Two dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C4F8/O2) using an electroplated Ni mask. Depth up to 100 μm with a profile angle of 83°–88° and a smooth bottom of the etched structure (Ra below 3 nm) were achieved at an etch rate of 0.9 μm/min. An ultrashort pulse Ti:sapphire laser operating at the wavelength of 800 nm and 5 kHz repetition rate was used for micromachining. Channels of 100 μm width and 140 μm height with a profile angle of 80–85° were obtained in 3 min using an average power of 160 mW and a pulse duration of 120 fs. A novel process for glass–glass anodic bonding using a conductive interlayer of Si/Al/Si has been developed to seal microfluidic components with good optical transparency using a relatively low temperature (350°C).

New guiding principles and concepts are currently investigated for developing high frequency devices capable to answer the RF manufacturer demand for telecommunication an remote transmission modern components. Beside the use of physically or chemically deposited piezoelectric overlays, the use of composite wafers composed by single crystal layers and wafers obtained by wafer bonding and lapping/polishing techniques offers attractive opportunities for overpassing the known limitations of acoustics-based radio-frequency devices. In this paper, we present different approaches for manufacturing such composite wafers and we describe different applications taking advantage of their unique characteristics. Lithium niobate is particularly considered for the piezoelectric layers because of its exceptional piezoelectric properties and its very high acoustic quality, and various substrate such as silicon, sapphire and lithium niobate again are used to guide and trap the excited waves. State-of-the-art Surface Acoustic Wave (SAW) devices, Harmonic Bulk Acoustic Resonators (HBARS) and Periodically Poled Transducers developed on such wafers are presented to illustrate the potential of this technological approach.

A new method to manufacture capacitive micromachined ultrasonic transducers (cMUT) combining a wafer bonding and a sacrificial layer processes is introduced. Devices with monocrystalline silicon membranes over a polysilicon electrode have been manufactured. From impedance measurements in air of a monocell test device biased under 140 V, a resonance at 8.0 MHz and an electromechanical coupling coefficient of 45% have been found. Underwater pulse-echo experiments of a cell array are presented.

Micro-machined Ultrasonic Transducer (MUT) structures are periodic, associating numerous elementary actuators. These transducers can be accurately analysed or even designed using mixed finite element analysis/boundary element methods (FEA/MEM). In this work, we report on the design and test of a cMUT structure based on a thin silicon membrane shaped in order to comply our modelling assumptions.

The time domain analysis is an interesting alternative to spectral domain computations for vibrating structures or wave-guides exhibiting short impulse responses. we propose a development allowing for solving periodic transient problems. As for harmonic computations, we mesh only one period of the array and we then apply boundary conditions relating its edges one another. A periodic excitation coefficient similar to the one used in the spectral domain is defined and use to scan all the possible excitation figures. It is then shown how to derive mutual time domain coefficients that describe the way the different cells of the array are coupled together. It is remarkable that in this time domain representation, no singularity arises on the computed signals, yielding very favourable conditions for the derivation of mutual coefficients. but none take into account comprehensive periodic boundary conditions. In this paper, we propose a method to solve periodic transient problems. As in the case of harmonic computations, we mesh only one period of the array and we then apply periodic boundary conditions. A periodic excitation coefficient similar to the one employed in the spectral domain is defined and is used to scan all possible excitation situations. The time excitation is represented by Dirac (or Heaviside) impulses. It is then shown how mutual time domain coefficients can be derived that describe the way the different cells of the array are coupled together. It is remarkable that in this time domain representation, no singularities arise in the computed signals, resulting in very favourable conditions for the derivation of mutual coefficients. This time domain representation may be more accessible for most readers and should provide an efficient approach for the characterization of massively periodic devices with low quality factors. The first section is devoted to the fundamentals of the adopted integration scheme, i.e. the Newmark approach. Results are then reported in the case of a 2-2 piezocomposite structure and also in the case of a 2D micro-machined ultrasonic transducer (MUT) operating in a vacuum. Cross-talk phenomena due to acoustic propagation in these structures are identified thanks to the derivation of their mutual parameters (admittance, front velocity).

A finite element analysis/boundary integral method (FEA/BIM) model is used to investigate the influence of the geometry and the composition of the interface on the properties of interface acoustic waves (IAW). The method considers a finite region treated by FEA and submitted to periodic boundary conditions, taking into account radiation in both the bottom and the top half-spaces. The influence of the IDT thickness and of the material choice for the interfacial film are discussed for some cuts and structures. It is found that the most significant contribution of the interface geometry is to the ability of an IAW device of efficiently guiding waves, i.e. to the propagation losses.

We present the last results concerning investigation of powder blasting techniques to micromachined complex-patterned piezoelectric composite transducers. This technology consists of a beam of eroding powder particles, etching an in-situ-masked PZT plate. We manufacture honeycomb-patterned structures, which can not be achieved with a standard saw-dicing technique.