Low hazard refractive index and density-matched fluid for quantitative imaging of concentrated suspensions of particles

A novel refractive index and density-matched liquid–solid suspension system taking into account chemical hazard and health concerns was developed and characterized. The solid phase is made of PMMA spheres, the refractive index of which being adapted with a mixture of 2,2′-thiodiethanol and phosphate-buffered saline (PBS), while the density is adapted with a mixture of PBS and glycerol. The proposed chemicals present low hazard characteristics in comparison with former solutions. Data collected from density and refractive index measurements of the solid phase and of the different fluid constituents are used to define a specific ternary mixture adapted to commercial grade micron-size particles. The defined mixture is validated in a micron-sized granular flow experiment. The described method can be applied to other low-density solids.