Polarimetric analysis of a fused sphere as a model for adherent particles

There are many situations of interest that are related to the geometry of soft spherical particles close - and adhering - to a surface. The case of biological cells is probably one of the most appealing ones because of their attachment/detachment processes, that are connected with their adhesion capacity and their ability to migrate. In this work, we perform imaging polarimetry on a model consisting of samples of latex spheres, or spherical caps, located on a flat transparent substrate. Different curvature degrees, achieved by gradual heating and melting, mimic the process of spreading associated to adhesion. Experiment-theory comparison allows us to identify specific states of adherence, and add some insight into experimental aspects like the contrast in the observation plane depending of the polarimetric parameter image selected, and also the effect of the numerical aperture (NA) of the microscope.