NT/ Researchers ‘unzip’ 2D materials with lasers

Paradigm

Published in

Paradigm

27 min readMay 13, 2024

Nanotechnology & nanomaterials biweekly vol.55, 29th April — 13th May

TL;DR

Researchers used commercially available tabletop lasers to create tiny, atomically sharp nanostructures in samples of a layered 2D material called hexagonal Boron Nitride (hBN). The new nanopatterning technique is a simple way to modify materials with light — and it doesn’t involve an expensive and resource-intensive clean room.
Researchers from Japan have been working hard to keep their cool — or at least — keep their nanodevices from overheating. By adding a tiny coating of silicon dioxide to micro-sized silicon structures, they were able to show a significant increase in the rate of heat dissipated. This work may lead to smaller and cheaper electronic devices that can pack in more microcircuits.
Scientists have delved into the composition of nanocomposites for ultraviolet metasurface fabrication and determined the ideal printing material for crafting them. Their findings are featured in the journal Microsystems & Nanoengineering.
A new technique in building DNA structures at a microscopic level has the potential to advance drug delivery and disease diagnosis, a study suggests. A team of scientists, from the universities of Portsmouth and Leicester in the UK, has developed an innovative way to customize and strengthen DNA origami.
Researchers at Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine have developed a nanoparticle that can penetrate the blood-brain barrier. Their goal is to kill primary breast cancer tumors and brain metastases in one treatment, and their research shows the method can shrink breast and brain tumors in laboratory studies.
A research team has developed a new thin film deposition process for tin selenide-based materials. This process utilizes the metal-organic chemical vapor deposition (MOCVD) method, enabling thin film deposition on large wafer surfaces at a low temperature of 200°C, achieving exceptional precision and scalability.
Drug delivery researchers at Oregon State University have developed a device with the potential to improve gene therapy for patients with inherited lung diseases such as cystic fibrosis. In cell culture and mouse models, scientists in the OSU College of Pharmacy demonstrated a novel technique for the aerosolization of inhalable nanoparticles that can be used to carry messenger RNA, the technology underpinning COVID-19 vaccines, to patients’ lungs.
Move over, graphene. There’s a new, improved two-dimensional material in the lab. Borophene, the atomically thin version of boron first synthesized in 2015, is more conductive, thinner, lighter, stronger and more flexible than graphene, the 2D version of carbon. Now, researchers have made the material potentially more useful by imparting chirality — or handedness — on it, which could make for advanced sensors and implantable medical devices.
When old food packaging, discarded children’s toys and other mismanaged plastic waste break down into microplastics, they become even harder to clean up from oceans and waterways. These tiny bits of plastic also attract bacteria, including those that cause disease. Researchers describe swarms of microscale robots (microrobots) that capture bits of plastic and bacteria from water. Afterward, the bots were decontaminated and reused.
An international research team led by Universität Hamburg, DESY, and Stanford University has developed a new approach to characterize the electric field of arbitrary plasmonic samples, like, for example, gold nanoparticles. Plasmonic materials are of particular interest due to their extraordinary efficiency at absorbing light, which is crucial for renewable energy and other technologies.

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

Unzipping hBN with ultrashort mid-infrared pulses

by Cecilia Y. Chen, Samuel L. Moore, Rishi Maiti, Jared S. Ginsberg, M. Mehdi Jadidi, Baichang Li, Sang Hoon Chae, Anjaly Rajendran, Gauri N. Patwardhan, Kenji Watanabe, Takashi Taniguchi, James Hone, D. N. Basov, Alexander L. Gaeta in Science Advances

In a new paper published in the journal Science Advances, researchers at Columbia Engineering used commercially available tabletop lasers to create tiny, atomically sharp nanostructures, or nanopatterns, in samples of a layered 2D material called hexagonal boron nitride (hBN).

While exploring potential applications of their nanopatterned structures with colleagues in the Physics Department, the team found that their laser-cut hBN samples could effectively create and capture quasiparticles called phonon-polaritons, which occur when atomic vibrations in a material combine with photons of light.

“Nanopatterning is a major component of material development,” explained engineering PhD student Cecilia Chen, who led the development of the technique. “If you want to turn a cool material with interesting properties into something that can perform specific functions, you need a way to modify and control it.”

