3D laser printing with bioinks from microalgae

Heidelberg researchers have successfully developed a new generation of biocompatible materials for additive manufacturing. Microalgae such as the diatom Odontella aurita and the green alga Tetraselmis striata, which are rich in lipids and photoactive pigments, are particularly suitable as “biofactories” for producing sustainable materials for 3D laser printing. An international research team led by Professor Dr. Eva Blasco from the Institute for Molecular Systems Engineering and Advanced Materials (IMSEAM) at Heidelberg University has, for the first time, manufactured inks for printing complex biocompatible 3D microstructures from raw materials extracted from these microalgae. These microalgae-based materials could potentially be used in the future as the basis for implants or scaffolds for 3D cell cultures.

Among the additive manufacturing techniques, two-photon 3D laser printing offers particular advantages for manufacturing at the micro- and nanoscale. Owing to its remarkable resolution, it finds application in numerous fields including optics and photonics, microfluidics, and biomedicine. The process involves focusing a laser beam on a liquid, photoreactive resin, a so-called “ink”. At the focal point, the laser light activates special molecules known as photoinitiators and triggers a chemical reaction, causing local solidification of the ink.

To date, petrochemical-based polymers have been mainly used as inks for this highly precise 3D laser printing process. However, these polymers contribute to the depletion of fossil fuels and the emission of greenhouse gases and can also contain toxic components, as Professor Blasco points out. Microalgae are particularly well suited as “biofactories” for the production of sustainable materials for 3D printing due to their rapid growth rate, CO2-fixation during cultivation, and biocompatibility. “Despite their advantages, microalgae have hardly been considered as raw materials for light-based 3D printing,” says Professor Blasco, whose group conducts research at the interface of macromolecular chemistry, materials science, and 3D nanofabrication.

The research team succeeded for the first time in extracting biocompatible materials for high-resolution 3D laser printing from microalgae. For their experiments, the researchers selected two species – the diatom Odontella aurita and the green alga Tetraselmis striata – that contain particularly high levels of lipids in the form of triglycerides. The team extracted the triglycerides and functionalized them with acrylates to facilitate rapid curing under light irradiation. The photoactive green pigments present in the microalgae proved to be suitable as photoinitiators. When exposed to light, they trigger the chemical reaction that solidifies the ink into a three-dimensional structure. “In this way we avoid using potentially toxic additives like the photoinitiators used in conventional inks,” explains first author Clara Vazquez-Martel, a doctoral candidate in Eva Blasco’s research team at IMSEAM.

Using the new ink system, the researchers were able to produce different 3D microstructures with high precision, exhibiting complex features such as overhanging roofs and cavities. Using cell culture experiments, the researchers also investigated the biocompatibility of the microalgae-based inks. They prepared 3D microscaffolds on which the cells were cultured for about 24 hours. They observed a survival rate of almost 100 percent. “Our results open up new possibilities not only for more sustainable 3D printing with light, but also for life science applications – from 3D cell cultures to biocompatible implants,” says Professor Blasco.

For more information: Heidelberg University

A new approach to fine-tuning quantum materials

Quantum materials, which have electronic properties governed by quantum mechanics principles like correlation and entanglement, can display unique behaviors under certain conditions, such as superconductivity, where electricity is transmitted without resistance. To achieve optimal performance, these materials must be finely tuned. A team led by Mingda Li, an associate professor in MIT’s Department of Nuclear Science and Engineering (NSE), has developed an ultra-precise method to adjust the characteristics of quantum materials, using Weyl semimetals as an example.

This new technique isn’t limited to Weyl semimetals; according to NSE postdoc Manasi Mandal, one of the lead authors of the paper detailing the group’s findings, it can be applied to any inorganic bulk material and thin films as well. The experiment described in the paper focused on a specific type of Weyl semimetal, a tantalum phosphide (TaP) crystal.

Materials can be classified by their electrical properties: metals conduct electricity readily, whereas insulators impede the free flow of electrons. A semimetal lies somewhere in between. It can conduct electricity, but only in a narrow frequency band or channel. Weyl semimetals are part of a wider category of so-called topological materials that have certain distinctive features. For instance, they possess curious electronic structures — kinks or “singularities” called Weyl nodes, which are swirling patterns around a single point (configured in either a clockwise or counterclockwise direction) that resemble hair whorls or, more generally, vortices. The presence of Weyl nodes confers unusual, as well as useful, electrical properties. And a key advantage of topological materials is that their sought-after qualities can be preserved, or “topologically protected,” even when the material is disturbed.

“That’s a nice feature to have,” explains Abhijatmedhi Chotrattanapituk, a PhD student in MIT’s Department of Electrical Engineering and Computer Science and the other lead author of the paper. “When you try to fabricate this kind of material, you don’t have to be exact. You can tolerate some imperfections, some level of uncertainty, and the material will still behave as expected.”

The “tuning” that needs to happen relates primarily to the Fermi level, which is the highest energy level occupied by electrons in a given physical system or material. Mandal and Chotrattanapituk suggest the following analogy: Consider a dam that can be filled with varying levels of water. One can raise that level by adding water or lower it by removing water. In the same way, one can adjust the Fermi level of a given material simply by adding or subtracting electrons.

To fine-tune the Fermi level of the Weyl semimetal, Li’s team did something similar, but instead of adding actual electrons, they added negative hydrogen ions (each consisting of a proton and two electrons) to the sample. The process of introducing a foreign particle, or defect, into the TaP crystal — in this case by substituting a hydrogen ion for a tantalum atom — is called doping. And when optimal doping is achieved, the Fermi level will coincide with the energy level of the Weyl nodes. That’s when the material’s desired quantum properties will be most fully realized.

For Weyl semimetals, the Fermi level is especially sensitive to doping. Unless that level is set close to the Weyl nodes, the material’s properties can diverge significantly from the ideal. The reason for this extreme sensitivity owes to the peculiar geometry of the Weyl node. If one were to think of the Fermi level as the water level in a reservoir, the reservoir in a Weyl semimetal is not shaped like a cylinder; it’s shaped like an hourglass, and the Weyl node is located at the narrowest point, or neck, of that hourglass. Adding too much or too little water would miss the neck entirely, just as adding too many or too few electrons to the semimetal would miss the node altogether.

To reach the necessary precision, the researchers utilized MIT’s two-stage “Tandem” ion accelerator — located at the Center for Science and Technology with Accelerators and Radiation (CSTAR) — and buffeted the TaP sample with high-energy ions coming out of the powerful (1.7 million volt) accelerator beam. Hydrogen ions were chosen for this purpose because they are the smallest negative ions available and thus alter the material less than a much larger dopant would. “The use of advanced accelerator techniques allows for greater precision than was ever before possible, setting the Fermi level to milli-electron volt [thousandths of an electron volt] accuracy,” says Kevin Woller, the principal research scientist who leads the CSTAR lab. “Additionally, high-energy beams allow for the doping of bulk crystals beyond the limitations of thin films only a few tens of nanometers thick.”

