The general aim of Master’s thesis is to design and execute electronics in the SMT device view for thin film gas sensors and to study principle of gas sensor functionality based on semiconducting oxides. The SMT device contains temperature controller and electronics which is able to scan the concentration of gas on the sensor surface. It is designed for controlling of four sensors and has to communicate with computer for setting of initial conditions and scanning of concentration of gas. The practical part of Master’s thesis contains design and construction of electronics and software making.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

The behaviour of a free-standing thin film differs from that of a film surface-bonded or embedded due to the boundary constraints. A general dearth of analytical models, in regard to prediction of the operational competence of a constrained Piezoelectric thin film, prevails. In conventional design of miniaturized thin film devices, several non classical effects, for instance the effect of boundary constraints, are not considered. To warrant the design and performance optimisation of thin film sensors, such effect must be taken into account in a forethoughtful manner. This thesis is an attempt to achieve such optimisation through modeling of thin films. The coupled problem of a film on a substrate is solved semi-analytically in theoretical cases; and by finite element analysis in realistic cases for damage identification in the host structure. We first propose a two-dimensional analytical model of a constrained Piezoelectric thin film embedded in a host. Analytical expressions of capacitance and voltage across the electrodes are obtained by assuming first order shear deformation across the film thickness. The bonding layer between the film and the substrate, which is assumed to be an equivalent single layer including electrodes, insulation layer, adhesive layer etc., is modeled by taking into account its viscoelastic property. Residual stress is incorporated in the constitutive model through equivalent residual strain. Simulations on 10 m thick PVDF and 100 mPZT films are conducted. They illustrate the dependence of voltage response and capacitance on the applied stress, as well as on the residual stress. A maximum percentage variation in capacitance, as compared to the conventional estimate, is about 2% in a PVDF film and +75% to-65% in a PZT film for various combinations of tensile stresses applied at the ends of the film. Effect of residual stress is also exemplified via comparative response of a 1 m PZT film deposited on Pt/Ti/Si(0 0 1), with and without residual stress. For this case, an almost +50% increase in the voltage and an equivalent drop in the capacitance is observed. Next, we look into the voltage response profile of this model by employing it as a sensor to identify a finite mode I and mode II sub-surface cracks in a finite size host. To model the embedded crack, additional perturbation functions in the displacement field due to linear elastic crack tips in an infinite solid under plane strain condition are introduced to accommodate the stress free conditions at its surfaces. The film model requires the interfacial displacement and traction conditions, which are obtained from the analysis of the host. The combined analysis of the film and crack models brings forth the voltage gradient along the film span as a direct indicator of the location of crack in the axial direction, whereas the voltage magnitude represents the size of the crack. Following this analysis, a quasi three-dimensional(3-D) model of a Piezoelectric thin film surface-bonded to the host structure is proposed. With due consideration of restriction on the thickness of the film, here the model is based on a reduced 3-D continuum mechanics approach. The displacement field in the film is assumed to vary according to the third-order shear deformation theory; and the electrical and mechanical boundary conditions on the surfaces of the film are accommodated in a consistent manner. The formulation yields a governing inhomogeneous system of second-order Partial Differential Equations(PDEs), which is dependent on the displacement field at the film-host interface through force terms. Semi-analytical expressions of potential difference and capacitance are obtained. This system is solved numerically for two unknown rotations about X and Y axes of the film by finite element method. A maximum variation of about 2.5% is obtained in the capacitance of a 10 m PVDF film, as compared to its conventional estimate. The operational performance of this model is assessed in terms of its voltage response over the film area for various displacement fields. Conformation of this response to the input displacement field attests to its mathematical integrity. Next, we ascertain the versatility of this model in its role as a sensor for Structural Health Monitoring. To deal with cracks in the host plate, finite size rectangular surfaces are introduced as crack faces. The film domain and the host domain are discretized with an a posteriori h-refinement strategy and compatible interfacial nodes at the film-host interface via finite element interpolation. The resulting coupled problem is solved by static finite element analysis. The nature of the voltage pattern over the film surface is peculiar to the mode of crack, and is a qualitative portrayal of its presence. To correlate the electric potential(voltage) –a distributed parameter – to the geometry and orientation of the crack, as well as to quantify it, electrostatic measures in terms of integrated potential difference