Elastic interactions of active cells with soft materials

I. B. Bischofs, S. A. Safran and U. S. Schwarz

Phys. Rev. E 69: 021911 (2004)

Anchorage-dependent cells collect information on the mechanical
properties of the environment through their contractile machineries
and use this information to position and orient themselves.  Since
the probing process is anisotropic, cellular force patterns during
active mechanosensing can be modelled as anisotropic force
contraction dipoles. Their build-up depends on the mechanical
properties of the environment, including elastic rigidity and
prestrain. In a finite sized sample, it also depends on sample
geometry and boundary conditions through image strain fields.  We
discuss the interactions of active cells with an elastic environment
and compare it to the case of physical force dipoles.  Despite
marked differences, both cases can be described in the same
theoretical framework.  We exactly solve the elastic equations for
anisotropic force contraction dipoles in different geometries (full
space, halfspace and sphere) and with different boundary
conditions. These results are then used to predict optimal position
and orientation of mechanosensing cells in soft material.