The mechanical properties of living cells are largely controlled by a variety of filament-motor networks optimized for diverse physiological processes. In the presence of ATP, such networks are capable of generating controlled contractile forces and spontaneous oscillations. We have developed a generic continuum framework to delineate the emergent phases of a permanently cross-linked active gel [1]. The gel is modeled as a two-component system consisting of a fluid permeating an active polymer network, with essential nonlinear ingredients. Activity is induced by transient motor cross-linkers that undergo an ATP-activated cycle and transmit contractile forces to the network. Our analysis shows that the gel can be tuned through three classes of dynamical steady states by increasing motor activity: a constant un-strained state of homogeneous density, a state where the local density exhibits sustained oscillations, and a steady-state which is spontaneously contracted, with a uniform mean density. Our active gel model holds relevance to many biophysical systems with motor-filament assemblies that behave as solids at low frequencies.
Publications:

[1] S. Banerjee and M.C. Marchetti, Instabilities and Oscillations in Isotropic Active Gels, Soft Matter, 2011, 7, 463.
[2] S. Banerjee, T.B. Liverpool and M.C. Marchetti, Generic phases of cross-linked active gels: Relaxation, Oscillation and Contractility, Europhysics Letters, 2011, 96, 58004.