Category Archives: electronics

Move your body and charge your phone

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These researchers are working to bring a device than can harvest bioenergy to market, from a November 20, 2024 University of Waterloo (Ontario, Canada) news release (also on EurekAlert),

A new technology that can generate electricity from vibrations or even small body movements means you could charge your laptop by typing or power your smartphone’s battery on your morning run. 

Researchers at the University of Waterloo have developed a tiny, wearable generator in response to the urgent need for sustainable, clean energy. It is also scalable for larger machines. 

“This is a real game changer,” said Dr. Asif Khan, the project’s lead researcher and a postdoctoral fellow in the Department of Electrical and Computer Engineering at Waterloo. “We have made the first device of its kind that can power electronics at low cost and with unprecedented efficiency.” 

The device uses the piezoelectric effect, which generates electrical energy by applying pressure to materials like crystal and certain ceramics. Piezoelectric materials are currently used in various sensing technologies including sonar, ultrasonic imaging and microwave devices.  

“Those older materials are brittle, expensive and have a limited ability to generate electricity,” said Dr. Dayan Ban, professor and researcher at the Waterloo Institute for Nanotechnology. “The materials we’ve created for the new generator are flexible, more energy-efficient and cost less.” 

In addition to Khan and Ban, the research team includes two other Waterloo professors, one professor from the University of Toronto, and their research groups.  

The researchers have filed a patent and are working with a Canadian company to commercialize their generator for use in aviation, specifically to power the systems on planes that monitor the status of safety equipment.  

Caption: The new generator contains materials that are flexible, energy-efficient and relatively less expensive. Credit: University of Waterloo

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

Breaking dielectric dilemma via polymer functionalized perovskite piezocomposite with large current density output by Asif Abdullah Khan, Avi Mathur, Lu Yin, Mahmoud Almadhoun, Jian Yin, Majid Haji Bagheri, Md Fahim Al Fattah, Araz Rajabi-Abhari, Ning Yan, Boxin Zhao, Vivek Maheshwari & Dayan Ban. Nature Communications volume 15, Article number: 9511 (2024) DOI: https://doi.org/10.1038/s41467-024-53846-6 Published: 04 November 2024

This paper is open access.

Electrodeposition and the creation of nanostructures

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Caption: In-situ liquid-cell transmission electron microscopy electrodeposition of PtNi [platinum-nickel] nanoparticle films on a carbon electrode during cyclic voltammetry. The electron beam (here in green color) illuminated the electrode (here in orange color) submerged in the platinum and nickel salt solution, enhancing the growth of the PtNi nanoparticle film (grey color) on the electrode. The film thickness increases with each cycle and by the fourth cycle reaction-rate limited growth of branched and porous structures were observed. Credit: Designed by: Weronika Wojtowicz: wojtowicz.vika@gmail.com; water background from https://pl.freepik.com.

This work comes from Poland according to a November 13, 2024 news item on phys.org, Note: A link has been removed,

Metallic nanoparticles, consisting of a few to several thousand atoms or simple molecules, are attracting significant interest. Electrodes coated with layers of nanoparticles (nanolayers) are particularly useful in areas such as energy production, serving as catalysts.

A convenient method for producing such layers on electrodes is electrodeposition, the subtle complexities of which have just been revealed by an international team of researchers led by scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow. Their paper is published in the journal Nano Letters.

Research on nanoparticles is yielding promising results for technologies related to energy, medicine, and electronics. One of the key challenges is effectively controlling the synthesis and growth of nanostructures. An international team of scientists, led by researchers from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, conducted an advanced experiment demonstrating the electrodeposition process of a platinum-nickel (PtNi) nanolayer on an electrode. Utilizing state-of-the-art imaging techniques, the researchers had a unique opportunity to observe in real-time how structures form at the atomic level, which is a significant step towards better designing materials with precisely controlled properties.

…

A November 13 ,2024 The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences press release (also on EurekAlert), which originated the news item, describes electrodeposition and how this research was conducted,

Electrodeposition is a rapid and convenient method for producing nanostructures. It involves immersing an electrode in a metal salt solution, from which the layer is to be grown, followed by applying an appropriate voltage that causes ions near the electrode surface to reduce, initiating layer growth. To closely examine the process of electrodeposition, transmission electron microscopy (TEM) techniques are essential. TEM allows for imaging materials with sub-angstrom resolution (i.e., less than one ten-millionth of a millimeter) since it uses an electron beam with a much shorter wavelength than visible light. Ideally, it would be possible to observe, in real-time, how nucleation (the initial growth stage where nanoparticle seeds form) and layer growth occur on the electrode. However, TEM imaging comes with certain limitations: the samples need to be as thin as possible and entirely dry. To overcome these challenges and enable the imaging of chemical reactions, the researchers utilized thus a special imaging technique in a liquid cell flow chamber.

“The flow cell consists of two silicon chips equipped with a 50-nanometer-thick SiN [silicon nitride]x membrane. This membrane is electron-transparent, and an additional electrode is placed on its surface. By applying a voltage, the microscope user can observe how the layer grows on the electrode. Experiments using such a cell require a special holder for flow experiments in the TEM”, explains Prof. Magdalena Parlińska-Wojtan, Ph.D., Eng. (IFJ PAN).

Experiments conducted at the Silesian University of Technology using a TEM microscope confirmed that the PtNi layer indeed grows directly on the electrode, providing crucial insights into the fundamentals of the entire process. An alternative mechanism would involve nanoparticles first forming in the electrolyte and then drifting toward the electrode to attach. This effect was also observed, but only in areas illuminated by the beam, due to the fact that the electron beam interacts with water, behaving like a reducing agent. Subsequent ‘dry’ observations revealed that the layer is actually composed of spherical nanoparticles with diameters of several tens of nanometers. Further magnification of TEM images showed that the surface of these nanoparticles consists of densely branched, fine dendritic structures (multiple branching).

“As part of our collaboration with the Fritz Haber Institute of the Max Planck Society in Berlin, we conducted an additional experiment by extending the reaction time and reducing the rate of voltage changes. This allowed us to observe additional effects: the nucleation of individual nanoparticles, which rapidly grow and merge to form a continuous layer. During voltage changes in subsequent electrodeposition cycles, the nanoparticles undergo alternating growth and dissolution. However, growth is a faster process than dissolution, which ultimately results in a stable layer”, explains Prof. Parlińska-Wojtan.

