Refractive-index-matched hydrogel materials for modeling flow-structure interactions

TL;DR

This paper introduces hydrogel materials, agarose and polyacrylamide, as flexible, cost-effective, refractive-index-matched models for flow-structure interaction studies in water, enabling high Reynolds number experiments and accurate shape modeling.

Contribution

It demonstrates the use of hydrogels as inexpensive, tunable, and optically clear models for flow studies, expanding capabilities beyond rigid, costly materials.

Findings

Hydrogels can be cast into desired shapes for flow experiments.

Hydrogels exhibit tunable flexibility matching biological materials.

Hydrogel models enable high Reynolds number flow measurements.

Abstract

In imaging-based studies of flow around solid objects, it is useful to have materials that are refractive-index-matched to the surrounding fluid. However, materials currently in use are usually rigid and matched to liquids that are either expensive or highly viscous. This does not allow for measurements at high Reynolds number, nor accurate modeling of flexible structures. This work explores the use of two hydrogels (agarose and polyacrylamide) as refractive-index-matched models in water. These hydrogels are inexpensive, can be cast into desired shapes, and have flexibility that can be tuned to match biological materials. The use of water as the fluid phase allows this method to be implemented immediately in many experimental facilities and permits investigation of high Reynolds number phenomena. We explain fabrication methods and present a summary of the physical and optical properties of both gels, and then show measurements demonstrating the use of hydrogel models in quantitative imaging.