for example, the team found that the impact of either adding highway fast-charging stations or increasing availability of supplementary long-range vehicles for up to four days a year meant that the number of homes that could meet their driving needs with a lower cost electric vehicle increased from 10 percent to 40 percent. This number rose to above 90 percent of households when fast-charging stations, workplace charging, overnight public charging, and up to 10 days of access to supplementary vehicles were all available. Importantly, charging options at residential locations (on or off-street) is key across all of these scenarios.

The study’s findings highlight the importance of making overnight charging capabilities available to more people. While those who have their own garages or off-street parking can often already easily charge their cars at home, many people do not have that option and use public parking. “It’s really important to provide access — reliable, predictable access — to charging for people, wherever they park for longer periods of time near home, often overnight,” Trancik says.

That includes locations such as hotels as well as residential neighborhoods, she says. “I think it’s so critical to emphasize these high-impact approaches, such as figuring out ways to do that on public streets, rather than haphazardly putting a charger at the grocery store or at the mall or any other public location.” Not that those aren’t also useful, she says, but public planning should be aiming to expand accessibility to a greater part of the population. Being strategic about infrastructure expansion will continue to be important even as fast chargers fall in cost and new designs begin to allow for more rapid charging, she adds.

More Electric Cars on the Road

Being strategic in placing infrastructure where it can be most convenient and effective could make a huge difference in the wider adoption of clean vehicles, Trancik says. Credit: Courtesy of Trancik Lab

The study should help to provide some guidance to policymakers at all levels who are looking for ways to facilitate the reduction of greenhouse gas emissions, since the transportation sector accounts for about a third of those emissions overall. “If you have limited funds, which you typically always do, then it’s just really important to prioritize,” Trancik says, noting that this study could indicate the areas that could provide the greatest return for those investments. The high-impact charging solutions they identify can be mixed and matched across different cities, towns, and regions, the reseachers note in their paper.

The researchers’ approach to analyzing high-resolution, real-world driving patterns is “valuable, enabling several opportunities for further research,” says Lynette Cheah, an associate professor of engineering systems and design at Singapore University of Technology and Design, who was not associated with this work. “Real-world driving data can not only guide infrastructure and policy planning, but also optimal EV charging management and vehicle purchasing and usage decisions. … This can provide greater confidence to drivers about the feasibility and operational implications of switching to EVs.”

Reference: “Personal vehicle electrification and charging solutions for high-energy days” by Wei Wei, Sankaran Ramakrishnan, Zachary A. Needell and Jessika E. Trancik, 21 January 2021, Nature Energy.
DOI: 10.1038/s41560-020-00752-y

The study was supported by the European Regional Development Fund, the Lisbon Portugal Regional Development Program, the Portuguese Foundation for Science and Technology, and the U.S. Department of Energy.

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Avalanching Nanoparticles Break Barriers to Imaging Cells in Real Time

Photon Avalanching Process

An illustration of the chain-reaction process that underlies the photon avalanching mechanism Columbia Engineering researchers have realized in their nanoparticles. In this process, the absorption of a single low-energy photon sets off a chain reaction of energy transfers and further absorption events that result in many highly excited ions within the nanoparticle, which then release their energy in the intense emission of many higher-energy photons. Credit: Mikolaj Lukaszewicz/ Polish Academy of Sciences

Study co-led by Berkeley Lab and Columbia Engineering could lead to simple, high-resolution bioimaging in real time by overcoming a fundamental property of light.

Since the earliest microscopes, scientists have been on a quest to build instruments with finer and finer resolution to image a cell’s proteins – the tiny machines that keep cells, and us, running. But to succeed, they need to overcome the diffraction limit, a fundamental property of light that long prevented optical microscopes from bringing into focus anything smaller than half the wavelength of visible light (around 200 nanometers or billionths of a meter) – far too big to explore many of the inner-workings of a cell.

For over a century, scientists have experimented with different approaches – from intensive calculations to special lasers and microscopes – to resolve cellular features at ever smaller scales. And in 2014, scientists were awarded the Nobel Prize in Chemistry for their work in super-resolution optical microscopy, a groundbreaking technique that bypasses the diffraction limit by harnessing special fluorescent molecules, unusually shaped laser beams, or sophisticated computation to visualize images at the nanoscale.

