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

Abstract

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 10 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).

Continuous-Flow Electrophoresis of DNA and Proteins in a Two-Dimensional Capillary-Well Sieve

“…The sieve structure is fabricated as per the integration process of the 1D CW motif previously reported but with a further refinement in the method of defining the capillaries (Figure b). The capillary integration primarily involves (1) patterning trenches within a thick dielectric layer through contact photolithography, (2) depositing a doped glass layer and forming self-enclosed trenches through the shadowing effect of the trench edges, and (3) subsequent thermal annealing (reflow) and shape transformation into cylindrical capillaries. , More importantly, thermal reflow is applied for an extended period of time to uniformly shrink the capillary diameter into scales that are accessible typically via advanced patterning tools. Distinct from the process of the 1D CW array, thermal reflow is followed by the atomic layer deposition (ALD) of alumina as the final step for those sieves where the fractionation is through steric interactions.…”

Optical Transport and Sorting of Fluorescent Nanodiamonds inside a Tapered Glass Capillary: Optical Sorting of Nanomaterials at the Femtonewton Scale

“…A direct consequence is that any flow inside the capillary leads on average to a faster transport of large particles, whereas small particles remain slower. This well-known phenomenon is the basic mechanism underlying hydrodynamic chromatography and field-flow fractionation techniques. − From the results shown in Figure , it can be inferred that the action of the optical force prevails over this phenomenon since optically propelled NDs still tend to be brighter and hence larger than NDs dragged by the water stream.…”

50-Fold Reduction of Separation Time in Open-Channel Hydrodynamic Chromatography via Lateral Vortices

“…Another consequence of the behavior of L vs Pe concerns the possibility of scaling up the device for separating suspended objects of micrometric size. For instance, if one considers a mixture of particles of diameters of 1 μm and 500 nm in a square channel of edge 10 μm (Rectangular microchannels with edges down to a few micrometers have been reported for HDC analysis .).…”