Susumu Kitagawa, Richard Robson and Omar Yaghi have been awarded the 2025 Nobel Prize for Chemistry “for developing metal-organic frameworks”.

The award includes a SEK 11m prize ($1.2m), which is shared equally by the winners. The prize will be presented at a ceremony in Stockholm on 10 December.

The prize was announced this morning by members of the Royal Swedish Academy of Science. Speaking on the phone during the press conference, Kitagawa noted that he was “deeply honoured and delighted” that his research had been recognized. 

A new framework

Beginning in the late 1980s and for the next couple of decades, the trio, who are all trained chemists, developed a new form of molecular architecture in that metal ions function as cornerstones that are linked by long organic carbon-based molecules.

Together, the metal ions and molecules form crystals that contain large cavities through which gases and other chemicals can flow.

“It’s a little like Hermione’s handbag – small on the outside, but very large on the inside,” noted Heiner Linke, chair of the Nobel Committee for Chemistry.

Yet the trio had to overcome several challenges before they could be used such as making them stable and flexible, which Kitagawa noted “was very tough”.

These porous materials are now called metal-organic frameworks (MOF). By varying the building blocks used in the MOFs, researchers can design them to capture and store specific substances as well as drive chemical reactions or conduct electricity.

“Metal-organic frameworks have enormous potential, bringing previously unforeseen opportunities for custom-made materials with new functions,” added Linke.

Following the laureates’ work, chemists have built tens of thousands of different MOFs.

3D MOFs are an important class of materials that could be used in applications as diverse as sensing, gas storage, catalysis and optoelectronics.  

MOFs are now able to capture water from air in the desert, sequester carbon dioxide from industry effluents, store hydrogen gas, recover rare-earth metals from waste, break down oil contamination as well as extract “forever chemicals” such as PFAS from water.

“My dream is to capture air and to separate air into CO₂, oxygen and water and convert them to usable materials using renewable energy,” noted Kitagawa. 

Their 2D versions might even be used as flexible material platforms to realize exotic quantum phases, such as topological and anomalous quantum Hall insulators.

Life scientific

Kitagawa was born in 1951 in Kyoto, Japan. He obtained a PhD from Kyoto University, Japan, in 1979 and then held positions at Kindai University before joining Tokyo Metropolitan University in 1992. He then joined Kyoto University in 1998 where he is currently based.

Robson was born in 1937 in Glusburn, UK. He obtained a PhD from University of Oxford in 1962. After postdoc positions at California Institute of Technology and Stanford University, in 1966 he moved to the University of Melbourne where he remained for the rest of his career.

Yaghi was born in 1965 in Amman, Jordan. He obtained a PhD from University of Illinois Urbana-Champaign, US, in 1990. He then held positions at Arizona State University, the University of Michigan and the University of California, Los Angeles, before joining the University of California, Berkeley, in 2012 where he is currently based.

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For many years, I’ve been a judge for awards and prizes linked to research and innovation in engineering and physics. It’s often said that it’s better to give than to receive, and it’s certainly true in this case. But another highlight of my involvement with awards is learning about cutting-edge innovations I either hadn’t heard of or didn’t know much about.

One area that never fails to fascinate me is the development of new and advanced materials. I’m not a materials scientist – my expertise lies in creating monitoring systems for engineering – so I apologize for any over-simplification in what follows. But I do want to give you a sense of just how impressive, challenging and rewarding the field of materials science is.

It’s all too easy to take advanced materials for granted. We are in constant contact with them in everyday life, whether it’s through applications in healthcare, electronics and computing or energy, transport, construction and process engineering. But what are the most important materials innovations right now – and what kinds of novel materials can we expect in future?

Drivers of innovation

There are several – and all equally important – drivers when it comes to materials development. One is the desire to improve the performance of products we’re already familiar with. A second is the need to develop more sustainable materials, whether that means replacing less environmentally friendly solutions or enabling new technology. Third, there’s the drive for novel developments, which is where some of the most ground-breaking work is occurring.

On the environmental front, we know that there are many products with components that could, in principle, be recycled. However, the reality is that many products end up in landfill because of how they’ve been constructed. I was recently reminded of this conundrum when I heard a research presentation about the difficulties of recycling solar panels.

Photovoltaic cells become increasingly inefficient with time and most solar panels aren’t expected to last more than about 30 years. Trouble is, solar panels are so robustly built that recycling them requires specialized equipment and processes. More often than not, solar panels just get thrown away despite mostly containing reusable materials such as glass, plastic and metals – including aluminium and silver.

