N. Savalli

A Novel Ferrofluidic Inclinometer

Inertial transducers based on the use of ferrofluids as inertial mass can be of great interest due to their peculiarities and due to the advantages that they show when compared to traditional devices. Ferrofluids are special solutions of magnetic particles in a carrier liquid whose density and other physical features can be controlled by an external magnetic field. In this paper, the development of a ferrofluidic inclinometer, which exhibits a tunable operating range and a valuable metrological feature and an intrinsic robustness against inertial shocks, is presented. The device consists of one excitation coil and two sensing coils wound around a glass pipe where a drop of ferrofluid is contained in a water environment. The magnetic force, which is induced by the excitation coil, attracts the ferrofluidic mass in a position that depends on the device inclination. The voltage at the output of the two sensing coils is related to the ferrofluidic mass displacement and thus reflects the tilt to be measured. Analytical models, simulations, and experimental results are presented to demonstrate the suitability of the proposed approach.

Development of novel optoelectromechanical systems based on "transparent metals" PBG structures

Developed a novel smart optoelectromechanical structure, fabricated using a multilayer, metal-dielectric photonic band gap (PBG) structure. We discuss innovative devices with electrically controllable optical properties that can be used as sensors with optical output signals for applications in harsh or hostile environments (pressure sensors, micro gravimeter, or micro accelerometer) or as optical modulators and optical limiters. Theoretical models of these novel devices together with experimental prototypes have been developed, and characterization of the devices has been performed. Moreover, microelectromechanical devices have been studied for application to this field and are presented. In particular, the problem of realizing highly sensitive accelerometers has been addressed, and it will be shown that the proposed approach allows detecting displacements of a few nanometers.

Modeling and design of novel photo-thermo-mechanical microactuators

Abstract In this paper, an innovative actuation strategy based on a photo-thermo-mechanical energy transformation is introduced. The basic idea is to exploit a new way to get the required actuation energy from light in a highly efficient way by means of micro-machined lenses. The use of micro-lenses provides a way to improve the efficiency of the actuation system, compared with the direct exploitation of the heating produced by light. Furthermore, lenses helps in obtaining localized heating of the micro-actuator, preserving the remaining part of the system. This actuation system can be useful in those application fields where high actuation power is required and an electrical power supply is not accessible or not feasible, for example in autonomous microsystems where on-board power source is strongly limited. In fact, the proposed approach does not require electrical power supply to provide the actuation energy. In this work, the modeling and design of a device based on this novel actuation strategy are presented. A simple thermal microactuator consisting in a bilayer cantilever is taken here into account in order to focus the design on a concrete device. A standard Si technology, coupled with a compatible micromachining post-process, is moreover considered.

Development of autonomous, mobile micro-electro-mechanical devices

In this work a novel approach to realize an autonomous micro-robot is addressed. A full CMOS compatible silicon micro-machining process has been adopted to realize the mechanical parts of the system. An innovative photo-thermo-mechanical actuation strategy together with silicon micro-machining technology are used for the realization of thermal microactuators which act as legs. The basic idea is to provide the actuation energy needed for the motion of the system through a light source and to improve the thermo-electro-mechanical efficiency by using an array of micro-lenses that concentrate the energy of the light beam on a small region of the actuators. Novel smart optical structures, based on Photonic Band Gap (PBG) materials, realized by using several periods of suitable metal-dielectric couples must be selectively deposited over the micro-lenses in order to suitably address the motion of the legs.

Bent beam MEMS Temperature Sensors for Contactless Measurements in Harsh Environments

A novel MEMS temperature sensor based on a cascade three-stage bent beam structure is described in this work. Three cascaded systems compose the structure in order to enhance sensor sensitivity. The structure is mechanically deforms as a response to the change in the ambient temperature and then a displacement is obtained that is furthermore amplified by the cascaded architecture. The final conversion is toward an electrical signal that is obtained by using an interdigited capacitor embedded into the moving tip of the MEMS sensor. The device has been conceived to operate into high temperature environments and to be remotely read-out. An external coil inductor has been figured out in this first prototype to realize a resonant LC circuit, where the capacitor changes with the temperature to be measured, and which can remotely be tuned with a magnetically coupled circuit reader. Analytical and numerical models have been developed and preliminary experimental results are reported here to show a good accordance with expectations. Vernier scales have been suitably positioned to quantify the deformations during the first characterization phase such to perform a comparison with the expected behavior.