As part of the research, another experiment was conducted in liquid environment using a different, but also unique, apparatus: a scanning transmission X-ray microscope (STXM), available at the National Synchrotron Radiation Center SOLARIS in Kraków. During STXM imaging, X-ray radiation is used. The resulting images do not have as high a resolution as the ones from electron microscopy, but they reveal other properties of the materials under study, such as the oxidation states of atoms in nanoparticles. The result of electrodeposition is not always pure metal; sometimes it is a metal oxide. Depending on whether it is a metal or an oxide (and the oxidation state of the oxide), materials absorb X-ray radiation at different energies. An STXM image taken with the appropriate energy beam allows for a detailed investigation of the produced nanoparticles. The STXM microscope at the SOLARIS center in Kraków also enabled an experiment in a liquid environment using a flow cell nearly identical to the one used in the TEM. The authors thus performed PtNi electrodeposition inside the STXM and, in real time, investigated the range of X-ray absorption by the nanoparticles. In this way, they determined that the layer actually consists of nickel(II) oxide and metallic platinum.

“Conducting an experiment using microscopic techniques in a liquid environment is quite a challenge. Nevertheless, our team succeeded in producing the expected PtNi layer using two different techniques, and the obtained results were complementary”, says Prof. Parlińska-Wojtan, emphasizing: “Such research is important for several reasons. The technical reason is that we are still exploring the capabilities and limitations of relatively new, high-end measurement tools. There was also a more important scientific reason: understanding the fundamental factors that govern the synthesis, growth, and properties of nanostructures. This knowledge may help in the future in the fabrication of nanostructured materials tailored better for applications such as fuel cells or medicine”.

The research results were published in Nano Letters and the journal’s editorial board recognized their work by featuring the accompanying graphic on the cover of one of their issues.

The Henryk Niewodniczański Institute of Nuclear Physics (IFJ PAN) is currently one of the largest research institutes of the Polish Academy of Sciences. A wide range of research carried out at IFJ PAN covers basic and applied studies, from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly publication output of IFJ PAN includes over 600 scientific papers in high-impact international journals. Each year the Institute hosts about 20 international and national scientific conferences. One of the most important facilities of the Institute is the Cyclotron Centre Bronowice (CCB), which is an infrastructure unique in Central Europe, serving as a clinical and research centre in the field of medical and nuclear physics. In addition, IFJ PAN runs four accredited research and measurement laboratories. IFJ PAN is a member of the Marian Smoluchowski Kraków Research Consortium: “Matter-Energy-Future”, which in the years 2012-2017 enjoyed the status of the Leading National Research Centre (KNOW) in physics. In 2017, the European Commission granted the Institute the HR Excellence in Research award. As a result of the categorization of the Ministry of Education and Science, the Institute has been classified into the A+ category (the highest scientific category in Poland) in the field of physical sciences.

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

Understanding the Growth of Electrodeposited PtNi Nanoparticle Films Using Correlated In Situ Liquid Cell Transmission Electron Microscopy and Synchrotron Radiation by Magdalena Parlinska-Wojtan, Tomasz Roman Tarnawski, Joanna Depciuch, Maria Letizia De Marco, Kamil Sobczak, Krzysztof Matlak, Mirosława Pawlyta, Robin E. Schaeublin, and See Wee Chee. Nano Lett. 2024, 24, 40, 12361–12367 DOI: https://doi.org/10.1021/acs.nanolett.4c02228 Published: August 15, 2024

This paper is open access.

About the same time in August 2024 that this paper from the Polish Academy of Sciences was published In Nano Letters there was another electrodeposition paper published by researchers at Northwestern University, which is mentioned in my August 23, 2024 posting, “Electricity (electrodeposition) could help fight coastal (beach) erosion.”

Explaining topological insulators with dance

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This must have been some high school physics class. A November 5, 2024 news item on ScienceDaily explains how physics topological insulators and dance intersected for three classes,

Science can be difficult to explain to the public. In fact, any subfield of science can be difficult to explain to another scientist who studies in a different area. Explaining a theoretical science concept to high school students requires a new way of thinking altogether.

This is precisely what researchers at the University of California San Diego did when they orchestrated a dance with high school students at Orange Glen High School in Escondido as a way to explain topological insulators.

The experiment, led by former graduate student Matthew Du and UC San Diego Associate Professor of Chemistry and Biochemistry Joel Yuen-Zhou, was published in Science Advances.

…

A November 5, 2024 University of California at San Diego (UC San Diego) news release (also on EurekAlert), which originated the news item, provides more detail about how the researchers employed dance to teach physics concepts, Note: A link has been removed,

“I think the concept is simple,” stated Yuen-Zhou. “But the math is much harder. We wanted to show that these complex ideas in theoretical and experimental physics and chemistry are actually not as impossible to understand as you might initially think.”

Topological insulators are a relatively new type of quantum material that has insulating properties on the inside, but have conductive properties on the outside. To use a Southern California staple, if a topological insulator was a burrito, the filling would be insulating and the tortilla would be conducting.

Since topological insulators are able to withstand some disorder and deformation, they can be synthesized and used under conditions where imperfections can arise. For this reason, they hold promise in the areas of quantum computing and lasers, and in creating more efficient electronics.

To bring these quantum materials to life, the researchers made a dance floor (topological insulator) by creating a grid with pieces of blue and red tape. Then to choreograph the dance, Du created a series of rules that governed how individual dancers moved.

These rules are based on what is known as a Hamiltonian in quantum mechanics. Electrons obey rules given by a Hamiltonian, which represents the total energy of a quantum system, including kinetic and potential energy. The Hamiltonian encodes the interactions of the electron in the potential energy of the material.

Each dancer (electron) had a pair of flags and was given a number that corresponded to a movement:

  •  1 = wave flags with arms pointing up
  •  0 = stand still
  • -1 = wave flags with arms pointing down

Subsequent moves were based on what a neighboring dancer did and the color of the tape on the floor. A dancer would mimic a neighbor with blue tape, but do the opposite of a neighbor with red tape. Individual mistakes or dancers leaving the floor didn’t disrupt the overall dance, exhibiting the robustness of topological insulators.