It seems ironic that solar panels, which enable sustainable living, could also contribute significantly to landfill. In fact, the problem could escalate significantly if left unaddressed. There are already an estimated 1.8 million solar panels in use the UK, and potentially billions around the world, with a rapidly increasing install base. Making solar panels more sustainable is surely a grand challenge in materials science.

Waste not, want not

Another vital issue concerns our addiction to new tech, which means we rarely hang on to objects until the end of their life; I mean, who hasn’t been tempted by a shiny new smartphone even though the old one is perfectly adequate? That urge for new objects means we need more materials and designs that can be readily re-used or recycled, thereby reducing waste and resource depletion.

As someone who works in the aerospace industry, I know first-hand how companies are trying to make planes more fuel efficient by developing composite materials that are stronger and can survive higher temperatures and pressures – for example carbon fibre and composite matrix ceramics. The industry also uses “additive manufacturing” to enable more intricate component design with less resultant waste.

Plastics are another key area of development. Many products are made from single type, recyclable materials, such as polyethylene or polypropylene, which benefit from being light, durable and capable of withstanding chemicals and heat. Trouble is, while polyethene and polypropene can be recycled, they both create the tiny “microplastics” that, as we know all too well, are not good news for the environment.

Bio-based materials are becoming more common for everyday items. Think about polylactic acid (PLA), which is a plant-based polymer derived from renewable resources such as cornstarch or sugar cane. Typically used for food or medical packaging, it’s usually said to be “compostable”, although this is a term we need to view with caution.

Sadly, PLA does not degrade readily in natural environments or landfill. To break it down, you need high-temperature, high-moisture industrial composting facilities. So whilst PLAs come from natural plants, they are not straightforward to recycle, which is why single-use disposable items, such as plastic cutlery, drinking straws and plates, are no longer permitted to be made from it.

Thankfully, we’re also seeing greater use of more sustainable, natural fibre composites, such as flax, hemp and bamboo (have you tried bamboo socks or cutlery?). All of which brings me to an interesting urban myth, which is that in 1941 legendary US car manufacturer Henry Ford built a car apparently made entirely of a plant-based plastic – dubbed the “soybean” car (see box).

The soybean car: fact or fiction?

Henry Ford’s 1941 “soybean” car, which was built entirely of a plant-based plastic, was apparently motivated by a need to make vehicles lighter (and therefore more fuel efficient), less reliant on steel (which was in high demand during the Second World War) and safer too. The exact ingredients of the plastic are, however, not known since there were no records kept.

Speculation is that it was a combination of soybeans, wheat, hemp, flax and ramie (a kind of flowering nettle). Lowell Overly, a Ford designer who had major involvement in creating the car, said it was “soybean fibre in a phenolic resin with formaldehyde used in the impregnation”. Despite being a mix of natural and synthetic materials – and not entirely made of soybeans – the car was nonetheless a significant advancement for the automotive industry more than eight decades ago.

Avoiding the “solar-panel trap”

So what technology developments do we need to take materials to the next level? The key will be to avoid what I coin the “solar-panel trap” and find materials that are sustainable from cradle to grave. We have to create an environmentally sustainable economic system that’s based on the reuse and regeneration of materials or products – what some dub the “circular economy”.

Sustainable composites will be essential. We’ll need composites that can be easily separated, such as adhesives that dissolve in water or a specific solvent, so that we can cleanly, quickly and cheaply recover valuable materials from complex products. We’ll also need recycled composites, using recycled carbon fibre, or plastic combined with bio-based resins made from renewable sources like plant-based oils, starches and agricultural waste (rather than fossil fuels).

Vital too will be eco-friendly composites that combine sustainable composite materials (such as natural fibres) with bio-based resins. In principle, these could be used to replace traditional composite materials and to reduce waste and environmental impact.

Another important trend is developing novel metals and complex alloys. As well as enhancing traditional applications, these are addressing future requirements for what may become commonplace applications, such as wide-scale hydrogen manufacture, transportation and distribution.

Soft and stretchy

Then there are “soft composites”. These are advanced, often biocompatible materials that combine softer, rubbery polymers with reinforcing fibres or nanoparticles to create flexible, durable and functional materials that can be used for soft robotics, medical implants, prosthetics and wearable sensors. These materials can be engineered for properties like stretchability, self-healing, magnetic actuation and tissue integration, enabling innovative and patient-friendly healthcare solutions.

