NT/ Nanobubble research to improve green hydrogen production

Paradigm

Published in

Paradigm

28 min readMay 27, 2024

Nanotechnology & nanomaterials biweekly vol.56, 13th May — 27th May

TL;DR

▫️ Researchers from the University of Twente discovered that micro- and nanobubbles on electrodes reduce the efficiency of water electrolysis for green hydrogen production.
▫️ A new technique from the Squires Lab creates colorful “FRETfluor” tags to label biomolecules, enhancing disease detection and genetic condition identification.
▫️ ETH Zurich developed a protein gel that breaks down alcohol in the gastrointestinal tract, reducing its harmful effects before entering the bloodstream.
▫️ A study in the *National Science Review* combines metal nanoplasmons with semiconductor optoelectronics for improved photonic chips.
▫️ Scientists improved X-ray imaging sharpness and processing speeds, enhancing medical imaging and security clearance.
▫️ City University of Hong Kong developed a pulse irradiation technique for synthesizing thin films at ultra-low temperatures.
▫️ Swedish researchers 3D printed silica glass micro-optics on optic fibers, enabling faster internet and improved connectivity.
▫️ An experimental plant virus treatment protects against metastatic cancers in mice, according to the University of California San Diego.
▫️ New research on two-dimensional materials like graphene shows that fast electronic processes can be probed with ion irradiation.
▫️ Deep learning enhances metalens camera image quality, making them viable for various imaging tasks, including microscopy and mobile devices.

Nanotech Market

Nanotechnology deals with the ability to see, understand, measure, predict, produce or control matter at the nanoscale (below 100 nanometers). The realm of nanotechnology lies between 0.1 and 100 nanometers, wherein a nanometer is defined as one-thousandth of a micron. As a versatile technology with widespread applications in a wide range of end-use sectors, nanotechnology is currently facing a mixed bag of challenges and opportunities as the COVID-19 pandemic continues to spread across the globe. With the world fighting its biggest public health crisis in history, nanotechnology healthcare applications are storming into the spotlight led by the focus on nano intervention in terms of designing effective ways to identify, diagnose, treat and eliminate the spread of COVID-19 infections. Their role as nanocarriers has the potential to design risk-free and effective immunization strategies. In the post-COVID-19 period, the use of nanotechnology solutions in the production of a multitude of devices & products will continue to grow.

Amid the COVID-19 crisis, the global market for Nanotechnology estimated at US$42.2 Billion in the year 2020, is projected to reach a revised size of US$70.7 Billion by 2026, growing at a CAGR of 9.2% over the analysis period. Nanocomposites, one of the segments analyzed in the report, is projected to record an 8.7% CAGR and reach US$35.4 Billion by the end of the analysis period. After a thorough analysis of the business implications of the pandemic and its induced economic crisis, growth in the Nanomaterials segment is readjusted to a revised 10.1% CAGR for the next 7-year period.

Global nanotechnology market to reach US $126.8 billion by the year 2027. Amid the COVID-19 crisis, the global market for Nanotechnology is estimated at US $54.2 billion in the year 2020 and is projected to reach a revised size of US $126 billion.

Latest News & Research

Threshold current density for diffusion-controlled stability of electrolytic surface nanobubbles

by Yixin Zhang et al in Proceedings of the National Academy of Sciences

In a novel study, published in Proceedings of the National Academy of Sciences, researchers from the University of Twente have made significant strides in understanding the behavior of micro- and nanobubbles on electrodes during water electrolysis. This process is crucial for (green) hydrogen production. These tiny bubbles form on the electrodes, blocking the flow of electricity and reducing the efficiency of the reaction.

A renewable hydrogen economy significantly reduces the impact of global warming compared to a fossil fuel economy. However, the production of hydrogen is significantly impeded by bubbles at the micro- and nanoscale. Therefore, researchers at the University of Twente try to precisely understand how these tiny bubbles form on and stick to the electrodes, to finally get rid of them.

Supported by advanced molecular simulations, Detlef Lohse and his team developed a theory that can successfully predict the electrical current density needed to let the nanobubbles grow uncontrollably and detach, thus freeing the electrode for further hydrogen production.

This finding is pivotal as it allows for the prediction and control of bubble behavior, ensuring that electrolysis can proceed with minimal disruption. The research builds upon the established stability theory for surface nanobubbles (Lohse-Zhang model) and extends it to include the electrolytic current density to predict the bubble behavior.

With the improved knowledge, scientists and engineers can now work towards enhancing the detachment of bubbles. Besides improving the overall efficiency of water electrolysis, this work can be used also for other systems where gas bubbles are formed, such as in catalysis.

