Ultramicrotomy‐Assisted Fabrication of Nanochannels for Efficient Ion Transport and Energy Generation

Abstract Nano‐ and angstrom‐scale channels fabricated from 2D‐layered materials provide a unique platform for studying fluidic behavior at atomic‐scale confinement, with applications in desalination, osmotic power generation, and fuel cells. While various fabrication methods exist, achieving precision, scalability, and minimal fabrication time is challenging. Ultramicrotomy‐based nanofabrication is shown here as an efficient approach to create nanofluidic membranes containing nanochannels with atomically flat walls. This approach is compatible with both bottom–up nanolaminates and top–down nanochannels, produces multiple devices from the same 2D assembly and allows swift variation of channel length. Integration of these membranes into macroscopic silicon fluidic‐chips is achieved maintaining the structural and functional properties. The robustness of the sliced membranes is demonstrated through restacked vermiculate laminates that sustain applied pressures and generate ionic streaming currents. Sliced pristine vermiculite channels exhibit charge‐selective ion transport, leading to osmotic power density ( P osm / A ) ranging from 9.2 to 300.4 Wm −2 under various KCl concentration gradients. Maximum conversion efficiency of 23.3% is obtained at a 100‐fold gradient, yielding P osm / A of 234.6 Wm −2 . Short channel lengths sliced by ultramicrotomy contribute to high P osm / A , promising applications of miniature energy devices for pressure‐driven electricity generation and osmotic power generation.