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International audience; Bulk piezoelectric cantilever beams are mostly assembled under serial bimorph topologies where the piezoelectric material is laminated around an inner shim material. The two PZT layers exhibit an individual thickness ranging from few tens to hundreds of micrometers according to the targeted application and its miniaturization requests. Designing such devices becomes a challenge and one needs FEM (finite element model) to properly define material thicknesses and overall piezoelectric energy harvester geometries. Unfortunately, bulk piezoelectric material are characterized using thicker samples which provide results slightly different from the actual characteristics of thinned-bulk piezoelectric materials. Previous works have addressed an approach to study the thin piezoelectric material layer relying on the electrical admittance analysis. Then, the effective coefficients of thinned-bulk piezoelectric material are identified and entered in a 3D FEM of the PZT layer. The electrical admittance is calculated, showing a good agreement with the experimental measurements.

International audience; More and more medical ultrasonic applications are strongly interested by the development of dual acoustic sources enable to emit high frequency ultrasound (echographic imaging) and low frequency pressure field (therapeutic ultrasounds). The use of the piezoelectricity to fabricate such device requires overcoming strong technological bottlenecks. The objective of this paper is to demonstrate that the technology of capacitive micro-machined ultrasonic transducer is able to take up this challenge. To this end a demonstrator was designed and manufactured. The first part of the paper is devoted to the design of the low and high frequency cMUTs. For the low acoustic source, a dedicated time domain model was used, taking into account the nonlinearity of the cMUT. Several simulations were conducted to optimize the emitted pressure field intensity at 1 MHz for a set of diaphragm with different sizes and geometries. The high frequency source was designed on the help of a linear model, where output parameters were central frequency, bandwidth and collapse voltage. The second part of this paper reports a set of characterization results and performances of the fabricated device: electrical impedance, mechanical displacements performed in water and acoustic pressure fields.