The procedure, in other words, involves bombarding the sample with hydrogen ions until a sufficient number of electrons are taken in to make the Fermi level just right. The question is: how long do you run the accelerator, and how do you know when enough is enough? The point being that you want to tune the material until the Fermi level is neither too low nor too high.

To streamline the protocol, the team has devised a theoretical model that first predicts how many electrons are needed to increase the Fermi level to the preferred level and translates that to the number of negative hydrogen ions that must be added to the sample. The model can then tell them how long the sample ought to be kept in the accelerator chamber.

The good news, Chotrattanapituk says, is that their simple model agrees within a factor of 2 with trusted conventional models that are much more computationally intensive and may require access to a supercomputer. The group’s main contributions are two-fold, he notes: offering a new, accelerator-based technique for precision doping and providing a theoretical model that can guide the experiment, telling researchers how much hydrogen should be added to the sample depending on the energy of the ion beam, the exposure time, and the size and thickness of the sample.

This could pave the way to a major practical advance, Mandal notes, because their approach can potentially bring the Fermi level of a sample to the requisite value in a matter of minutes — a task that, by conventional methods, has sometimes taken weeks without ever reaching the required degree of milli-eV precision.

For more information: Applied Physics Review

Image: Ion implantation using a tandem accelerator on bulk material. Selected ion species are injected toward the terminal, and ions with specific energies are directed toward the sample. Credits Ella Maru Studio

New 3D reconstruction method aids analysis of property-defining defects

An international research collaboration, including a group from Cornell Engineering, has used a new X-ray-based reconstruction technique to observe topological defects in a nanoscale self-assembly-based cubic network structure of a polymer-metal composite material over a large sample volume for the first time. This technique and the new insights gained could be applied to studying other mesoscale structures with similar defects, which underpin many physical phenomena and can lead to new or enhanced material properties in both natural and synthetic self-assembled materials. Ulrich Wiesner, the Spencer T. Olin Professor in the Department of Materials Science and Engineering, emphasized that this new polymer, structure, and technique allow for unprecedented sample volumes to be reconstructed, enabling detailed examination of defect structures and their frequency.

The question regarding the importance of defects in BCP SA-generated materials has always been elusive, Wiesner said, in part because technologies necessary to measure large-enough sample volumes – with correspondingly larger defect structures – have been slow to develop.

The new technology – hard X-ray ptychography, which was conducted at the Swiss Light Source (SLS), at the Paul Scherrer Institute in Switzerland – is an advanced form of tomography that can penetrate deeper into a material than is possible with beams in electron microscopes. This technique allowed the researchers to reconstruct a very large sample volume of a BCP SA-derived polymer-metal composite material.

“If you have a smaller defect such as a line or a point defect, when you perturb the system, often you can ‘correct’ the defect structure,” Wiesner said. “In contrast, topological defects are so large, they are very stable against external perturbations.”

Once the triblock terpolymer was synthesized, researchers in the group of Ulli Steiner at the Adolphe Merkle Institute in Fribourg, Switzerland, a long-time collaborator of Wiesner, generated thin films from it and replaced one of the terpolymer blocks with gold, so the material could withstand repeated exposure to the intense coherent X-ray beams at SLS.

Imaging and image reconstruction at the SLS finally revealed a co-continuous network known as a single-diamond structure, with topological defects that the researchers expect would have substantial effects on mechanical and other properties. Importantly, the defects most closely resemble topological textures found in nematic liquid crystals and in Hydra single-celled organisms, suggesting that self-assembly can be used as a model process to investigate the role of topology in nature.

Wiesner said this collaborative research could pave the way for future studies in an area that his lab has already explored: block copolymer-directed superconductors.

“You would expect that your macroscopic, electronic or transport properties of the superconductor will depend on defects in your materials,” he said. “That’s what I’m really excited about: Now we have a technique that allows us to visualize larger volumes of these materials and to generate defect structure – property correlations.”

For more information: Nature Nanotechnology

Image: Pictured is a two-dimensional, cut-through reconstructed sample volume showing three adjacent crystal grains (red, blue, green) separated by a 100-nanometer-thick grain boundary (yellow) together with the positions of two topological defects (plus and minus signs).

Argonne Lab’s ‘AI-NERD’ predicts material behavior with unprecedented accuracy

Imagine scientific breakthroughs happening without a scientist running every experiment; a new AI development at Argonne National Laboratory, AI-NERD (Artificial Intelligence for Non-Equilibrium Relaxation Dynamics), takes a concrete step toward this vision, marking a significant advancement in autonomous materials discovery. The field of material science faces a challenge as the demand for new, better-performing materials in areas like renewable energy and aerospace outpaces researchers’ ability to discover and characterize them using traditional methods. Traditionally, understanding how materials change at the atomic level has relied on slow, labor-intensive experiments, and observing such microscopic dynamics is challenging. Techniques like X-ray photon correlation spectroscopy (XPCS) offer insights into atomic behavior, but the data generated are incredibly complex. AI-NERD promises to accelerate materials research by addressing these challenges.

This approach leverages unsupervised deep learning, specifically an autoencoder neural network, to analyze complex X-ray data and unveil the hidden “fingerprints” of material behavior. By teaching itself to recognize patterns in XPCS data without expert training, AI-NERD creates condensed material “fingerprints” from intricate X-ray scattering patterns. This breakthrough enables researchers to map and analyze material behavior in previously impossible ways.

“The goal of the AI is just to treat the scattering patterns as regular images or pictures and digest them to figure out what are the repeating patterns. The AI is a pattern recognition expert,” said James (Jay) Horwath Argonne National Laboratory, the first author of the study.

These fingerprints are more than just patterns—they are condensed representations of a material’s structure and behavior, distilling volumes of  of XPCS data into essential features. As Horwath explained, “You can think of it like having the material’s genome, it has all the information necessary to reconstruct the entire picture.”

What sets AI-NERD apart is its ability to learn and identify patterns without expert guidance. This unsupervised learning approach allows the system to discover hidden relationships and trends in material behavior that might elude scientists. By processing and categorizing X-ray scattering images, AI-NERD creates a comprehensive map of material dynamics, offering researchers a new lens for viewing atoms and molecules.

In the research, the scientists used a technique called Uniform Manifold Approximation and Projection (UMAP) to transform their complex dataset into a simple two-dimensional picture, as shown in the visual above. UMAP is similar to another popular method called t-distributed Stochastic Neighbor Embedding (tSNE). Both of these methods try to preserve the relationships between data points when reducing dimensions. For a brief overview of word embeddings, check out the article “What embeddings are and how to explore them in R&D.”

This development in AI-assisted materials research at Argonne National Laboratory is part of a broader trend of artificial intelligence revolutionizing materials science. In recent years, several notable advancements have paved the way for AI-NERD’s development.

In 2023, researchers made significant strides in using AI for materials synthesis and characterization. For instance, one team developed an AI system capable of extracting “recipes” for producing materials from scientific papers. This system could identify correlations between precursor chemicals and resulting crystal structures, streamlining the material discovery process.

Another group created an AI system that recognizes patterns across different materials recipes. This innovation allows the AI to suggest alternative recipes for known materials, potentially opening up new avenues for synthesis.