In addition to topology, Yuen-Zhou’s lab also studies chemical processes and photonics, and it was in thinking of light waves that they realized the movement of a group of people also resembled a wave. This gave Yuen-Zhou the idea of using dance to explain a complex topic like topological insulators. Implementing this idea seemed like a fun challenge to Du, who is currently a postdoctoral scholar at the University of Chicago and takes salsa lessons in his free time.

Du, who comes from a family of educators and is committed to scientific outreach, says the project gave him an appreciation for being able to distill science into its simplest elements.

“We wanted to demystify these concepts in a way that was unconventional and fun,” he stated. “Hopefully, the students were able to see that science can be made understandable and enjoyable by relating it to everyday life.”   

Full list of authors: Matthew Du, Juan B. Pérez-Sánchez, Jorge A. Campos-Gonzalez-Angulo, Arghadip Koner, Federico Mellini, Sindhana Pannir-Sivajothi, Yong Rui Poh, Kai Schwennicke, Kunyang Sun, Stephan van den Wildenberg, Alec Barron and Joel Yuen-Zhou (all UC San Diego); and Dylan Karzen (Orange Glen High School).

This research was supported by an National Science Foundation CAREER grant (CHE 1654732).

Here’s what it looked like,

series of overhead images of dancers on dance floor grid
Snapshots showing dancers on the edge of the topological insulator moving in a clockwise direction. Courtesy of University of California at San Diego

You may find this helps you to understand what’s happening in the pictures,

Before getting to a link and citation for the paper, here’s the paper’s abstract,

Topological insulators are insulators in the bulk but feature chiral energy propagation along the boundary. This property is topological in nature and therefore robust to disorder. Originally discovered in electronic materials, topologically protected boundary transport has since been observed in many other physical systems. Thus, it is natural to ask whether this phenomenon finds relevance in a broader context. We choreograph a dance in which a group of humans, arranged on a square grid, behave as a topological insulator. The dance features unidirectional flow of movement through dancers on the lattice edge. This effect persists when people are removed from the dance floor. Our work extends the applicability of wave physics to dance. [emphasis mine]

I wonder if we’re going to see some ‘wave physics’ inspired dance performances.

Finally, here’s a link to and a citation for the paper,

Chiral edge waves in a dance-based human topological insulator by Matthew Du, Juan B. Pérez-Sánchez, Jorge A. Campos-Gonzalez-Angulo, Arghadip Koner, Federico Mellini, Sindhana Pannir-Sivajothi, Yong Rui Poh, Kai Schwennicke, Kunyang Sun, Stephan van den Wildenberg, Dylan Karzen, Alec Barron, and Joel Yuen-Zhou. Science Advances 28 Aug 2024 Vol 10, Issue 35 DOI: 10.1126/sciadv.adh7810

This paper is open access.

I think this is the first year I’ve stumbled across two stories about physics and dance in one year. Here’s the other one, “Happy Canada Day! Breakdancing at the 2024 Paris Summer Olympics: physics in action + heat, mosquitoes, and sports” in a July 1, 2024 posting.

Miniature, soft lithium-ion battery constructed from biocompatible hydrogel droplets for bio-integrated devices

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The original headline for the University of Oxford press release was “Batteries for miniature bio-integrated devices and robotics” but it’s not clear to me what they mean by robotics (soft robots? robotic prostheses? something else?).

An October 25, 2024 news item on ScienceDaily announces the research,

University of Oxford researchers have made a significant step towards realising miniature, soft batteries for use in a variety of biomedical applications, including the defibrillation and pacing of heart tissues. The work has been published today [October 25, 2024] in the journal Nature Chemical Engineering.

…

An October 28, 2024 University of Oxford press release (also on EurekAlert but published October 25, 2024), which originated the lightly edited news item and posting on EurekAlert, provides more technical detail about this advance, Note: Links have been removed,

The development of tiny smart devices, smaller than a few cubic millimeters, demands equally small power sources. For minimally invasive biomedical devices that interact with biological tissues, these power sources must be fabricated from soft materials. Ideally, these should also have features such as high capacity, biocompatibility and biodegradability, triggerable activation, and the ability to be controlled remotely. To date, there has been no battery that can fulfil these requirements all at once.

To address these requirements, researchers from the University of Oxford’s Department of Chemistry and Department of Pharmacology have developed a miniature, soft lithium-ion battery constructed from biocompatible hydrogel droplets. Surfactant-supported assembly (assembly aided by soap-like molecules), a technique reported by the same group last year in the journal Nature (DOI: 10.1038/s41586-023-06295-y), is used to connect three microscale droplets of 10 nanolitres volume. Different lithium-ion particles contained in each of the two ends then generate the output energy.

‘Our droplet battery is light-activated, rechargeable, and biodegradable after use. To date, it is the smallest hydrogel lithium-ion battery and has a superior energy density’ said Dr Yujia Zhang (Department of Chemistry, University of Oxford), the lead researcher for the study and a starting Assistant Professor at the École Polytechnique Fédérale de Lausanne. ‘We used the droplet battery to power the movement of charged molecules between synthetic cells and to control the beating and defibrillation of mouse hearts. By including magnetic particles to control movement, the battery can also function as a mobile energy carrier.’

Proof-of-concept heart treatments were carried out in the laboratory of Professor Ming Lei (Department of Pharmacology), a senior electrophysiologist in cardiac arrhythmias. He said: ‘Cardiac arrhythmia is a leading cause of death worldwide. Our proof-of-concept application in animal models demonstrates an exciting new avenue of wireless and biodegradable devices for the management of arrhythmias.’

Professor Hagan Bayley (Department of Chemistry), the research group leader for the study, said: ‘The tiny soft lithium-ion battery is the most sophisticated in a series of microscale power packs developed by Dr Zhang and points to a fantastic future for biocompatible electronic devices that can operate under physiological conditions.’

The researchers have filed a patent application through Oxford University Innovation. They envisage that the tiny versatile battery, particularly relevant to small-scale robots for bioapplications, will open up new possibilities in various areas including clinical medicine.

