Streaming enhanced flow-mediated transport

TL;DR

This paper explores how oscillations in an active body can generate flow patterns that enhance the transport of passive objects in viscous fluids, with applications in microfluidics and medicine.

Contribution

It introduces a method of superimposing oscillations on active bodies to generate viscous streaming, improving passive object transport in fluid flows.

Findings

Oscillations significantly improve transport efficiency across various Reynolds numbers.

Flow mechanisms are identified that enable enhanced transport.

Principles extend to three-dimensional shapes.

Abstract

We investigate the capability of an active body (master) to manipulate a passive object (slave) purely via contactless flow-mediated mechanisms, motivated by potential applications in microfluidic devices and medicine (drug delivery purposes). We extend prior works on active-passive cylinder pairs by superimposing periodic oscillations to the master's linear motion. In a viscous fluid, such oscillations produce an additional viscous streaming field, which is leveraged for enhancing slave transport. We see that superimposing oscillations robustly improves transport across a range of Reynolds numbers. Comparison with results without oscillations highlights the flow mechanisms at work, which we capitalize on to design (master) geometries for augmented transport. These principles are found to extend to three-dimensional active-passive shapes as well.