While machine learning continues to be something of a trending subject, its use in material science is not new. In 2018, researchers at Virginia Tech developed a machine learning framework that trains “on the fly” to accelerate the development of computational models for materials design.

Similarly, AI system called ARTIST from Aalto University and the Technical University of Denmark debuted in 2019 to instantly determine how a molecule will react to light, potentially accelerating the development of flexible electronics and other technologies.

In nuclear materials research, University of Wisconsin-Madison and Oak Ridge National Laboratory unveiled an AI system was trained to detect and analyze microscopic radiation damage in potential nuclear reactor materials in 2018. It outperformed human experts in both accuracy and speed.

In particular, the development of AI-NERD promises to boost the analysis of XPCS data in particular. As the upgraded Advanced Photon Source comes online, generating 500 times brighter X-ray beams than its predecessor, the need for efficient data processing becomes even more critical. “The data we get from the upgraded APS will need the power of AI to sort through it,” Horwath emphasizes. AI-NERD’s ability to create material “fingerprints” and identify patterns in large datasets could advance researchers’ understanding of material dynamics for an array range of applications.

For more information: Nature Communications

Image: The AI-NERD model learns to produce a unique ‘fingerprint’ for each sample of XPCS data enabling the identification of trends and repeating patterns. 

Researchers develop first voxel building blocks for 3D-printed organs

A research team at the University of Virginia School of Engineering and Applied Science, led by Assistant Professor Liheng Cai and his Ph.D. student Jinchang Zhu, has developed biomaterials with controlled mechanical properties that match various human tissues, potentially serving as the first building blocks for human-compatible organs printed on demand. Zhu highlighted this advancement as a significant leap compared to existing bioprinting technologies.

Their unique bioprinting method is called digital assembly of spherical particles. The DASP technique deposits particles of biomaterial in a supporting matrix, both of which are water-based, to build 3D structures that provide a suitable environment for the cells to grow. The assembly process is how “voxels,” the 3D version of pixels, construct 3D objects.

“Our new hydrogel particles represent the first functional voxel we have ever made,” Zhu said. “With precise control over mechanical properties, this voxel may serve as one of the basic building blocks for our future printing constructs.

“For example, with this level of control, we could print organoids, which are 3D cell-based models that function as human tissue, to study disease progression in the search for cures.”

The particles are polymer hydrogels engineered to mimic human tissue by tweaking the arrangement and chemical bonds of single-molecule monomers, which link together in chains to form networks.

Encapsuled within the particles are actual human cells.

Compared to other hydrogel bio-inks, Cai and Zhu’s are less toxic and more biocompatible for cells, they said. Their “double network” hydrogels—formed from two intertwined molecular networks—are mechanically strong, but highly tunable for mimicking the physical characteristics of human tissue.

Cai and Zhu first described their DASP technology in 2021. That work proved the concept of using biomaterial voxels as building blocks and, through lab experiments, demonstrated a DASP-printed material that functioned like a pancreas with glucose-stimulated insulin release.

But DASP 1.0 could only print brittle hydrogels with limited tunability. In their latest paper in Nature Communications, Cai and Zhu present DASP 2.0, which introduces the double-network hydrogel bio-inks formed using a “click chemistry” to rapidly cross-link, or bond, the molecular structures.

Part of what enabled this advancement was improvements to the team’s bioprinter. They designed a multichannel nozzle to mix the hydrogel components on demand. Premixing isn’t possible because the cross-linking occurs so fast, going from liquid droplets to an elastic water-swollen gel within 60 seconds.

In previous studies, the team determined that drop formation and rapid detachment from the nozzle are essential to mimic the mechanical properties—such as elasticity or stiffness—of the target human tissue.

DASP achieves this by depositing large droplets from a narrow and fast-moving nozzle into the matrix, immediately suspending them.

“We’ve now laid the foundation for voxelated bioprinting,” Cai said. “When fully realized, DASP’s applications will include artificial organ transplant, disease and tissue modeling, and screening candidates for new drugs. And it probably won’t stop there.”

For more information: Nature Communications

Image: Reminiscent of a raspberry, this voxelated hollow sphere made of a single layer of droplets was generated using digital assembly of spherical particles, or DASP, a 3D bioprinting process developed in assistant professor of materials science and engineering Liheng Cai’s lab. (Soft Biomatter Lab, UVA Engineering). Credit: University of Virginia School of Engineering and Applied Science/Liheng Cai

Single-crystal cathodes for faster-charging, longer-lasting EVs

A team at Pohang University of Science and Technology has unveiled a groundbreaking single-crystal synthesis technique. This innovation significantly boosts the resilience of cathode materials, a key component in electric vehicle batteries.

Professor Kyu-Young Park from the Graduate Institute of Ferrous & Eco Materials Technology and the Department of Materials Science and Engineering, along with PhD candidate Kyoung Eun Lee and alumna Yura Kim from the same institute at Pohang University of Science and Technology (POSTECH), collaborated with the POSCO Holdings N.EX.T Hub.

Lithium (Li) secondary batteries, widely employed in electric vehicles, function by converting electrical energy into chemical energy during charging and reversing the process to release electrical energy during discharge. This process involves the movement of Li+ ions between a cathode and an anode.

The cathode materials in these batteries typically include nickel (Ni) due to their high lithium-ion storage capacity. However, traditional nickel-based materials exhibit a polycrystalline structure composed of numerous small crystals. This structure is prone to structural degradation during charge and discharge cycles, leading to a considerable reduction in battery lifespan.

To tackle this issue, one proposed solution involves producing the cathode material in a “single-crystal” form. This approach aims to enhance the structural, chemical stability, and durability of nickel-based cathode materials by synthesizing them into large, single particles or “single crystals.”

Single-crystal materials are typically synthesized at high temperatures, where they undergo a process of becoming rigid. However, the precise mechanisms of this hardening process during synthesis and the specific conditions under which it occurs are still not fully understood.

To enhance the durability of nickel cathode materials for electric vehicles, the researchers concentrated on identifying a critical temperature threshold conducive to synthesizing high-quality single-crystal materials. They conducted experiments across different synthesis temperatures to pinpoint the optimal conditions for producing single crystals in the synthesis of a specific nickel-based cathode material (N884). The team systematically evaluated how varying temperatures affected the material’s capacity and long-term performance.

The researchers found that conventional polycrystalline materials synthesized below a specific critical temperature degrade over time when used in secondary batteries. In contrast, synthesizing these materials above this critical temperature enables the production of high-quality single crystals through a process known as “densification.”

During densification, the internal grain size of the material increases, and empty spaces within the structure are densely filled. This transformation results in single crystals that are exceptionally hard and resistant to degradation over prolonged periods, significantly enhancing their durability.

Based on these insights, the team confirmed that synthesizing single crystals above the critical temperature represents a more advantageous strategy for material design. They also proposed an effective method for synthesizing high-quality single crystal materials.

For more information: POSTECH

Into another dimension: Nanoscale trilayer exhibits ultrafast charge transfer in semiconductor materials

Advancements in optoelectronic semiconductor technology are heavily reliant on the controlled movement of charges and excitons—pairs of electrons and holes—towards specific directions to generate fuel or electricity. Mirroring the mechanism of photosynthesis, where pigments capture solar energy and funnel it to a reaction center for conversion and utilization, photons in this process create electron-hole pairs. These pairs must be parted to kick-start chemical reactions.

