| We base our analysis on the framework of active polar gels in a confined quasi-two-dimensional (Hele-Shaw) geometry. In this regime and in the absence of myosin, the problem can be mapped into a Laplacian free-boundary problem. We perform a weakly-nonlinear bifurcation analysis of a family of rotational symmetric interfaces. Exact numerical analysis reveals a novel inherently nonlinear mechanism of cell motility, which operates combined with the morphological instability of lamellar fragments, that is capable to sustain motion, achieving a nontrivial stationary shape of the fragment. We show that this mechanism is operative with only polymerization forces, in the absence of myosin. |
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