Single-molecule fluorescence multiplexing by multi-parameter spectroscopic detection of nanostructured FRET labels

by Jiachong Chu et al, in Nature Nanotechnology

Researchers often study biomolecules such as proteins or amino acids by chemically attaching a “fluorophore,” a sensitive molecule that absorbs and re-emits energy from light.

When activated by a laser and imaged through a high-powered microscope, these fluorophore tags or labels explode in a rainbow of color and information. They provide a wealth of insight that can, for example, help detect diseases or identify genetic conditions.

To detect more than one type of molecule at a time, or “multiplex” measurements, additional types of fluorophores that emit different colors of light are used. But it is surprisingly difficult to tell different colors apart at the single-molecule level. This is why most microscopes only look at three to four colors.

Researchers can break this color barrier using advanced techniques that involve days-long rounds of labeling and imaging or employ complicated setups with many lasers. Finding a simple and fast way to see many colors, however, has remained a major challenge.

Researchers at the UChicago Pritzker School of Molecular Engineering have a novel solution to this challenge, outlined in a paper published in Nature Nanotechnology. A new technique outlined by the Squires Lab uses three simple chemical building blocks to engineer dozens of “FRETfluor” tags, creating a more beautiful, nuanced spectrum of colors researchers can use to label biomolecules.
“Our approach is easier. It’s one shot of labeling, one shot of imaging,” said co-first author Jiachong Chu, a UChicago Pritzker Molecular Engineering Ph.D. candidate. “That means you can do more with less. Currently, our novel technique is the best in the field.”

Individual molecules are small and cell samples are comparatively huge, complicated and messy. The ultimate goal of this area of research — one that the PME team’s paper put closer than ever — is multiplexing.

“Multiplexing samples means to be able to, in the same measurement, measure more than one species of molecule so maybe you have 10 or 50, or hundreds of different proteins that you want to identify,” said Neubauer Family Assistant Professor of Molecular Engineering Allison Squires. “With this new technique, we can do dozens. I believe we can extend that to hundreds.”

To tackle this challenge, the Squires Lab team found an innovative new way to use a well-established technique: Förster Resonance Energy Transfer or FRET. FRET is a mechanism that describes how energy is transferred between light-sensitive molecules. It’s one way for researchers to measure the distance between different parts of a molecule, or to report when two molecules interact. FRET signals are exceptionally sensitive to the properties of the participating fluorophores, which the UChicago team used to tune their FRETfluor labels.

“This project utilizes FRET in a new way,” said co-first author Ayesha Ejaz, a Ph.D. candidate in Chemistry. “FRET is commonly used for measuring distances and observing dynamics in biomolecules. We changed the spacing between a donor and acceptor dye to create different FRET efficiencies and other properties which we use to identify the different constructs.”

The 27 tags used in the PME team’s research were 27 “FRETfluors” they designed using a simple combination of DNA, a green cyanine dye (Cy3) and a red cyanine dye (Cy5). In addition to glowing in different colors, FRETfluors each exhibit other tunable properties such as the timing of how photons are emitted, or what the orientations of these photons are.

Together, these properties can be used to identify a FRETfluor in just a fraction of a second, at ultra-low concentrations. Ejaz said one possible future direction for this research is to eventually replace ordinary fluorophore tags with these FRETfluors.

“Usually, when people want to look at multiple things — such as different parts of a cell — at once, they label each component with a different fluorescent tag that emits a certain color of light. But fluorescent tags are limited to four or five colors,” Ejaz said.
“If FRETfluors can be used instead, then we can increase the number of ‘colors’ that are available for fluorescence microscopy. We are currently testing how well the FRETfluors work in different types of experiments and environments which will give us a better understanding of all the possibilities.”
“I’m excited to see the FRETfluors in action,” she said.

For Squires, much of the appeal of the new multiplexing technique comes from sensitivity combined with simplicity.

“Everybody wants to multiplex their favorite assay, and there are lots of existing strategies that will work in certain situations,” she said. “There are techniques that work well when you have tons of time, or when your sample is dead so that nothing moves.

“We’re attacking the problem where you don’t have tons of time. You want to know what disease somebody has while there’s still time to fight it, or you have only a teeny tiny bit of sample and you get one shot to identify each molecule as it flows through your channel. We can identify FRETfluors in a fraction of a second down to tens of femtomolar concentrations.”

Simplicity is key, both by using common chemicals to make the FRETfluors and by pioneering a technique that only needs one laser for readout.

