Nanofluidic Rocking Brownian Motors

TL;DR

This paper presents a nanofluidic device that uses asymmetric energy landscapes and oscillating electric fields to control and sort nanoparticles, demonstrating high-resolution transport and separation capabilities at the nanoscale.

Contribution

It introduces a novel method for controlling nanoparticle transport using energy landscapes shaped by nanofluidic geometries combined with rocking Brownian motors, enabling precise sorting.

Findings

Successfully separated 60 nm and 100 nm particles within seconds.

High spatio-temporal resolution enabled detailed comparison with theoretical models.

Model predicts separation of particles with only 1 nm size difference.

Abstract

Control and transport of nanoscale objects in fluids is challenging because of the unfavorable scaling of most interaction mechanisms to small length scales. We design energy landscapes for nanoparticles by accurately shaping the geometry of a nanofluidic slit and exploiting the electrostatic interaction between like charged particles and walls. Directed transport is performed by combining asymmetric potentials with an oscillating electric field to achieve a rocking Brownian motor. Using 60\,nm diameter gold spheres, we investigate the physics of the motors with high spatio-temporal resolution, enabling a parameter-free comparison with theory. We fabricated a sorting device that separates 60- and 100-nanometer particles in opposing directions within seconds. Modeling suggests that the device separates particles with a radial difference of 1 nanometer.