Deriving inspiration from the natural process of photosynthesis, National Renewable Energy Laboratory (NREL) researchers developed a mixed-dimensionality (2D/1D/2D) trilayer of semiconductors to enable exciton dissociation. This exciton dissociation step, a splitting and spatial separation of excited electron–hole pairs, is a microscopic process that is fundamental to the performance of photovoltaic systems.

As the clean energy transition progresses, advances in photovoltaic systems, which convert sunlight into electricity, are crucial. Photovoltaics rely on the light-activated creation of separated electron-hole pairs to drive an external circuit.

“In this study, we were able to create light-activated electron hole pairs and separate them for a long time, longer than previously reported similar systems,” said NREL’s Alexis Myers, a graduate student researcher.

The diverse and tunable electronic and optical properties of quantum-confined low-dimensional materials such as two-dimensional (2D) transition metal dichalcogenides (TMDCs) and one-dimensional (1D) single-walled carbon nanotubes (SWCNTs) make them prime candidates for fundamental studies on charge and exciton transfer. These types of materials have enhanced electron-hole Coulomb interactions, where the electrostatic force causes the attraction between an electron and an electron hole to form an exciton. To separate the charges, researchers must overcome the attraction, made more difficult by the large binding energies.

These materials exhibit large exciton binding energies—the energy needed for exciton dissociation—which can inhibit generation of electrical currents for photovoltaics, photodetectors, and sensors or chemical bonds in solar fuel schemes. So, NREL researchers sought to develop a hetero-trilayer that would address this challenge.

“Extending charge separation lifetimes is necessary to increase the chance of charge extraction,” Myers said. “The creation of bilayers and trilayers comes from this desire to increase the distance between separated charges. However, it’s unclear in the literature whether the ‘separated’ charges are still electrostatically bound across the interface. So, though separated, the Coulomb interaction is still present, which can decrease charge separation lifetimes. In the trilayer, we were able to track the movements of electrons and holes sequentially through each layer, confirming they are indeed no longer bound to each other.”

Complex, low-dimensional heterostructures—like TMDCs—exhibit longer lifetimes, initiating important photochemical reactions, which are critical to generating electricity in photovoltaics. Alexis Myers and team developed a mixed-dimensionality hetero-trilayer of SWCNTs between two semiconductors that enables a photoinduced charge transfer cascade where electrons (negative charge carriers) move in one direction while holes (positive charge carriers) move in the other direction.

The hetero-trilayer mimics the natural charge transfer cascade observed in plant photosynthesis, which inspired its development. A key part of the heterostructure is the one-dimensional middle layer, which helps the charge carriers diffuse efficiently from one 2D layer to the other.

The study also looked at the mechanics of carrier diffusion in TMDCs. Using transient absorption spectroscopy, researchers tracked exciton dissociation and charge diffusion across the hetero-trilayer, observing ultrafast electron transfer to one layer and hole transfer to the another. The trilayer architecture appears to facilitate ultrafast hole transfer and exciton dissociation, resulting in a long-lived charge separation.

The charge transfer cascade enables an excited state—where electrons and holes reside in separate places within the trilayer—where photochemical reactions could be initiated. Longer charge separation lifetimes could mean greater electric current generation because more electrons and holes have not recombined.

The trilayer produced double the carrier yield compared with a 2D/1D bilayer. It also empowered the separated charges to overcome the interlayer exciton binding energies of unbound separated charges, a key challenge with such materials.

“These materials have high electrostatic interaction between the electron and hole, yet we have shown that we can successfully separate them through efficient diffusion along the SWCNT mesh,” said NREL’s Alejandra Hermosilla Palacios, a materials science postdoctoral researcher. “Kinetic analysis of the different steps is necessary to understand the efficiency in these systems. We have mostly focused on the diffusion of charges thanks to the SWCNTs. We would like to understand how charges diffuse or move in the TMDC layer to better propose new systems that could lead to higher efficiencies—more electrons and holes generated—and even longer-lived charges (chance for higher electric current generation).”

In previous charge transfer cascades, the mechanism for charge transfer is unclear or does not proceed as expected.

“Our results suggest that well-defined charge transfer cascades can result in longer charge separated lifetimes and higher charge yield (or efficient transfer), paving the way for better understanding of how charges are moving through these systems and how we can continue to optimize them,” Myers said.

“Our results show promising implications for the development of nanoscale optoelectronic devices like solar cells and solar fuel architectures,” Hermosilla Palacios said. “Mixed-dimensionality heterostructures demonstrate photophysics and technological advantages that may enhance and accelerate innovation in optoelectronics.”

For more information: ACS Nano

Image: Charge movement in a mixed-dimensionality hetero-trilayer material: Photoexcited electrons and holes travel from the transition metal dichalcogenide layer (top) through single-walled carbon nanotubes (middle), resulting in a long charge recombination lifetime of 1.2 microseconds, which has potential applications in optoelectronics and energy harvesting. Image by Alexis Myers, NREL.

A Dune-inspired spacesuit turns astronaut pee into drinking water

In the iconic sci-fi saga Dune, the inhabitants of the parched world of Arrakis don unique garments known as stillsuits to reclaim their body’s water. Drawing inspiration from this concept, engineers have developed an innovative prototype spacesuit that transforms astronauts’ urine into potable water.

Presently, astronauts don a maximum absorbency garment, akin to a sophisticated diaper with layers of super-absorbent polymers, to manage bodily waste while in their spacesuits. This solution, however, has been criticized for discomfort, leakage, and the potential to cause urinary tract infections.

“I’ve been a fan of the Dune series for as long as I can remember,” says Sofia Etlin, a space medicine and policy researcher at Cornell University. “Building a real life stillsuit was always a bit of a dream.”

Current spacesuit designs also incorporate an in-suit drinking bag, or IDB, that carries less than a liter of water. Astronauts can sometimes go for eight- to 12-hour spacewalks, which often includes enormous amounts of physical exertion, Etlin says. NASA’s future Artemis missions on the moon will probably see explorers spending at least as much time or longer on the lunar surface, though current plans have them carrying IDBs of the same size, she says.

Etlin and her colleagues designed and built a new type of undergarment with a collection cup that goes over an astronaut’s private parts. Urine is routed into a filtration system that first removes salty water from the urine and then uses a pump to take the salt out from that water. The filtered water is enriched with electrolytes and then sent into the IDB.

A fictional Fremen’s stillsuit is powered by body movement, but astronauts will have to carry a 20.5-volt battery as part of this new design. The total system, including pumps, sensors and display screen, weighs around 8 kilograms and can purify half a liter of water in five minutes.

Sweat — which fictional stillsuits also collect — would be easier to filter than urine, Etlin says. But she and her colleagues decided to focus on a single waste product for their first prototype. “One step at a time,” she says.

The team hopes to further test its system during simulated moon and Mars missions here on Earth and eventually during real spacewalks.

