  The mechanical properties of the cell depend crucially on the tension of its
cytoskeleton, a biopolymer network that is put under stress by active motor
proteins. While the fibrous nature of the network is known to strongly affect
the transmission of these forces to the cellular scale, our understanding of
this process remains incomplete. Here we investigate the transmission of forces
through the network at the individual filament level, and show that active
forces can be geometrically amplified as a transverse motor-generated force
force "plucks" the fiber and induces a nonlinear tension. In stiff and densely
connnected networks, this tension results in large network-wide tensile
stresses that far exceed the expectation drawn from a linear elastic theory.
This amplification mechanism competes with a recently characterized
network-level amplification due to fiber buckling, suggesting that that fiber
networks provide several distinct pathways for living systems to amplify their
molecular forces.
