Mechanical metamaterials have attracted significant attention due to their programmable internal structure and extraordinary mechanical properties. However, most of them are still in their prototype stage without direct applications. This research developed an easy-to-use mechanical metamaterial with tailorable large negative Poisson′s ratios. This metamaterial was microstructural, with cylindrical-shell-based units and was manufactured by the 3D-printing technique. It was found numerically that the present metamaterial could achieve large negative Poisson′s ratios up to −1.618 under uniaxial tension and −1.657 under uniaxial compression, and the results of the following verification tests agreed with simulation findings. Moreover, stress concentration in this new metamaterial is much smaller than that in most of existing re-entrance metamaterials.

In this study, a metamaterial is developed and manufactured by additive manufacturing technique for a novel wearable piezoelectric energy harvester (PEH). This PEH converts electricity from the kinetic energy associated with walking by attached polyvinylidene fluoride (PVDF) membranes. Finite element method analysis was conducted to simulate the dynamic compression on insoles corresponding to actual walking or running. The simulation results were verified by experiments. It was found that a triple-layer PVDF structure can produce an output voltage of 4.15 V and one insole with a triple-layer PVDF structure array can provide an 8.6 mW output power at running.