  In this paper we propose a new lattice structure having macroscopic Poisson's
ratio arbitrarily close to the stability limit -1. We tested experimentally the
effective Poisson's ratio of the micro-structured medium; the uniaxial test has
been performed on a thermoplastic lattice produced with a 3d printing
technology. A theoretical analysis of the effective properties has been
performed and the expression of the macroscopic constitutive properties is
given in full analytical form as a function of the constitutive properties of
the elements of the lattice and on the geometry of the microstructure. The
analysis has been performed on three micro-geometry leading to an isotropic
behaviour for the cases of three-fold and six-fold symmetry and to a cubic
behaviour for the case of four-fold symmetry.