The new nanopatterning technique, developed in the lab of Professor Alexander Gaeta, is a simple way to modify materials with light — and it doesn’t involve an expensive and resource-intensive clean room.

Several well-established techniques exist to modify materials and create desired nanopatterns, but they tend to require extensive training and expensive overhead. Electron beam lithography machines, for example, must be housed in carefully controlled clean rooms, while existing laser options involve high heat and plasmas that can easily damage samples; the size of the laser itself also limits the size of the patterns that can be created.

The Gaeta lab’s technique takes advantage of what’s known in the optics and photonics community as “optical driving.” All materials vibrate at a particular resonance. Chen and her colleagues can enhance those vibrations by tuning their lasers to that frequency — corresponding to a wavelength of 7.3 micrometers, in the case of hBN — which they first demonstrated in research published last November in Nature Communications. In the newly published work, they pushed hBN to even more intense vibrations, but rather than damaging the underlying atomic structure, the lasers broke the crystal lattice cleanly apart. According to Chen, the effect was visible under the microscope and looked like unzipping a zipper.

The resulting lines across the sample were atomically sharp and much smaller — just a few nanometers — than the mid-infrared laser wavelengths used to create them.

“Usually, you need a shorter wavelength to make a smaller pattern,” said Chen. “Here, we can create very sharp nanostructures using very long wavelengths. It’s a paradoxical phenomenon.”

To explore what they could do with their nanopatterned samples, the engineering team teamed up with physicist Dmitri Basov’s lab, which specializes in creating and controlling nano-optical effects in different 2D materials — including creating phonon-polaritons in hBN. These vibrating quasiparticles can help scientists “see” beyond the diffraction limit of conventional microscopes and detect features in the material that give rise to quantum phenomena. They could also be a key component to miniaturizing optical devices, as electronics have become smaller over the years.

“Modern society is based on miniaturization, but it’s been much harder to shrink devices that rely on light than electrons,” explained physics PhD student and co-author Samuel Moore. “By harnessing strong hBN atomic vibrations, we can shrink infrared light wavelengths by orders of magnitude.”

Ultrasharp edges are needed to excite phonon-polaritons — normally, they are launched from the sides of flakes of hBN prepared via what’s known as the “Scotch tape” method, in which a bulk crystal is mechanically peeled into thinner layers using household tape. However, the team found that the laser-cut lines offer even more favorable conditions for creating the quasiparticles.

“It’s impressive how the laser-cut hBN regions launch phonon polaritons even more efficiently than the edge, suggesting an ultra-narrow unzipped hBN region that strongly interacts with infrared light,” said Moore.

As the new technique can create nanostructures anywhere on a sample, they also unzipped two lines in parallel. This creates a small cavity that can confine the phonon-polaritons in place, which enhances their nano-optical sensitivity. The team found that their unzipped cavities had comparable performance in capturing the quasiparticles to conventional cavities created in clean rooms.

“Our results suggest that our preliminary structures can compete with those created from more established methods,” noted Chen.

The technique can create many customizable nanopatterns. Beyond two-line cavities, it can create any number of parallel lines. If such arrays can be produced on-demand with any desired spacings, it could greatly improve phonon-polaritons’ imaging ability and would be a huge achievement, said Moore.

A break can be extended as long as desired once started, and samples as thick as 80 nanometers and as thin as 24 nanometers have been unzipped — theoretically, the bound could be much lower. This gives researchers plenty of options to modify hBN and explore how its nanopatterning can influence its resulting properties, without having to gear up in a clean room bunny suit.

“It really just depends on your ultimate goal,” said Chen.

That said, she still sees plenty of room to improve. Because hBN is a series of repeating hexagons, the technique only produces straight or angled lines meeting at either 60° or 120° at the moment, though Chen thinks combining them into triangles should be possible. Currently, the breaks can only occur in-plane as well; if they can determine how to target out-of-plane vibrations, they could potentially shave a bulk crystal down into different three-dimensional shapes. They are also limited by the power of their lasers, which they spent years carefully tuning to work stably at the desired wavelengths. While their mid-IR setup is well-suited to modifying hBN, different lasers would be needed to modify materials with different resonances.

