Massively-parallel ultra-high-aspect-ratio nanochannels as mesoporous membranes

Abstract

Many fabrication technologies have been used to build nano/mesoporous materials/filters with a good size control, but the integration of these systems into a microsystem format has been a challenge. Microfabricated nanofilters suffer from small open volume and low throughput. In this paper, we developed a novel fabrication strategy for massively-parallel, regular vertical nanochannel membranes with a uniform, well-controlled gap size of ~50 nm and a depth up to ~40 μm, by using only standard semiconductor fabrication techniques. The vertical nanofilter membranes were fabricated into an anisotropic nanofilter array, which demonstrates the ability to integrate nanofilters and micron-sized channels/pores seamlessly. We demonstrated efficient continuous-flow separation of large DNAs and small molecules in a two-dimensional vertical nanochannel array device. These ultrahigh-aspect-ratio nanochannels have the advantage of large open volume, enabling for high-throughput applications.

Experimental Verification of Overlimiting Current by Surface Conduction and Electro-Osmotic Flow in Microchannels

“…Noticeable progress has been made in understanding electroconvection during ion concentration polarization (ICP) due to electro-osmotic flows near the membrane or nanochannel interface driving salt depletion [5,[7][8][9][10]. Due to the complexity of direct numerical simulation of the Poisson equation (for electric potential), Nernst-Planck equations (for ion concentrations), and Navier-Stokes equations (for fluid flows) in multidimensional geometries [9,11,12], as well as inherent limitations of the classical dilute solution model [13], it is crucial to directly observe particle motions and flow fields in precisely controlled micro-or nanofluidic geometries [14,15].…”

Chemistry in nanochannel confinement

“…10 nm in lateral size (i.e., parallel to the surface), and down to a few nm in vertical size (i.e., perpendicular to the substrate) can be achieved. Lithographically defined nanochannels that have lateral dimensions of 50 nm, but depths of up to 40 μm were recently reported by Mao et al [74]; the fabrication process used was a combination of deep reactive ion etching and thin film growth to narrow the channels. The interfacing of these nanochannels with larger fluidic structures has been described in several of the papers that have already been mentioned in this paper, although we would like to add the excellent work by Cao et al, who managed to construct gradient nanostructures to connect microfluidics to nanochannels, to this list [75].…”

Microfluidic Chips for Point‐of‐Care Immunodiagnostics

“…Nanochannels with ultra-high aspect ratios of 400 have been fabricated and used to fractionate biomolecules. [ 70 ] Microporous thermoformed polymer fl exible microfl uidic chips have been produced using hot embossing. [ 71 ] Tapered channels are produced using diffuse ultraviolet light [ 72 ] or laser ablation and integrated into a threedimensional microfl uidic chip.…”