By breaking the rules of atomic order, scientists have created MXenes unlike any seen before. Nine metals now share a single atom-thin sheet, their once-neat layers dissolved into a patchwork of possibility. The result could redefine how we design materials for the harshest places on Earth and beyond.
History has shown that materials science has long prized symmetry and stability, celebrating crystals whose atoms lock into place like repeating tiles on an infinite floor. It is this type of order that gives rise to strength, conductivity, and control in a laboratory and real-world setting. But in one peculiar family of carbides, the script of symmetry and stability shifted. Here, what should have been chaos turned out to be strength, as if disorder and order were two faces of the same design.
That paradox emerged from work led by researchers at Purdue and Drexel Universities, who set out to see what would happen if they pushed a well-known family of layered carbides beyond its limits. The idea was both straightforward and bold: take a structure prized for its order and force it to host different layers of metals simultaneously to see how far it would go before collapsing into useless disorder.
Much to the scientists’ surprise, that collapse never came. Instead, the material reached a tipping point. Once a specific threshold was crossed, order ceased, as predicted by the researchers. But instead of failure, entropy itself stepped in as the stabilizer, holding the structure together as a two-dimensional sheet. What looked like chaos instead uncovered a hidden strength. Out of that deliberate disorder came a new approach to designing materials.
MAX Phases: The Scaffolding Beneath
To understand what made this experiment possible, you must step back half a century into the 1970s, when scientists discovered a curious set of layered ceramics they called MAX phases. Their formula – written as Mₙ₊₁AXₙ – hid a simple idea: sheets of transition metals bound to carbon or nitrogen, stacked with intervening layers of “A” elements like aluminum or silicon.
What made these materials unusual was their ability to combine qualities rarely found together. They had the toughness of ceramics, able to resist heat and wear, but also conducted electricity much like metals. That combination earned them attention, and their architecture proved especially interesting. The metal layers fell into distinct positions, some bonded outward to the A-layers and others inward to the carbon. It was a framework that seemed to invite both order and potentially, disruption.
For decades, these MAX phases were studied for their durability and conductivity. But their real importance emerged in 2011, when researchers realized MAX phases were more than simply layered ceramics. By carefully etching away their A-layers, they could peel the structure into ultrathin sheets just a few atoms thick. These sheets became known as MXenes.
From MAX to MXene
While MXenes inherited the toughness and conductivity of their parent phases, their real promise lay in the surfaces exposed when etched. Scientists discovered that these surfaces could be fine-tuned with oxygen, hydroxyl, or fluorine, giving them a way to adjust Mxene behavior for different tasks.
What emerged was a new class of two-dimensional materials, versatile in ways that graphene and other atom-thin sheets were not. MXenes could disperse in water, self-assemble into films, and be modified at the surface, almost like programmable matter. Within a few years they were being tested for energy storage, electromagnetic shielding, catalysis, and sensors.
The Breakthrough: Entropy Takes Over
Yet for all their promise, MXenes were still bound by their MAX origins. Most were made from ordered phases with only a few metals, and that very order, once their strength, became their limitation. To push those possibilities to their limit, the Purdue–Drexel team set out to force MAX phases to their breaking point.
They synthesized 40 different compositions, layering anywhere from two to nine transition metals into the same structure. Each new metal introduced competing preferences – some tending toward one atomic site, others toward another.
“Imagine making cheeseburgers with two to nine ingredients (layers),” said Babak Anasori of Purdue University. “However, if we add one or more ingredients … then the metals do not follow any preference for order, and true disorder (high entropy) is achieved.”
With up to about six metals, the system behaved as expected: enthalpy, the energetic pull toward order, kept the structure biased. But once the count rose to seven or more, something shifted. Energetic preferences dissolved, and every configuration became equally likely. Entropy – enthalpy’s disordered doppelganger – stepped in and took over.
What should have collapsed turned instead into stability. Etching these high-entropy MAX phases into MXenes erased the neat divide between order and disorder, leaving a patchwork of possibilities spread across an atom-thin sheet. That patchwork carried into their chemistry: oxygen groups came to dominate their surfaces, while hydroxyl and fluorine fell away as more metals were introduced.
Properties of Entropy-Forged MXenes
Despite that disorder, the MXenes retained their parent metallic character. In fact, their electrical resistivity dropped dramatically as the number of metals increased, in some cases by nearly an order of magnitude. Infrared emissivity fell in parallel, pointing to materials that could endure the extreme environments of heat and radiation.
“This study indicates that short-range ordering – the arrangement of atoms over a short distance of a few atomic diameters – in high-entropy materials determines the impact of entropy versus enthalpy on their structures and properties,” said Brian Wyatt, a postdoctoral researcher at Purdue and first author of the study.
The result was not fragility, but resilience born of a platform strengthened by complexity. What began as a limit-test became a new way to engineer strength: designing within disorder itself.
Why It Matters: Tough Jobs, Real Applications
The implications go far beyond the laboratory. By showing that disorder can be engineered, these MXenes open a new frontier in materials design. Metallic, conductive, and dispersible in water, these MXenes endure where most materials fail. That resilience makes them candidates for the toughest jobs imaginable; from the vacuum of space to the crushing pressures of the deep ocean and the corrosive grind of electrochemical systems.
“We want to continue pushing the boundaries of what materials can do, especially in extreme environments where current materials fall short,” said Anasori.
Their tunable surfaces add another layer of promise. MXenes show exceptional sensitivity to gases such as oxygen, ammonia, and nitrogen dioxide. Their two-dimensional structure gives them high surface area, while their adjustable terminations make them unusually selective and responsive. Unlike graphene or MoS₂, MXenes can be tuned both from the surface down and, through entropy, from the lattice up.
Bigger Picture
While MXenes’ story is only just beginning, history has shown that new materials often reframe the boundaries of possibility. Bronze enabled early tools and weapons. Steel reshaped cities and industry. And silicon gave rise to the digital world. MXenes may represent the next step in that lineage.
What makes this chapter different is the principle at its core. In trying to break order, scientists found a new way to build without it. Entropy became the architect.
“This is exactly where AI will become an enabling technology,” said Anasori. “Guidance from computational science, machine learning and AI will be crucial for navigating the infinite sea of new materials, guiding their development and helping to select the structures and compositions with required properties for specific technologies.”
What that future will look like depends on how far high-entropy MXenes can be scaled, purified, and tailored to real-world needs, such as batteries that can endure extreme environments, sensors that can detect volatile and toxic gases, or materials able to survive where others have historically failed. Even if we don’t yet know what the future of Mxenes holds, the lesson here is that purpose can be found in disorder, and strength can emerge from what looks like, at first glance, chaos.
This study was published in the journal Science.
Sources: Purdue University, Drexel University
