Hello, We are using silver-coated hollow glass-spheres with 4µm mean-diameter in our µPIV-measurements. Unfortunately these particles start conglomerating in paraffin oil (and water) and they get stuck in our microstructures instead of just floating around the structures. Has anyone experience in using silver-coated hollow glass-spheres and knows how to avoid the clustering of the particles in paraffin/water. Many thx Sebastian Große