Probing rheology and mechanics of compressed microgel suspensions*

The unusual and adjustable mechanical properties of compressed microgel suspensions arise from the high deformability and responsiveness to external stimuli, such as temperature and pH, of the constituent microgel particles. Compressed microgel suspensions exhibit a three order of magnitude difference between the bulk and shear moduli that can be further altered by applying an external stimulus which drives the swelling transition in microgels. These properties make compressed microgel suspensions ideal for the development of new materials able to autonomously recover their internal structure after mechanical damage. We use mesoscale simulations to understand the mechanical and rheological response of compressed microgel suspensions and to establish how this response depends on the properties of individual microgels. Our findings show that at high packing fractions deformation occurs mainly as a result of particles shrinking, indicating particle interpenetration is relatively small. We further show that rheological and mechanical responses of the suspensions are directly related to the single particle modulus that sets the scale for particle shrinking.