Regardless, Chen is excited about the team’s concept and what it might be able to do in the future. As a member of the ultrafast-laser subgroup in the Gaeta Lab, Chen helped with their transition from creating and studying high-powered lasers to using those as tools to probe the optical properties of 2D materials.

That problem shared similarities to other problems Chen tackles in her time outside the lab as a boulderer, a form of rock climbing in which climbers scrabble up low, rugged rock faces without harness equipment to catch them if they fall.

“In bouldering, the potential climbing routes are called problems, and there’s no right answer to solving them,” she said. The best solutions cannot be brute forced, she continued: “You have to come up with a plan or you won’t be successful, whether figuring out how to exploit macroscopic features in a boulder or microscopic ones in a tiny crystal.”

Enhanced Far-Field Thermal Radiation through a Polaritonic Waveguide

by Saeko Tachikawa et al in Physical Review Letters

Researchers from Japan have been working hard to keep their cool — or at least — keep their nanodevices from overheating. By adding a tiny coating of silicon dioxide to micro-sized silicon structures, they were able to show a significant increase in the rate of heat dissipated. This work may lead to smaller and cheaper electronic devices that can pack in more microcircuits.

As consumer electronics become ever more compact, while still boasting increased processing power, the need to manage waste heat from microcircuits has grown to become a major concern.

Some scientific instruments and nanoscale machines require careful consideration of how localized heat will be shunted out of the device in order to prevent damage.

Some cooling occurs when heat is radiated away as electromagnetic waves — similar to how the sun’s power reaches the Earth through the vacuum of space. However, the rate of energy transfer can be too slow to protect the performance of sensitive and densely packed integrated electronic circuits.

For the next generation of devices to be developed, novel approaches may need to be established to address this issue of heat transmission.

In a study recently published in the journal Physical Review Letters, researchers from Institute of Industrial Science, The University of Tokyo, showed how the rate of radiative heat transfer can be doubled between two micro-scale silicon plates separated by a tiny gap.

The key was using a coating of silicon dioxide that created a coupling between the thermal vibrations of the plate at the surface (called phonons) and the photons (which make up the radiation).

“We were able to show both theoretically and experimentally how electromagnetic waves were excited at the interface of the oxide layer that enhanced the rate of heat transfer,” lead author of the study, Saeko Tachikawa says.

The small size of the layers compared with the wavelengths of the electromagnetic energy and its attachment to the silicon plate, which carries the energy without loss, allowed the device to surpass the normal limits of heat transfer, and thus cool faster.

Because current microelectronics are already based on silicon, the findings of this research could be easily integrated into future generations of semiconductor devices.

“Our work provides insight into possible heat dissipation management strategies in the semiconductor industry, along with various other related fields such as nanotech manufacturing,” says senior author, Masahiro Nomura.

The research also helps to establish a better fundamental understanding of how heat transfer works at the nanoscale level, since this is still an area of active research.

Tailoring high-refractive-index nanocomposites for manufacturing of ultraviolet metasurfaces

by Hyunjung Kang et al in Microsystems & Nanoengineering

Researchers have delved into the composition of nanocomposites for ultraviolet metasurface fabrication and determined the ideal printing material for crafting them.

Metasurfaces, ultra-thin optical devices, possess the remarkable ability to control light down to a mere nanometer thickness. Metasurfaces have consistently been the subject of research as a pivotal technology for the advancement of next-generation displays, imaging, and biosensing. Their reach extends beyond visible light, delving into the realms of infrared and ultraviolet light.

Nanoimprint lithography is a technology in metasurface production, akin to a stamp generating numerous replicas from a single mold. This innovative technique promises affordable and large-scale manufacturing of metasurfaces, paving the way for their commercial viability. However, the resin utilized as the printing material suffers from a drawback — a low refractive index, hindering efficient light manipulation.

To tackle this challenge, researchers are actively exploring nanocomposites, integrating nanoparticles into the resin to boost its refractive index. Yet, the efficacy of this approach depends on various factors such as nanoparticle type and solvent choice, necessitating a systematic analysis for optimal metasurface performance.

In their research, the team meticulously designed experiments to evaluate the impact of nanoparticle concentration and solvent selection on pattern transfer and UV metaholograms.