“We only label to target once and only do the readout once,” Chu said. “Under that context, we can create 27 different tags that can be used at the same time.”

Squires described how existing techniques could be used together with FRETfluors for more multiplexing gains — “you could introduce fancy laser excitation schemes or incorporate other fluorophores that have slightly different properties” — that would improve the readouts from existing labels.

Applying these multipliers to their new, more powerful technique, Squires said, can open up worlds of new research and applications.

“These improvements to imaging and flow-based biomedical assays will enable the next generation of innovation,” Squires said.

Single-site iron-anchored amyloid hydrogels as catalytic platforms for alcohol detoxification

by Jiaqi Su in Nature Nanotechnology

Most alcohol enters the bloodstream via the mucous membrane layer of the stomach and the intestines. These days, the consequences of this are undisputed: even small amounts of alcohol impair people’s ability to concentrate and to react, increasing the risk of accidents.

Drinking large quantities on a regular basis is detrimental to one’s health: common consequences include liver disease, inflammation of the gastrointestinal tract and cancer. According to the World Health Organization, around 3 million people die every year from excessive alcohol consumption.

Researchers at ETH Zurich have now developed a protein gel that breaks down alcohol in the gastrointestinal tract. In a study recently published in the journal Nature Nanotechnology, they show that in mice, the gel converts alcohol quickly, efficiently and directly into harmless acetic acid before it enters the bloodstream, where it would normally develop its intoxicating and harmful effects.
“The gel shifts the breakdown of alcohol from the liver to the digestive tract. In contrast to when alcohol is metabolized in the liver, no harmful acetaldehyde is produced as an intermediate product,” explains Professor Raffaele Mezzenga from the Laboratory of Food & Soft Materials at ETH Zurich. Acetaldehyde is toxic and is responsible for many health problems caused by excessive alcohol consumption.

In the future, the gel could be taken orally before or during alcohol consumption to prevent blood alcohol levels from rising and acetaldehyde from damaging the body. In contrast to many products available on the market, the gel combats not only the symptoms of harmful alcohol consumption but also its causes.

Yet, the gel is only effective as long as there is still alcohol in the gastrointestinal tract. This means it can do very little to help with alcohol poisoning, once the alcohol has crossed into the bloodstream. Nor does it help to reduce alcohol consumption in general.

“It’s healthier not to drink alcohol at all. However, the gel could be of particular interest to people who don’t want to give up alcohol completely, but don’t want to put a strain on their bodies and aren’t actively seeking the effects of alcohol,” Mezzenga says.

The researchers used ordinary whey proteins to produce the gel. They boiled them for several hours to form long, thin fibrils. Adding salt and water as a solvent then causes the fibrils to cross-link and form a gel. The advantage of a gel over other delivery systems is that it is digested very slowly. But to break down the alcohol, the gel needs several catalysts.

The researchers used individual iron atoms as the main catalyst, which they distributed evenly over the surface of the long protein fibrils.

“We immersed the fibrils in an iron bath, so to speak, so that they can react effectively with the alcohol and convert it into acetic acid,” says ETH researcher Jiaqi Su, the first author of the study.

Tiny amounts of hydrogen peroxide are needed to trigger this reaction in the intestine. These are generated by an upstream reaction between glucose and gold nanoparticles. Gold was chosen as a catalyst for hydrogen peroxide because the precious metal is not digested and therefore stays effective for longer in the digestive tract. The researchers packed all these substances — iron, glucose and gold — into the gel. This resulted in a multi-stage cascade of enzymatic reactions that ultimately converts alcohol into acetic acid.

The researchers tested the effectiveness of the new gel on mice that were given alcohol just once as well as on mice that were given alcohol regularly for ten days.

Thirty minutes after the single dose of alcohol, the prophylactic application of the gel reduced the alcohol level in the mice by 40%. Five hours after alcohol intake, their blood alcohol level had dropped by as much as 56% compared to the control group. Harmful acetaldehyde accumulated less in these mice, and they exhibited greatly reduced stress reactions in their livers, which was reflected in better blood values.

In the mice that were given alcohol for ten days, the researchers were able to demonstrate not only a lower alcohol level but also a lasting therapeutic effect of the gel: the mice that were given the gel daily in addition to alcohol showed significantly less weight loss, less liver damage and hence better fat metabolism in the liver as well as better blood values.

Other organs in the mice, such as the spleen or the intestine, as well as their tissues also showed much less damage caused by alcohol.

In an earlier study of administering iron through whey protein fibrils, the researchers had discovered that iron reacts with alcohol to form acetic acid. As this process was too slow and too ineffective at the time, they changed the form in which they attached the iron to the protein fibrils.

