Fifteen years after the landmark discovery of MXenes at Drexel University, a research team led by the College of Engineering has achieved a significant structural breakthrough by transforming these two-dimensional conductive nanomaterials into one-dimensional nanoscrolls. This development, detailed in a study published in the journal Advanced Materials, introduces a scalable and precise method for creating ultra-thin, tubular structures that possess higher conductivity and greater mechanical versatility than their flat counterparts. These nanoscrolls, which are approximately 100 times thinner than a human hair, represent a fundamental shift in how scientists can manipulate matter at the nanoscale to enhance energy storage, biosensing, and wearable technology.
The discovery of MXenes in 2011—a family of transition metal carbides, nitrides, and carbonitrides—revolutionized the field of materials science due to their exceptional metallic conductivity and hydrophilic surfaces. However, while 2D flakes are ideal for certain applications, their tendency to stack closely together has historically limited their efficiency in specific industrial and electronic contexts. By "scrolling" these sheets into 1D tubes, the Drexel team has effectively bypassed these limitations, creating a material that functions as a "highway" for ions and electrons.
The Evolution of MXene Morphology: From Sheets to Pipes
The transition from 2D to 1D morphology is more than a geometric curiosity; it is a strategic engineering feat that addresses the physical constraints of flat nanomaterials. In standard 2D MXene applications, the flakes typically lie flat on top of one another. This stacking creates a "tortuous path" for ions or molecules attempting to navigate between the layers—a phenomenon known as the nano-confinement effect. This confinement can slow down the charging of batteries or the filtration process in desalination systems.
"Two-dimensional morphology is very important in many applications. However, there are applications where 1D morphology is superior," explained Yury Gogotsi, PhD, Distinguished University and Bach professor in Drexel’s College of Engineering and a lead author of the study. Gogotsi compared the structural difference to construction materials: "It’s like comparing steel sheets to metal pipes or rebar. One needs sheets to make car bodies, but to pump water or reinforce concrete, long tubes or rods are needed."
By converting these nanosheets into hollow, tubular scrolls, the researchers have eliminated the bottleneck of confinement. The resulting 1D geometry allows for rapid transport, as ions can move freely through the open center and along the outer surfaces of the scrolls. This makes the material approximately ten thousand times thinner than a standard water pipe while maintaining the structural integrity required for high-performance applications.
The Janus Reaction: A Scalable Chemical Mechanism
The primary challenge in creating MXene nanoscrolls has been the difficulty of achieving consistency and scalability. While carbon nanotubes—a 1D form of graphene—have been studied for decades, MXenes offer a richer chemistry and easier processing. Previous attempts to scroll MXenes often resulted in uneven yields or damaged material. The Drexel team overcame this by utilizing what is known as a "Janus reaction."
To initiate the scrolling process, researchers start with multilayer MXene flakes. By carefully adjusting the chemical environment and introducing water, they induce a change in the surface chemistry on one side of the material. This creates a structural imbalance—named after the two-faced Roman god Janus—where one side of the flake experiences more surface tension than the other. This internal strain forces the layers to peel apart and curl into tight, uniform scrolls.
Crucially, this method has proven to be highly scalable. The team successfully produced 10-gram batches of nanoscrolls, a significant amount in the realm of nanotechnology research, suggesting that industrial-scale manufacturing is within reach. The researchers applied this technique to six different types of MXenes, including:
- Two forms of titanium carbide (Ti3C2 and Ti2C)
- Niobium carbide (Nb2C)
- Vanadium carbide (V2C)
- Tantalum carbide (Ta2C)
- Titanium carbonitride (Ti3CN)
This diversity demonstrates the robustness of the method across different chemical compositions, allowing engineers to tailor the scrolls for specific electrical or mechanical properties.
Breakthroughs in Ion Transport and Energy Storage
One of the most immediate impacts of MXene nanoscrolls is expected in the field of energy storage and water purification. In traditional battery electrodes made of 2D materials, ions must zigzag through layers, which increases resistance and heat. The 1D scrolls act as high-speed conduits, potentially leading to batteries that charge significantly faster and last longer.