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

A microscale soft lithium-ion battery for tissue stimulation by Yujia Zhang, Tianyi Sun, Xingyun Yang, Linna Zhou, Cheryl M. J. Tan, Ming Lei & Hagan Bayley. Nature Chemical Engineering volume 1, pages 691–701 (2024) DOI: https://doi.org/10.1038/s44286-024-00136-z Published online: 25 October 2024 Issue Date: November 2024

This paper is open access.

Now, I want to highlight a few items from the paper’s introduction, Note: Links have been removed,

The miniaturization of electronic devices is a burgeoning area of research1,2,3. Therefore, the development of tiny batteries to power these devices is of critical importance, and techniques such as three-dimensional (3D) printing4,5,6 and micro-origami assembly7 [emphases mine] are beginning to have an impact. For minimally invasive applications in biomedicine, batteries are also preferred to be soft, biocompatible and biodegradable, with additional functionality and responsiveness, such as triggerable activation and remote-controlled mobility8. However, at present, such a multifunctional microscale soft battery is not available. Although hydrogel-based lithium-ion (Li-ion) batteries demonstrate some of these features9,10,11,12, none currently exhibits microscale fabrication of the battery architecture, in terms of self-assembled integration of hydrogel-based cathode, separator and anode at the submillimeter level. Manual assembly of precrosslinked compartments11 or multistep deposition and crosslinking4 is necessary to avoid the mixing of materials from different compartments at the pregel (liquid) state or during the gelation process. This limitation not only makes it difficult to shrink hydrogel-based functional architectures but also hinders the implementation of high-density energy storage.

Toward that end, Zhang et al. have reported a miniaturized ionic power source by depositing lipid-supported networks of nanoliter hydrogel droplets13. The power source mimics the electrical eel [emphasis mine] by using internal ion gradients to generate ionic current14, and can induce neuronal modulation. However, the ionic power source has several limitations [emphasis mine] that should be addressed. First, the stored salt gradient produces less power than conventional Li-ion batteries, and the device cannot be fully recharged. Second, activation of the power source relies on temperature-triggered gelation and oil for buffer exchange, which is a demanding requirement. Third, the functionality of the power source is limited to the generation of ionic output, leaving the full versatility of synthetic tissues unexploited15,16,17. Last, but not least, while the power source can modulate the activity of neural microtissues, organ-level stimulation necessitates a higher and more stable output performance in physiological environments18.

Here, we present a miniature, soft, rechargeable Li-ion droplet battery (LiDB) made by depositing self-assembling [emphasis mine], nanoliter, lipid-supported, silk hydrogel droplets. The tiny hydrogel compartmentalization produces a superior energy density. The battery is switched on by ultraviolet (UV) light, which crosslinks the hydrogel and breaks the lipid barrier between droplets. The droplets are soft, biocompatible and biodegradable. The LiDBs can power charge molecule translocation between synthetic cells, defibrillate mouse hearts with ventricular arrhythmias and pace heart rhythms. Further, the LiDB can be translocated from one site to another magnetically.

This team has integrated a number of cutting edge (I think you can still call them that) techniques such as 3D printing and origami along with inspiration from electric eels (biomimicry) for using light as a power source. .Finally, there’s self-assembly or, as it’s sometimes known, bottom-up engineering, just like nature.

This work still needs to be tested in human clinical trials but taking that into account: Bravo to the researchers!

Supercapacitors and memristors

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Yes, as this October 23, 2024 Science China Press press release on EurekAlert notes, supercapacitors and memristors are not usually lumped together,

In a groundbreaking development, Professor Xingbin Yan and his team have successfully merged two seemingly disparate research areas: supercapacitors, traditionally used in energy storage, and memristors, integral to neuromorphic computing. Their study introduces a novel phenomenon—the memristive effect in supercapacitors.

“Scientifically, we combine two seemingly disparate research areas: supercapacitors, traditionally used in energy storage, and memristors, integral to neuromorphic computing.” Prof. Xingbin Yan said, “the introduction of memristive behavior in supercapacitors not only enriches the fundamental physics underlying capacitive and memristive components but also extends supercapacitor technology into the realm of artificial synapses. This advancement opens new avenues for developing neuromorphic devices with advanced functionalities, offering a fresh research paradigm for the field.”

In 1971, Chua et al. at UC Berkeley introduced the memristor, proposing it as the fourth fundamental circuit element. Memristors have variable resistance that retains its value after current stops, mimicking neuron behavior, and are considered key for future memory and AI devices. In 2008, HP Labs [R. Stanley Williams and his team] developed nanoscale memristors based on TiO2. However, solid-state devices struggle with simulating chemical synapses. Fluidic memristors are promising due to their biocompatibility and ability to perform various neuromorphic functions. Confining ions in nanoscale channels allows for functionalities like ion diodes and switches, with some systems exhibiting memristive effects.

In 2021, Bocquet [Marc Bocquet, Aix-Marseille Université] et al. predicted that two-dimensional nanoscopic channels could achieve ionic memory functions. Their simulations showed strong nonlinear transport effects in these channels. They confined electrolytes to a monolayer and observed that salts could form tightly bound pairs. Following this, Bocquet’s team created nanoscale fluidic devices with salt solutions, showing hysteresis effects and variable memory times. Similarly, Mao et al. found comparable results with polymer electrolyte brushes, demonstrating hysteresis and frequency-dependent I-V curves. Both studies highlight advancements in controlling ions in nanofluidic devices, mimicking biological systems.

Supercapacitors are known for their higher power density, rapid response, and long lifespan, making them essential for applications in electronics, aerospace, transportation, and smart grids. Recently, a novel type of capacitive ionic device, called supercapacitor-diodes (CAPodes), has been introduced. These devices enable controlled and selective unidirectional ion transport, enhancing the functionality of supercapacitors.

In supercapacitors, charge storage occurs through ion adsorption or rapid redox reactions at the electrode surface, a principle similar to that in fluidic memristors. Inspired by CAPodes, the innovative idea is to explore whether a supercapacitor can be designed with nano-ion channels within the electrode material to achieve memory performance similar to that of fluidic memristors. If feasible, this would not only enhance traditional energy storage but also enable hysteresis in the transport and redistribution of electrolyte ions under varying electric fields.