“Instead of using larger nanoparticles, we opted for individual iron atoms, which can be distributed more evenly on the surface of the fibrils and therefore react more effectively and quickly with the alcohol,” Mezzenga says.

The researchers have already applied for a patent for the gel. While several clinical tests are still required before it can be authorized for human use, the researchers are confident that this step will also be successful, as they already showed that the whey protein fibrils that make up the gel are edible.

Optoelectronic tuning of plasmon resonances via optically modulated hot electrons

by Jiacheng Yao et al in National Science Review

Photonic computing, storage, and communication are the foundation for future photonic chips and all-optical neural networks. Nanoscale plasmons, with their ultrafast response speed and ultrasmall mode volume, play an important role in the integration of photonic chips. However, due to the limitations of materials and fundamental principles in many previous systems, they are often incompatible with existing optoelectronics, and their stability and operability are greatly compromised. A recent report in National Science Review describes research on the dynamic and reversible optical modulation of surface plasmons based on the transport of hot carriers. This research combines the high-speed response of metal nanoplasmons with the optoelectronic modulation of semiconductors.

By optically exciting the hot electrons, it modulates the charge density in gold and the conductivity of the nanogaps, which ultimately renders reversible and ultrafast switching of the plasmon resonances. Thus, it provides an important prototype for optoelectronic switches in nanophotonic chips.

This research was led by the research group of Professor Ding Tao at Wuhan University, in collaboration with Professor Hongxing Xu, Associate Professor Li Zhou and Research Professor Ti Wang, as well as Professor Ququan Wang from the Southern University of Science and Technology.

The research team first prepared Au@Cu2-xS core-shell nanoparticles and characterized their microstructure. The experimental results showed that the sol-gel method can yield Au@Cu2-xS core-shell nanoparticles with different shell thicknesses, providing an ideal carrier for realizing ultrafast dynamic control of nanoscale plasmons. Au@Cu2-xS nanoparticles on different substrates can achieve ultrafast dynamic control of plasmons.

Under laser irradiation, the plasmonic resonance peak of Au@Cu2-xS nanoparticles on the SiO2/Si substrate exhibits a red shift , while the plasmonic resonance peak of Au@Cu2-xS nanoparticles on the Au substrate exhibits a blue shift. When the laser is turned off, the resonance peaks return to their initial positions. All the optoelectronic tuning processes have shown reversibility, controllability, and relatively fast response speeds.

Transient absorption (TA) spectra and theoretic calculations indicate that the optical excitation of the Au@Cu2-xS plasmonic composite structure can cause the hot electrons in Au to transfer to Cu2-xS, leading to a decrease in the electron density of Au and a red shift of the localized surface plasmon resonance (LSPR).

In contrast, when the Au@Cu2-xS is placed on an Au substrate (NPoM structure), the hot electrons can be transported through the Cu2-xS layer to the Au substrate, increasing the conductivity of the nanogap and causing a blue shift of the coupled plasmon polaritons. This plasmonic control strategy based on hot carrier transport is particularly suitable for the integration of optoelectronic devices, providing device prototypes for photonic computing and interconnection.

The Nanoplasmonic Purcell Effect in Ultrafast and High‐Light‐Yield Perovskite Scintillators

by Wenzheng Ye et al, in Advanced Materials

Scientists have made a breakthrough in significantly improving the sharpness of X-ray imaging and potentially boosting the speeds at which X-ray scans can be processed. This lays the groundwork for both better medical imaging and faster security clearance.

Key to the advance is a layer of gold added to devices that help visualize X-rays.X-rays used in health and security scans are invisible, but they can be pictured using detectors that have “scintillating” materials that absorb the radiation and “light up” in a way similar to glow-in-the-dark paint. The visible light emitted by the scintillating materials is captured by sensors to create images based on the X-rays. The brighter the light, the sharper and more detailed the visuals.

The researchers, co-led by Nanyang Technological University, Singapore (NTU Singapore) and Poland’s Lukasiewicz Research Network-PORT Polish Center for Technology Development, discovered that adding a gold layer to the scintillating materials made the visible light they gave off 120% brighter. On average the light emitted had an intensity of around 88 photons per kiloelectronvolt, data from the study published in Advanced Materials showed.

As a result, the X-ray images produced were, in general, 38% sharper and the ability to distinguish between different parts of the images was improved by 182%.

With the gold layer, the time the scintillating materials took to stop emitting light after absorbing the X-rays was also shortened by 1.3 nanoseconds on average, or nearly 38%, meaning they were ready for the next round of radiation more quickly. This suggests the potential for gold to speed up the processing of X-ray scans.

