Vertically Aligned Nanopatterns of Amine-Functionalized Ti₃C₂ MXene via Soft Lithography

Thin films of well-stacked two-dimensional MXene flakes have been used in various applications, especially in sensors and microscale energy storage devices, such as micro-supercapacitors. Miniaturization and integration of devices, as well as maximization of device performance require nanoscale patterning of MXene, beyond what can be achieved using inkjet or screen printing. However, nanoscale patterning technology for MXene is yet to be developed. In the present work, a simple fabrication method is demonstrated for manufacturing Ti₃C₂T_x MXene films with vertically aligned nanopatterns via soft lithography. This process involves polydimethylsiloxane (PDMS) stamping with line-patterned PDMS molds. The feature size of the vertical line patterning of MXene is controlled with the nanometers accuracy by swelling of the PDMS mold by toluene, which also guides vertical alignment of MXene flakes. As a result, vertically aligned MXene nanopatterns are fabricated with a width of ridges less than 200 nm and 2-µm regular spacing between the ridges. The oleylamine-functionalized MXene flakes are also developed for better dispersion in toluene, providing a general protocol to fabricate MXene dispersions in nonpolar solvents.