In desalination systems, where the goal is to move ions out of saltwater, the reduced resistance of the tubular structure could lead to more energy-efficient membranes. The hollow nature of the scrolls provides a dual-surface area for ion interaction, effectively doubling the available real estate for electrochemical reactions compared to tightly packed sheets.
Advancing Biosensing and Molecular Detection
The unique geometry of the nanoscrolls also offers transformative potential for the medical and environmental sensing industries. In 2D stacked structures, the active sites where molecules bind to the material are often "hidden" between layers. This makes it difficult for large biomolecules, such as proteins or DNA fragments, to reach the sensing surface.
"The open, hollow structure of the scroll solves this by allowing the analytes easy access to the MXene surface," Gogotsi noted. This accessibility, combined with the material’s high electrical conductivity and mechanical stiffness, ensures a strong and stable signal for sensors. The researchers envision these scrolls being used in biosensors that can detect diseases at earlier stages, as well as in gas sensors for monitoring air quality or industrial leaks.
Wearable Electronics and Smart Textiles
As the demand for "ionotronic" devices—electronics that use ions rather than just electrons—grows, MXene nanoscrolls are positioned to become a foundational component of wearable technology. These devices require materials that are both highly conductive and mechanically resilient to withstand constant movement and stretching.
The Drexel team found that the rigid, tubular structure of the scrolls allows them to anchor firmly within soft polymers. This creates a reinforced conductive network that remains stable even when the material is bent or stretched. Furthermore, the researchers discovered that the orientation of the nanoscrolls in a solution can be controlled using an electric field.
"Imagine manipulating millions of tubules 100 times thinner than a human hair to make them build a wire or stand up vertically to make a brush," said Teng Zhang, PhD, a postdoctoral researcher at Drexel and co-author of the study. This level of control allows the scrolls to be aligned with synthetic fibers in textiles, paving the way for smart fabrics that can track health metrics, provide haptic feedback, or even store energy within the threads of a garment.
The Quantum Frontier: Flexible Superconductivity
Perhaps the most scientifically provocative aspect of the research is the discovery of superconductivity in flexible MXene films. Superconductivity—the ability of a material to conduct electricity with zero resistance—is typically found in rigid, brittle ceramics or metals cooled to extreme temperatures.
Previously, superconductivity in MXenes was only observed in pressed pellets or powders, which are impractical for modern electronics. By using niobium carbide scrolls, the Drexel researchers observed the first instance of superconductivity in free-standing, solution-processed films that retain mechanical flexibility.
The researchers hypothesize that the scrolling process introduces a specific lattice strain and curvature that stabilizes the superconducting state. "The scrolling process introduces specific lattice strain and curvature that are absent in flat sheets," Gogotsi explained. This discovery is a major step toward making superconducting materials more usable in practical applications, such as quantum sensors, high-speed interconnects for supercomputers, and advanced data storage devices.
Industrial Implications and Future Outlook
The ability to process superconducting and high-conductivity materials at room temperature into flexible coatings or wires is a significant hurdle cleared for the tech industry. As quantum computing moves from theoretical labs to industrial development, the need for flexible, scalable nanomaterials becomes paramount.
The Drexel research team plans to continue investigating the quantum behaviors of these nanoscrolls, looking for other "emergent phenomena" that occur when 2D sheets are forced into 1D shapes. With a scalable production method now established, the focus will likely shift toward integrating these nanoscrolls into commercial prototypes for batteries, sensors, and smart textiles.
"We expect many other interesting phenomena caused by scrolling and are going to study them," Zhang concluded. As the global nanotechnology market continues to expand—projected to reach hundreds of billions of dollars in the coming decade—Drexel’s MXene nanoscrolls stand as a testament to the enduring power of material innovation. By rethinking the shape of one of the world’s most versatile materials, researchers have opened a new chapter in the history of nanotechnology, one where the "highways" of the future are built at the atomic level.
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