These boosts can be explained because gold is “plasmonic,” meaning the electrons in the metal react to radiation by moving in synchronized wave-like patterns, akin to ripples forming after a pebble is dropped into water.

These rippling electrons, also called plasmons, can interact with scintillating materials to accelerate the emission of visible light by the materials after they react with X-rays. This then causes the light given off to become more intense.

This contrasts with non-plasmonic materials, whose electrons do not interact with radiation in the same way. As a result, they do not move in a coordinated wave-like manner and do not speed up visible light emission by scintillating materials.

For the research, the experiments used gold just 70 nanometers thick, or about 1,000 times thinner than a strand of hair. Using a thin layer of gold helps to keep material costs down and keeps the size of future X-ray detectors compact.

The researchers added the plasmonic gold layer to a scintillating material called butylammonium lead bromide, from the “perovskite” family of compounds. Perovskites are known for their ability to convert sunlight into electricity in solar cells.

This “nanoplasmonic” study was conducted in collaboration between the CNRS-International-NTU-Thales Research Alliance, an NTU-based French-Singaporean joint research laboratory; Institut Lumière Matière CNRS based in Université Claude Bernard Lyon 1 in France; and Nano Center Indonesia.

Nanyang Assistant Professor Wong Liang Jie, study co-lead from NTU Singapore’s School of Electrical and Electronic Engineering, said, “Our results highlight the enormous potential of nanoplasmonics in optimizing ultra-fast imaging systems where high spatial resolution and high contrast are needed, such as X-ray bioimaging and microscopy.”

Asst Prof Wong said that the improvements in X-ray detection demonstrated by the study stand to benefit airport security clearance too, as items in luggage might be more easily detected with crisper and higher-quality X-ray images, while bags could be screened more quickly.

Dr. Muhammad Danang Birowosuto, study co-lead from the Lukasiewicz Research Network-PORT Polish Center for Technology Development and a former NTU researcher, said, “Combining this improvement with other technologies will result in state-of-the-art functionalities in radiation imaging, such as to enhance X-ray analysis done in color or improve the accuracy of ‘time-of-flight’ X-ray medical imaging.”

A spokesman for multinational corporation Thales said that “the idea of combining the physical phenomena of photonic structures — structures that change how light behaves — with scintillating materials for X-ray detectors represents an interesting concept to increase the efficiency of the current generation of detectors.”
“Thales continues to monitor scientific advances in this area with great interest and welcomes Asst Prof Wong’s breakthrough in this area,” the spokesman added.

The inspiration to use gold as a plasmonic material together with scintillating materials arose from a marriage of two research areas that had not been explored before for X-ray detectors.

Members of the research team previously found that after certain substances absorbed visible light, they also gave off visible light, which could get brighter if thin plasmonic gold at the nanometer scale was added.

At the time, other members of the team, who study how nano-sized structures enhance X-ray generation, were also working on X-ray detection.

Looking at the nanoplasmonic findings, an idea struck the team: Since X-ray detection in X-ray scanners also depends on substances absorbing radiation to emit visible light, could nanoscale plasmonic materials augment detectors in these scanners?

The scientists then set out to prove this experimentally with gold.

The researchers are next planning to add nano-sized notch-like patterns to the surface of the gold layer to boost the visible light given off by X-ray absorbing scintillating materials, as earlier research has shown that tiny notches can enhance visible light production.

Dr. Dennis Schaart, head of the medical physics and technology section in the radiation science and technology department at the Netherlands’ Delft University of Technology, said that the findings “open a new avenue for the improvement of radiation imaging detectors based on scintillators.”

Scintillators convert X-ray or gamma-ray photons into measurable light signals for applications such as medical imaging in computed tomography (CT) scans, non-destructive testing like those for quality assurance in industrial production, and security clearance using airport baggage scanners.

Dr. Schaart — who researches novel technologies for medical imaging and radiation oncology and was not involved in the study — said that the performance limits of commonly known scintillation mechanisms are close to being reached. But there remains a persistent demand for even better solutions.

“The findings presented in this latest research point the way towards a new class of scintillation detectors in which the intensity and speed of light emission are enhanced through the manipulation of quantum-mechanical phenomena,” he said.
“In principle, this offers highly exciting prospects for scintillator developers to engineer optimal materials for a wide variety of applications. If the results presented in the research can be reproduced and scaled towards industrially produced scintillators, this will likely contribute to, for example, more accurate, more affordable and more accessible medical diagnosis, as well as faster security scans.”