It “would be amazing for us,” says Julio Rezende of the Federal University of Rio Grande do Norte in Natal, Brazil, who leads Habitat Marte, a Mars analog mission in Brazil. “I believe this technology would bring a lot of benefits.”

Rezende sees potential terrestrial spin-offs, too, such as a similar system that could be used for firefighters combating forest fires or hikers on long trails.

For more information: Frontiers in Space Technology

Image: The new spacesuit design (illustrated) that collects urine and recycles it into drinking water weighs around 8 kilograms and can purify half a liter of water in five minutes. FREMAN SPACE TEAM (ILLUSTRATION), NASA

New technique enables ultrafast imaging of light-matter interactions

Scientists at the SLAC National Accelerator Laboratory, part of the Department of Energy, have uncovered novel properties in an ultrathin material that could revolutionize the way we handle light. This breakthrough is anticipated to benefit optoelectronic devices—those that sense, modulate, or produce light—as well as advance our understanding of light polarization within substances.

These insights emerged during sessions with the laboratory’s rapid “electron camera.” A wide array of common applications, including medical imaging systems, fiber optics, and light-emitting diodes (LEDs), rely on the capabilities of optoelectronic devices.

The team, led by SLAC and Stanford Professor Aaron Lindenberg, discovered that an ultrathin film of tungsten ditelluride, which has desirable properties for polarizing light used in optical devices, will polarize incoming light in a circular pattern when oriented in a particular direction and exposed to linear terahertz radiation.

Terahertz radiation falls between the microwave and infrared regions in the electromagnetic spectrum. It offers new possibilities for material property management and characterization. Scientists want to figure out how to harness light to create optoelectronic devices.

The MeV-UED, the world-leading instrument for ultrafast electron diffraction at the Linac Coherent Radiation Source (LCLS) at SLAC, can capture interactions at ultrafast speeds, which is precisely what is needed to capture a material’s activity under terahertz radiation.

This new work used the femtosecond electron pulses to visualize the electric and magnetic fields of the incoming terahertz pulses, which caused the electrons to wiggle back and forth. Normally, the MeV-UED is used to visualize the motion of atoms by measuring how they scatter electrons after hitting a sample with an electron beam.

Images of the electrons in the investigation that displayed a circular pattern rather than a straight line indicated circular polarization.

The substance was so thin, just 50 nm thick.

Scientists are eager to use these incredibly thin materials, sometimes referred to as two-dimensional (2D) materials, to reduce the size and increase the functionality of optoelectronic devices. According to Lindenberg, they see themselves building devices out of layers of 2D structures, much like Legos.

A distinct material would make up each 2D structure, which would be perfectly aligned to provide a particular kind of optical response. These many shapes and functionalities can be combined to create small devices with potential uses, such as optoelectronic devices or medical imaging.

For more information: SLAC National Accelerator Laboratory

Image: Snapshot taken by SLAC’s high-speed electron camera, an instrument for ultrafast electron diffraction (MeV-UED), showing evidence of circular polarization of terahertz light by an ultrathin sample of tungsten ditelluride. Image Credit: Sie et al., Nano Letters

 

Soft, stretchy electrode simulates touch sensations using electrical signals

Researchers at the University of California San Diego have developed a soft, stretchy electronic device that simulates pressure or vibration sensations when worn on the skin. This innovative device represents a step toward creating haptic technologies capable of reproducing a more varied and realistic range of touch sensations

The device consists of a soft, stretchable electrode attached to a silicone patch. It can be worn like a sticker on either the fingertip or forearm. The electrode, in direct contact with the skin, is connected to an external power source via wires. By sending a mild electrical current through the skin, the device can produce sensations of either pressure or vibration depending on the signal’s frequency.

“Our goal is to create a wearable system that can deliver a wide gamut of touch sensations using electrical signals—without causing pain for the wearer,” said study co-first author Rachel Blau, a nano engineering postdoctoral researcher at the UC San Diego Jacobs School of Engineering.

Existing technologies that recreate a sense of touch through electrical stimulation often induce pain due to the use of rigid metal electrodes, which do not conform well to the skin. The air gaps between these electrodes and the skin can result in painful electrical currents.

To address these issues, Blau and a team of researchers led by Darren Lipomi, a professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at UC San Diego, developed a soft, stretchy electrode that seamlessly conforms to the skin.

The electrode is made of a new polymer material constructed from the building blocks of two existing polymers: a conductive, rigid polymer known as PEDOT:PSS, and a soft, stretchy polymer known as PPEGMEA. “By optimizing the ratio of these [polymer building blocks], we molecularly engineered a material that is both conductive and stretchable,” said Blau.

The polymer electrode is laser-cut into a spring-shaped, concentric design and attached to a silicone substrate. “This design enhances the electrode’s stretchability and ensures that the electrical current targets a specific location on the skin, thus providing localized stimulation to prevent any pain,” said Abdulhameed Abdal, a Ph.D. student in the Department of Mechanical and Aerospace Engineering at UC San Diego and the study’s other co-first author. Abdal and Blau worked on the synthesis and fabrication of the electrode with UC San Diego nano engineering undergraduate students Yi Qie, Anthony Navarro and Jason Chin.

In tests, the electrode device was worn on the forearm by 10 participants. In collaboration with behavioral scientists and psychologists at the University of Amsterdam, the researchers first identified the lowest level of electrical current detectable. They then adjusted the frequency of the electrical stimulation, allowing participants to experience sensations categorized as either pressure or vibration.

“We found that by increasing the frequency, participants felt more vibration rather than pressure,” said Abdal. “This is interesting because biophysically, it was never known exactly how current is perceived by the skin.”

The new insights could pave the way for the development of advanced haptic devices for applications such as virtual reality, medical prosthetics and wearable technology.

For more information: Science Robotics

Image: Soft, stretchable electrode recreates sensations of vibration or pressure on the skin through electrical stimulation. Photos by Liezel Labios/UC San Diego Jacobs School of Engineering

Scientists develop the next generation of highly efficient memory materials with atom-level control

Similar to the butterfly effect, tiny adjustments can yield significant outcomes. Researchers at Pohang University of Science and Technology (POSTECH) achieved a breakthrough by modifying a material called ‘spin-orbit torque (SOT).’ This material is now a key focus in next-generation DRAM memory.

This research team, led by Professor Daesu Lee and Yongjoo Jo, a Ph.D. candidate, from the Department of Physics and Professor Si-Young Choi from the Department of Materials Science and Engineering at POSTECH, achieved highly efficient field-free SOT magnetization switching through atom-level control of composite oxides.

SOT arises from the interaction between the spin (magnetic property) and motion (electrical property) of electrons. This phenomenon controls the magnetic state through the movement of spin when current flows. By utilizing magnetic information instead of electrical information, memory power consumption is reduced, making it advantageous for non-volatile memory which retains information even when powered off.

Researchers have been actively exploring various materials including semiconductors and metals for these applications. Particularly, there is significant interest in discovering materials that exhibit both magnetism and the “spin-Hall effect.”

The study of efficient magnetization switching via SOTs has garnered much attention. However, a challenge remains: opposite spin currents generated within a single layer tend to cancel each other out.