And have you heard of e-textiles, which integrate electronic components into everyday fabrics? These materials could be game-changing for healthcare applications by offering wearable, non-invasive monitoring of physiological information such as heart rate and respiration.

Further applications could include advanced personal protective equipment (PPE), smart bandages and garments for long-term rehabilitation and remote patient care. Smart textiles could revolutionize medical diagnostics, therapy delivery and treatment by providing personalized digital healthcare solutions.

Towards “new gold”

I realize I have only scratched the surface of materials science – an amazing cauldron of ideas where physics, chemistry and engineering work hand in hand to deliver groundbreaking solutions. It’s a hugely and truly important discipline. With far greater success than the original alchemists, materials scientists are adept at creating the “new gold”.

Their discoveries and inventions are making major contributions to our planet’s sustainable economy from the design, deployment and decommission of everyday items, as well as finding novel solutions that will positively impact way we live today. Surely it’s an area we should celebrate and, as physicists, become more closely involved in.

The post Is materials science the new alchemy for the 21st century? appeared first on Physics World.

Inspired by the Japanese art of kirigami, researchers in Canada and France have designed a parachute that can safely and accurately deliver its payloads when dropped directly above its target. Tested in realistic outdoor conditions, the parachute’s deformable design stabilizes the airflow around its porous structure, removing the need to drift as it falls. With its simple and affordable design, the parachute could have especially promising uses in areas including drone delivery and humanitarian aid.

When a conventional parachute is deployed, it cannot simply fall vertically towards its target. To protect itself from turbulence, which can cause its canopy to collapse, it glides at an angle that breaks the symmetry of the airflow around it, stabilizing the parachute against small perturbations.

But this necessity comes at a cost. When dropping a payload from a drone or aircraft, this gliding angle means parachutes will often drift far from their intended targets. This can be especially frustrating and potentially dangerous for operations such as humanitarian aid delivery, where precisely targeted airdrops are often vital to success.

To address this challenge, researchers led by David Mélançon at Polytechnique Montréal looked to kirigami, whereby paper is cut and folded to create elaborate 3D designs. “Previously, kirigami has been used to morph flat sheets into 3D shapes with programmed curvatures,” Mélançon explains. “We proposed to leverage kirigami’s shape morphing capability under fluid flow to design new kinds of ballistic parachutes.”

Wind-dispersed seeds

As well as kirigami, the team drew inspiration from nature. Instead of relying on a gliding angle, many wind-dispersed seeds are equipped with structures that stabilize the airflow around them: including the feathery bristles of dandelion seeds, which create a stabilized vortex in their wake; and the wings of sycamore and maple seeds, which cause them to rapidly spin as they fall. In each case, these mechanisms provide plants with passive control over where their seeds land and germinate.

For their design, Mélançon’s team created a parachute that can deform into a shape pre-programmed by a pattern of kirigami cuts, etched into a flexible disc using a laser cutter. “Our parachutes are simple flat discs, with circumferential slits inspired by a kirigami motif called a closed loop,” Mélançon describes. “Instead of attaching the payload with strings at the outer edge of the disk, we directly mount it its centre.”

When dropped, a combination of air resistance and the weight of the free-falling payload deformed the parachute into an inverted, porous bell shape. “The slits in the kirigami pattern are stretched, forcing air through its multitude of small openings,” Mélançon continues. “This ensures that the air flows in an orderly manner without any major chaotic turbulence, resulting in a predictable trajectory.”

The researchers tested their parachute extensively using numerical simulations combined with wind tunnel experiments and outdoor tests, where they used the parachute to drop a water bottle from a hovering drone. In this case, the parachute delivered its payload safely to the ground from a height of 60 m directly above its target.

Easy to make

Mélançon’s team tested their design with a variety of parachute sizes and kirigami patterns, demonstrating that designs with lower load-to-area ratios and more deformable patterns can reach comparable terminal velocity to conventional parachutes – with far greater certainty over where they will land. Compared with conventional parachutes, which are often both complex and costly to manufacture, kirigami-based designs will be far easier to fabricate.

“Little hand labour is necessary,” Mélançon says. “We have made parachutes out of sheets of plastic, paper or cardboard. We need a sheet of material with a certain rigidity, that’s all.”

By building on their design, the researchers hope that future studies will pave the way for new improvements in package home delivery. It could even advance efforts to deliver urgently needed aid during conflicts and natural disasters to those who need it most.

The parachute is described in Nature.