Pulse irradiation synthesis of metal chalcogenides on flexible substrates for enhanced photothermoelectric performance

by Yuxuan Zhang et al in Nature Communications

The synthesis of metallic inorganic compound thin films typically requires high-temperature processes, which hampers their applications on flexible substrates. Recently, a research team at City University of Hong Kong (CityUHK) developed a pulse irradiation technique that synthesizes a variety of thin films in an extremely short time under ultra-low temperature.

The strategy effectively addresses the compatibility and cost issues of traditional high-temperature synthesis, and the prepared thermoelectric films exhibit excellent optoelectronic performance in the visible and near-infrared spectrum range, which is promising for wearable electronics and integrated optoelectronic circuits.

“Scalable film fabrication is key to meeting the requirements of next-generation optoelectronic devices. Our progress in this work ingeniously avoids the difficulties with traditional thin film preparation techniques, making it more broadly applicable for practical use,” said Professor Johnny Ho, Associate Vice-President (Enterprise) and Professor in the Department of Materials Science and Engineering at CityU, who led the study.

The key advantage of the low-temperature synthesis technique developed in this study is its applicability to various flexible substrates. The research team also made an intriguing discovery regarding the thermal effect of these substrates on the optoelectronic response of the resulting thermoelectric thin films. This finding opens up opportunities for achieving wide-spectrum detection capabilities.

The demand for flexible optoelectronic devices has spurred the need for advanced techniques with high throughput and low processing temperatures. However, when crystalline films are required, additional high-temperature processes are required. This requirement poses significant challenges when working with thermally unstable substrates and other device components.

To overcome these obstacles, the research team developed a novel pulse irradiation synthesis method that achieves both a low processing temperature and an ultra-short reaction time, surpassing the capabilities of conventional techniques.

With the new method for preparing metal sulfide thin films at low temperatures, these detectors can now achieve higher performance on suitable flexible substrates. This creates exciting possibilities for thermal imaging applications in security monitoring, fire detection, military surveillance, and other fields.

Additionally, the photothermoelectric effect allows for the conversion of invisible infrared light into electrical signals, paving the way for applications in high-speed communications and optical signal processing.

Looking ahead, the research team’s plans involve primarily optimizing performance and adjusting parameters, expanding material systems, and exploring the integration and feasibility of practical applications. These efforts aim to further enhance the potential of low-temperature synthesized metallic inorganic compound thin films and pave the way for the realization of advanced flexible optoelectronic devices.

Printing of Glass Micro-Optics with Subwavelength Features on Optical Fiber Tips

by Lee-Lun Lai et al, 3D in ACS Nano

In a first for communications, researchers in Sweden 3D printed silica glass micro-optics on the tips of optic fibers — surfaces as small as the cross section of a human hair. The advance could enable faster internet and improved connectivity, as well as innovations like smaller sensors and imaging systems. Reporting in the journal ACS Nano, researchers at KTH Royal Institute of Technology in Stockholm say integrating silica glass optical devices with optical fibers enables multiple innovations, including more sensitive remote sensors for environment and health care.

The printing techniques they report also could prove valuable in production of pharmaceuticals and chemicals.

KTH Professor Kristinn Gylfason says the method overcomes longstanding limitations in structuring optical fiber tips with silica glass, which he says often require high-temperature treatments that compromise the integrity of temperature-sensitive fiber coatings.

In contrast to other methods, the process begins with a base material that doesn’t contain carbon. That means high temperatures are not needed to drive out carbon in order to make the glass structure transparent.

The study’s lead author, Lee-Lun Lai, says the researchers printed a silica glass sensor that proved more resilient than a standard plastic-based sensor after multiple measurements.

“We demonstrated a glass refractive index sensor integrated onto the fiber tip that allowed us to measure the concentration of organic solvents. This measurement is challenging for polymer-based sensors due to the corrosiveness of the solvents,” Lai says.
“These structures are so small you could fit 1,000 of them on the surface of a grain of sand, which is about the size of sensors being used today,” says the study’s co-author, Po-Han Huang.

The researchers also demonstrated a technique for printing nanogratings, ultra-small patterns etched onto surfaces at the nanometer scale. These are used to manipulate light in precise ways and have potential applications in quantum communication.

Gylfason says the ability to 3D print arbitrary glass structures directly on fiber tip opens new frontiers in photonics.

“By bridging the gap between 3D printing and photonics, the implications of this research are far-reaching, with potential applications in microfluidic devices, MEMS accelerometers and fiber-integrated quantum emitters,” he says.