In this study, Professors Daesu Lee and Si-Young Choi from POSTECH addressed the problem by systematically modifying the material’s seemingly insignificant structure. Strontium ruthenate (SrRuO3), a complex oxide known for exhibiting both magnetism and spin-Hall effects, has been widely used in SOT research.

The team synthesized SrRuO3 with asymmetric spin-Hall effects on the top and bottom surface layers by minutely adjusting the atomic lattice structure of these layers. By creating an imbalance in the spin-Hall effect with a strategically designed asymmetric surface structure, they were able to control the magnetization in a specific direction.

Building on this approach, the team successfully achieved efficient magnetization switching without the need for a magnetic field. By incorporating SOT into a device based on SrRuO3, they could reorient the magnetic domain using only an electric current to write and read data.

The resulting memory device demonstrated the highest efficiency (2 to 130 times greater) and lowest power consumption (2 to 30 times lower) compared to any known single-layer, field-free system to date. This magnetization switching was accomplished without a magnetic field while preserving the conventional properties of SrRuO3 used in previous studies.

Professor Daesu Lee of POSTECH says, “The asymmetric SrRuO3 synthesized by the team is a crucial platform for studying the interaction between ferromagnetism and the spin-Hall effect.” He added, “We look forward to further research to uncover new SOT mechanisms and develop highly efficient, room-temperature, single-phase SOT materials.”

For more information: Nano Letters

Image: Atomic structure of asymmetric SrRuO3 thin films and spin-orbit torque magnetization switching results controlled at the atomic layer level. Credit: POSTECH

Recent advances in twisted bilayer graphene

Graphene, a widely studied 2D material, exhibits exceptional physical and electronic properties. Twisting two graphene monolayers at a small angle creates twisted bilayer graphene (tBLG), which forms a superlattice. The moiré pattern resulting from relative layer orientation has driven significant progress in graphene research, enhancing its optical and electrical properties, including superconductivity.

The mechanical, optical, and electronic properties of multilayer graphene structures can be tailored by altering the stacking order, interlayer spacing, and relative twisting angle (θ). Similarly, tBLG is fabricated by stacking two single-layer graphene sheets, synthesized by chemical vapor deposition (CVD), at a specific twisting angle.

The unusual stacking imparts various angle-dependent properties to tBLG.

Moiré patterns are generated by graphene-graphene interactions resulting from the relative layer orientations. These highly periodic patterns are responsible for the extraordinary optical and electronic properties of tBLG. Additionally, tBLG exhibits twisting angle-dependent Dirac spectra (similar to chirality dependence in carbon nanotubes), Fermi velocity, magnetoresistance oscillations, and quantum Hall effect.

Innovative methods are being explored to fabricate tBLG with small twist angles. For example, hexagonal boron nitride is utilized to obtain graphene layers with rotationally aligned crystal axes. tBLG is also prepared by cutting, rotating, and stacking a graphene layer through femtosecond laser micromachining and precise transfer.

Other methods for preparing tBLG films include controlled hydrophilic and hydrophobic boundary folding of single-layer graphene and vertical stacking.

Easy twisting and stacking of two graphene layers can result in a uniform and ordered moiré superlattice capable of exhibiting unusual superconductivity and correlations in tBLG. However, the twist angle becomes rigid after interlayer stacking. Alternatively, mechanical elastic strain can help control the electronic structure of tBLG by regulating the lattice spacing and symmetry.

A recent study reviewed various innovations in straining tBLG by in-plane and out-of-plane modes. It included the characterizations and calculations performed to quantitatively tune the strain-engineered electronic structures.

Another study demonstrated a topological superconducting state in tBLG depending only on the moiré minibands instead of the twist angle tuning. The method involved subjecting tBLG to induced Rashba spin-orbit coupling, s-wave superconductivity, and exchange field and is valid for 1.3 to 3 degrees twist angles. This approach could be feasible for developing a tBLG-based quantum computer.

Despite several research advances and potential applications, significant challenges remain in achieving controlled twisting of two graphene layers to fabricate and characterize tBLG. Additionally, precise stacking of bilayer graphene at the first magic angle of 1.1 degrees to observe superconductivity is tedious due to the intrinsic disruptions caused by strain and angular disorder.

Modifications in the twist angle significantly alter the spatial wavefunction distribution. While this allows engineering bandgaps in tBLG for electronic applications, the localized wavefunction at certain twist angles leads to a sudden reduction in carrier mobility. This can negatively influence the tBLG-based device performance. Hence, careful considerations are required to obtain preferred electronic characteristics and carrier mobility for ideal device functioning.

The ultrathin nature of tBLG leads to localized stretching or compression due to substrate deformation or thermal stresses during fabrication. Despite the positive impact of these localized strains on the physical properties of the material, their non-uniformity hinders practical device applications of the material.

The constant improvements in the synthesis, characterization, and electronic structure determination techniques are anticipated to accelerate the tBLG-related advances and applications. This, in turn, may lead to the advancement of “twistronics,” the fusion of “twist” and “electronics,” which exploits the electronic properties of layered materials like graphene changing with the twist angle.

The strain engineering of twisted 2D materials like tBLG can further expand “twistronics” and “straintronics” into the realm of “strain-twistronics.” Consequently, novel ferroelectric and optoelectronic devices with tunable characteristics and regulated performance may become a reality in the future.

For more information: AZO Nano

Well-known university to gift new students ‘golden keys’ made with space-grade craftsmanship

The Harbin Institute of Technology (HIT) has announced its 2024 admission notifications. This year, each new student will be given a “golden key” made using space-grade materials. The keys come in three different color schemes and symbolize spacecraft crossing the troposphere, stratosphere, and outer space.

On Tuesday, HIT announced that they will be gifting each incoming student a “golden key” made with titanium alloy, a high-performance material used in critical components of aerospace vehicles.

The keys are made using 3D printing technology and polished with a coating used in space station docking technology, symbolizing the students unlocking the doors to the universe and the future.

The design of the 2024 admission notification letters from HIT resembles a book, with a cover featuring a customizable pattern using grating technology, with the main image being the outline of a key. Upon opening the box, students will find a message from the university president along with the “golden key.”

Professor Huang Lujun, Professor Geng Lin and their team from the School of Materials Science and Engineering were responsible for manufacturing the titanium alloy keys. They overcame challenges in integrated control and surface finishing to achieve high-performance titanium alloy and surface polishing, according to a press report by bjnews.com.

Additionally, Professor Wang Langping’s team utilized comprehensive ion implantation and surface strengthening technology to prepare the coating on the titanium alloy keys. The technology solved technical challenges related to high wear resistance and anti-cold welding in core components of space docking mechanisms, providing crucial support for over 10 successful dockings of Shenzhou, Tianzhou spacecraft, and the space station.

For more information: Harbin Institute of Technology 

Image: HIT’s key 

Nanosized blocks spontaneously assemble in water to create tiny floating checkerboards

The scientific community has successfully engineered nanosized cubes that exhibit the remarkable ability to spontaneously form a two-dimensional checkerboard pattern when placed on the surface of water. This innovative research introduces a simple and efficient approach to creating complex nanostructures through the application of a technique known as self-assembly.