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Nothing is really known about the origin of the world-famous “pitch-drop experiment” at the School of Physics, Trinity College Dublin. Discovered in the 1980s during a clear-out of dusty cupboards, this curious glass funnel contains a dark, black substance. All we do know is that it was prepared in October 1944 (assuming you trust the writing on it). We don’t know who filled the funnel, with what exactly, or why.

Placed on a shelf at Trinity, the funnel was largely ignored by generations of students passing by. But anyone who looked closely would have seen a drop forming slowly at the bottom of the funnel, preparing to join older drops that had fallen roughly once a decade. Then, in 2013 this ultimate example of “slow science” went viral when a webcam recorded a video of a tear-drop blob of pitch falling into the beaker below.

The video attracted more than two million hits on YouTube (a huge figure back then) and the story was covered on the main Irish evening TV news. We also had a visit from German news magazine Der Spiegel, while Discover named it as one of the top 100 science stories of 2013. As one of us (SH) described in a 2014 Physics World feature, the iconic experiment became “the drop heard round the world”.

Pitching the idea

Inspired by that interest, we decided to create custom-made replicas of the experiment to send to secondary schools across Ireland as an outreach initiative. It formed part of our celebrations of 300 years of physics at Trinity, which dates back to 1724 when the college established the Erasmus Smith’s Professorship in Natural and Experimental Philosophy.

An outreach activity that takes 10 years for anything to happen is obviously never going to work. Technical staff at Trinity’s School of Physics, who initiated the project, therefore experimented for months with different tar samples. Their goal was a material that appears solid but will lead to a falling drop every few months – not every decade.

After hitting upon a special mix of two types of bitumen in just the right proportion, the staff also built a robust experimental set-up consisting of a stand, a funnel and flask to hold any fallen drops. Each was placed on a wooden base and contained inside a glass bell jar. There were also a thermometer and a ruler for data-taking along with a set of instructions.

On 27 November 2024 we held a Zoom call with all participating schools, culminating in the official call to remove the funnel stopper

Over 100 schools – scattered all over Ireland – applied for one of the set-ups, with a total of 37 selected to take part. Most kits were personally hand-delivered to schools, which were also given a video explaining how to unpack and assemble the set-ups. On 27 November 2024 we held a Zoom call with all participating schools, culminating in the official call to remove the funnel stopper. The race was on.

Joining the race

Each school was asked to record the temperature and length of the thread of pitch slowly emerging from the funnel. They were also given a guide to making a time-lapse video of the drop and provided with information about additional experiments to explore the viscosity of other materials.

To process incoming data, we set up a website, maintained by yet another one of our technical staff. It contained interactive graphs showing the increased in drop length for every school, together with the temperature when the measurement was taken. All data were shared between schools.

After about four months, four schools had recorded a pitch drop and we decided to take stock at a half-day event at Trinity in March 2025. Attended by more than 80 pupils aged 12–18 and teachers from 17 schools, we were amazed by how much excitement our initiative had created. It spawned huge levels of engagement, with lots of colourful posters.

By the end of the school year, most had recorded a drop, showing our tar mix had worked well. Some schools had also done experiments testing other viscous materials, such as syrup, honey, ketchup and oil, examining the effect of temperature on flow rate. Others had studied the flow of granular materials, such as salt and seeds. One school had even captured on video the moment their drop fell, although sadly nobody was around to see it in person.

Some schools displayed the kits in their school entrance, others in their trophy cabinet. One group of students appeared on their local radio station; another streamed the set-up live on YouTube. The pitch-drop experiment has been a great way for students to learn basic scientific skills, such as observation, data-taking, data analysis and communication.

As for teachers, the experiment is an innovative way for them to introduce concepts such as viscosity and surface tension. It lets them explore the notion of multiple variables, measurement uncertainty and long-time-scale experiments. Some are now planning future projects on statistical analysis using the publicly available dataset or by observing the pitch drop in a more controlled environment.

Wouldn’t it be great if other physics departments followed our lead?

The post How the slowest experiment in the world became a fast success appeared first on Physics World.

Adding energy to a system usually heats it up, but physicists at the University of Innsbruck in Austria have now discovered a scenario in which this is not the case. Their new platform – a one-dimensional fluid of strongly interacting atoms cooled to just a few nanokelvin above absolute zero and periodically “kicked” using an external force – could be used to study how objects transition from being quantum and ordered to classical and chaotic.

Our everyday world is chaotic and chaos plays a crucial and often useful role in many areas of science – from nonlinear complex systems in mathematics, physics and biology to ecology, meteorology and economics. How a system evolves depends on its initial conditions, but this evolution is, by nature, inherently unpredictable.