Specifically, they manipulated the concentration of zirconium dioxide (ZrO2), a nanocomposite renowned for its effectiveness in UV metahologram production, ranging from 20% to 90%. The findings showed that the highest pattern transfer efficiency was attained at an 80% concentration level.

Moreover, when combining ZrO2 at an 80% concentration with various solvents such as methylisobutyl ketone, methyl ethyl ketone, and acetone for metahologram realization, the conversion efficiency soared in the ultraviolet spectrum (325 nm), reaching impressive levels of 62.3%, 51.4%, and 61.5%, respectively.

This research marks a significant milestone by establishing an optimal metric for achieving metaholograms specifically tailored for the ultraviolet domain, as opposed to the visible range, while also pioneering the development of new nanocomposites.

Professor Junsuk Rho from Pohang University of Science and Technology (POSTECH) said, “The use of titanium dioxide (TiO2) and silicon (Si) nanocomposites instead of ZrO2 expands the applicability to visible and infrared light.”
“Our future research endeavors will focus on refining the preparation conditions for optimal nanocomposites, thus propelling the advancement, application and expansion of optical metasurface fabrication technology.”

Functionalizing DNA Origami by Triplex-Directed Site-Specific Photo-Cross-Linking

by Shantam Kalra et al in Journal of the American Chemical Society

A new technique in building DNA structures at a microscopic level has the potential to advance drug delivery and disease diagnosis, a study suggests. A team of scientists, from the universities of Portsmouth and Leicester in the UK, has developed an innovative way to customize and strengthen DNA origami.

DNA origami is the method of creating nanostructures with remarkable precision using DNA strands as building blocks. However, these structures are delicate and can fall apart easily under biological conditions, like changes in temperature or exposure to certain enzymes found in living organisms.

In a paper, published in the Journal of the American Chemical Society, researchers have presented a unique way to make the origami structures stronger and more versatile in a one-pot reaction, via a process known as triplex-directed photo-cross-linking.

By strategically modifying DNA strands during the design process, they were able to introduce additional nucleotide sequences — which are the basic building blocks of DNA — that serve as attachment points for functional molecules.

Attachment of the molecules was achieved by using triplex-forming oligonucleotides carrying a cross-linking agent. They then used a chemical process involving UVA light to permanently link these molecules to the DNA shapes.

A particular benefit of this approach is the generation of “super-staples” that act to weave the structure together. The paper says cross-linking to regions outside of the origami core dramatically reduces the structure’s sensitivity to heat and disassembly by enzymes.

Senior author, Dr. David Rusling from the University of Portsmouth’s School of Pharmacy and Biomedical Sciences, said, “The potential applications of this technique are far-reaching. The ability to tailor DNA origami structures with specific functionalities holds immense promise for advancing medical treatments and diagnostics.
“We envision a future where DNA origami structures could be used to deliver drugs or DNA directly to diseased cells, or to create highly sensitive diagnostic tools.”

Current applications of DNA origami in biomedicine include vaccines, biological nanosensors, drug delivery, structural biology, and delivery vehicles for genetic materials.

Co-author Dr. Andrey Revyakin, formerly from the University of Leicester, said, “My lab has struggled for years to make DNA origami structures that remain functional in real-life biological applications. Dr. Rusling’s triplex-based method, which ‘upgrades’ the classical DNA double-helix with an additional, third strand, stabilizes the DNA shapes, and does so with great precision, without affecting the functional modules of the molecule.”

The paper says the new strategy is scalable and cost-effective, as it works with existing origami structures, does not require scaffold redesign, and can be achieved with just one DNA strand.

Dr. Rusling added, “What is really exciting about this technique is that it did not change the underlying origami DNA sequence, offering the ability to use these structures as carriers for synthetic genes.”

Simultaneous targeting of peripheral and brain tumors with a therapeutic nanoparticle to disrupt metabolic adaptability at both sites

by Dhar, Shanta in Proceedings of the National Academy of Sciences

Researchers at Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine have developed a nanoparticle that can penetrate the blood-brain barrier. Their goal is to kill primary breast cancer tumors and brain metastases in one treatment, and their research shows the method can shrink breast and brain tumors in laboratory studies.

Brain metastases, as these secondary tumors are called, most commonly arise from solid tumors like breast, lung and colon cancer and are often associated with a poor prognosis. When cancer breaches the brain, it can be difficult for treatment to follow, in part because of the blood-brain barrier, a near-impenetrable membrane that separates the brain from the rest of the body.