“It’s a cool way to get materials to build themselves,” said study co-senior author Andrea Tao, a professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the University of California San Diego. “You don’t have to go into a nanofabrication lab and do all these complex and precise manipulations.”

Each nanocube is composed of a silver crystal with a mixture of hydrophobic (oily) and hydrophilic (water-loving) molecules attached to the surface. When a suspension of these nanocubes is introduced to a water surface, they arrange themselves such that they touch at their corner edges. This arrangement creates an alternating pattern of solid cubes and empty spaces, resulting in a checkerboard pattern.

The self-assembly process is driven by the surface chemistry of the nanocubes. A high density of hydrophobic molecules on the surface brings the cubes together to minimize their interaction with water. Meanwhile, the long chains of hydrophilic molecules cause enough repulsion to create voids between the cubes, creating the checkerboard pattern.

To fabricate the structure, researchers applied drops of the nanocube suspension onto a petri dish containing water. The resulting checkerboard can be easily transferred to a substrate by dipping the substrate into the water and slowly withdrawing it, allowing the nanostructure to coat it.

This study stems from a collaborative effort between multiple research groups that are part of the UC San Diego Materials Research Science and Engineering Center (MRSEC). The work featured a synergistic combination of computational and experimental techniques. “We’ve built a continuous feedback loop between our computations and experiments,” said Tao. “We used computer simulations to help us design the materials at the nanoscale and predict how they will behave. We also used our experimental results in the lab to validate the simulations, fine tune them and build a better model.”

In designing the material, researchers chose silver crystal nanocubes due to the Tao lab’s expertise in their synthesis. Determining the optimal surface chemistry required extensive computational experimentation, which was led by Gaurav Arya, a professor in the Department of Mechanical Engineering and Materials Science at Duke University and co-senior author of the study.

The simulations identified the best molecules to attach to the nanocubes and predicted how the cubes would interact and assemble on the water surface. The simulations were iteratively refined using experimental data obtained by Tao’s lab. Electron microscopy performed by the lab of study co-author Alex Frañó, a professor in the Department of Physics at UC San Diego, confirmed the formation of the desired checkerboard structures.

Tao envisions applications for the nanocube checkerboard in optical sensing. “Such a nanostructure can manipulate light in interesting ways,” she explained. “The spaces between the cubes, particularly near the corner edges where the cubes connect, can act as tiny hotspots that focus or trap light. That could be useful for making new types of optical elements like nanoscale filters or waveguides.”

For more information: Nature Communications

Image: SEM image of the mesophase constructed with edge–edge connected checkerboard lattice obtained with Ag NCs post-synthetically modified with a feedstock mixture of 50 µM PEG20k-SH and 6 µM C16-SH. Scale bar = 500 nm, inset = 100 nm.

Ontario Tech University and Penn State sign MOU on engineering studies, research

Penn State’s College of Engineering and Ontario Tech University’s Faculty of Engineering and Applied Science (FEAS) have officially established a memorandum of understanding (MOU). This agreement aims to harness the combined expertise of both institutions in the fields of engineering and applied sciences.

The MOU was initiated by Akhlesh Lakhtakia, Evan Pugh University Professor and Charles G. Binder Professor of Engineering Science and Mechanics at Penn State, and Moustafa El-Gindy, professor in the FEAS at Ontario Tech University.

“The Ontario Tech Faculty of Engineering and Applied Science is excited about the opportunities to advance research and innovation through this partnership with Penn State,” said Hossam Kishawy, dean of the Faculty of Engineering and Applied Science at Ontario Tech University. “Both institutions value integrity, inclusion and ingenuity, and recognize the vital role of exchanging knowledge and educational experience to drive forward the field of engineering.”

The five-year agreement aims to enhance Ontario Tech and Penn State’s research, innovation and educational excellence in a variety of collaborative endeavors, including:

  • Professional training programs.
  • Faculty and scholar exchanges.
  • Joint research projects and educational programs.
  • Exchange of scientific materials, publications and information.
  • Joint seminars and other academic events.

“Global collaborations position the Penn State College of Engineering for success and contribute to our overall mission as a land-grant institution,” said Tonya Peeples, Harold and Inge Marcus Dean of Engineering in the college. “We look forward to the potential for funding joint research projects and knowledge exchange that this agreement may help enable.”

For more information: Penn State University

AI chips could get a sense of time

Researchers have developed the first memristor with a tunable ‘relaxation time,’ potentially enabling artificial neural networks to process time-dependent data more efficiently. The study was led by the University of Michigan.

Memristors, electrical components that store information in their electrical resistance, could reduce AI’s energy needs by about a factor of 90 compared to today’s graphical processing units. Already, AI is projected to account for about half a percent of the world’s total electricity consumption in 2027, which has the potential to balloon as more companies sell and use AI tools.

“Right now, there’s a lot of interest in AI, but to process bigger and more interesting data, the approach is to increase the network size. That’s not very efficient,” said Wei Lu, the James R. Mellor Professor of Engineering at U-M and co-corresponding author of the study with John Heron, U-M associate professor of materials science and engineering.

The problem is that GPUs operate very differently from the artificial neural networks that run the AI algorithms—the whole network and all its interactions must be sequentially loaded from the external memory, which consumes both time and energy. In contrast, memristors offer energy savings because they mimic key aspects of the way that both artificial and biological neural networks function without external memory. To an extent, the memristor network can embody the artificial neural network.

“We anticipate that our brand-new material system could improve the energy efficiency of AI chips six times over the state-of-the-art material without varying time constants,” said Sieun Chae, a recent U-M Ph.D. graduate in materials science and engineering and co-first-author of the study with Sangmin Yoo, a recent U-M PhD graduate in electrical and computer engineering.

In a biological neural network, timekeeping is achieved through relaxation. Each neuron receives electrical signals and sends them on, but it isn’t a guarantee that a signal will move forward. Some threshold of incoming signals must be reached before the neuron will send its own, and it has to be met in a certain amount of time. If too much time passes, the neuron is said to relax as the electrical energy seeps out of it. Having neurons with different relaxation times in our neural networks helps us understand sequences of events.

Memristors operate a little differently. Rather than the total presence or absence of a signal, what changes is how much of the electrical signal gets through. Exposure to a signal reduces the resistance of the memristor, allowing more of the next signal to pass. In memristors, relaxation means that the resistance rises again over time.

While Lu’s group had explored building relaxation time into memristors in the past, it was not something that could be systematically controlled. But now, Lu and Heron’s team have shown that variations on a base material can provide different relaxation times, enabling memristor networks to mimic this timekeeping mechanism.

The team built the materials on the superconductor YBCO, made of yttrium, barium, carbon and oxygen. It has no electrical resistance at temperatures below -292 Fahrenheit, but they wanted it for its crystal structure. It guided the organization of the magnesium, cobalt, nickel, copper and zinc oxides in the memristor material.