While we know how chaos emerges in classical systems, how it does so in quantum materials is still little understood. When this happens, the quantum system reverts to being a classical one.

The quantum kicked rotor

Researchers have traditionally studied chaotic behaviour in driven systems – that is, rotating objects periodically kicked by an external force. The quantum version of these is the quantum kicked rotor (QKR). Here, quantum coherence effects can prevent the system from absorbing external energy, meaning that, in contrast to its classical counterpart, it doesn’t heat up – even if a lot of energy is applied. This “dynamical localization” effect has already been seen in dilute ultracold atomic gases.

The QKR is a highly idealized single-particle model system, explains study lead Hanns-Christoph Nägerl. However, real-world systems contain many particles that interact with each other – something that can destroy dynamical localization. Recent theoretical work has suggested that this localization may persist in some types of interacting, even strongly interacting, many-body quantum systems – for example, in 1D bosonic gases.

In the new work, Nägerl and colleagues made a QKR by subjecting samples of ultracold caesium (Cs) atoms to periodic kicks by means of a “flashed-on lattice potential”. They did this by loading a Bose–Einstein condensate of these atoms into an array of narrow 1D tubes created by a 2D optical lattice formed by laser beams propagating in the x–y plane at right angles to each other. They then increased the power of the beams to heat up the Cs atoms.

Many-body dynamical localization

The researchers expected the atoms to collectively absorb energy over the course of the experiment. Instead, when they recorded how their momentum distribution evolved, they found that it actually stopped spreading and that the system’s energy reached a plateau. “Despite being continually kicked and strongly interacting, it no longer absorbed energy,” says Nägerl. “We say that it had localized in momentum space – a phenomenon known as many-body dynamical localization (MBDL).”

In this state, quantum coherence and many-body interactions prevent the system from heating up, he adds. “The momentum distribution essentially freezes and retains whatever structure it has.”

Nägerl and colleagues repeated the experiment by varying the interaction between the atoms – from zero (non-interacting) to strongly interacting. They found that the system always localizes.

Quantum coherence is crucial for preventing thermalization

“We had already found localization for our interacting QKR in earlier work and set out to reproduce these results in this new study,” Nägerl tells Physics World. “We had not previously realised the significance of our findings and thought that perhaps we were doing something wrong, which turned out not to be the case.”

The MBDL is fragile, however – something the researchers proved by introducing randomness into the laser pulses. A small amount of disorder is enough the destroy the localization effect and restore diffusion, explains Nägerl: the momentum distribution smears out and the kinetic energy of the system rises sharply, meaning that it is absorbing energy.

“This test highlights that quantum coherence is crucial for preventing thermalization in such driven many-body systems,” he says.

Simulating such a system on classical computers is only possible for two or three particles, but the one studied in this work, reported in Science, contains 20 or more. “Our new experiments now provide precious data to which we can compare the QKR model system, which is a paradigmatic one in quantum physics,” adds Nägerl.

Looking ahead, the researchers say they would now like to find out how stable MBDL is to various external perturbations. “In our present work, we report on MBDL in 1D, but would it happen in a 2D or a 3D system?” asks Nägerl. “I would like to do an experiment in which we have a 1D + 1D situation, that is, where the 1D is allowed to communicate with just one neighbouring 1D system (via tunnelling; by lowering the barrier to this system in a controlled way).”

Another way of perturbing the system would be to add a local defect – for example a bump in the potential of a different atom, he says. “Generally speaking, we would like to measure the ‘phase diagram’ for MBDL, where the axes of the graph would quantify the strength of the various perturbations we apply.”

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Physicists at Osaka Metropolitan University in Japan and the Korea Advanced Institute of Science and Technology (KAIST) claim to have observed the quantum counterpart of the classic Kelvin-Helmholtz instability (KHI), which is the most basic instability in fluids. The effect, seen in a quantum gas of ⁷Li atoms, produces a new type of exotic vortex pattern called an eccentric fractional skyrmion. The finding not only advances our understanding of complex topological quantum systems, it could also help in the development of next-generation memory and storage devices.

Topological defects occur when a system rapidly transitions from a disordered to an ordered phase. These defects, which can occur in a wide range of condensed matter systems, from liquid crystals and atomic gases to the rapidly cooling early universe, can produce excitations such as solitons, vortices and skyrmions.

Skyrmions, first discovered in magnetic materials, are swirling vortex-like spin structures that extend across a few nanometres in a material. They can be likened to 2D knots in which the magnetic moments rotate about 360° within a plane.

