Michel de Labachelerie

Miniaturized pH biosensors based on electrochemically modified electrodes with biocompatible polymers.

Potentiometric pH sensors based on linear polyethylenimine (L-PEI) and linear polypropylenimine(L-PPI), two synthetic enzymes and biocompatible polymers, films were prepared by electropolymerization of three different monomers: ethylenediamine (EDA), 1,3-diaminopropane (1,3-DAP) and diethylenetriamine (DETA) in order to be used in clinical, dermatological and biological applications, such as in vivo analysis. In a first step a biosensor was tested which consisted in a platinum wire protruded from glass sheath. The polymer film coated on these platinum electrodes showed good linear potentiometric responses to pH changes from pH 3 to 10. Resulting electrodes present both good reversibility and good stability versus time. The effect of the different polymer film thicknesses to potentiometric responses was also studied. This study allowed us to develop a miniaturized pH biosensor in the second step. This sensor was fabricated using photo-lithography, followed by sputtering and lift-off processes, and it included an electronic detection system. We have also successfully studied the potentiometric responses to pH changes of this device over a period of 1 month, and so we propose this new pH micro-biosensor as an alternative to classical pH sensors currently used in dermatology.

Lateral optical accelerometer micromachined in (100) silicon with remote readout based on coherence modulation

Abstract A novel type of optical silicon accelerometer is demonstrated. A non-conventional wet etching technique for (100) silicon allows us to make a highly symmetrical seismic mass with a pure lateral translation movement. This ensures a low sensitivity to accelerations that are not along the sensing axis. To detect the displacement of the seismic mass due to accelerations, an optical fiber can be easily and precisely implemented to form a Fabry-Perot interferometer. A detection method based on coherence modulation allows remote acceleration sensing through a fiber-optic link without any electrical link between the measurement region and the signal output. The sensitivity of the demonstrated system is 1.8 V g −1 for a measurement range of ±10 g and a resolution of less than 1mg. Moreover, the fabrication technique and the multiplexing capability of the detection method open the way to a 3D single-chip accelerometer, the measurements of which could be sent directly through a single optical link.

Fabrication of a new highly-symmetrical, in-plane accelerometer structure by anisotropic etching of (100) silicon

In this paper, we present a silicon bulk-microfabrication method which helps to overcome simultaneously several limitations of multi-axis micro-accelerometers. The method demonstrates an orginal solution to the building of a symmetrical structure by using double-side wet etching. This is a low-cost alternative to existing techniques for the fabrication of highly-symmetrical, single crystal silicon structures. The proposed approach provides low mechanical cross-sensitivities as well as the possibility of a batch fabrication process of the whole three-dimensional device without loss of accuracy due to assembly operation. For the fabrication of thin suspended beams with vertical sidewalls, a non-conventional alignment of from the wafer flat was used. This alignment allows one to fabricate two perpendicular devices on one wafer in the same etching step. The etching was performed with a simple standard wet etching process in a KOH solution. A number of structures were fabricated to demonstrate the feasibility of this method. Aspect ratios (beam height over beam thickness) of over 35 were easily achieved. Undercut directions were determined and design rules for the mask layout were established. To describe the mechanical behaviour of the fabricated structure, an analytical model was implemented and a finite-element simulation was performed. First measurements of the seismic mass displacement were performed with an optical comparator, and they agree with theoretically obtained results. The new design offers the possibility of a two-axis accelerometer system on one wafer, consisting of two sensor elements rotated by . A three-axis monolithic accelerometer system with intrinsic perpendicular alignment due to the rectangular symmetry of the (100) planes can be realized, by including a third sensor element sensitive to vertical accelerations.

Collective wet etching of a 3D monolithic silicon seismic mass system

We present a simple two-step etching process based on anisotropic wet etching of (100) silicon. As one example a system of three seismic masses on one chip has been fabricated. All three masses are symmetrically suspended by four high aspect ratio beams. The highly symmetrical design minimizes mechanical cross-sensitivities. Moreover, the three devices exhibit almost perfect rectangular alignment due to the orientation along the directions of the silicon crystal. Besides experimental results, design rules for the photolithography-masks are presented.

An integrated pulse tube refrigeration device with micro exchangers: design and experiments

The cooling of electronic components is of great interest to improve their capabilities, especially for CMOS components. The purpose of this paper is to present the principle and the design of a micro cooler dedicated to such application. The originality of the approach concerns both the use of a thermodynamic system and the use of a micro-fabrication technology entirely compatible with the small scale of the component. The cooling function is assumed by a pulsed gas in a small canal (pulse tube) made of glass and of silicon. Specific micro heat exchangers, also made of silicon, have been designed from the results of a study concerning both the pressure drop and the transitory thermal response. The actual micro-cooler performances are estimated in an experimental way by means of temperature and pressure measurements.

Modeling and Characterization of Lamé-mode Microresonators Realized by UV-LIGA

We report in this paper the study of a new metallic microresonator realized by UV-LIGA technique. This kind of device is excited electrostatically and takes advantage of the contour modes or Lame-modes of the structure. Design methods of such device are presented and simulated with a Finite Element Program. Details on the microfabrication process are also presented. The vibration modes are detected with an optical bench setup and preliminary electrical results are presented. A comparison between experiments and numerical predictions are finally discussed.

Design and test of new high-Q microresonators fabricated by UV-LIGA

We report in this paper the study of a new metallic microresonator realized by UV-LIGA technique. This kind of device is excited electrostatically and takes advantage of the contour modes or Lame-modes of the structure. Design methods of such device are presented and simulated with a Finite Element Program. Details on the microfabrication process are also presented. The vibration modes are detected with an optical bench set-up and preliminary electrical results are presented. A comparison between experiments and numerical predictions are finally discussed.

Fabrication and characterization of high-Q microresonators using thin plate mechanical mode

The growing place of electronics devices in our society increases the demand of small devices such as RF filters, time references and oscillators. The aim of this work concerns the design and characterization of a new kind of crystalline silicon microresonator fabricated using a DRIE (Deep Reactive Ion Etching) technique. This device can be fabricated by IC compatible techniques. This kind of microresonators is electrostatically actuated and uses a contour or Lamé mode as fundamental mode of vibration. Its size gives the resonant frequency and behavior. The mechanical characterization of one microresonator is carried out using an optical bench set-up. The first results obtained on a device show a high Q factor in air close to 1000 at the resonant frequency of 10.3 MHz.

MINIATURE PULSE TUBE FOR THE COOLING OF ELECTRONIC DEVICES: FUNCTIONING PRINCIPLES AND PRACTICAL MODELING

The miniaturization of refrigerating systems represents a very current scientific and technical challenge to improve the performances of numerous electronic components. This work presents a global approach to the problem and suggests studying the cooling by means of small channels filled with an oscillating gas: the double inlet pulse tube refrigerator (DIPTR). A great level of miniaturization based on the technology of carving silicon is exposed. This study proposes to apply an electric analogy for modeling both hydrodynamic and thermal phenomena. Considering the complexity of the theoretical problem including mechanical, thermal, thermodynamical, and acoustic considerations, the authors take care to summarize the main governing equations in a particular form so any scientific engineer could understand the DIPTR principle.

Laser diode wavelength locking using a micromachined silicon mirror

The fine control of laser diodes emission wavelength is usually done by controlling the diode temperature and current, however, the internal wavelength selection mechanisms inside the diode cavity are not strong enough to get a complete coverage of the tuning range, and the diode wavelength usually hops to unpredictable places, leaving some wavelength intervals difficult to access.