Researchers at the Department of Energy’s Oak Ridge National Laboratory have developed a reusable adhesive made from waste polymers that is stronger than commercial glues, works in wet and dry conditions, and bonds materials ranging from wood and glass to metal and plastics. Inspired by mussels’ sticking power, the adhesive uses reversible chemical crosslinkers that let it soften, release and be reused, unlike conventional single-use glues. The innovation could simplify manufacturing and repair by replacing the many specialized adhesives used today and may have significant economic impact in the global adhesives and sealants market, valued at about $87 billion and projected to reach nearly $119 billion by 2032.

“Most adhesives are made for one specific application,” said Anisur Rahman, a research and development staff member at ORNL who led a study with former ORNL postdoctoral researcher Mary Danielson, now a research assistant professor with the University of Tennessee-Oak Ridge Innovation Institute. “Our adhesive can be used for diverse applications, including structural or pressure-sensitive uses, and it performs reliably in both wet and dry environments,” he said. “None of the commercial adhesives can be used this way.” 

Beginning with common polymers from beverage bottles, fabric fibers and packaging films, the research team developed a process that saves materials, energy and money. “We took material destined for the landfill and turned it into something valuable,” Danielson said.

The researchers have applied for a patent for their versatile glue. 

How the reversible bonds work

Traditional structural adhesives rely on permanent crosslinks that make removal difficult. “You apply traditional adhesives once; you cannot reuse them,” Rahman said. 

“You basically have to rip an assembly apart to debond it,” Danielson added. “You’ve damaged both the part you’re glueing to and the part you’re glueing from. If you make a mistake when you’re gluing something and you allow it to cure, it’s done.“

In the ORNL adhesive, crosslinkers act like reversible attachments, akin to Velcro. Heating breaks dynamic chemical bonds in the polymer, allowing the adhesive to release without damaging surfaces. As the material cools, the bonds reform.

“If something is damaged or misapplied, you’re able to completely remove it and put it back on with full integrity,” Danielson said.

The team debonded and rebounded the adhesive more than 10 times with no loss in performance. 

“Normally in the marketplace, structural adhesives typically have shear strength — a measure of adhesion — in the 7- to 10-megapascal range,” Rahman said. “Our adhesives also stay well above that range but maintain reusability.”

The researchers can also retrieve the glue chemically, using an excess of amine molecules to break the adhesive into its monomer subunits. “We can recover all chemicals used in this adhesive,” Rahman said.

Mussel-inspired design

A polymer is a long chain or network made of monomers, or chemical subunits of one type. Using no solvents or catalysts, the scientists added amine, a nitrogen-containing chemical group, to the waste polymer and heated it to just below the polymer’s melting temperature. Under these mild conditions, the amine broke the polymer down into monomers that each contained four amine groups.

Next, to design the adhesive, ORNL researchers mimicked mussel foot proteins, which contain both hydrophilic and hydrophobic components that enable strong adhesion even in wet environments.

“We used a crosslinker, or hardener, that has both water-loving (hydrophilic) and water-hating (hydrophobic) components together in the same molecule,” Rahman said. “We mix the hardener and the monomer. It creates an adhesive resin that acts like a mussel foot protein.”

“For any glue that is a cross-linked network of two components, it takes time to complete the reaction between the two components,” Danielson said. “To repair boats, submarines and pipelines, our glue can be applied underwater using hand pressure until it sets.” 

Curing happens when a large four-armed monomer interacts with the crosslinking hardener. The monomer’s amine group reacts with the hardener’s acetoacetate group to produce a resin, or matrix with hydrophilic and hydrophobic characteristics. Whether the protein sticks or releases depends on the balance of those properties. 

“Our glue maintained strong adhesion across different environmental conditions, including seawater, extremely low temperature (100 degrees Celsius below zero), and both acidic and basic conditions,” Rahman said.

National lab capabilities enabled the achievement

Rahman conceived the concept of transforming deconstructed polymer waste into an adhesive. He and Danielson designed and led experiments and drafted the paper. Chuyi Pan, a summer intern from the University of Pennsylvania, assisted in synthesizing the adhesive. Tomonori Saito of ORNL and the University of Tennessee, Knoxville, reviewed and edited the manuscript drafts.

