Nanoscale materials ripple in the cold, study finds 

Two-dimensional materials only a few atoms thick hold great promise for a variety of technological uses, including energy storage, sensors and superconductivity. UIC researchers have discovered that one class of these ultra-thin materials shows a rippling behavior similar to what we see when we shuffle cards or leaf through a book. That rippling action could help in the design of new technologies, the researchers said.  

The ultra-thin materials called MXenes are accordion-like layers of atoms that scientists can customize by adding different chemical groups to create desired properties. A collaboration between the team of Robert Klie, UIC professor and head of physics, and researchers at University of Chicago and Argonne have studied the structure of these materials using high-end instruments at the UIC Electron Microscopy Core.  

In the new paper, UIC doctoral alum Francisco Lagunas Vargas watched  MXenes at extreme cold temperatures to see them in their native state. At room temperature, the powerful electron beam of the microscope can disrupt the sample, scrambling the structure of the material. Cooling the sample to 100 degrees Kelvin – almost 300 degrees below zero Fahrenheit – limited this damage.

In the ultra-cold conditions, Lagunas saw a process called ripplocation, where the flat layers of the MXene buckle and bend into wavy structures. The movement is similar to shuffling a well-used deck of playing cards, Lagunas said. 

“If you shuffle cards where you do the bridge and you do it too hard, it’ll bend the card severely,” Lagunas said. “That’s basically what we’re doing in the microscope, which is really wild to think about, because it’s happening in a material that is less than a nanometer thick.” 

The ripples would likely change the function of a MXene, Lagunas said, perhaps in ways that will make them more useful for future applications. The same electron beam used in microscopy could also be a nanoscale tool for designing these materials for flexible technologies. 

“We were able to show that, if you find the right conditions, you can use the electron probe to directly manipulate the structure of these materials at unbelievably small scales,” Lagunas said. 

Lagunas, who graduated from UIC in 2023, was recently hired as a faculty member at Washington University in St. Louis. He credits Klie and the UIC Electron Microscopy Core with opening his eyes to the wonders of the atomic world and changing his academic trajectory. 

“The fact that we had access to state-of-the-art tools at UIC was a game changer for my career,” Lagunas said. “You’re often the first person in the world to ever see those things, so there’s a sense of discovery whenever you use these tools. You wrap up your day and you’re like, I just saw something really cool, and it has direct impacts on technology.”