Eccentric fractional skyrmions contain singularities

Skyrmions are topologically stable, which makes them robust to external perturbations, and are much smaller than the magnetic domains used to encode data in today’s disk drives. That makes them ideal building blocks for future data storage technologies such as “racetrack” memories. Eccentric fractional skyrmions (EFSs), which had only been predicted in theory until now, have a crescent-like shape and contain singularities – points in which the usual spin structure breaks down, creating sharp distortions as it becomes unsymmetrical.

“To me, the large crescent moon in the upper right corner of Van Gogh’s ‘The Starry Night’ also looks exactly like an EFS,” says Hiromitsu Takeuchi at Osaka, who co-led this new study with Jae-Yoon Choi of KAIST. “EFSs carry half the elementary charge, which means they do not fit into traditional classifications of topological defects.”

The KHI is a classic phenomenon in fluids in which waves and vortices form at the interface between two fluids moving at different speeds. “To observe the KHI in quantum systems, we need a structure containing a thin superfluid interface (a magnetic domain wall), such as in a quantum gas of ⁷Li atoms,” says Takeuchi. “We also need experimental techniques that can skilfully control the behaviour of this interface. Both of these criteria have recently been met by Choi’s group.”

The researchers began by cooling a gas of ⁷Li atoms to near absolute zero temperatures to create a multi-component Bose-Einstein condensate – a quantum superfluid containing two streams flowing at different speeds. At the interface of these streams, they observed vortices, which corresponded to the predicted EFSs.

The behaviour of the KHI is universal

“We have shown that the behaviour of the KHI is universal and exists in both the classical and quantum regimes,” says Takeuchi. This finding could not only lead to a better understanding of quantum turbulence and the unification of quantum and classic hydrodynamics, it could also help in the development of technologies such as next-generation storage and memory devices and spintronics, an emerging technology in which magnetic spin is used to store and transfer information using much less energy than existing electronic devices.

“By further refining the experiment, we might be able to verify certain predictions (some of which were made as long ago as the 19th century) about the wavelength and frequency of KHI-driven interface waves in non-viscous quantum fluids, like the one studied in this work,” he adds.

“In addition to the universal finger pattern we observed, we expect structures like zipper and sealskin patterns, which are unique to such multi-component quantum fluids,” Takeuchi tells Physics World. “As well as experiments, it is necessary to develop a theory that more precisely describes the motion of EFSs, the interaction between these skyrmions and their internal structure in the context of quantum hydrodynamics and spontaneous symmetry breaking.”

The study is detailed in Nature Physics.

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The way in which new materials are designed is changing, with data becoming ever more important in the discovery and design process. Designing soft materials is a particularly tricky task that requires selection of different “building blocks” (monomers in polymeric materials, for example) and optimization of their arrangement in molecular space.

Soft materials also exhibit many complex behaviours that need to be balanced, and their molecular and structural complexities make it difficult for computational methods to help in the design process – often requiring costly trial and error experimental approaches instead. Now, researchers at Hokkaido University in Japan have combined artificial intelligence (AI) with data mining methods to develop an ultra-sticky hydrogel material suitable for very wet environments – a difficult design challenge because the properties that make materials soft don’t usually promote adhesion. They report their findings in Nature.

Challenges of designing sticky hydrogels

Hydrogels are a permeable soft material composed of interlinked polymer networks with water held within the network. Hydrogels are highly versatile, with properties controlled by altering the chemical makeup and structure of the material.

Designing hydrogels computationally to perform a specific function is difficult, however, because the polymers used to build the hydrogel network can contain a plethora of chemical functional groups, complicating the discovery of suitable polymers and the structural makeup of the hydrogel. The properties of hydrogels are also influenced by factors including the molecular arrangement and intermolecular interactions between molecules (such as van der Waals forces and hydrogen bonds). There are further challenges for adhesive hydrogels in wet environments, as hydrogels will swell in the presence of water, which needs to be factored into the material design.

Data driven methods provide breakthrough

To develop a hydrogel with a strong and lasting underwater adhesion, the researchers mined data from the National Center for Biotechnology Information (NCBI) Protein database. This database contains the amino acid sequences responsible for adhesion in underwater biological systems – such as those found in bacteria, viruses, archaea and eukaryotes. The protein sequences were synthetically mimicked and adapted for the polymer strands in hydrogels.

“We were inspired by nature’s adhesive proteins, but we wanted to go beyond mimicking a few examples. By mining the entire protein database, we aimed to systematically explore new design rules and see how far AI could push the boundaries of underwater adhesion,” says co-lead author Hailong Fan.

