Pressure-Driven Chromatographic Separation Modes in Self-Enclosed Integrated Nanocapillaries.

This study presents pressure-driven chromatographic separation characteristics of integrated nanofluidic channels (nanocapillaries) featuring distinct cross-sectional geometries: cylindrical, triangular, and rectangular profiles. Cylindrical and triangular nanocapillaries are self-enclosed robust conduits realized through standard semiconductor processing techniques using low-resolution photolithography. Specifically, capillaries in nominal radius 300 and 500 nm have been investigated for chromatographic separation in comparison to 750 nm deep nanoslits as well as triangular capillaries featuring an inscribed circle about 500 nm in radius. Chromatograms have been obtained from 10 mm long nanocapillaries under various modes: normal- and reversed-phase, ion-valence, and hydrodynamic chromatography. The van Deemter plots based on the linear mobile phase velocity for 300 nm radius capillaries and 750 nm deep slits show excellent agreement with the plate heights theoretically predicted. The minimum plate heights achieved are typically below 2 μm and the theoretical plate numbers are in the order of 105 plates/m for the most chromatography modes investigated in the pressure range up to 100 psi. A comparatively high resolving power is achieved with cylindrical nanocapillaries especially those 300 nm in radius. Self-enclosed robust nanocapillaries demonstrated here could facilitate a pressure-driven chromatographic analysis of extremely low-volume samples (e.g., single cell).