  Mechanical coupling between a cell and substrate relies on focal adhesions,
clusters of adhesion proteins linking stress fibers (bundles of actin proteins)
inside the cell with surrounding tissue. Focal adhesions have been demonstrated
to both measure and regulate the mechanical traction along the stress fibers.
We present a quantitative model for focal adhesion mechano-sensing and stress
regulation based on stress amplification at the critical point of a
condensation transition of the adhesion proteins.
