Observation of Flux Reversal in a Symmetric Optical Thermal Ratchet

TL;DR

This paper demonstrates a symmetric optical thermal ratchet that induces flux reversal in colloidal particles, with transport direction changing based on cycle frequency and trap separation, highlighting a novel symmetry-breaking mechanism.

Contribution

It introduces a new thermal ratchet model using three symmetric states where spatiotemporal symmetry is broken by the sequence, leading to flux reversal.

Findings

Flux reversal depends on cycle frequency.

Flux reversal depends on inter-trap separation.

Transport direction can be controlled by cycle parameters.

Abstract

We demonstrate that a cycle of three holographic optical trapping patterns can implement a thermal ratchet for diffusing colloidal spheres, and that the ratchet-driven transport displays flux reversal as a function of the cycle frequency and the inter-trap separation. Unlike previously described ratchet models, the approach we describe involves three equivalent states, each of which is locally and globally spatially symmetric, with spatiotemporal symmetry being broken by the sequence of states.