Comparison of 2D and 3D images of colloidal gels*

The Advanced Colloidal Experiment (ACE-M-1) was an experiment that was conducted by NASA to study colloidal gel structures in a microgravity context. Using the Light Microscopy Module, 2D images of the gels were generated. To quantify such gels’ properties, we conduct similar ground-based experiments, where we use colloidal polymethyl methacrylate (PMMA) particles and polystyrene as a depletant. We employ fluorescence confocal microscopy to take both 2D and 3D images of our colloidal gels.   We then consider how the 2D and 3D images are related.  In particular, we examine how the number of neighbors to each particle seen in 2D compares with the true number of 3D neighbors.  We additionally look at other structural quantities such as the pair correlation function.