Avalanching Nanoparticles

At left: Experimental PASSI (photon avalanche single-beam super-resolution imaging) images of thulium-doped avalanching nanoparticles separated by 300 nanometers. At right: PASSI simulations of the same material. Credit: Berkeley Lab and Columbia University

Now, as reported in a cover article in the journal Nature, a team of researchers co-led by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Columbia University’s Fu Foundation School of Engineering and Applied Science (Columbia Engineering) has developed a new class of crystalline material called avalanching nanoparticles (ANPs) that, when used as a microscopic probe, overcomes the diffraction limit without heavy computation or a super-resolution microscope.

The researchers say that the ANPs will advance high-resolution, real-time bio-imaging of a cell’s organelles and proteins, as well as the development of ultrasensitive optical sensors and neuromorphic computing that mimics the neural structure of the human brain, among other applications.

“These nanoparticles make every simple scanning confocal microscope into a real-time super-resolution microscope, but what they do isn’t exactly super-resolution. They actually make the diffraction limit much lower,” but without the process-heavy computation of previous techniques, said co-author Bruce Cohen, a staff scientist in Berkeley Lab’s Molecular Foundry and Molecular Biophysics & Integrated Bioimaging Division. Scanning confocal microscopy is a technique that produces a magnified image of a specimen, pixel by pixel, by scanning a focused laser across a sample.

A surprise discovery

The photon avalanching nanoparticles described in the current study are about 25 nanometers in diameter. The core contains a nanocrystal doped with the lanthanide metal thulium, which absorbs and emits light. An insulating shell ensures that the part of the nanoparticle that’s absorbing and emitting light is far from the surface and doesn’t lose its energy to its surroundings, making it more efficient, explained co-author Emory Chan, a staff scientist in Berkeley Lab’s Molecular Foundry.

A defining characteristic of photon avalanching is its extreme nonlinearity. This means that each doubling of the laser intensity shone to excite a microscopic material more than doubles the material’s intensity of emitted light. To achieve photon avalanching, each doubling of the exciting laser intensity increases the intensity of emitted light by 30,000-fold.

But to the researchers’ delight, the ANPs described in the current study met each doubling of exciting laser intensity with an increase of emitted light by nearly 80-million-fold. In the world of optical microscopy, that is a dazzling degree of nonlinear emission. And since the study’s publication, “we actually have some better ones now,” Cohen added.

The researchers might not have considered thulium’s potential for photon avalanching if it weren’t for Chan’s study in 2016, which calculated the light-emitting properties of hundreds of combinations of lanthanide dopants when stimulated by 1,064-nanometer near-infrared light. “Surprisingly, thulium-doped nanoparticles were predicted to emit the most light, even though conventional wisdom said that they should be completely dark,” noted Chan.

According to the researchers’ models, the only way that thulium could be emitting light is through a process called energy looping, which is a chain reaction in which a thulium ion that has absorbed light excites neighboring thulium ions into a state that allows them to better absorb and emit light.

Those excited thulium ions, in turn, make other neighboring thulium ions more likely to absorb light. This process repeats in a positive feedback loop until a large number of thulium ions are absorbing and emitting light.

“It’s like placing a microphone close to a speaker – the feedback caused by the speaker amplifying its own signal blows up into an obnoxiously loud sound. In our case, we are amplifying the number of thulium ions that can emit light in a highly nonlinear way,” Chan explained. When energy looping is extremely efficient, it is called photon avalanching since a few absorbed photons can cascade into the emission of many photons, he added.

At the time of the 2016 study, Chan and colleagues hoped that they might see photon avalanching experimentally, but the researchers weren’t able to produce nanoparticles with sufficient nonlinearity to meet the strict criteria for photon avalanching until the current study.

To produce avalanching nanoparticles, the researchers relied on the Molecular Foundry’s nanocrystal-making robot WANDA (Workstation for Automated Nanomaterial Discovery and Analysis) to fabricate many different batches of nanocrystals doped with different amounts of thulium and coated with insulating shells. “One of the ways we were able to achieve such great photon-avalanching performance with our thulium nanoparticles was by coating them with very thick, nanometer-scale shells,” said Chan, who co-developed WANDA in 2010.

Growing the shells is an exacting process that can take up to 12 hours, he explained. Automating the process with WANDA allowed the researchers to perform other tasks while ensuring a uniformity of thickness and composition among the shells, and to fine-tune the material’s response to light and resolution power.

