This paper reports on the experimental and theoretical study of flexible piezoelectric transducers with an active area of ~1cm 2 made of a thin active composite material (~3μm thick) over a thin metallic foil (~25μm of Stainless Steel). The composite material structure is made of vertical piezoelectric nanowires (NWs) embedded into a PMMA dielectric matrix. The open circuit voltage was measured on different devices under manual and automatic bending. The performance was evaluated in function of the thickness of the top layer of PMMA in the composite structure of different devices. It was found that the output voltage increased as the thickness of the top layer was reduced. These preliminary results confirm the theoretical FEM simulations and give important guidelines for the optimization of flexible piezoelectric transducers.