  Cork is a natural amorphous material with near-zero Poisson's ratio that is
ubiquitously used for sealing glass bottles. It is an anisotropic,
transversally isotropic, composite that can hardly be scaled down. Here, we
propose a new class of isotropic and reusable cork-like metamaterial that is
designed from an hybrid truss-lattice material to show an isotropic Poisson's
ratio close to zero. Optimization is conducted using a multi-objective genetic
algorithm, assisted by an elliptical basis function neural network, and coupled
with finite element simulations. The optimal micro-structured metamaterial,
fabricated by two-photon lithography with a lattice constant of 300
\micro\meter, has an almost isotropic Poisson's ratio smaller than 0.08 in all
directions. It can recover $96.6\%$ of its original shape after a compressional
test exceeding $20\%$ strain.
