Dense array of elastic hairs obstructing a fluidic channel

TL;DR

This paper investigates how dense arrays of elastic hairs in microfluidic channels affect flow resistance, modeling the system as a deformable porous media to enable passive flow control design.

Contribution

It introduces a combined experimental and theoretical analysis of fluid flow through elastic hair arrays, modeling the deformation as a deformable porous medium and identifying key dimensionless parameters.

Findings

Nonlinear hydraulic resistance observed in hair-occluded channels

Deformation modeled as a deformable porous media affecting flow

Design principles for passive flow control elements derived

Abstract

Dense arrays of soft hair-like structures protruding from surfaces in contact with fluids are ubiquitous in living systems. Fluid flows can easily deform these soft hairs which in turn impacts the flow properties. At the microscale, flows are often confined which exacerbates this feedback loop since the hair deformation has a strong impact on the flow geometry. Here, I investigate experimentally and theoretically pressure driven flows in laminar channels obstructed by a dense array of elastic hairs. I show that the system displays a nonlinear hydraulic resistance that I model by treating the hair bed as a deformable porous media. The porous media height and thus degree of confinement results from the deflection of individual hairs. The resulting fluid-structure interaction model is leveraged to identify the dimensionless drag force $\hat{f}_0$ controlling the elasto-viscous coupling and used to design passive flow control elements for microfluidic networks.