The Sylvester team’s nanoparticle may one day be used to treat the metastases with the added benefit of treating the primary tumor at the same time, according to Shanta Dhar, Ph.D., an associate professor of Biochemistry and Molecular Biology and assistant director of Technology and Innovation at Sylvester, who led the study. She is the senior author of a paper published May 6 in the journal Proceedings of the National Academy of Sciences.

By loading the particle with two prodrugs that target mitochondria, the energy production center of the cell, the researchers showed that their method could shrink breast and brain tumors in preclinical studies.

“I always say nanomedicine is the future, but of course we have already been in that future,” said Dhar, referring to commercially available COVID-19 vaccines, which use nanoparticles in their formulation. “Nanomedicine is definitely also the future for cancer therapeutics.”

The new method uses a nanoparticle made of a biodegradable polymer, previously developed by Dhar’s team, coupled with two drugs also developed in her lab that take aim at cancer’s energy sources. Because cancer cells often have a different form of metabolism than healthy cells, stifling their metabolism can be an effective way to kill tumors without harming other tissues.

One of these drugs is a modified version of a classic chemotherapy drug, cisplatin, which kills cancer cells by damaging DNA in rapidly growing cells, effectively halting their growth. But tumor cells can repair their DNA, sometimes leading to cisplatin resistance.

Dhar’s team modified the drug to shift its target from nuclear DNA, the DNA that makes up our chromosomes and genome, to mitochondrial DNA. Mitochondria are our cells’ energy sources and contain their own, much smaller genomes — and, importantly for cancer therapeutic purposes, they don’t have the same DNA-repair machinery that our larger genomes do.

Because cancer cells can switch between different energy sources to sustain their growth and proliferation, the researchers combined their modified cisplatin, which they call Platin-M and attacks the energy-generating process known as oxidative phosphorylation, with another drug they developed, Mito-DCA, that specifically targets a mitochondrial protein known as a kinase and inhibits glycolysis, a different kind of energy generation.

Dhar said it was a long route to develop a nanoparticle that can access the brain. She has been working on nanoparticles for her whole independent career, and in a previous project studying different forms of polymers, the researchers noticed that a small fraction of some of these nanoparticles reached the brain in preclinical studies. By honing those polymers further, Dhar’s team developed a nanoparticle that can cross both the blood-brain barrier and the outer membrane of mitochondria.

“There have been a lot of ups and downs to figuring this out, and we’re still working to understand the mechanism by which these particles cross the blood-brain barrier,” Dhar said.

The team then tested the specialized drug-loaded nanoparticle in preclinical studies and found that they work to shrink both breast tumors and breast cancer cells that were seeded in the brain to form tumors there. The nanoparticle-drug combination also appeared to be nontoxic and significantly extended survival in lab studies.

Next, the team wants to test their method in the lab to replicate human brain metastases more closely, perhaps even using patient-derived cancer cells. They also want to test the drug in laboratory models of glioblastoma, a particularly aggressive brain cancer.

“I’m really interested in polymer chemistry, and using that toward medical purposes really fascinates me,” said Akash Ashokan, a University of Miami doctoral student working in Dhar’s lab and co-first author on the study along with doctoral student Shrita Sarkar. “It’s great to see that applied toward cancer therapeutics.”

Phase‐Centric MOCVD Enabled Synthetic Approaches for Wafer‐Scale 2D Tin Selenides

by Sungyeon Kim et al in Advanced Materials

A research team has developed a new thin film deposition process for tin selenide-based materials. This process utilizes the metal-organic chemical vapor deposition (MOCVD) method, enabling thin film deposition on large wafer surfaces at a low temperature of 200°C, achieving exceptional precision and scalability.

MOCVD is a cutting-edge technique that employs gaseous precursors to carry out chemical reactions with outstanding precision, making it possible to deposit thin films on wafer-scale materials used in semiconductors.

Thanks to this innovative method, the team was able to synthesize tin selenide materials (SnSe2, SnSe) with uniform thicknesses in just a few nanometers on wafer units.

