Piezoelectric-transducer energy harvester, in particular for powering an autonomous cardiac capsule, with a bending stiffness gradient oscillating structure

An autonomous device housing, within a device body:

• an electronic unit;
• an energy storage element;
• and
• a piezoelectric-transducer energy harvester, PEH, for powering the electronic unit and/or charging the energy storage element,
• wherein the PEH comprises a pendular unit subjected to external stresses applied to the harvester,
• wherein the pendular unit comprises:
• a beam that is elastically deformable in bending;
• a beam mount clamping a proximal end of the beam;
• and an inertial mass mounted at a free, distal end of the beam,
• wherein the beam is a piezoelectric beam adapted to convert into an oscillating electric signal a mechanical energy produced by oscillations of the pendular unit,
• wherein the piezoelectric beam comprises a flexible structure including:
• a central core;
• a piezoelectric layer on at least one face of the central core;
• and at least one surface electrode on an external face of the piezoelectric layer,
• wherein the central core of the flexible structure is a semiconductor material adapted to form an integrated circuit substrate,
• wherein the substrate made of a semiconductor material of the flexible structure central core includes monolithic integrated structures,
• and wherein the arrangement, over the extend of the central core substrate, of said monolithic integrated structures forms in the longitudinal direction a plurality of successive areas having different piezoelectric beam bending stiffness coefficients from an area to another.

A method for manufacturing a piezoelectric-transducer energy harvester, PEH, comprising the following successive steps:

• a) obtaining a central core made of a semiconductor material, adapted to form an integrated circuit substrate;
• b) integrating monolithic structures in the semiconductor material substrate of the central core,
• wherein the arrangement, over the extend of the central core substrate, of said monolithic integrated structures forms in the longitudinal direction a plurality of successive areas having different piezoelectric beam bending stiffness coefficients from an area to another;
• c) depositing a piezoelectric layer on at least one face of the central core;
• and
• d) depositing at least one surface electrode on an external face of the piezoelectric layer.