Ph. Renaud

Modelization and characterization of asymmetrical thermal micro-actuators

Structures of very high aspect ratio which are mechanically stiff in the substrate direction and flexible in the direction parallel to the substrate are studied. Such structures can be exploited to produce thermal flexure actuators which are capable of large motion produced by thermal expansion. The magnitude of the deflection depends strongly on geometry and material properties. Structures fabricated by laser micro-machining are characterized and compared to numerical simulations.

Fabrication process of high aspect ratio elastic structures for piezoelectric motor applications

Briefly reports on advances in the fabrication technology of components for millimeter size ultrasonic piezoelectric motors. A very large height to width aspect ratio with good lateral patterning resolution is required for the active component in acoustic mode conversion. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. The main advantages over past fabrication methods are better flexibility in the design, simplicity of the fabrication process and the combination of metallic materials (Ni) with polymeric materials (SU-8). The mechanical properties of SU-8 have been measured using free cantilever beam structures.

New design of micromachined capacitive force sensor

Anisotropic etching of a (110) oriented silicon wafer has been used to realize a differential capacitive force sensor. This design is based on a simple concept allowing force to be measured in the plane of the sensor, giving a new and original product in the field of small force measurements. These sensors can be adjusted to measure force in the range 0.01 N to 10 N or, in a low rigidity version, to act as a high precision displacement sensor with an expected resolution of 20 nm. These sensors are planed to be used with a commercial capacitance measurement chip (nominal capacitance: 1 pF, resolution: 1 fF).

Impedance Spectroscopy Cell Analysis in Microchannels

This paper presents a micromachined high throughput flow-cytometer capable of discriminating cells using their electrical parameters as measured by impedance spectroscopy. The system is based on a set of electrodes integrated in a microchannel to measure the differential impedance in two successive segments as the cell passes consecutively through each. This analyzer is intended to drive a sorting actuator realising a subsequent cell separation. Size reduction and integration of functions are essential in achieving precise measurements and high throughput.

Fast Heating and Cooling for High Temperature Chemical Microreactors

Many chemical reactions, like the dehydrogenation of gaseous methanol to formaldehyde, require fast heating and cooling of the gases in order to control precisely the residence time at the reaction temperature (on the order of hundreds of ms) to minimise consecutive reactions. For these applications, microsystems are of great interest thanks to their characteristic high surface-to-volume ratio and low thermal inertia [1–3]. Heater and cooler units were developed with compatible micromachining technologies in view of a future integration in a complete microreactor system.

Piezoelectric Cantilever Beams Actuated By PZT Sol-gel Thin Film

Micromachined silicon cantilever beams actuated by the converse piezoelectric effect are of great interest for actuator applications [1], and for the characterization of piezoelectric thin films [2]. In this work a study of the mechanical response of piezoelectrically operated heterogeneous bimorph structures is given and compared with finite elements simulations. Determination of the piezoelectric parameter d/sub 31/ using interferometric displacement measurements, electrical impedance measurements, and finite element calculation will be discussed.

Polyimide-Based Microfluidic Devices with Nanoporous Membranes for Filtration and Separation of Particles and Molecules

The development of polyimide-based, microfluidic devices with nanoporous membranes is reported. Microchannels are fabricated from spin-on polyimide by a lamination technique. High aspect ratio nanopores are created in the polyimide channel walls by ion irradiation and subsequent ion-track etching. The devices can be used for on-chip filtration and separation of particles or as microstructures for drug delivery.

Simulation of integrated electromagnetic device systems

The simulation of integrated electromagnetic sensors and actuators can be performed in conjunction with the electronics to simulate a complete microsystem. A reluctant micro-relay and an inductive displacement sensor are characterized using finite elements. Macro-models using extracted parameters are coded with analog hardware description languages for circuit simulators, with the goal of global system simulation and optimization. The methodology is applicable to all integrated and hybrid transducers which can be modeled using a discrete variable formulation.