Heron calls this type of oxide, an entropy-stabilized oxide, the “kitchen sink of the atomic world”—the more elements they add, the more stable it becomes. By changing the ratios of these oxides, the team achieved time constants ranging from 159 to 278 nanoseconds, or trillionths of a second. The simple memristor network they built learned to recognize the sounds of the numbers zero to nine. Once trained, it could identify each number before the audio input was complete.

These memristors were made through an energy-intensive process because the team needed perfect crystals to precisely measure their properties, but they anticipate that a simpler process would work for mass manufacturing.

“So far, it’s a vision, but I think there are pathways to making these materials scalable and affordable,” Heron said. “These materials are earth-abundant, nontoxic, cheap and you can almost spray them on.”

For more information: Nature Electronics

Image: The entropy-stabilized oxide is sandwiched between the superconductor YBCO, on which it was grown, and a titanium and platinum electrode. The many colors represent the different components of the entropy-stabilized oxide. By tweaking the ratios of the components, the team could create memristors that relaxed at different rates after exposure to an electrical current, mimicking the way that neurons sense time. Credit: Sieun Chae and Sangmin Yoo, University of Michigan.

Researchers develop novel resin for 3D printing intraocular devices

Innovative resin for 3D printing intraocular lens (IOL) devices, developed by University of East Anglia researchers, could revolutionize cataract and refractive surgeries. This breakthrough enhances the production of eye implants, which are essential for people with cataracts whose natural lenses have clouded, affecting vision.

Historically, IOLs have been made from a variety of materials, including glass and silicone, although more recently, the industry has significantly evolved to predominantly use acrylic materials.

Currently hydrophilic and hydrophobic acrylic are the most commonly used materials due to their excellent optical clarity, flexibility, biocompatibility with the body and for their stability and safety within the eye.

Current methods of making IOLs use lathing and molding techniques. While these methods offer the production of well-engineered and high-optical quality devices, they also come with inherent limitations, particularly in terms of design complexity and customisation.

Dr. Aram Saeed said: “3D printing could significantly enhance the production of ocular devices, not only improving speed and precision in manufacturing but also enabling greater complexity and customization in design. Our proof-of-concept paper is the first in a series that will detail our developments in this area and set the stage for transforming eye care practices globally. Our work combines material science with healthcare technology and requires extensive know-how in developing these types of ocular devices. As we continue to publish our findings and share our advancements, we aim to be at the forefront of the industry, working with industrial partners and researchers worldwide to refine and enhance the technology.”

The study found that the 3D-printed lenses have good optical clarity, can be folded, and can be implanted into a human capsular bag.

Co-author Michael Wormstone, Emeritus Professor at UEA’s School of Biological Sciences, said: “If successful in further developments, this new technology could transform the industry by enabling portable manufacturing solutions, especially beneficial in remote and economically disadvantaged areas. It also has the potential to support the production of premium, customized lenses that could enhance surgical outcomes in more advanced healthcare settings.”

The team’s efforts have been recognized with the awarding of a United States patent assigned to UEA Enterprise Limited, a business entity of the university focused on fostering innovation and commercializing research.

The UEA researchers continue to work closely with industry partners to refine the technology. It is hoped that clinical trials could start in the next few years.

For more information: Current Eye Research

Kentucky Junior wins international science fair

Grace Sun, a junior at Paul Laurence Dunbar High School in Kentucky, earned the top prize at the 2024 Regeneron International Science & Engineering Fair (ISEF) in the Materials Science category. Her entry, “Novel Chemical Doping Strategy to Enhance N-Type Organic Electrochemical Transistors,”researches building a better organic electrochemical transistor that she hopes will be used to develop new electronic devices that could help detect and treat serious illnesses like diabetes, epilepsy, and organ failure.

ISEF drew nearly 2,000 students from all over the world. Capping this year’s competition in Los Angeles, Regeneron and Society for Science presented Grace the $75,000 honor for the George D. Yancopoulos Innovator Award, which goes to the best first-place project based on outstanding and innovative research as well as the potential impact of her work.

Dunbar High School also had two other students to place in their respective divisions at ISEF. Alex Thuringer was fourth in Engineering Technology for “An Improved Color Filter Array Design Using Metafilters,” and Joseph Vulakh placed fourth in Mathematics for “Twisted Homogeneous Racks over the Alternating Groups.”

For more information: Fayette County Public Schools

Image: Grace Sun at the Los Angeles competition.

Organic semiconductors doped with air to increase conductivity in new study

Researchers have discovered that doping organic semiconductors with air can significantly enhance their electrical conductivity. This breakthrough could lead to more efficient organic electronic devices, such as flexible displays and sensors

Semiconductors are the foundation of all modern electronics. Now, researchers at Linköping University have developed a new method where organic semiconductors can become more conductive with the help of air as a dopant. The study is a significant step towards future cheap and sustainable organic semiconductors.

“We believe this method could significantly influence the way we dope organic semiconductors. All components are affordable, easily accessible, and potentially environmentally friendly, which is a prerequisite for future sustainable electronics,” says Simone Fabiano, associate professor at Linköping University.

Semiconductors based on conductive plastics instead of silicon have many potential applications. Among other things, organic semiconductors can be used in digital displays, solar cells, LEDs, sensors, implants, and for energy storage.

To enhance conductivity and modify semiconductor properties, so-called dopants are typically introduced.

These additives facilitate the movement of electrical charges within the semiconductor material and can be tailored to induce positive (p-doping) or negative (n-doping) charges. The most common dopants used today are often either very reactive (unstable), expensive, challenging to manufacture, or all three.

Now, researchers at Linköping University have developed a doping method that can be performed at room temperature, where inefficient dopants such as oxygen are the primary dopant, and light activates the doping process.

“Our approach was inspired by nature, as it shares many analogies with photosynthesis, for example. In our method, light activates a photocatalyst, which then facilitates electron transfer from a typically inefficient dopant to the organic semiconductor material,” says Simone Fabiano.

The new method involves dipping the conductive plastic into a special salt solution – a photocatalyst – and then illuminating it with light for a short time. The duration of illumination determines the degree to which the material is doped. Afterwards, the solution is recovered for future use, leaving behind a p-doped conductive plastic in which the only consumed substance is oxygen in the air.

This is possible because the photocatalyst acts as an “electron shuttle”, taking electrons or donating them to material in the presence of sacrificial weak oxidants or reductants. This is common in chemistry but has not been used in organic electronics before.

“It’s also possible to combine p-doping and n-doping in the same reaction, which is quite unique. This simplifies the production of electronic devices, particularly those where both p-doped and n-doped semiconductors are required, such as thermoelectric generators. All parts can be manufactured at once and doped simultaneously instead of one by one, making the process more scalable,” says Simone Fabiano.

The doped organic semiconductor has better conductivity than traditional semiconductors, and the process can be scaled up. Simone Fabiano and his research group at the Laboratory of Organic Electronics showed earlier in 2024 how conductive plastics could be processed from environmentally friendly solvents like water; this is their next step.

“We are at the beginning of trying to fully understand the mechanism behind it and what other potential application areas exist. But it’s a very promising approach showing that photocatalytic doping is a new cornerstone in organic electronics,” says Simone Fabiano, a Wallenberg Academy Fellow.

For more information: Nature