In this design, the nanochannels of the ZIF-7 electrode in an aqueous supercapacitor allow for the enrichment and dissipation of anionic species (OH−) under varying voltage regimes. This results in a hysteresis effect in ion conductivity, which imparts memristive behavior to the supercapacitor. Consequently, the CAPistor combines the programmable resistance and memory functions of an ionic memristor with the energy storage capabilities of a supercapacitor. This integration opens up new possibilities for extending supercapacitors’ traditional applications into advanced fields such as biomimetic nanofluidic ionics and neuromorphic computing.

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

Constructing a supercapacitor-memristor through non-linear ion transport in MOF nanochannels by Pei Tang, Pengwei Jing, Zhiyuan Luo, Kekang Liu, Xiaoxi Zhao, Yining Lao, Qianqian Yao, Chuyi Zhong, Qingfeng Fu, Jian Zhu, Yanghui Liu, Qingyun Dou, Xingbin Yan. National Science Review, Volume 11, Issue 10, October 2024, nwae322, DOI: https://doi.org/10.1093/nsr/nwae322 Published: 11 September 2024

This paper is open access.

Viscous electronics and graphene

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Caption: From cars on a highway to a viscous fluid like oil, our understanding of electron behaviour is being changed by new research. Credit: College of Design and Engineering, National University of Singapore

An October 21, 2024 news item on phys.org announces the new research illustrated in the above, Note: Links have been removed,

In high school science class, we learned that plugging a cable into an electrical circuit sets off a flow of electrons, powering everything from our lights to our phones. Traditionally, we’ve understood how electrons behave in metals and semiconductors through this simple model: electrons are imagined as tiny, independent particles, much like cars on an open highway—each one moving freely, without interacting much with the others.

It’s a straightforward perspective that has been the foundation of electronics for many years, helping us understand and design the electronic devices that underpin much of modern life.

However, this traditional view falls short in the case of some emerging quantum materials such as the ultrathin, and highly conductive material graphene. In these materials, rather than behaving like individual cars on a highway, electrons instead act together in a way that resembles a viscous fluid such as oil. This finding could be transformative for the future development of a broad range of technologies.

Assistant Professor Denis Bandurin and his team, who are from the Department of Materials Science and Engineering at the College of Design and Engineering at the National University of Singapore, are exploring how quantum materials interact with electromagnetic radiation at the nanoscale to uncover new scientific phenomena and their potential use in developing future technologies.

…

An October 21, 2024 National University of Singapore (NUS) press release (also on EurekAlert but lightly edited) by Asst Prof Denis Bandurin, which originated the news item, delves further into the topic,

In a recent study, published in Nature Nanotechnology, the team reported that when graphene is exposed to electromagnetic radiation of terahertz frequencies, electron fluid heats up and its viscosity is drastically reduced, resulting in lower electrical resistance – much like how oil, honey and other viscous fluids flow more easily as they are heated on a stove.

Advancing the frontiers of THz waves detection

Terahertz (THz) waves are a special and technologically challenging part of the electromagnetic spectrum – situated between microwaves and infrared light – that have a vast range of potential applications. Being able to detect THz waves could unlock major advances in technologies.

In communications for example, current Wi-Fi technology operates at several GHz, limiting how much data can be transmitted. THz radiation, with its much higher frequency, could serve as the “carrier frequency” for ultrafast, beyond 5G networks, enabling faster data transfer for Internet of Things (IoT) connected devices, self-driving cars and countless other applications.

In medical imaging and industrial quality control, THz waves can penetrate many materials, making them useful for non-invasive scans. They are also safer than X-rays, providing a highly selective and precise imaging tool.

Going further afield, THz vision enables observational astronomy, allowing scientists to observe distant galaxies and exoplanets that cannot be seen by visible light.

THz radiation therefore offers huge potential. However, until recently, detecting it has been a significant challenge. THz waves are too fast for traditional semiconductor chips to handle and too slow for conventional optoelectronic devices.

The Viscous Electron Bolometer

The study by the NUS team showed that by harnessing the viscosity reduction effect, scientists can create innovative devices that can detect THz waves by sensing the changes in electrical resistance. Indeed, in the current study, Asst Prof Bandurin and his team has developed a new class of electronic device called a viscous electron bolometer.

Representing the first practical, real-world application of viscous electronics – a concept that was once thought to be purely theoretical – these bolometers are able to sense changes in resistance extremely accurately and quickly, operating, in principle, at the pico-second scale. In other words, trillionths of a second.

Understanding and exploiting the way electrons move together as a collective fluid opens the way for us to completely rethink the design of electronic devices. With this in mind, Asst Prof Bandurin and his team are actively working on optimising these viscous electron bolometers for practical applications.

As scientists uncover more secrets in the emerging world of quantum materials, it’s clear that traditional models of electron behaviour are no longer sufficient. By embracing this new understanding of viscous electronics, we could be on the verge of unlocking a new wave of technological possibilities.

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

Viscous terahertz photoconductivity of hydrodynamic electrons in graphene by M. Kravtsov, A. L. Shilov, Y. Yang, T. Pryadilin, M. A. Kashchenko, O. Popova, M. Titova, D. Voropaev, Y. Wang, K. Shein, I. Gayduchenko, G. N. Goltsman, M. Lukianov, A. Kudriashov, T. Taniguchi, K. Watanabe, D. A. Svintsov, S. Adam, K. S. Novoselov, A. Principi & D. A. Bandurin. Nature Nanotechnology (2024)
DOI: https://doi.org/10.1038/s41565-024-01795-y Published: 07 October 2024

This paper is behind a paywall.

For anyone who noted the name ‘K.S. Novoselov’, it’s Konstantin Novoselov who along with Andre Geim received the 2011 Nobel prize in physics for their work with graphene.

Ancient 3D paper art (kirigami) and modern wireless technology

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The first nanokirigami (or nano-kirigami) story featured here was in a January 29, 2019 posting (Manipulating light at the nanoscale with kirigami-inspired technique). This latest story features a two-dimensional material and the kirigami technique, also, some researchers from the University of British Columbia (Canada).

