Stiff square structure with a negative Poisson's ratio

A novel 2D cellular structure achieved by alternating rectangular surface indents on the vertical ribs of the unit cells was designed. And the Poisson's ratios of several structures were determined using the finite element method(FEM) as a function of geometric parameters. The simulation results showed that the Poisson's ratio of the 2D cellular structure was sensitive to the cell dimensional ratio, and the value can be tuned from positive to negative(the minimum can reach -1.05). Samples with identical geometric variables were fabricated via 3D printing, and their Poisson's ratios were measured and compared with the ones from simulation. Excellent agreement was found between the experimental results and the simulation. The stiffness of the model can be higher than honeycomb made of regular hexagons with appropriate geometric parameters.