ORNL researchers performed vital characterizations. Bobby Sumpter simulated the energies with which the adhesive bound to different surface materials. Catalin Gainaru used rheology to characterize its stress and relaxation. Honghai Zhang and Vilmos Kertesz performed mass spectrometry to quantify different molecules. Zoriana Demchuk’s lifecycle analysis of the ORNL glue showed it was more energy-efficient to make than commercial adhesives. 

Toward strong and weak bonding applications

The team has also explored using this pioneering chemistry to advance vehicles. ORNL’s glue maintained strong adhesion between dissimilar substrates — a crucial requirement in automotive and aerospace applications, where joining composites to aluminum or steel presents notable challenges.

Next, the scientists aim to tune crosslinking to enable weaker, temporary bonds for removable labels, adhesive bandages, drug-delivery patches and other applications. 

ORNL’s versatile, high-performance glue is poised to make an impact that sticks in situations from the mundane to the extraordinary. Potential uses range from household items that require gentle removal, like press-on nails and price tags, to repairs in remote or extreme environments, including underwater or outer space — settings where specialty glues may be unavailable. 

The DOE Office of Science supported the research. The work used resources of the Center for Nanophase Materials Sciences, a DOE Office of Science user facility at ORNL.

For more information: Science Advances

Image: From left, Mary Danielson and Anisur Rahman, leaders of an ORNL project to invent a versatile reusable glue from polymer waste, examine its bonding performance. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Scientists in Sweden have developed a simple method to make the universe’s normally invisible binding forces visible by using gold flakes, salt water and light. The Chalmers University of Technology team created a platform that displays these tiny forces—often described as “nature’s invisible glue,” responsible for effects like dust sticking to surfaces or lizards climbing walls—as shifting colors. The technique offers a faster, more accessible way to study how matter organizes itself at the smallest scales.

Inside the lab, doctoral student Michaela Hošková holds up a small glass container filled with millions of micrometer-sized gold flakes suspended in a salt solution. Using a pipette, she places a droplet of the mixture onto a gold-coated glass plate positioned under an optical microscope. The flakes are immediately drawn toward the surface but stop just short of fully attaching, leaving nanometer-sized gaps between the flakes and the gold substrate.

These tiny liquid-filled gaps act like miniature light chambers. Light reflects back and forth inside them, producing visible colors. When the setup is illuminated with a halogen lamp and the reflected light is analyzed with a spectrometer, the different wavelengths become clear. On the connected monitor, flakes shimmer and shift in colors such as red and green against a golden yellow background.

“What we are seeing is how fundamental forces in nature interact with each other. Through these tiny cavities, we can now measure and study the forces we call ‘nature’s glue’ – what binds objects together at the smallest scales. We don’t need to intervene in what is happening, we just observe the natural movements of the flakes,” says Michaela Hošková, a doctoral student at the Department of Physics at Chalmers University of Technology.

By examining the light captured in the cavities, the team can analyze the balance between two competing forces – one that pulls the flakes together and one that keeps them apart. The attractive force, known as the Casimir effect, causes the gold flakes to move toward each other and toward the surface. The opposing electrostatic force develops in the salt solution and prevents the flakes from fully sticking. When these forces reach equilibrium, a process called self-assembly occurs, forming the cavities that make the measurements possible.

“Forces at the nanoscale affect how different materials or structures are assembled, but we still do not fully understand all the principles that govern this complex self-assembly. If we fully understood them, we could learn to control self-assembly at the nanoscale. At the same time, we can gain insights into how the same principles govern nature on much larger scales, even how galaxies form,” says Michaela Hošková.

The new platform builds on several years of research in Professor Timur Shegai’s group at the Department of Physics. Four years ago, the team showed that a pair of gold flakes could form a self assembled resonator. They have now expanded that discovery into a broader method for investigating fundamental forces.

In this system, the gold flakes function as tiny floating sensors. According to the researchers, the approach could be valuable across physics, chemistry, and materials science.

“The method allows us to study the charge of individual particles and the forces acting between them. Other methods for studying these forces often require sophisticated instruments which cannot provide information down to the particle level,” says research leader Timur Shegai.

