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Micro and Nano Systems Design
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Micro and Nano Systems Design Group

Last update 26 Nov 2016

 

Coordinator: Brahim MEZGHANI

Permanent members: Farès Tounsi, Sami Gomri.

Thesis Members: Mohamed Hadj Said, Hela Almabrouk, Ezeddine Ayechi, Sedki Amor, Maha Kharroubi, Gada Ben Salah, Asma Khelil.

Master Members: Faycel Slama.

Undergraduate Members:

Cooperation: Laboratoire TIMA, Grenoble, France and IIT, Bombay, India

 

 

Introduction to the research topic

 

En combinant des micromoteurs avec des éléments optiques, mécaniques et informatiques, les fabricants de machines ouvrent la porte à une révolution technologique aussi importante que celle de la micro-électronique: Les MEMS "Micro-Electro Mechanical Systems" ou microsystèmes électromécaniques. On cherche à adapter la taille et le processus de fabrication des machines actuelles à ceux des circuits intégrés.Ce n'est qu'à la fin des années 1980 que l'on commença à voir apparaître les premiers microsystèmes qui visaient à associer la microélectronique à différentes fonctions non électroniques de détection, de perception ou d'interaction avec l'extérieur. Aujourd’hui, la quasi-totalité des disciplines scientifiques ou techniques est impliquée dans les activités de développement des microsystèmes : électronique, mécanique, science des matériaux, robotique, optique, opto-électronique, télécommunication, thermique, fluidique, chimie, biomédical… L’intérêt grandissant pour les microsystèmes en termes de recherche et de marché réside dans le fait qu’au-delà de la diminution des tailles et des coûts de fabrication des dispositifs, la miniaturisation permet de multiplier les fonctionnalités intégrées aux systèmes et de répondre à de nouveaux besoins qui ne cessent de se multiplier.

 

 

 

Activities Summary:

 

Subject 1 : Design, modeling and fabrication of a new Electrodynamic CMOS MEMS microphone

Members : Mohamed Hadj Said (Thesis)

Abstract:  The new sensor design consists of an internal inductor fabricated on top of a flexible suspended membrane and a fixed external inductor, on top of the substrate. Operation mode is based on the variation of mutual inductance between both inductors. Extensive analysis and modeling has been conducted on this new design. The analysis has been mainly performed on the Electromagnetic and electroacoustic behavior of the sensor. This includes both electrical and mechanical investigation (induced voltage - mutual inductance and produced magnetic field). Moreover, the electroacoustic analysis includes the frequency response, sensitivity expression derivation and the response with/without damping.

A new layout is now under preparation in the Center of Excellence in Nanoelectronics of the IIT-Bombay. This is done under a joint research project with the IIT-Bombay to fabricate the device and test it. This will offer a unique opportunity not only to prove the feasibility of such design, but also to validate the numerous derived models.

 

Subject 2 : Design and modeling of micromachined convective accelerometers

Members : Hela Almabrouk (Thesis)

Abstract: There exists single, dual and three sensitive axis MEMS thermal accelerometers. All three sensors have similar operating mode concerning common mode and convection phenomena. One way to enhance and optimize the performance of this monolithic sensor resides in studying and modeling the system geometry to choose the best compromise between different key parameters. In such mechanical sensor, Finite Element Modeling (FEM) simulation is considered to be the best alternative. This is true provided that the developed model is accurate. A newly developed 3D geometry model meets this requirement since it uses actual shape and size of each element of the accelerometer. Using this model in FEM simulations, where all geometrical forms are volumes describing actual situations, will therefore allow a good understanding of sensor sensitivity evolution as a function of various physical and geometrical parameters. This will give an optimization of accelerometer geometry and in particular optimal heater-detectors distance and both heater and detector lengths.

The modeling research work which was done on these sensors was based on the new 3D model. This model was adapted to all three accelerometer designs and then both conductive and convective behavior governing equations were derived. Obviously, these expressions can be used to predict, at an early design stage, the sensor sensitivity level of any technologically possible convective accelerometer design.

 

Subject 3 : Design, modeling and fabrication of a new design for a Piezoresistive MEMS Accelerometer

Members : Ezzeddine AYACHI (Master)

Abstract: The piezoresistive behavior is one among several mechanisms for acceleration sensing. Each of these mechanisms has its own advantages and disadvantages. Under a joint project with IIT-Bombay, we intend to develop a new design for a three-dimensional piezoresistive micromachined accelerometer. This sensor can be used in sophisticated motion control systems necessary in wide industrial fields such as automotive and robotics industries. The detection principle is based on piezoresistive gauges deposited on top of arms in a location where stress is at its maximum. The advantage of the proposed accelerometer lies in the new form of the used arms that ensures a maximum stress in a well-defined location.

