Point response of a 2D packing of soft colloidal spheres near the jamming transition.

We have created a 2D jammed packing by confining a bidisperse mixture of thermoresponsive NIPA microgel spheres between two glass slides with a thickness of roughly the larger sphere diameter. The packing is subjected to a point compression created by local heating with optical tweezers. We use particle tracking microscopy to characterize the response as a function of particle volume fraction both above and below the jamming transition.