Published on March 13th, 2018 | By: April Gocha0
New materials for flexible electronics: Deposition technique bends possibilities with MXene thin filmsPublished on March 13th, 2018 | By: April Gocha
[Image above] Credit: Grant Hutchinson; Flickr CC BY-NC-ND 2.0
Ever since their discovery about seven years ago, MXene materials have been gaining momentum. [In case you haven’t been paying attention, MXenes are 2-D transition metal carbides and nitrides.]
Which—when you consider the materials’ long list of useful properties and potential applications—is not the least bit surprising.
However, one type of application has thus far remained largely absent from that list—flexible devices, such as wearables, foldable electronics, electronic skins, and adaptable displays.
Flexible electronics are certainly forecast to play a major role in our digital futures. But it’s no simple task to find a suitable material for flexible electronics—one with good electrical conductivity that can be maintained even when the material is repeatedly bent, stretched, pulled, and deformed.
While MXenes’ conductive properties make them good candidates for electronics, previous fabrication methods have mostly limited the form of these materials to stiff sheets rather than bendable films.
Now, a team of scientists from Texas A&M University (College Station, Texas) has developed a technique to build flexible MXene thin films that could enable new possibilities for future flexible electronics.
Using an aqueous assembly process called layer-by-layer deposition, the team applied layers of 2-D metal carbides—they used Ti3C2Tx nanosheets, derived from the parent Ti3AlC2 MAX phase—in thin sheets on a glass substrate, layering the MXenes in between polymer sheets.
By sequentially depositing layers of MXene materials with polymers, the researchers built robust composite thin films, held tightly together and tightly to the substrate’s surface by attractive electrostatic interactions between the layers of negatively charged MXenes and positively charged polyelectrolytes.
But what’s really key to these robust films is that they can also survive large-scale deformations while maintaining electrical conductivity, a necessary characteristic for materials suitable for flexible electronic devices.
Putting the materials to the test, the scientists show that the layered films hold up relatively well to repeated cycles of bending, stretching, pulling, and twisting—and despite the physical deformation, the materials still maintain their electrical conductivity.
In the open access paper describing the work, published in Science Advances, the researchers show that they can successfully deposit layers by immersion or spraying onto a glass substrate—plus the technique also works for a variety of substrate materials, including cloth, flexible or stretchable plastics, and nylon fiber, opening a wide swath of potential applications.
And in addition to vast possibilities for diverse kinds of flexible devices, MXene thin films could also enable strain sensors to detect deformation of materials or objects.
The open-access paper, published in Science Advances, is “Surface-agnostic highly stretchable and bendable conductive MXene multilayers” (DOI: 10.1126/sciadv.aaq0118).
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