The platform may also help scientists better understand how particles behave in liquids, including whether they remain stable or tend to clump together. That knowledge could improve how medicines move through the body, support the design of more effective biosensors, and contribute to better water filtration systems. It is also relevant for everyday products such as cosmetics, where preventing unwanted clumping is essential.

“The fact that the platform allows us to study fundamental forces and material properties shows its potential as a truly promising research platform,” says Timur Shegai.

In the laboratory, Hošková opens a small box containing a finished version of the device. Using tweezers, she places it into the microscope. Two thin glass plates enclose everything needed to examine nature’s invisible glue.

“What I find most exciting is that the measurement itself is so beautiful and easy. The method is simple and fast, based only on the movement of gold flakes and the interaction between light and matter,” says Michaela Hošková, zooming in on a gold flake whose colors immediately reveal the forces at work.

Gold flakes about 10 micrometers in size are placed in a salt solution, meaning water that contains free ions. When a droplet is added to a gold-coated glass surface, the flakes are drawn toward it, and nanometer-sized cavities (100-200 nanometers) form. This self assembly results from the balance between two forces: the Casimir force, a measurable quantum effect that pulls objects together, and the electrostatic force that arises between charged surfaces in a salt solution.

A halogen lamp shines light into the cavities, where it becomes trapped and reflected. An optical microscope and spectrometer then separate the light into its component wavelengths so the colors can be identified. By adjusting the salt concentration and observing how the flakes shift relative to the surface, researchers can measure the underlying forces. To prevent evaporation, the droplet containing the gold flakes is sealed and covered with a second glass plate.

The platform was developed at Chalmers’ Nanofabrication Laboratory, Myfab Chalmers, and at the Chalmers Materials Analysis Laboratory (CMAL).

For more information: PNAS

Image: Researchers at Chalmers University of Technology, Sweden, have discovered a quick and easy way to study the hidden forces that bind the smallest objects in the universe together. Using gold, salt water, and light, they have created a platform on which the forces can be seen through colors. Two thin glass plates hold everything needed to study nature’s invisible glue. Credit: Chalmers University of Technology | Mia Halleröd Palmgren

Researchers at the University of Vienna have demonstrated quantum interference in sodium nanoparticles containing more than 7,000 atoms—and produced clusters of nearly 10,000—showing that even large metallic particles can exhibit quantum behavior. Lead author Sebastian Pedalino said the results challenge the assumption that such objects must behave classically, confirming that quantum mechanics remains valid at this scale without the need for alternative models. 

The team, led by Markus Arndt and Stefan Gerlich, achieved the breakthrough using sodium clusters exceeding 170,000 atomic mass units, larger than most proteins, marking a significant advance toward the long-sought goal of sustaining quantum superposition in increasingly complex systems.

The test was conducted using the multi-scale cluster interference experiment (MUSCLE). 

To observe interference, the team had to minimize environmental disturbances that would destroy coherence. They produced the sodium clusters under cryogenic conditions (77 K, the temperature of liquid nitrogen) to reduce thermal decoherence, and ran the interferometer in ultra-high vacuum (about 9 × 10⁻⁹ mbar, roughly 10⁻¹¹ of atmospheric pressure) to limit collisions with gas molecules.

The scientists produced sodium clusters containing roughly 5,000 to 10,000 atoms and sent them through a three-grating interferometer made from standing ultraviolet laser light. The first grating spatially confined the particles to build up coherence, and the second grating acted as a beam splitter for the clusters’ matter wave. Scanning the third grating revealed an interference fringe pattern, and the team showed the fringe visibility followed the quantum prediction rather than a classical shadow-pattern model

The study achieved a macroscopicity value of 15.5. This metric quantifies how strictly an experiment tests the limits of quantum theory. This study has a value 10 times higher than any previous experiment. 

This new level of sensitivity presents new opportunities for nanotechnology and materials science, opening new doors for measuring properties of nanoparticles and investigating the transition of matter from individual atoms to bulk metallic solids. 

For more information: University of Vienna

Image: MUSCLE at the University of Vienna, where quantum interference of massive nanoparticles was detected. To isolate vibrations, the experiment is mounted on a table weighing several tons that floats on an air cushion. Credit: S. Pedalino / Uni Wien