  A model of multicellular systems with several types of cells is developed
from the phase field model. The model is presented as a set of partial
differential equations of the field variables, each of which expresses the
shape of one cell. The dynamics of each cell is based on the criteria for
minimizing the surface area and retaining a certain volume. The effects of cell
adhesion and excluded volume are also taken into account. The proposed model
can be used to find the position of the membrane and/or the cortex of each cell
without the need to adopt extra variables. This model is suitable for numerical
simulations of a system having a large number of cells. The two-dimensional
results of cell adhesion, rearrangement of a cell cluster, and chemotaxis as
well as the three-dimensional results of cell clusters on the substrate are
presented.
