# Dynamics of individual Brownian rods in a microchannel flow

## TL;DR

This paper investigates the orientational behavior of silica microrods in microchannel flow, revealing complex tumbling dynamics and the influence of rotational diffusion, with experiments and simulations showing rods lose initial orientation in about a second.

## Contribution

It provides a detailed analysis of three-dimensional rod orientations and identifies deviations from classical Jeffery theory in microfluidic conditions.

## Key findings

- Identification of in-plane tumbling behavior not explained by Jeffery theory
- Quantification of orientation memory loss in about one second
- Correlation between rotational diffusion and particle trajectories

## Abstract

We study the orientational dynamics of heavy silica microrods flowing through a microfluidic channel. Comparing experiments and Brownian dynamics simulations we identify different particle orbits, in particular in-plane tumbling behavior, which cannot be explained by classical Jeffery theory, and we relate this behavior to the rotational diffusion of the rods. By constructing the full, three-dimensional, orientation distribution, we describe the rod trajectories and quantify the persistence of Jeffery orbits using temporal correlation functions of the Jeffery constant. We find that our colloidal rods lose memory of their initial configuration in about a second, corresponding to half a Jeffery period.