To achieve deposition at low temperatures, the team strategically separated the temperature sections for ligand decomposition and thin film deposition. By adjusting the ratio of tin and selenium precursors as well as the flow rate of argon gas carrying the precursor, they were able to meticulously control the deposition process, resulting in high crystallinity, regular alignment, and controlled phase and thickness of the thin films.

This advanced process allowed for the uniform deposition of thin films at a low temperature of approximately 200°C, regardless of the substrate used, showcasing its potential for various electronic applications on a large scale. The team successfully applied this method to the entire wafer, maintaining chemical stability and high crystallinity in both types of tin selenide thin films.

The research team was led by Professor Joonki Suh in the Graduate School of Semiconductor Materials and Devices Engineering and the Department of Materials Science and Engineering at UNIST, in collaboration with Professor Feng Ding from the Chinese Academy of Sciences in China, Professor Sungkyu Kim from Sejong University, and Professor Changwook Jeong of UNIST.

Lead author Kim emphasized the significance of this study in overcoming limitations of existing deposition methods, demonstrating the capability to deposit polyphase materials over large areas without altering chemical composition. This breakthrough opens doors for applications in electronic devices and further research on tin selenide-based materials.

Professor Suh highlighted the innovative nature of this study in proposing a unique process strategy based on thermodynamic and dynamic behavior according to the phase of semiconductor thin film materials. The team aims to advance research on electronic device applications by developing customized processes for next-generation semiconductor materials.

Microfluidic Platform Enables Shearless Aerosolization of Lipid Nanoparticles for mRNA Inhalation

Jeonghwan Kim et al in ACS Nano

Drug delivery researchers at Oregon State University have developed a device with the potential to improve gene therapy for patients with inherited lung diseases such as cystic fibrosis.

In cell culture and mouse models, scientists in the OSU College of Pharmacy demonstrated a novel technique for the aerosolization of inhalable nanoparticles that can be used to carry messenger RNA, the technology underpinning COVID-19 vaccines, to patients’ lungs.

The findings are important because the current nebulization method for nanoparticles subjects them to shear stress, hindering their ability to encapsulate the genetic material and causing them to aggregate in certain areas of the lungs rather than spread out evenly, the researchers said.

Sahay’s lab studies lipid nanoparticles, or LNPs, as a gene delivery vehicle with a focus on cystic fibrosis, a progressive genetic disorder that results in persistent lung infection and affects 30,000 people in the U.S., with about 1,000 new cases identified every year.

One faulty gene — the cystic fibrosis transmembrane conductance regulator, or CFTR — causes the disease, which is characterized by lung dehydration and mucus buildup that blocks the airway.

Lipids are organic compounds containing fatty tails and are found in many natural oils and waxes, and nanoparticles are tiny pieces of material ranging in size from one- to 100-billionths of a meter. Messenger RNA delivers instructions to cells for making a particular protein.

With the coronavirus vaccines, the mRNA carried by the lipid nanoparticles instructs cells to make a harmless piece of the virus’ spike protein, which triggers an immune response from the body. As a therapy for cystic fibrosis, the genetic material would fix the flaw in patients’ CFTR gene.

“We utilized a novel microfluidic chip that helps in generation of plumes that carry nanoparticles and does not cause any shear stress,” Sahay said. “This device is based on the similar idea of an ink-jet cartridge that generates plumes to print words on paper.”

Four years ago, Sahay said, an Oregon-based startup called Rare Air Health Inc. contacted him about the prospect of using microfluidic technology for the aerosolization and delivery of lipid nanoparticles.

Microfluidics is the study of how fluids behave as they travel through or are confined in microminiaturized devices equipped with channels and chambers. Surface forces as opposed to volumetric forces dominate fluids at the microscale, meaning fluids act much differently there than what is observed in everyday life.

“When Rare Air came to me, I thought the device might work great for our purposes, and what followed were extensive studies that demonstrated the superiority of this device in generating aerosolized nanoparticles as compared to clinically used vibrating mesh nebulizers,” Sahay said.
“The device does not let the nanoparticles aggregate and can deliver mRNA with higher precision than existing tech. The additional cool thing is that this device can be digitally controlled, and Rare Air is developing prototypes for human use.”

In addition to Sahay, the other Oregon State researchers on the study were Yulia Eygeris, Jeonghwan Kim, Antony Jozić and Elissa Bloom. Scientists from Funai Microfluidic Systems of Lexington, Kentucky, were also part of the collaboration.

