Jamming of 2D foams

We probe the jamming of 2D wet foams by lateral compression of a bidisperse foam monolayer sandwiched between a glass plate and a fluid surface. Boundaries and residual gravitational effects prevent the foam to be truly unjammed, obstructing the observation of a jammed/unjammed transition. Instead, we find a clear transition from a ``gravity jammed'' to a ``boundary jammed'' state, where the bulk modulus jumps from essentially zero to a finite value, in agreement with theory. In addition, we probe the nonaffine bubble motion, which becomes large near this transition.