Plasmonic Brownian Ratchets for Directed Transport of Analytes

TL;DR

This paper presents a plasmonic Brownian ratchet that enables low-power, directed transport of nanoscale particles, improving control in microfluidic and lab-on-a-chip systems for biological and chemical analysis.

Contribution

It introduces a novel plasmonic ratchet design optimized via simulations and experimentally demonstrated to efficiently rectify thermal motion of nanoparticles at low optical powers.

Findings

Achieved directed transport of 40 nm polystyrene spheres up to 2.4 μm/s.

Operates effectively at low optical power of 0.785 kW/cm^2.

Provides a robust method for nanoscale analyte manipulation in microfluidic devices.

Abstract

Controlled long-range transport of micro- and nano-scale objects is a key requirement in lab-on-a-chip and microfluidic applications, enabling the efficient capture, concentration, manipulation, and detection of analytes. Traditional methods such as microfluidic pumps and optical trapping face challenges including high power consumption and limited range of action. This study introduces a plasmonic Brownian ratchet designed for the directed transport of dielectric nanometer-sized particles at low optical powers. Through numerical simulations, the ratchet geometry was optimized to enhance electric fields, optical forces, and trapping potentials. Experimentally, the plasmonic ratchet demonstrated the ability to rectify random thermal motion of 40 nm polysterene spheres over extended distances in a specific direction, achieving velocities up to 2.4 $\mu$m/s at excitation powers as low as 0.785 kW/cm^2. This plasmonic ratchet offers a robust and efficient solution for the targeted delivery and concentration of nanoscale analytes on chips, with significant implications for advancing applications in the life sciences.