Nicolas Tiercelin

A Millimeter-Wave Microstrip Antenna Array on Ultra-Flexible Micromachined Polydimethylsiloxane (PDMS) Polymer

The use of polydimethylsiloxane (PDMS), an ultra flexible polymer, as a substrate for the realization of reconfigurable microwave devices in the 60-GHz band is presented. As bulk PDMS is demonstrated to be lossy at millimeter waves, membrane-supported devices are considered. A new reliable and robust technological process has been developed to micromachine membrane-supported transmission lines and microstrip antenna arrays. It is shown that transmission lines printed on 20-¿m-thick membranes exhibit similar performances as bulk substrates commonly used at millimeter-wave frequencies. A microstrip antenna array has been also designed and fabricated to demonstrate the feasibility of directive antennas supported by large membranes. Promising applications for mechanical beam-steering, beam-forming, and frequency-tunable antennas are expected.

Enhanced magnetoelectric effect in nanostructured magnetostrictive thin film resonant actuator with field induced spin reorientation transition

We report the use of a magnetic instability of the spin reorientation transition type to enhance the magnetoelectric sensitivity in magnetostrictive-piezoelectric structures. We present the theoretical study of a clamped beam resonant actuator composed of a piezoelectric element on a nonpiezo substrate actuated by a magnetostrictive layer. The experiments are made on a polished 150μm thick 18×3mm2 lead zirconate titanate (PZT) plate glued to a 50μm silicon plate and coated with a giant magnetostrictive nanostructured Nx(TbCo25nm∕FeCo5nm) layer. Another set of experiments was done with PZT substrate only. Results agree with analytical theory.

Magnetoelectric effect near spin reorientation transition in giant magnetostrictive-aluminum nitride thin film structure

Hybrid giant magnetostrictive-piezoelectric film/film structures exhibiting magnetoelectric (ME) effect associated with a magnetic instability of the spin reorientation transition type are presented. We first present the theoretical study of a clamped beam actuator composed of a piezoelectric layer on a substrate actuated by a magnetostrictive layer. The actuator is a polished 50u2002μm thick 18×5u2002mm2 silicon substrate coated by an electrode, aluminum nitride, and magnetostrictive nanostructured layer. A ME coefficient of 30u2002Vu2009Oe−1u2009cm−1 at a 35 KHz longitudinal resonance was measured. Nonlinear excitation of this mode showed a “nonlinear” dynamic ME coefficient of 4u2002Vu2009Oe−1u2009cm−1.

Stress-mediated magnetoelectric memory effect with uni-axial TbCo2/FeCo multilayer on 011-cut PMN-PT ferroelectric relaxor

We present here the implementation of a magnetoelectric memory with a voltage driven writing method using a ferroelectric relaxor substrate. The memory point consists of a magnetoelastic element in which two orthogonal stable magnetic states are defined by combining uni-axial anisotropy together with a magnetic polarization in the hard axis direction. Using a ferroelectric relaxor substrate, an anisotropic stress is created in the magnetic element when applying a voltage across electrodes. Because of the inverse magnetostrictive effect, the effective anisotropy of the magnetic element is controlled by the applied voltage and used to switch magnetization from one state to the other.

Multilayer magnetostrictive structure based surface acoustic wave devices

This study addresses the experimental and theoretical investigations of guided elastic waves propagation in piezo-magnetic multi-layered structure. The structure is composed of a 20×TbCo2(5nm)/FeCo(5nm) nanostructured multi-layer deposited between two Aluminum (Al) Inter-Digitals Transducers forming a surface acoustic wave delay line, on a Y-cut LiNbO3 substrate. We compare the calculated and measured phase velocity variation under the action of the external magnetic field orientation and magnitude. We find quantitative agreement between the measured and modeled phase velocity shift for all external magnetic field configurations (hard axis and easy axis) and for different shape modes of elastic waves at their first and third harmonic operation frequencies. The shear horizontal mode exhibits a maximum phase velocity shift close to 20% for a ratio close to 1 between magneto-elastic film thickness and wavelength.

Vibrotactile using micromachined electromagnetic actuators array

One motivating application of this technology is the development of a tactile display interface, where discrete mechanical actuators apply vibratory excitation at discrete locations on the skin. Specifically, this paper describes the development fabrication and characterization of a 4 x 4 micro-actuator array of vibrating pixels for fingertip tactile communication. The vibrting pixels are generated by using an electromagnetic microresonator. The fabrication sequence and the actuation performance of the array are also presented.

A Millimeter-Wave Inflatable Frequency-Agile Elastomeric Antenna

This letter reports a millimeter-wave frequency-agile microstrip antenna printed on an ultrasoft elastomeric polydimethylsiloxane (PDMS) substrate. The microstrip patch antenna is supported by a PDMS membrane suspended over an air cavity. The distance H between the patch and the ground plane, and thus the resonant frequency of the antenna, are tuned using pneumatic actuation, taking advantage of the extreme softness of the PDMS membrane. A continuous frequency shift varying from 55.35 to 51 GHz (≈8%) has been obtained for a tuning range of H between 200 and 575 μm. In all configurations, the antenna remains matched and its radiation characteristics are very satisfactory.

Giant magnetostriction thin films for multi-cantilever micro-structures driving

Abstract First results on the realisation of a micrometer GaInAs multi-cantilever structure (50×30×1 μm 3 each) driven by amorphous TbFe magnetostrictive thin films are presented. Magneto-elastic properties of the cantilevers were studied by dynamic excitation methods. A resonance of the bimorph cantilevers was observed at an excitation frequency of 0.8 MHz with a Q -factor of about 10 3 . The coercive force of the magnetic films sputtered on micro-cantilevers was found to be H c =8 Oe.

Millimeter-wave patch array antenna on ultra flexible micromachined Polydimethylsiloxane (PDMS) substrate

A new microfabrication process of millimeter wave patch antenna on micromachined PDMS substrates has been elaborated, implemented and validated. The amount of loss in microstrip lines printed on 20 µm thick membranes is around 0.5 dB/cm at 60 GHz. A 4×2 patch antenna array supported on an ultra flexible PDMS membrane has been characterized. Large membranes could easily be obtained with the proposed microfabrication process. The very high softness of PDMS coupled to MEMS actuators is extremely promising for the design of mechanical wide angle beam-steering and beam-forming antennas. The very “clean” elaborated technological fabrication process also opens the path to biomedical applications.

Magnetically Actuated Microvalves for Active Flow Control

This paper describes the design, fabrication and characterization of silicon based, high flow rate microvalves for the active control of separated air flows. The fabricated system provides pulsed microjets with an outlet speed reaching 150 m/s at an actuation frequency ranging from static actuation to 2.2 kHz, using either electromagnetic actuation or a self oscillating mode. After a brief introduction, the microvalve dimensioning and fabrication process are presented. The actuation techniques used are then described and discussed.