Harnessing an avalanche at the nanoscale

Scanning confocal microscopy experiments led by co-author P. James Schuck, an associate professor of mechanical engineering at Columbia Engineering who was a senior scientist in Berkeley Lab’s Molecular Foundry, showed that nanoparticles doped with moderately high concentrations of thulium exhibited nonlinear responses greater than expected for photon avalanching, making these nanoparticles one of the most nonlinear nanomaterials known to exist.

Changhwan Lee, a graduate student in Schuck’s lab, performed a battery of optical measurements and calculations to confirm that the nanoparticles met the strict criteria for photon avalanching. This work is the first time all the criteria for photon avalanching have been met in a single nanometer-sized particle.

The extreme nonlinearity of the avalanching nanoparticles allowed Schuck and Lee to excite and image single nanoparticles spaced closer than 70 nanometers apart. In conventional “linear” light microscopy, many nanoparticles are excited by the laser beam, which has a diameter of greater than 500 nanometers, making the nanoparticles appear as one large spot of light.

The authors’ technique – called photon avalanche single-beam super-resolution imaging (PASSI) – takes advantage of the fact that a focused laser beam spot is more intense in its center than on its edges, Chan said. Since the emission of the ANPs steeply increases with laser intensity, only the particles in the 70-nanometer center of the laser beam emit appreciable amounts of light, leading to the exquisite resolution of PASSI.

The current study, the researchers say, immediately opens new applications in ultrasensitive infrared photon detection and conversion of near-infrared light into higher energies for super-resolution imaging with commercially available scanning confocal optical microscopes, and improved resolution in state-of-the-art super-resolution optical microscopes.

“That’s amazing. Usually in optical science, you have to use really intense light to get a large nonlinear effect – and that’s no good for bioimaging because you’re cooking your cells with that power of light,” said Schuck, who has continued his collaborative research at the Molecular Foundry as a user. “But with these thulium-doped nanoparticles, we’ve shown that they don’t require that much input intensity to get a resolution that’s less than 70 nanometers. Normally, with a scanning confocal microscope, you’d get 300 nanometers. That’s a pretty good improvement, and we’ll take it, especially since you’re getting super-resolution images essentially for free.”

Now that they have successfully lowered the diffraction limit with their photon avalanching nanoparticles, the researchers would like to experiment with new formulations of the material to image living systems, or detect changes in temperature across a cell’s organelle and protein complex.

“Observing such highly nonlinear phenomena in nanoparticles is exciting because nonlinear processes are thought to pattern structures like stripes in animals and to produce periodic, clocklike behavior,” Chan noted. “Nanoscale nonlinear processes could be used to make tiny analog-to-digital converters, which may be useful for light-based computer chips, or they could be used to concentrate dim, uniform light into concentrated pulses.”

“These are such unusual materials, and they’re brand new. We hope that people will want to try them with different microscopes and different samples, because the great thing about basic science discoveries is that you can take an unexpected result and see your colleagues run with it in exciting new directions,” Cohen said.

Read First Nanomaterial Developed That Demonstrates “Photon Avalanching” for more on this research.

Reference: “Giant nonlinear optical responses from photon avalanching nanoparticles” Changhwan Lee, Emma Xu, Yawei Liu, Ayelet Teitelboim, Kaiyuan Yao, Angel Fernandez-Bravo, Agata Kotulska, Sang Hwan Nam, Yung Doug Suh, Artur Bednarkiewicz, Bruce E. Cohen, Emory M. Chan and P. James Schuck, 13 January 2021, Nature.
DOI: 10.1038/s41586-020-03092-9

Chan, Cohen, and Schuck co-led the study along with Artur Bednarkiewicz of the Polish Academy of Sciences, and Yung Doug Suh of the Korea Research Institute of Chemical Technology (KRICT) and Sungkyunkwan University (SKKU), South Korea. Their co-authors include Changhwan Lee (lead author), Emma Xu, and Kaiyuan Yao of Columbia Engineering; Yaiwei Liu (Chinese Academy of Sciences), Ayelet Teitelboim, and Angel Fernandez-Bravo of Berkeley Lab’s Molecular Foundry; Agata Kotulska of the Polish Academy of Sciences; and Sang Hwan Nam of the Korea Research Institute of Chemical Technology.

The Molecular Foundry is a DOE Office of Science user facility at Berkeley Lab.

This research was supported in part by the DOE Office of Science, including funding from Programmable Quantum Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy.

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