An October 14, 2024 news item on ScienceDaily announces that the newly applied (ancient) technique could change wireless technology,

The future of wireless technology — from charging devices to boosting communication signals — relies on the antennas that transmit electromagnetic waves becoming increasingly versatile, durable and easy to manufacture. Researchers at Drexel University [Pennsylvania, US] and the University of British Columbia [UBC; Canada] believe kirigami, the ancient Japanese art of cutting and folding paper to create intricate three-dimensional designs, could provide a model for manufacturing the next generation of antennas.

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An October 14, 2024 Drexel University news release (also on EurekAlert), which originated the news item, provides more information (Note: Links have been removed),

Recently published in the journal Nature Communications, research from the Drexel-UBC team showed how kirigami — a variation of origami — can transform a single sheet of acetate coated with conductive MXene ink into a flexible 3D microwave antenna whose transmission frequency can be adjusted simply by pulling or squeezing to slightly shift its shape.

The proof of concept is significant, according to the researchers, because it represents a new way to quickly and cost-effectively manufacture an antenna by simply coating aqueous MXene ink onto a clear elastic polymer substrate material.

“For wireless technology to support advancements in fields like soft robotics and aerospace, antennas need to be designed for tunable performance and with ease of fabrication,” said Yury Gogotsi, PhD, Distinguished University and Bach Professor in Drexel’s College of Engineering, and a co-author of  the research. “Kirigami is a natural model for a manufacturing process, due to the simplicity with which complex 3D forms can be created from a single 2D piece of material.”

Standard microwave antennas can be reconfigured either electronically or by altering their physical shape. However, adding the necessary circuitry to control an antenna electronically can increase its complexity, making the antenna bulkier, more vulnerable to malfunction and more expensive to manufacture. By contrast, the process demonstrated in this joint work leverages physical shape change and can create antennas in a variety of intricate shapes and forms. These antennas are flexible, lightweight and durable, which are crucial factors for their survivability on movable robotics and aerospace components.

To create the test antennas, the researchers first coated a sheet of acetate with a special conductive ink, composed of a titanium carbide MXene, to create frequency-selective patterns. MXene ink is particularly useful in this application because its chemical composition allows it to adhere strongly to the substrate for a durable antenna and can be adjusted to reconfigure the transmission specifications of the antenna.

MXenes are a family of two-dimensional nanomaterials discovered by Drexel researchers in 2011 whose physical and electrochemical properties can be adjusted by slightly altering their chemical composition. MXenes have been widely used in the last decade for applications that require materials with precise physiochemical behavior, such as electromagnetic shielding, biofiltration and energy storage. They have also been explored for telecommunications applications for many years due to their efficiency in transmitting radio waves and their ability to be adjusted to selectively block and allow transmission of electromagnetic waves.

Using kirigami techniques, originally developed in Japan the 4th and 5th centuries A.D., the researchers made a series of parallel cuts in the MXene-coated surface. Pulling at the edges of the sheet triggered an array of square-shaped resonator antennas to spring from its two-dimensional surface. Varying the tension caused the angle of the array to shift — a capability that could be deployed to quickly adjust the communications configuration of the antennas. 

The researchers assembled two kirigami antenna arrays for testing. They also created a prototype of a co-planar resonator — a component used in sensors that naturally produces waves of a certain frequency — to showcase the versatility of the approach. In addition to communication applications, resonators and reconfigurable antennas could also be used for strain-sensing, according to the team.

“Frequency selective surfaces, like these antennas, are periodic structures that selectively transmit, reflect, or absorb electromagnetic waves at specific frequencies,” said Mohammad Zarifi, principal research chair, an associate professor at UBC, who helped  lead the research. “They have active and/or passive structures and are commonly used in applications such as antennas, radomes, and reflectors to control wave propagation direction in wireless communication at 5G and beyond platforms.”

The kirigami antennas proved effective at transmitting signals in three commonly used microwave frequency bands: 2-4 GHz, 4-8 GHz and 8-12 GHz. Additionally, the team found that shifting the geometry and direction of the substrate could redirect the waves from each resonator.

The frequency produced by the resonator shifted by 400 MHz as its shape was deformed under strain conditions – demonstrating that it could perform effectively as a strain sensor for monitoring the condition of infrastructure and buildings.

According to the team, these findings are the first step toward integrating the components on relevant structures and wireless devices. With kirigami’s myriad forms as their inspiration, the team will now seek to optimize the performance of the antennas by exploring new shapes, substrates and movements.

 “Our goal here was to simultaneously improve the adjustability of antenna performance as well as create a simple manufacturing process for new microwave components by incorporating a versatile MXene nanomaterial with kirigami-inspired designs,” said Omid Niksan, PhD, from [the] University of British Columbia, who was an author of the paper. “The next phase of this research will explore new materials and geometries for the antennas.”

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

MXene-based kirigami designs: showcasing reconfigurable frequency selectivity in microwave regime by Omid Niksan, Lingyi Bi, Yury Gogotsi & Mohammad H. Zarifi. Nature Communications volume 15, Article number: 7793 (2024) DOI: https://doi.org/10.1038/s41467-024-51853-1 Published: 06 September 2024

This paper is open access.

Neuromorphic wires (inspired by nerve cells) amplify their own signals—no amplifiers needed

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Katherine Bourzac’s September 16, 2024 article for the IEEE (Institute for Electrical and Electronics Engineers) Spectrum magazine provides an accessible (relatively speaking) description of a possible breakthrough for neuromorphic computing, Note: Links have been removed,

In electrical engineering, “we just take it for granted that the signal decays” as it travels, says Timothy Brown, a postdoc in materials physics at Sandia National Lab who was part of the group of researchers who made the self-amplifying device. Even the best wires and chip interconnects put up resistance to the flow of electrons, degrading signal quality over even relatively small distances. This constrains chip designs—lossy interconnects are broken up into ever smaller lengths, and signals are bolstered by buffers and drivers. A 1-square-centimeter chip has about 10,000 repeaters to drive signals, estimates R. Stanley Williams, a professor of computer engineering at Texas A&M University.

