A novel parallel nanomixer for high-throughput single-molecule fluorescence detection

This paper introduces a novel fluidic device based on syringe-driven flow of fluorescent species through a parallel array of nanochannels, in which the geometrical confinement enables long observation times of non-immobilized\ud molecules. Extremely low flow rates are achieved by operating the array of nanochannels in parallel with a larger microchannel. The addition of a second microfluidic inlet allows for mixing different species in a well-defined volume,\ud enabling the study of irreversible reactions such as DNA synthesis in real-time using single-molecule fluorescence resonance energy transfer. Devices are fabricated in glass with the purpose of high-throughput single-molecule\ud fluorescence detection

A Landau-Squire nanojet

Fluid jets are found in nature at all length scales, from microscopic to cosmological. Here we report on an electroosmotically driven jet from a single glass nanopore about 75 nm in radius with a maximum flow rate ~15 pL/s. A novel anemometry technique allows us to map out the vorticity and velocity fields that show excellent agreement with the classical Landau-Squire solution of the Navier Stokes equations for a point jet. We observe a phenomenon that we call flow rectification: an asymmetry in the flow rate with respect to voltage reversal. Such a nanojet could potentially find applications in micromanipulation, nanopatterning, and as a diode in microfluidic circuits.Comment: 20 pages, 4 figure

Mass transport in electrochemical nanogap sensors

Nanofluidic thin-layer cells based on redox cycling allow for extremely sensitive electrochemical detection. Here we establish a physical mass-transfer model for analyte molecules in these transducers which takes into account advective and diffusive transport of both oxidized and reduced species as well as reversible dynamic adsorption at the sensor surfaces. We use finite-element modeling to determine the transient response of nanogap sensors; numerically we predict that the response time can be reduced substantially by pressure-driven advection while the faradaic limiting current remains unaffected by this flow for all experimentally accessible flow rate

Challenges of Biomolecular Detection at the Nanoscale: Nanopores and Microelectrodes

The interest in analytical devices, which typically rely on the reactivity of a biological component for specificity, is growing rapidly. In this Perspective, we highlight current challenges in all-electrical biosensing as these systems shrink toward the nanoscale and enable the detection of analytes at the single-molecule level. We focus on two sensing principles: nanopores and amperometric microelectrode devices

Brownian motion in electrochemical nanodevices

Diffusion dominates mass transport in most electrochemical systems. In classical experimental systems on the micrometer scale or larger, this is adequately described at the mean-field level. However, nanoscale detection devices are being developed in which a handful or even single molecules can be detected. Brownian dynamics become manifest in these systems via the associated fluctuations in electrochemical signals. Here we describe the state of the art of these electrochemical nanodevices, paying particular attention to the role of Brownian dynamics and emphasizing areas in which theoretical understanding remains limited