Confluent and non-confluent phases in a model of cell tissue

The Voronoi-based cellular model is highly successful in describing the motion of two-dimensional confluent cell tissues. In this model, the energy of each cell is determined solely by its geometric shape and size, and the interaction between adjacent cells is a byproduct of this additive energy. We generalize this model so as to allow zero or partial contact between cells in an open system. We identify several phases, two of which (solid confluent and liquid confluent) were found in previous studies that imposed confluency but others that are novel. Transitions in this model may be relevant for understanding both normal development as well as cancer metastasis.