Williams is one of the pioneers of neuromorphic computing, which takes inspiration from the nervous system. Axons, the electrical cables that carry signals from the body of a nerve cell to synapses where they connect with projections from other cells, are made up of electrically resistant materials. Yet they can carry high fidelity signals over long distances. The longest axons in the human body are about 1 meter, running from the base of the spine to the feet. Blue whales are thought to have 30 m long axons stretching to the tips of their tails. If something bites the whale’s tail, it will react rapidly. Even from 30 meters away, “the pulses arrive perfectly,” says Williams. “That’s something that doesn’t exist in electrical engineering.”

That’s because axons are active transmission lines: they provide gain to the signal along their length. Williams says he started pondering how to mimic this in an inorganic system 12 years ago. A grant from the US Department of Energy enabled him to build a team with the necessary resources to make it happen. The team included Williams, Brown, and Suhas Kumar, a materials physicist at Sandia.

Axons are coated with an insulating layer called the myelin sheath. Where there are gaps in the sheath, negatively charged sodium ions and positively charged potassium ions can move in and out of the axon, changing the voltage across the cell membrane and pumping in energy in the process. Some of that energy gets taken up by the electrical signal, amplifying it.

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Williams and his team wanted to mimic this in a simple structure. They didn’t try to mimic all the physical structures in axons—instead, they sought guidance in a mathematical description of how they amplify signals. Axons operate in a mode called the “edge of chaos,” which combines stable and unstable qualities. This may seem inherently contradictory. Brown likens this kind of system to a saddle that’s curved with two dips. The saddle curves up towards the front and the back, keeping you stable as you rock back and forth. But if you get jostled from side to side, you’re more likely to fall off. When you’re riding in the saddle, you’re operating at the edge of chaos, in a semistable state. In the abstract space of electrical engineering, that jostling is equivalent to wiggles in current and voltage.

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There’s a long way to go from this first experimental demonstration to a reimagining of computer chip interconnects. The team is providing samples for other researchers [emphasis mine] who want to verify their measurements. And they’re trying other materials to see how well they do—LaCoO3 [lanthanum colbalt oxide] is only the first one they’ve tested.

Williams hopes this research will show electrical engineers new ideas about how to move forward. “The dream is to redesign chips,” he says. Electrical engineers have long known about nonlinear dynamics, but have hardly ever taken advantage of them, Williams says. “This requires thinking about things and doing measurements differently than they have been done for 50 years,” he says.

If you have the time, please read Bourzac’s September 16, 2024 article in its entirety. For those who want the technical nitty gritty, here’s a link to and a citation for the paper,

Axon-like active signal transmission by Timothy D. Brown, Alan Zhang, Frederick U. Nitta, Elliot D. Grant, Jenny L. Chong, Jacklyn Zhu, Sritharini Radhakrishnan, Mahnaz Islam, Elliot J. Fuller, A. Alec Talin, Patrick J. Shamberger, Eric Pop, R. Stanley Williams & Suhas Kumar. Nature volume 633, pages 804–810 (2024) DOI: https://doi.org/10.1038/s41586-024-07921 Published online: 11 September 2024 Issue Date: 26 September 2024

This paper is open access.

Huge leap forward in computing efficiency with Indian Institute of Science’s (IISc) neuromorphic (brainlike) platform

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This is pretty thrilling news in a September 11, 2024 Indian Institute of Science (IISc) press release (also on EurekAlert), Note: A link has been removed,

In a landmark advancement, researchers at the Indian Institute of Science (IISc) have developed a brain-inspired analog computing platform capable of storing and processing data in an astonishing 16,500 conductance states within a molecular film. Published today in the journal Nature, this breakthrough represents a huge step forward over traditional digital computers in which data storage and processing are limited to just two states. 

Such a platform could potentially bring complex AI tasks, like training Large Language Models (LLMs), to personal devices like laptops and smartphones, thus taking us closer to democratising the development of AI tools. These developments are currently restricted to resource-heavy data centres, due to a lack of energy-efficient hardware. With silicon electronics nearing saturation, designing brain-inspired accelerators that can work alongside silicon chips to deliver faster, more efficient AI is also becoming crucial.

“Neuromorphic computing has had its fair share of unsolved challenges for over a decade,” explains Sreetosh Goswami, Assistant Professor at the Centre for Nano Science and Engineering (CeNSE), IISc, who led the research team. “With this discovery, we have almost nailed the perfect system – a rare feat.”

The fundamental operation underlying most AI algorithms is quite basic – matrix multiplication, a concept taught in high school maths. But in digital computers, these calculations hog a lot of energy. The platform developed by the IISc team drastically cuts down both the time and energy involved, making these calculations a lot faster and easier.

The molecular system at the heart of the platform was designed by Sreebrata Goswami, Visiting Professor at CeNSE. As molecules and ions wiggle and move within a material film, they create countless unique memory states, many of which have been inaccessible so far. Most digital devices are only able to access two states (high and low conductance), without being able to tap into the infinite number of intermediate states possible.

By using precisely timed voltage pulses, the IISc team found a way to effectively trace a much larger number of molecular movements, and map each of these to a distinct electrical signal, forming an extensive “molecular diary” of different states. “This project brought together the precision of electrical engineering with the creativity of chemistry, letting us control molecular kinetics very precisely inside an electronic circuit powered by nanosecond voltage pulses,” explains Sreebrata Goswami.

Tapping into these tiny molecular changes allowed the team to create a highly precise and efficient neuromorphic accelerator, which can store and process data within the same location, similar to the human brain. Such accelerators can be seamlessly integrated with silicon circuits to boost their performance and energy efficiency. 

A key challenge that the team faced was characterising the various conductance states, which proved impossible using existing equipment. The team designed a custom circuit board that could measure voltages as tiny as a millionth of a volt, to pinpoint these individual states with unprecedented accuracy.

The team also turned this scientific discovery into a technological feat. They were able to recreate NASA’s iconic “Pillars of Creation” image from the James Webb Space Telescope data – originally created by a supercomputer – using just a tabletop computer. They were also able to do this at a fraction of the time and energy that traditional computers would need.

