Ion Transport in Nanofluidic Funnels

Abstract

We report fabrication of nanofluidic channels with asymmetric features (e.g., funnels) that were cast in high modulus poly(dimethylsiloxane) and had well-defined geometries and dimensions. Masters used to cast the funnels were written in the negative tone resist SU-8 by electron beam lithography. Replicated funnels had taper angles of 5, 10, and 20 degrees and were 80 nm wide at the tip, 1 microm wide at the base, and 120 nm deep. The planar format permitted easy coupling of the funnels to microfluidic channels and simultaneous electrical and optical characterization of ion transport. All three designs rectified ion current, and the 5 degrees funnel exhibited the highest rectification ratio. Fluorescence measurements at the funnel base showed that an anionic probe was enriched and depleted in the high and low conductance states, respectively.

Nernst-Planck model of photo-triggered, pH–tunable ionic transport through nanopores functionalized with “caged” lysine chains

“…Nanoscale pores have been studied extensively in the last decade due to the new basic phenomena involved and the potential applications in medicine, [1][2][3] nanofluidics, [4][5][6][7] membrane science 8,9 and biotechnology. 10,11 Polymer samples containing single asymmetric nanopores and multipore arrays obtained by track-etching 12 are of particular interest because they mimic some of the transport properties of biological ion channels.…”

Field-effect reconfigurable nanofluidic ionic diodes

“…Several nanofluidic platforms based on nanopores and nanochannels were reported to produce ionic current rectification by symmetry breaking 15 in geometries [16][17][18][19] , surface charge distributions (either intrinsic material properties 20,21 or chemically modified properties 22,23 ), bath concentrations 24 , or a combination of them, for example, by positively and negatively patterning charged regions in conical nanopores 25 . Nevertheless, it has not been possible to change the predefined rectifying properties obtained by these approaches once the devices are made.…”

Thermally modulated biomolecule transport through nanoconfined channels

“…In the past years, nanopore-based device is attracting more and more attentions for its potential applications in selective molecular separation [1,2], biosensing [3,4], energy storage [5,6], controlled release [7,8], drug delivery [9,10], nanofluidics, and nanoelectronics [11][12][13][14]. It is generally believed that the premise of this method is how to obtain proper nanopores and how to design effective fluidic device.…”