Mechanically Stable PMMA-Based Large-Area Nano-Channels with Sub-10 nm Depth

Abstract

Artificial sub-microfluidic and nanofluidic devices allow for studying mass or ion transport effects under spatial confinement. It remains challenging to fabricate large-scale, nanofluidic channels of well-defined thickness for fundamental studies and practical applications, especially for extreme confinement conditions (e.g., with sub-10 nm channel height). Here, a strategy is reported to fabricate large-scale nano-channels with the channel height down to 5.0 nm. The fabrication is enabled by developing ultra-flat and ultra-thin polymethylmethaacrylate (PMMA) layers as the spacer. The ease of scaling up the channel length to a millimeter in the lateral dimensions with high mechanical stability is demonstrated. Furthermore, experimental evidence is provided of the role of the mechanical coupling between the spacer and capping materials in determining the device's mechanical properties, and how controlling the channel width and the top graphite thickness can be employed to tailor the device's mechanical properties. Finally, employing near-field IR experiments, the decay constant is established for the near-field absorption intensity of PMMA molecules inside the channel by increasing the top layer thickness. This work develops a novel method for fabricating large-area, mechanically stable nano-channels for nanofluidic devices and lays the foundation for further in situ spectroscopic studies of electrochemistry within sub-10 nm confinement.