The researchers used information from the database to initially design and synthesize 180 bioinspired hydrogels, each with a unique polymer network and all of which showed adhesive properties beyond other hydrogels. To improve them further, the team employed machine learning to create hydrogels demonstrating the strongest underwater adhesive properties to date, with instant and repeatable adhesive strengths exceeding 1 MPa – an order-of-magnitude improvement over previous underwater adhesives. In addition, the AI-designed hydrogels were found to be functional across many different surfaces in both fresh and saline water.

“The key achievement is not just creating a record-breaking underwater adhesive hydrogel but demonstrating a new pathway – moving from biomimetic experience to data-driven, AI-guided material design,” says Fan.

A versatile adhesive

The researchers took the three best performing hydrogels and tested them in different wet environments to show that they could maintain their adhesive properties for long time periods. One hydrogel was used to stick a rubber duck to a rock by the sea, which remained in place despite continuous wave impacts over many tide cycles. A second hydrogel was used to patch up a 20 mm hole on a pipe filled with water and instantly stopped a high-pressure leak. This hydrogel remained in place for five months without issue. The third hydrogel was placed under the skin of mice to demonstrate biocompatibility.

The super strong adhesive properties in wet environments could have far ranging applications, from biomedical engineering (prosthetic coatings or wearable biosensors) to deep-sea exploration and marine farming. The researchers also note that this data-driven approach could be adapted for designing other functional soft materials.

When asked about what’s next for this research, Fan says that “our next step is to study the molecular mechanisms behind these adhesives in more depth, and to expand this data-driven design strategy to other soft materials, such as self-healing and biomedical hydrogels”.

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Researchers in the US have directly imaged a class of extremely low-energy atomic vibrations called moiré phasons for the first time. In doing so, they proved that these vibrations are not just a theoretical concept, but are in fact the main way that atoms vibrate in certain twisted two-dimensional materials. Such vibrations may play a critical role in heat and charge transport and how quantum phases behave in these materials.

“Phasons had only been predicted by theory until now, and no one had ever directly observed them, or even thought that this was possible,” explains Yichao Zhang of the University of Maryland, who co-led the effort with Pinshane Huang of the University of Illinois at Urbana-Champaign. “Our work opens up an entirely new way of understanding lattice vibrations in 2D quantum materials.”

A second class of moiré phonons

When two sheets of a 2D materials are placed on top of each other and slightly twisted, their atoms form a moiré pattern, or superlattice. This superlattice contains quasi-periodic regions of rotationally aligned regions (denoted AA or AB) separated by a network of stacking faults called solitons.

Materials of this type are also known to possess distinctive vibrational modes known as moiré phonons, which arise from vibrations of the material’s crystal lattice. These modes vary with the twist angle between layers and can change the physical properties of the materials.

In addition to moiré phonons, two-dimensional moiré materials are also predicted to host a second class of vibrational mode known as phasons. However, these phasons had never been directly observed experimentally until now.

Imaging phasons at the picometre scale

In the new work, which is published in Science, the researchers used a powerful microscopy technique called electron ptychography that enabled them to image samples with spatial resolutions as fine as 15 picometres (1 pm = 10^-12 m). At this level of precision, explains Zhang, subtle changes in thermally driven atomic vibrations can be detected by analysing the shape and size of individual atoms. “This meant we could map how atoms vibrate across different stacking regions of the moiré superlattice,” she says. “What we found was striking: the vibrations weren’t uniform – atoms showed larger amplitudes in AA-stacked regions and highly anisotropic behaviour at soliton boundaries. These patterns align precisely with theoretical predictions for moiré phasons.”

Zhang has been studying phonons using electron microscopy for years, but limitations on imaging resolutions had largely restricted her previous studies to nanometre (10^-9 m) scales. She recently realized that electron ptychography would resolve atomic vibrations with much higher precision, and therefore detect moiré phasons varying across picometre scales.

She and her colleagues chose to study twisted 2D materials because they can support many exotic electronic phenomena, including superconductivity and correlated insulated states. However, the role of lattice dynamics, including the behaviour of phasons in these structures, remains poorly understood. “The problem,” she explains, “is that phasons are both extremely low in energy and spatially non-uniform, making them undetectable by most experimental techniques. To overcome this, we had to push electron ptychography to its limits and validate our observations through careful modelling and simulations.”