Cascaded “Triple-Bent-Beam” MEMS Sensor for Contactless Temperature Measurements in Nonaccessible Environments

A microelectromechanical systems (MEMS) temperature sensor based on a cascade three-stage “bent-beam” structure is described in this paper. A suspended structure mechanically deforms in response to the change in ambient temperature, and then, a displacement is obtained; the structure is composed of three cascaded systems in order to enhance sensor sensitivity. The final conversion is made to an electrical signal that is obtained by using an interdigitated capacitor having one electrode fixed to the substrate and one electrode embedded into the moving tip of the MEMS sensor. The device has been conceived to operate passively in harsh environments where high temperatures could harm active electronic devices. The readout of the unknown temperature is therefore remotely performed by coupling the variable MEMS capacitor to a fixed inductor to compose a resonant LC circuit, which is magnetically coupled to a reader circuit placed outside the environment where the measurement takes place. The temperature to be measured is therefore first converted into a displacement that, in turn, induces a change in a capacitor value; a variation in the resonant frequency of an LC circuit is finally observed through the remote readout circuit. This paper focuses on the analytical and numerical modeling of both the temperature-to-displacement and displacement-to-capacitance conversions, on the design and fabrication of an experimental prototype, on the experimental validation where results are extensively presented and commented, and, finally, on the design of the integrated resonant device for contactless measurements.

Hybrid telemetric MEMS for high temperature measurements into harsh industrial environments

A temperature sensor that could be interrogated contactless represents an attractive solution for measurements into harsh environments such as in presence of high temperatures that do not permit the correct working of electronics. This paper discusses a telemetric system consisting of two coupled planar inductors, which constitute a coupled transformer with the primary one connected to the measurement electronics and the secondary one to a capacitive MEMS sensor that is designed for high-temperature environments. The proposed hybrid sensor is composed by the capacitive MEMS bonded to the planar inductor. The hybrid sensor behaves as an LC resonant circuit in which the MEMS represents the capacitance and the planar inductor is the inductance. The whole system has been tested in the laboratory and several results are reported. The proposed telemetric temperature system can be a solution for efficiency monitoring and predictive maintenance for harsh and complex environments.