Systemic Administration of Cowpea Mosaic Virus Demonstrates Broad Protection Against Metastatic Cancers

by Young Hun Chung et al in Advanced Science

An experimental treatment made from a plant virus is effective at protecting against a broad range of metastatic cancers in mice, according to a new study from the University of California San Diego.

The treatment, composed of nanoparticles fashioned from the cowpea mosaic virus — a virus that infects black-eyed pea plants — showed remarkable success in improving survival rates and suppressing the growth of metastatic tumors across various cancer models, including colon, ovarian, melanoma and breast cancer. Similar outcomes were also observed when the treatment was administered to mice whose tumors were surgically removed.

The new study builds upon previous research by the lab of Nicole Steinmetz, a professor of nanoengineering, director of the Center for Nano-ImmunoEngineering and co-director of the Center for Engineering in Cancer, all at UC San Diego. Steinmetz and colleagues have been using cowpea mosaic virus nanoparticles to trigger the immune system to fight cancer and prevent it from spreading and recurring.

In early studies, the approach involved injecting the plant virus nanoparticles directly into tumors to stimulate an immune response. Even though the virus is non-infectious in mammals, the body’s immune cells still recognize it as foreign, triggering a robust immune reaction against the existing tumor, as well as any future tumors.

Now, Steinmetz and her team show that the plant virus nanoparticles do not need to be injected directly into tumors to be effective. Administering the nanoparticles systemically improved survival rates and inhibited metastasis across various cancer types.

“Here, we do not treat established tumors or metastatic disease — we prevent them from forming. We are providing a systemic treatment to wake up the body’s immune system to eliminate the disease before metastases even form and settle,” said Steinmetz.

To make the nanoparticles, the researchers grew black-eyed pea plants in the lab and infected them with cowpea mosaic virus. Millions of copies of the virus were grown and harvested in the form of ball-shaped nanoparticles, which required no further modification before use in experiments.

“Nature’s powerful nanoparticles, as produced in black-eyed pea plants,” said Steinmetz.

The researchers tested the efficacy of the treatment in mouse models of colon, ovarian, melanoma and breast cancers. Mice injected with cowpea mosaic virus nanoparticles — and then challenged with metastatic tumors a week later — exhibited improved survival rates and reduced tumor growth compared to untreated mice. Even when challenged with new tumors a month later, treated mice exhibited similar outcomes.

The researchers are particularly excited about the treatment’s effectiveness post-surgery. In another set of experiments, administering the nanoparticles after surgical removal of tumors resulted in improved survival rates and decreased tumor regrowth in mice.

“Even if you perform surgery to remove the tumors, no surgery is perfect and there is outgrowth of metastasis if no additional treatment is provided,” said Steinmetz.
“Here, we use our plant virus nanoparticles after surgery to boost the immune system to reject any residual disease and prevent circulating tumor cells from metastatic seeding. We found that it works really, really well.”

The goal is to gear up for clinical trials. As the research progresses, the team will be conducting safety studies and exploring the treatment’s efficacy in pet animals with cancer. Future studies will also focus on understanding the mechanisms underlying the immune-boosting properties of cowpea mosaic virus nanoparticles.

Nonequilibrium Dynamics of Electron Emission from Cold and Hot Graphene under Proton Irradiation

by Yifan Yao et al in Nano Letters

Two-dimensional materials such as graphene promise to form the basis of incredibly small and fast technologies, but this requires a detailed understanding of their electronic properties. New research demonstrates that fast electronic processes can be probed by irradiating the materials with ions first.

A collaboration involving researchers at the University of Illinois Urbana-Champaign and the University of Duisburg-Essen has shown that when graphene is irradiated with ions, or electrically charged atoms, the electrons that are ejected give information about the graphene’s electronic behavior.

Moreover, the Illinois group performed the first calculations involving high-temperature graphene, and the Duisburg-Essen group experimentally verified the predictions by irradiation.

“Irradiating materials and observing the change in properties to deduce what’s going on inside the material is a well-established technique, but now we are taking first steps towards using ions instead of laser light for that purpose,” said André Schleife, the Illinois group lead and a professor of materials science & engineering.
“The advantage is that ions allow highly localized, short-time excitations in the material compared to what laser light can do. This enables high-precision studies of how graphene and other 2D materials evolve over time.”

When an ion collides with a 2D material, energy is transferred to both the atomic nuclei and electrons. Some of the electrons are given enough energy to be ejected from the material. The features of these so-called “secondary electrons” are determined by the characteristics of the electrons in the material such as their temperature and distribution of energies.