“Funai focuses on inkjet tech and building these chips at scale; they worked closely to enable the device to be suitable for aerosolization,” said Sahay, who in addition to his role at OSU serves as an advisor and consultant to Rare Air. “This study demonstrates a marriage between new devices and formulation science that might hugely impact human health.”

Chiral Induction in 2D Borophene Nanoplatelets through Stereoselective Boron–Sulfur Conjugation

by Teresa Aditya, Parikshit Moitra, Maha Alafeef, David Skrodzki, Dipanjan Pan in ACS Nano

Move over, graphene. There’s a new, improved two-dimensional material in the lab. Borophene, the atomically thin version of boron first synthesized in 2015, is more conductive, thinner, lighter, stronger and more flexible than graphene, the 2D version of carbon. Now, researchers at Penn State have made the material potentially more useful by imparting chirality — or handedness — on it, which could make for advanced sensors and implantable medical devices. The chirality, induced via a method never before used on borophene, enables the material to interact in unique ways with different biological units such as cells and protein precursors.

The team, led by Dipanjan Pan, Dorothy Foehr Huck & J. Lloyd Huck Chair Professor in Nanomedicine and professor of materials science and engineering and of nuclear engineering, published their work — the first of its kind, they said — in ACS Nano.

“Borophene is a very interesting material, as it resembles carbon very closely including its atomic weight and electron structure but with more remarkable properties. Researchers are only starting to explore its applications,” Pan said. “To the best of our knowledge, this is the first study to understand the biological interactions of borophene and the first report of imparting chirality on borophene structures.”

Chirality refers to similar but not identical physicality, like left and right hands. In molecules, chirality can make biological or chemical units exist in two versions that cannot be perfectly matched, as in a left and right mitten. They can mirror each other precisely, but a left mitten will never fit the right hand as well as it fits the left hand.

Borophene is structurally polymorphic, which means its boron atoms can be arranged in different configurations to give it different shapes and properties, much like how the same set of Lego blocks can be built into different structures. This gives researchers the ability to “tune” borophene to give it various properties, including chirality.

“Since this material has remarkable potential as a substrate for implantable sensors, we wanted to learn about their behavior when exposed to cells,” Pan said. “Our study, for the first time ever, showed that various polymorphic structures of borophene interact with cells differently and their cellular internalization pathways are uniquely dictated by their structures.”

The researchers synthesized borophene platelets — similar to the cellular fragments found in blood — using solution state synthesis, which involves exposing a powdered version of the material in a liquid to one or more external factors, such as heat or pressure, until they combine into the desired product.

“We made the borophene by subjecting the boron powders to high-energy sound waves and then mixed these platelets with different amino acids in a liquid to impart the chirality,” Pan said. “During this process, we noticed that the sulfur atoms in the amino acids preferred to stick to the borophene more than the amino acids’ nitrogen atoms did.”

The researchers found that certain amino acids, like cysteine, would bind to borophene in distinct locations, depending on their chiral handedness. The researchers exposed the chiralized borophene platelets to mammalian cells in a dish and observed that their handedness changed how they interacted with cell membranes and entered cells.

According to Pan, this finding could inform future applications, such as development of higher-resolution medical imaging with contrast that could precisely track cell interactions or better drug delivery with pinpointed material-cell interactions. Critically, he said, understanding how the material interacts with cells — and controlling those interactions — could one day lead to safer, more effective implantable medical devices.

“Borophene’s unique structure allows for effective magnetic and electronic control,” Pan said, noting the material could have additional applications in health care, sustainable energy and more. “This study was just the beginning. We have several projects underway to develop biosensors, drug delivery systems and imaging applications for borophene.”

Magnetic Microrobot Swarms with Polymeric Hands Catching Bacteria and Microplastics in Water

by Martina Ussia, Mario Urso, Cagatay M. Oral, Xia Peng, Martin Pumera in ACS Nano

When old food packaging, discarded children’s toys and other mismanaged plastic waste break down into microplastics, they become even harder to clean up from oceans and waterways. These tiny bits of plastic also attract bacteria, including those that cause disease. In a study in ACS Nano, researchers describe swarms of microscale robots (microrobots) that captured bits of plastic and bacteria from water. Afterward, the bots were decontaminated and reused.