Scaling issues and design of MEMS

Preface. Introduction. 1. Scaling of MEMS. 1.1 Introduction to Scaling Issues. 1.2 Examples of Dimensional Scaling Potentials. 1.2.1 Scaling effects on a cantilever beam. 1.2.2 Scaling of electrostatic actuators. 1.2.3 Scaling of thermal actuators. 1.3 Motivation, Fabrication and Scaling of MEMS. 1.4 Scaling as a Methodological Approach. References. 2. Scaling of Microactuators - an Overview. 2.1 Electrostatic Actuators. 2.1.1 Transverse combs modelling. 2.1.2 Lateral combs modelling. 2.2 Magnetic Transducers. 2.2.1 Magnetic actuators. 2.2.2 Ferromagnetic transducers. 2.3 Thermal Actuators. 2.3.1 Thermomechanical actuators. Acknowledgements. References. 3. Scaling of Thermal Sensors. 3.1 Thermoelectric Sensors. 3.2 Application: Dew-Point Relative Humidity Sensors. 3.2.1 Device structures and operating principles. 3.2.2 Device modelling and simulations. 3.2.3 Device design. 3.3 Conclusions. Acknowledgements. References. 4. Inductive Sensors for Magnetic Fields. 4.1 Inductive Microsensors for Magnetic Particles. 4.1.1 Integrated inductive sensors. 4.1.2 Planar differential transformer. 4.1.3 Signal-conditioning circuits. 4.1.4 Simulation of the planar differential transformer. 4.1.5 Experimental results. 4.2 Magnetic Immunoassay Systems. Acknowledgements. References. 5. Scaling of Mechanical Sensors. 5.1 Introduction. 5.2 Device Modelling and Fabrication Processes. 5.2.1 Fabrication processes. 5.2.2 Devices modelling. 5.2.3 Accelerometers. 5.2.4 Resonant mass sensors. 5.3 Experimental Device Prototypes. 5.3.1 CMOS devices. 5.3.2 SOI devices. 5.3.3 Finite element modelling. 5.4 Scaling Issues on Microaccelerometers and Mass Sensors. 5.5 Some Experimental Results. 5.6 Vibrating Microgyroscopes. 5.6.1 Coupled vibratory gyroscopes. Acknowledgements. References. 6. Scaling of Energy Sources. 6.1 Introduction. 6.2 Energy Supply Strategies for Autonomous Microsystems. 6.2.1 Use of microlenses in photothermomechanical actuation. 6.2.2 Technologies, materials and design of photothermomechanical actuators. 6.3 Photothermomechanical and Photothermoelectric Strategies for Highly Efficient Power Supply of Autonomous Microsystems. 6.3.1 Photothermoelectric power generation. 6.4 Efficiency of the Combined Energy Supply Strategy 166. References. 7. Technologies and Architectures for Autonomous MEMS Microrobots. 7.1 Design Issues in Microrobots. 7.2 A Microrobot Architecture Based on Photothermal Strategy. 7.3 A Microrobot as a Paradigm for the Analysis of Scaling in Microsystems. References. 8. Moving towards the Nanoscale. 8.1 Semiconductor-Based Nano-Electromechanical Systems. 8.2 Nanofabrication Facilities. 8.3 Overview of Nanosensors. 8.3.1 Use of AFM for materials and nanodevices characterization. 8.3.2 Scanning thermal microscopy (SThM). 8.3.3 Scanning Hall probe microscopy. 8.3.4 Mechanical resonant immunospecific biological detector. 8.3.5 Micromechanical sensor for differential detection of nanoscale motions. 8.3.6 Nanomagnetic sensors. 8.3.7 Nano-wire piezoresistors. 8.3.8 Nanometre-scale mechanical resonators. 8.3.9 Electric charge mechanical nanosensor. 8.4 Concluding Remarks. References. 9. Examples of Scaling Effects Analysis - DIEES-MEMSLAB. 9.1 Introduction. 9.2 Examples of Scaling Cantilever Beam Devices. 9.3 DIEES-MEMSLAB-Tutorial. 9.3.1 Introduction. 9.3.2 Descriptions of the microstructures and analytical methods. 9.4 Conclusions. References. 10. Concluding Remarks. Index.

Novel Ferrofluidic Inertial Sensors

A novel inertial sensor based on ferrofluids is presented in this work. The proposed device exhibits a widely tunable operating range and high sensitivity. The ferrofluid is a special solution of magnetic particles in a colloidal suspension whose flow or density and other physical features can be controlled by magnets or magnetic fields. The device prototype is made of one excitation coil and two internal sensing coils, in a differential configuration, wound around a glass pipe where the ferrofluid is contained. The bias magnetic force, induced by the excitation coil, attracts the ferrofluid at the pipes centre thus exploiting the role of an equivalent mechanical spring. The force to be measured reflects therefore in the inertial mass amplitudes oscillation that are sensed by using the built-in differential transformer whose output voltage is a function of the ferrofluidic agglomerate position. Analytical models, simulations and experimental results are presented to demonstrate the suitability of the proposed approach

instrumentationnotes - CANBUS Networked Sensors Use in Orientation Tools for the Visually Impaired Wired versus Wireless Technology

Researchers in the measurement and sensor group working at the Dipartimento di Ingegneria Elettrica, Elettronica e dei Sistemi (DIEES) of the University of Catania are dedicating their efforts to the development of innovative sensing strategies and methodologies to improve the quality-of-life of people with depressed receptors. In this article, new results concerning the controlled area network bus (CANBUS) assistive system developed at the DIEES laboratories to support visually impaired people in orientation and mobility tasks are presented, with an emphasis on the users localization feature.