This work opens new possibilities for understanding (and eventually controlling) how vibrations behave in complex 2D systems, she tells Physics World. “Phasons can affect how heat flows, how electrons move, and even how new phases of matter emerge. If we can harness these vibrations, we could design materials with programmable thermal and electronic properties, which would be important for future low-power electronics, quantum computing and nanoscale sensors.”

More broadly, electron ptychography provides a powerful new tool for exploring lattice dynamics in a wide range of advanced materials. The team is now using electron ptychography to study how defects, strain and interfaces affect phason behaviour. These imperfections are common in many real-world materials and devices and can cause their performance to deteriorate significantly. “Ultimately, we hope to capture how phasons respond to external stimuli, like how they evolve with change in temperature or applied fields,” Zhang reveals. “That could give us an even deeper understanding of how they interact with electrons, excitons or other collective excitations in quantum materials.”

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Small levitating platforms that can stay airborne indefinitely at very high altitudes have been developed by researchers in the US and Brazil. Using photophoresis, the devices could be adapted to carry small payloads in the mesosphere where flight is notoriously difficult. It could even be used in the atmospheres of moons and other planets.

Photophoresis occurs when light illuminates one side of a particle, heating it slightly more than the other. The resulting temperature difference in the surrounding gas means that molecules rebound with more energy on the warmer side than the cooler side – producing a tiny but measurable push.

For most of the time since its discovery in the 1870s, the effect was little more than a curiosity. But with more recent advances in nanotechnology, researchers have begun to explore how photophoresis could be put to practical use.

“In 2010, my graduate advisor, David Keith, had previously written a paper that described photophoresis as a way of flying microscopic devices in the atmosphere, and we wanted to see if larger devices could carry useful payloads,” explains Ben Schafer at Harvard University, who led the research. “At the same time, [Igor Bargatin’s group at the University of Pennsylvania] was doing fascinating work on larger devices that generated photophoretic forces.”

Carrying payloads

These studies considered a wide variety of designs: from artificial aerosols, to thin disks with surfaces engineered to boost the effect. Building on this earlier work, Schafer’s team investigated how lightweight photophoretic devices could be optimized to carry payloads in the mesosphere: the atmospheric layer at about 50–80 km above Earth’s surface, where the sparsity of air creates notoriously difficult flight conditions for conventional aircraft or balloons.

“We used these results to fabricate structures that can fly in near-space conditions, namely, under less than the illumination intensity of sunlight and at the same pressures as the mesosphere,” Schafer explains.

The team’s design consists two alumina membranes – each 100 nm thick, and perforated with nanoscale holes. The membranes are positioned a short distance apart, and connected by ligaments. In addition, the bottom membrane is coated with a light-absorbing chromium layer, causing it to heat the surrounding air more than the top layer as it absorbs incoming sunlight.

As a result, air molecules move preferentially from the cooler top side toward the warmer bottom side through the membranes’ perforations: a photophoretic process known as thermal transpiration. This one-directional flow creates a pressure imbalance across the device, generating upward thrust. If this force exceeds the device’s weight, it can levitate and even carry a payload. The team also suggests that the devices could be kept aloft at night using the infrared radiation emitted by Earth into space.

Simulations and experiments

Through a combination of simulations and experiments, Schafer and his colleagues examined how factors such as device size, hole density, and ligament distribution could be tuned to maximize thrust at different mesospheric altitudes – where both pressure and temperature can vary dramatically. They showed that platforms 10 cm in radius could feasibly remain aloft throughout the mesosphere, powered by sunlight at intensities lower than those actually present there.

Based on these results, the team created a feasible design for a photophoretic flyer with a 3 cm radius, capable of carrying a 10 mg payload indefinitely at altitudes of 75 km. With an optimized design, they predict payloads as large as 100 mg could be supported during daylight.

“These payloads could support a lightweight communications payload that could transmit data directly to the ground from the mesosphere,” Schafer explains. “Small structures without payloads could fly for weeks or months without falling out of the mesosphere.”

With this proof of concept, the researchers are now eager to see photophoretic flight tested in real mesospheric conditions. “Because there’s nothing else that can sustainably fly in the mesosphere, we could use these devices to collect ground-breaking atmospheric data to benefit meteorology, perform telecommunications, and predict space weather,” Schafer says.

Requiring no fuel, batteries, or solar panels, the devices would be completely sustainable. And the team’s ambitions go beyond Earth: with the ability to stay aloft in any low-pressure atmosphere with sufficient light, photophoretic flight could also provide a valuable new approach to exploring the atmosphere of Mars.

The research is described in Nature.

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