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 . 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.
 S. Banerjee and M.C. Marchetti, Instabilities and Oscillations in Isotropic Active Gels, Soft Matter, 2011, 7, 463.
 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.