G. Lissorgues

Selective nucleation in silicon moulds for diamond MEMS fabrication

We present a new and original approach for the fabrication of diamond MEMS using MPCVD. This process does not rely on diamond etching using conventional techniques such as e.g. RIE: here our MEMS structures are geometrically defined using silicon moulds in which diamond is grown selectively. The moulds can be prepared from silicon using DRIE and enabling a wide range of geometries. The critical point is the selectivity of diamond growth which dramatically depends on the nucleation process. Two nucleation methods for selective diamond growth inside silicon moulds were explored in parallel and compared, namely, the bias enhanced nucleation (BEN) and the nano-seeding technique. With both methods, MEMS structures were successfully fabricated and characterized, leading to values for the Young modulus above 830 GPa, thus comparing well with literature values. We believe our approach will ease the routine fabrication of large area diamond MEMS wafers for improved advanced device fabrication.

New tunable RF MEMS microinductors design

This paper outlines the capabilities of RF MEMS tunable microinductors designed using mechanical displacements that change the magnetic coupling coefficient between circuits. The design and fabrication of a first and an optimized second tunable microinductor prototype are presented. We report a 50% inductance variation from 1.5 to 5 GHz measured on the first test wafers. Moreover, these tunable inductors, which have continuous variations, can be integrated with tunable capacitors into reconfigurable RF systems suitable for future wideband RF communications. The design of basic functions, such as a simple phase shifter cell or a tunable impedance, is lastly described.

Non-invasive measurement of blood flow using magnetic disturbance method

Current laser Doppler method of blood flow sensing requires optical contact to the skin, tend to be bulky and have performance subjective to body fluids (e.g. blood, perspiration) and environmental contaminants (e.g. mud, water). This paper proposes a novel method of noninvasive acquisition of blood flow by measuring the magnetic disturbance created due to blood flowing through a localized magnetic field. The proposed system employs a GMR based magnetic sensor and magnet of 3 mm radius, placed on a major blood vessel. The magnetic field generated by the magnet acts both as the biasing field for the sensor and also the uniform magnetic flux for blood flow disturbance. As such, the system is compact, operates at room temperature and is able to sense through clothing. The signal acquired from the magnetic and optical methods are compared using the post-occlusive reactive hyperaemia test, where measurement results on 6 different healthy subjects are found to have error of less than 5%, showing the successful use of the magnetic method to measure blood flow.

Measurement of Blood Pressure using magnetic method of blood pulse acquisition

Current cuffless method of Arterial Blood Pressure (ABP) measurements can be continuously calculated from pulse wave velocity and the Pulse Transit Time (PTT). PTT is usually recorded as the time delay from the R wave of Electrocardiographic (ECG) signal to the upstroke of a peripheral pulse wave signal measured using Photoplethysmographic (PPG) sensors or alternatively from the sound of Phonocardiographic (PCG) signal. This paper proposes an alternative novel method of measuring the magnetic disturbance, using a Giant-Magneto-Resistance (GMR) based sensor, created by blood flow in a uniform magnetic field for peripheral pulse wave signal measurements allowing an optical independent measurement system for ABP. The magnetic disturbance created by blood flow in a uniform magnetic field allows for the sensing of the peripheral pulse wave… Measurements were done on 10 subjects aged between 22 to 25 years old where the ABP measured using the PTT correlates well within 8% error with respect to the Mean Arterial blood Pressure (MAP) measured from commercially available cuff based automated ABP measurement devices.

Influence of RF signal power on tunable MEMS capacitors

Capacitive structures are sensitive to the electrostatic force created by the RF signal going through them. In the case of MEMS tunable capacitors, the consequences on performances and capacitance values are to be quantified. Two systems are studied: one-gap with RF signal and actuation voltage on same electrodes, and two-gaps with RF signal separated from actuation. Computational results show great influence of power on pull-in, even for low power levels, for both MEMS capacitor structures.

Microfabrication of new microelectrode arrays equipped with a ground surface configuration for focal neural microstimulation

Extracellular electrical stimulation of the central nervous system has been used empirically for decades, with both fundamental and clinical goals. Currently, microelectrode arrays (MEAs) offer new possibilities for CNS microstimulation, allowing in principle to activate only neurons located in the vicinity of the stimulation sites. To overcome the lack of focality of monopolar stimulations, multipolar approaches are commonly used, multiplying therefore the number of electrodes of the arrays and the complexity of the connection system behind. To overcome these limitations, we developed a ground surface configuration consisting in surrounding all the electrodes with a conductive surface laying over the MEA substrate, and using it for the stimulation current return. We first report the microfabrication of a prototype of MEA equipped with this configuration. We also perform experimental recordings of the potential field induced by microstimulations and confirm the expected increased focality with the ground surface configuration. This will open the way to focal pixel-like microstimulation of neural networks using MEAs.

Effects of a loop array layer on a micro-inductor for future RF MEMS components

Tunable micro-inductors can be designed controlling magnetic coupling coefficient. This paper presents the inductance variation produced by loops strongly magnetically coupled with a micro-inductor. A compact lumped element model, based on the geometry, gives result in good agreement with measurements in the RF frequency range. Then, this model will be applied to the study of the tunable MEMS inductor described below.

Continuous Intra Ocular Pressure Measurement Sensor for Glaucoma Diagnostic

Glaucoma is an ocular pathology usually associated with an increase in Intra Ocular Pressure (IOP). In this study, we are developing disposable eye lenses including a specific micro fabricated pressure sensor to measure IOP all day long. The information data will be wireless transferred via magnetic coupling to an external receiver. Our first work deals with the sensor design and fabrication. Simulation results based on classical electronic circuit tools will be presented and lead to several sensor solutions working at different RF frequencies. The fabrication process of the first sensors will also be described and an early IOP characterisation set-up will be presented to try to later quantify the sensor sensitivity, with IOP variations measured in the range 20 to 70mmHg.

Model of mutual coupling between two bonding wires on glass substrate

This paper presents a simple model of mutual coupling between 2 bonding wires. The model has been compared to 3D full wave electromagnetic simulation up to 20 GHz. A good accordance was obtained.

Optical actuation and detection of MEMS resonators: Behavioral modeling and phase noise simulations

Optical actuation and detection of MEMS resonators can improve the resolution of their motion detection compared to standard detection techniques (capacitive, piezoelectric). In this paper, a behavioral model of MEMS resonator with optical actuation and detection and the associated oscillator circuit are presented and used to determine its performances.