Abstract
We develop a hydrodynamic theory of active permeating gels with viscoelasticity in which a polymer network is embedded in a background fluid. This situation is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network, which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We first present the general ideas for the case of a passive, isotropic gel and then extend this description to a polar, active gel. We discuss two specific cases to illustrate the role of permeation in active gels: self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization; and non-equilibrium deswelling of a gel driven by molecular motors.
Highlights
Motivated by cytoskeletal dynamics in cells, we have developed a hydrodynamic theory describing active, polar, viscoelastic gels
A key result of this work is that by introducing the elastic deformation in the polymer component of the gel as a macroscopic variable, we obtained constitutive relations that describe the effects of permeation of the solvent driven by elastic stresses
These stresses can be generated by active processes, such as the action of motor molecules [1]
Summary
We first consider a passive viscoelastic gel to illustrate how the standard hydrodynamic approach [14, 15] can be extended to include the elastic strain in the polymer component as a slowly relaxing yet non-hydrodynamic variable. Our approach generalizes those of [16,17,18] by using Onsager theory to obtain generic constitutive relations that describe solvent permeation and elastic strain relaxation in a gel at long times
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