“There’s a delay between the ion’s ‘impact’ and secondary electron emission, and that’s the key piece of information that we were after in our simulations,” said Yifan Yao, the study’s lead author and a graduate student in Schleife’s research group. “We did this for graphene at absolute zero with no thermal energy present as well as graphene that has thermal energy and a higher temperature. We’re actually the first to be simulating ‘hot’ graphene like this.”

The Illinois group performed calculations based on graphene irradiated with hydrogen ions — bare protons — and computed how secondary electrons were released over time and their resulting energy spectrum. These results agreed well with the Duisburg-Essen group’s results that used argon and xenon ions.

In addition, the computational study provides insight into the underlying mechanisms of secondary electron emission. High-temperature graphene released more secondary electrons, and a careful examination of the charge distributions indicated that the atomic nuclei in the material’s lattice rather than the material’s electrons are responsible.

According to Schleife, the promise of this technique goes beyond precision 2D material measurements.

“Looking years into the future, there’s a possibility that ion irradiation can be used to deliberately introduce defects into materials and manipulate them,” he said. “But, in the near term, we have shown that irradiation can be used as a high-precision measurement technique.”

Deep-learning enhanced high-quality imaging in metalens-integrated camera

by Yanxiang Zhang, Yue Wu, Chunyu Huang, Zi-Wen Zhou, Muyang Li, Zaichen Zhang, Ji Chen in Optics Letters

Researchers have leveraged deep learning techniques to enhance the image quality of a metalens camera. The new approach uses artificial intelligence to turn low-quality images into high-quality ones, which could make these cameras viable for a multitude of imaging tasks including intricate microscopy applications and mobile devices.

Metalenses are ultrathin optical devices — often just a fraction of a millimeter thick — that use nanostructures to manipulate light. Although their small size could potentially enable extremely compact and lightweight cameras without traditional optical lenses, it has been difficult to achieve the necessary image quality with these optical components.

“Our technology allows our metalens-based devices to overcome the limitations of image quality,” said research team leader Ji Chen from Southeast University in China. “This advance will play an important role in the future development of highly portable consumer imaging electronics and can also be used in specialized imaging applications such as microscopy.”

In Optica Publishing Group journal Optics Letters, the researchers describe how they used a type of machine learning known as a multi-scale convolutional neural network to improve resolution, contrast and distortion in images from a small camera — about 3 cm × 3 cm × 0.5 cm — they created by directly integrating a metalens onto a CMOS imaging chip.

“Metalens-integrated cameras can be directly incorporated into the imaging modules of smartphones, where they could replace the traditional refractive bulk lenses,” said Chen. “They could also be used in devices such as drones, where the small size and lightweight camera would ensure imaging quality without compromising the drone’s mobility.”

The camera used in the new work was previously developed by the researchers and uses a metalens with 1000-nm tall cylindrical silicon nitride nano-posts. The metalens focuses light directly onto a CMOS imaging sensor without requiring any other optical elements. Although this design created a very small camera the compact architecture limited the image quality. Thus, the researchers decided to see if machine learning could be used to improve the images.

Deep learning is a type of machine learning that uses artificial neural networks with multiple layers to automatically learn features from data and make complex decisions or predictions. The researchers applied this approach by using a convolution imaging model to generate a large number of high- and low-quality image pairs. These image pairs were used to train a multi-scale convolutional neural network so that it could recognize the characteristics of each type of image and use that to turn low-quality images into high-quality images.

“A key part of this work was developing a way to generate the large amount of training data needed for the neural network learning process,” said Chen. “Once trained, a low-quality image can be sent from the device to into the neural network for processing, and high-quality imaging results are obtained immediately.”

To validate the new deep learning technique, the researchers used it on 100 test images. They analyzed two commonly used image processing metrics: the peak signal-to-noise ratio and the structural similarity index. They found that the images processed by the neural network exhibited a significant improvement in both metrics. They also showed that the approach could rapidly generate high-quality imaging data that closely resembled what was captured directly through experimentation.

The researchers are now designing metalenses with complex functionalities — such as color or wide-angle imaging — and developing neural network methods for enhancing the imaging quality of these advanced metalenses. To make this technology practical for commercial application would require new assembly techniques for integrating metalenses into smartphone imaging modules and image quality enhancement software designed specifically for mobile phones.

“Ultra-lightweight and ultra-thin metalenses represent a revolutionary technology for future imaging and detection,” said Chen. “Leveraging deep learning techniques to optimize metalens performance marks a pivotal developmental trajectory. We foresee machine learning as a vital trend in advancing photonics research.”