The team includes several students and research fellows at IISc. Deepak Sharma performed the circuit and system design and electrical characterisation, Santi Prasad Rath handled synthesis and fabrication, Bidyabhusan Kundu tackled the mathematical modelling, and Harivignesh S crafted bio-inspired neuronal response behaviour. The team also collaborated with Stanley Williams [also known as R. Stanley Williams], Professor at Texas A&M University and Damien Thompson, Professor at the University of Limerick. 

The researchers believe that this breakthrough could be one of India’s biggest leaps in AI hardware, putting the country on the map of global technology innovation. Navakanta Bhat, Professor at CeNSE and an expert in silicon electronics led the circuit and system design in this project. “What stands out is how we have transformed complex physics and chemistry understanding into groundbreaking technology for AI hardware,” he explains. “In the context of the India Semiconductor Mission, this development could be a game-changer, revolutionising industrial, consumer and strategic applications. The national importance of such research cannot be overstated.” 

With support from the Ministry of Electronics and Information Technology, the IISc team is now focused on developing a fully indigenous integrated neuromorphic chip. “This is a completely home-grown effort, from materials to circuits and systems,” emphasises Sreetosh Goswami. “We are well on our way to translating this technology into a system-on-a-chip.”  

Caption: Using their AI accelerator, the team recreated NASA’s iconic “Pillars of Creation” image from the James Webb Space Telescope data on a simple tabletop computer – achieving this in a fraction of the time and energy required by traditional systems. Credit: CeNSE, IISc

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

Linear symmetric self-selecting 14-bit kinetic molecular memristors by Deepak Sharma, Santi Prasad Rath, Bidyabhusan Kundu, Anil Korkmaz, Harivignesh S, Damien Thompson, Navakanta Bhat, Sreebrata Goswami, R. Stanley Williams & Sreetosh Goswami. Nature volume 633, pages 560–566 (2024) DOI: https://doi.org/10.1038/s41586-024-07902-2 Published online: 11 September 2024 Issue Date: 19 September 2024

This paper is behind a paywall.

How memristors retain information without a power source? A mystery solved

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A September 10, 2024 news item on ScienceDaily provides a technical explanation of how memristors, without a power source, can retain information,

Phase separation, when molecules part like oil and water, works alongside oxygen diffusion to help memristors — electrical components that store information using electrical resistance — retain information even after the power is shut off, according to a University of Michigan led study recently published in Matter.

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A September 11, 2024 University of Michigan press release (also on EurekAltert but published September 10, 2024), which originated the news item, delves further into the research,

Up to this point, explanations have not fully grasped how memristors retain information without a power source, known as nonvolatile memory, because models and experiments do not match up.

“While experiments have shown devices can retain information for over 10 years, the models used in the community show that information can only be retained for a few hours,” said Jingxian Li, U-M doctoral graduate of materials science and engineering and first author of the study.

To better understand the underlying phenomenon driving nonvolatile memristor memory, the researchers focused on a device known as resistive random access memory or RRAM, an alternative to the volatile RAM used in classical computing, and are particularly promising for energy-efficient artificial intelligence applications. 

The specific RRAM studied, a filament-type valence change memory (VCM), sandwiches an insulating tantalum oxide layer between two platinum electrodes. When a certain voltage is applied to the platinum electrodes, a conductive filament forms a tantalum ion bridge passing through the insulator to the electrodes, which allows electricity to flow, putting the cell in a low resistance state representing a “1” in binary code. If a different voltage is applied, the filament is dissolved as returning oxygen atoms react with the tantalum ions, “rusting” the conductive bridge and returning to a high resistance state, representing a binary code of “0”. 

It was once thought that RRAM retains information over time because oxygen is too slow to diffuse back. However, a series of experiments revealed that previous models have neglected the role of phase separation. 

“In these devices, oxygen ions prefer to be away from the filament and will never diffuse back, even after an indefinite period of time. This process is analogous to how a mixture of water and oil will not mix, no matter how much time we wait, because they have lower energy in a de-mixed state,” said Yiyang Li, U-M assistant professor of materials science and engineering and senior author of the study.

To test retention time, the researchers sped up experiments by increasing the temperature. One hour at 250°C is equivalent to about 100 years at 85°C—the typical temperature of a computer chip.

Using the extremely high-resolution imaging of atomic force microscopy, the researchers imaged filaments, which measure only about five nanometers or 20 atoms wide, forming within the one micron wide RRAM device.  

“We were surprised that we could find the filament in the device. It’s like finding a needle in a haystack,” Li said. 

The research team found that different sized filaments yielded different retention behavior. Filaments smaller than about 5 nanometers dissolved over time, whereas filaments larger than 5 nanometers strengthened over time. The size-based difference cannot be explained by diffusion alone.

Together, experimental results and models incorporating thermodynamic principles showed the formation and stability of conductive filaments depend on phase separation. 

The research team leveraged phase separation to extend memory retention from one day to well over 10 years in a rad-hard memory chip—a memory device built to withstand radiation exposure for use in space exploration. 

Other applications include in-memory computing for more energy efficient AI applications or memory devices for electronic skin—a stretchable electronic interface designed to mimic the sensory capabilities of human skin. Also known as e-skin, this material could be used to provide sensory feedback to prosthetic limbs, create new wearable fitness trackers or help robots develop tactile sensing for delicate tasks.

“We hope that our findings can inspire new ways to use phase separation to create information storage devices,” Li said.

Researchers at Ford Research, Dearborn; Oak Ridge National Laboratory; University at Albany; NY CREATES; Sandia National Laboratories; and Arizona State University, Tempe contributed to this study.

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

Thermodynamic origin of nonvolatility in resistive memory by Jingxian Li, Anirudh Appachar, Sabrina L. Peczonczyk, Elisa T. Harrison, Anton V. Ievlev, Ryan Hood, Dongjae Shin, Sangmin Yoo, Brianna Roest, Kai Sun, Karsten Beckmann, Olya Popova, Tony Chiang, William S. Wahby, Robin B. Jacobs-Godrim, Matthew J. Marinella, Petro Maksymovych, John T. Heron, Nathaniel Cady, Wei D. Lu, Suhas Kumar, A. Alec Talin, Wenhao Sun, Yiyang Li. Matter DOI: https://doi.org/10.1016/j.matt.2024.07.018 Published online: August 26, 2024

This paper is behind a paywall.