When dispersing microspheres in a fluid, often a surfactant is required.

We usually recommend Tween surfactants because they are easy to use and known for their ability to act as emulsifiers, stabilizers, and solubilizers. Tween surfactants are often used in formulations where it is necessary to mix hydrophilic (water-soluble) and hydrophobic (water-insoluble) components (e.g. polyethylene fluorescent seeding particles in water).

Tween is a polysorbate-type non-ionic bio-compatible surfactant often used in cell culture media to help disperse lipophilic compounds and improve cell growth. Polysorbate molecules each contain a hydrophilic head group and a hydrophobic tail.

Tween has been classified as non-hazardous and safe to use in cosmetic formulations.
Tween surfactants are often used to disperse tracers and seeding particles for PIV and flow visualization in aqueous solutions.