The size of microplastics, which measure 5 millimeters or less, adds another dimension to the plastic pollution problem because animals can eat them, potentially being harmed or passing the particles into the food chain that ends with humans. So far, the health effects for people are not fully understood. However, microplastics themselves aren’t the only concern. These pieces attract bacteria, including pathogens, which can also be ingested. To remove microbes and plastic from water simultaneously, Martin Pumera and colleagues turned to microscale robotic systems, comprised of many small components that work collaboratively, mimicking natural swarms, like schools of fish.

To construct the bots, the team linked strands of a positively charged polymer to magnetic microparticles, which only move when exposed to a magnetic field. The polymer strands, which radiate from the surface of the beads, attract both plastics and microbes. And the finished products — the individual robots — measured 2.8 micrometers in diameter. When exposed to a rotating magnetic field, the robots swarmed together. By adjusting the number of robots that self-organized into flat clusters, the researchers found that they could alter the swarm’s movement and speed.

In lab experiments, the team replicated microplastics and bacteria in the environment by adding fluorescent polystyrene beads (1 micrometer-wide) and actively swimming Pseudomonas aeruginosa bacteria, which can cause pneumonia and other infections, to a water tank. Next, the researchers added microrobots to the tank and exposed them to a rotating magnetic field for 30 minutes, switching it on and off every 10 seconds. A robot concentration of 7.5 milligrams per milliliter, the densest of four concentrations tested, captured approximately 80% of the bacteria. Meanwhile, at this same concentration, the number of free plastic beads also gradually dropped, as they were drawn to the microrobots. Afterward, the researchers collected the robots with a permanent magnet and used ultrasound to detach the bacteria clinging to them. They then exposed the removed microbes to ultraviolet radiation, completing the disinfection. When reused, the decontaminated robots still picked up plastic and microbes, albeit smaller amounts of both. This microrobotic system provides a promising approach for ridding water of plastic and bacteria, the researchers note.

Far-Field Petahertz Sampling of Plasmonic Fields

by Kai-Fu Wong et al in Nano Letters

An international research team led by Universität Hamburg, DESY, and Stanford University has developed a new approach to characterize the electric field of arbitrary plasmonic samples, like, for example, gold nanoparticles. Plasmonic materials are of particular interest due to their extraordinary efficiency at absorbing light, which is crucial for renewable energy and other technologies.

In the journal Nano Letters, the researchers report on their study, which will advance the fields of nanoplasmonics and nanophotonics with their promising technology platforms.

Localized surface plasmons are a unique excitation of electrons in nanoscale metals such as gold or silver where the mobile electrons within the metal oscillate collectively with the light-electric field. This condenses optical energy, which in turn enables applications in photonics and energy conversion, for example in photocatalysis.

To advance such applications, it is important to understand the details of the plasmon drive and damping. However, one problem for the development of related experiments is that the processes take place on extremely short time scales (within few femtoseconds).

The attosecond community, including lead authors Matthias Kling and Francesca Calegari, have developed tools to measure the oscillating electric field of ultrashort laser pulses. In one of these field sampling methods, an intense laser pulse is focused in air between two electrodes, generating a measurable current. The intense pulse is then overlayed with a weak signal pulse to be characterized.

The signal pulse modulates the ionization rate and consequently the generated current. Screening the delay between the two pulses provides a time-dependent signal proportional to the electric field of the signal pulse.

“We employed this configuration for the first time to characterize the signal field emerging from a resonantly excited plasmonic sample,” says Francesca Calegari, lead scientist at DESY, physics Professor at Universität Hamburg and a spokesperson of the Cluster of Excellence “CUI: Advanced Imaging of Matter.”

The difference of the reconstructed pulse with plasmon interaction to the reference pulse allowed the scientists to trace the emergence of the plasmon and its fast decay which they confirmed by electrodynamic model calculations.

“Our approach can be used to characterize arbitrary plasmonic samples in ambient conditions and in the far-field,” adds CUI scientist Prof. Holger Lange. Additionally, the precise characterization of the laser field emerging from nanoplasmonic materials could constitute a new tool to optimize the design of phase-shaping devices for ultrashort laser pulses.