Analytical analysis of sensor dimensions is being done and FEM analysis carried out on the structure. This is to investigate stress field and therefore maximum stress locations where the piezoresistor’s will have to be implemented. At a future stage, the design of proximity microelectronics has to be achieved. Subsequently, an optimized structure of this sensor can be fabricated and then characterized.

 

Subject 4 : Design, modeling and fabrication of an improved Electrostatic RF-MEMS switch

Members : Maha Kharroubi (Thesis)

Abstract: Surface Acoustic Wave (SAW) sensors are a class of MEMS devices which rely on the modulation of surface acoustic waves to detect a physical phenomenon. The advantages of using MEMS-based SAW devices include increasing the performance and scale down the chip size permitting its integration in many devices. In order to generate the SAW, we use Inter-Digitated Transducers (IDT). Using a geometry design variation, the length, width, position, and thickness of the electrodes as well as the number and the pattern of the IDT, the performance of the transducer can be optimized (frequency, band width, etc…).

In the frame of a joint research project between the ENIS and Stellenbosch University in South Africa, we intend to use SAW structures as a primary gas/particle/pathogen detector in order to increase the sensitivity of the device. This is done by the inclusion of nanostructures on the active sensing area of the device. Possible nanostructures include graphene, carbon nanotubes and zinc oxide nanowires. This will require extensive modeling of different SAW configurations and dimensions, with the addition of the effect of the nanostructures.

This research subject is currently under study with our colleagues from the Stellenbosch University. The ultimate objectives of this joint research project will be:

ü      Determine the optimum SAW structure to act as primary sensing device for gas/particle/ pathogen detection.

ü      Determine the affectivity of the introduction of various nanostructures, such as graphene, carbon nanotubes and zinc oxide nanowires to enlarge the detection area and thus theoretically increase detection sensitivity.

ü      Develop simulation models for the final sensing device incorporating the optimized IDT device and the nanostructures on the sensing area.

ü      Fabrication and testing of the optimized sensor

 

Subject 5 : Towards the Development of Inexpensive High-Performance Organic-Inorganic Hybrid Photo-Thermo-Electric Generators

Members : Asma Khalil (Thesis)

Abstract: The photovoltaic effect is the process allowing the conversion of light into electricity, this process needs semiconductors materials in order to convert the photons into electrons. The photovoltaic solar cell technology with its different generations is a multidisciplinary field involving classical disciplines like physics, chemistry and materials sciences, beside new emerging technologies such as optoelectronics, organic electronics and nano electronics. These technologies have been tremendously expanded in the last decades, serving the development of photovoltaic solar cells and making the field rich and attracting for several famous worldwide universities, institutes and research centers.

The research focus would be on the organic solar cells, particularly, the improvement of electrical parameters such as open circuit voltage (Voc) and short circuit current (Jsc) and others. It is important at a first stage to understand all the physical, material and optical aspects behind the topic. Then a temperature dependent study will apply. In fact, in the desert environment, it is very hot in summer time, therefore the environmental temperature rises that can cause to reduce the efficiency of the photovoltaic (PV) solar cells. In this research project, we would focus how the heat energy from the sun and the extra solar spectrum that could not be absorbed by active layer of the PV cell should be utilized in thermo-electric (TE) generator efficiently. In this way the reduced efficiency due to the elevated temperature can be compensated by adding the output power from the TE cell.

1- Fabrication of bulk heterjuction solar cells using newly proposed inexpensive transparent substrates.

2- Optimization of the temperature dependence performance of the bulk heterjuction solar cells for their utilization in the high temperature environment applications.

 

Subject 6 :  Contribution to the design and development of a new architecture optimized for the treatment of patients with S.A.S "Apnea Sleep Syndrome"

Members : Ghada Ben Salah (Thesis)

Abstract: Sleep apnea syndrome (SAS) or, more specifically, sleep apnea-hypopnea syndrome (SAHS) affects the population, mainly in the age range of 40-65 years. This syndrome not only has a very negative impact on the sleep of millions of patients, but it can lead to death if not properly treated. To treat this pathology, there was only one reference treatment for a long time: Continuous Positive Pressure (CPAP). But this type of treatment is uncomfortable for some patients. Consequently, there is a significant need for additional therapeutic alternatives for patients who are noncompliant with CPAP therapy. Hypoglossal nerve (HGN) stimulation is under investigation by multiple groups as a possible alternative therapy. That’s way in this thesis we will design a new optimized architecture of a medical implant based on nerve electrical stimulation for subjects suffering from this disease.

Keywords :

Sleep apnea, electrical stimulation, hypoglossal nerve, medical implant.

The main objectives:

1.      -Definition of inputs and outputs of the medical device.

2.      -Development of the desired system block by block.

3.      -Simulation of blocks using ADS software using 0.18 μm technology.

4.      -Experimental test of the implant after the integration of the lay-out (cadence tool).