and its spatial gradients on the film surface are proffered. The numerical implications of these measures are elicited through simulation results of various crack sizes in damaged and healthy hosts under identical conditions of stress and boundary. The pattern of these measures in a damaged host becomes oscillatory as compared to straight lines observed in a healthy host. Furthermore, the reduced 3-D model is extended to perform dynamic analysis with the inclusion of inertial terms in the governing equilibrium equations. Subsequently, the acceleration terms appear in the governing inhomogeneous system of PDEs in the force terms. Finite element analyses of this extended film model on an isotropic beam with surface and sub-surface cracks, and on a composite plate with delamination, are then performed in the time domain. In all cases, an excellent conformation of the voltage profile at any point in the film domain to the velocity profile at the corresponding point in the film-host interface is observed. Again, to quantify the extent of damage in the host, we proffer electrical measures based on the Lpnorm, of second order, of the voltage and its directional derivatives. We exemplify the numerical implications of these measures in the time domain through sensitivity analysis in regard to the defected areas, and their region of occurrence relative to the film sensor. The response of the film model educes that the relatively flat curves after the first incident pulse in a healthy structure shoots off to a monotonic pattern in damaged hosts. The measures depict high degree of sensitivity in regard to the variation in the area of damage of any nature. An apposition of the static and dynamic analyses is elaborated towards the end of this dissertation. It proves to be very insightful in the damage assessment of the host structure, for it shows the utility of the dynamic model to sense the location of the damage occurrence, whereas a more in-depth assessment on its nature and mode of the crack would demand a static analysis in its proximal regions. To sum up, in light of these models and the proposed measures, this thesis establishes salient justifications pertaining to their pragmatic significance. We believe that these results represent an important contribution towards the ongoing research on understanding the role of boundary constraints in mechanically thin Piezoelectric films.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

Man’s desire to replicate/mimic the nature’s creation provided an impetus and inspiration to the rapid advancements and progress made in the sensors and actuators technology. A normal human being has five basic sensory organs, which helps and guides him in performing the routine tasks. This underlines the importance of basic sensory organs in a human life. In a similar fashion, sensors and actuators are of paramount importance for most of the science and engineering applications. The aim of the present thesis work is to explore the application of piezoelectric ZnO thin films deposited on a flexible substrate for the development of sensors and actuators. Detailed study was performed on the suitability of three different flexible substrates namely Phynox, Kapton and Mylar. However, Phynox alloy substrate was found to be a suitable substrate material for the above mentioned applications. Sputtering technique was chosen for the deposition of ZnO thin films on to Phynox substrate. The necessary process parameters were optimized to achieve good quality piezoelectric thin films. In the present work, sensors have been developed by utilizing the direct piezoelectric effect of ZnO thin films deposited on Phynox alloy substrate. These includes a flow sensor for gas flow rate measurement, impact sensor for non-destructive material discrimination study and a Thin Film Sensor Array (TFSA) for monitoring the impact events. On the other hand, using the converse piezoelectric effect of ZnO thin films, actuators have also been developed. These include a thin film micro actuator and a Thin Film Micro Vibrator (TFMV) for vibration testing of micro devices. The thesis is divided into following seven chapters. Chapter 1: This chapter gives a general introduction about sensors and actuators, piezoelectric thin films, flexible substrates, thin film deposition processes and characterization techniques. A brief literature survey of different applications of piezoelectric thin films deposited on various flexible substrates in device development is presented. Chapter 2: A novel flexible metal alloy (Phynox) and its properties along with its applications are discussed in this chapter. ZnO thin films were deposited on Phynox substrate by Rf reactive magnetron sputtering technique. The sputtering process parameters such as: Ar:O2 gas ratio, substrate temperature and RF power were optimized for the deposition of good quality piezoelectric ZnO thin films. The deposited ZnO thin films were characterized using XRD, SEM, AFM and d31 coefficient measurement techniques. Chapter 3: It reports on the comparative study of properties of piezoelectric ZnO thin films deposited on three different types of flexible substrates. The substrate materials employed were a metal alloy (Phynox), polyimide (Kapton), and polyester (Mylar). Piezoelectric ZnO thin films deposited on these flexible substrates were characterized by XRD, SEM, AFM and d31 coefficient measurement techniques. A vibration sensing test was also performed for the confirmation of good piezoelectric property. Compared to the polymer flexible substrates, the metal alloy flexible substrate (Phynox) was found to be more suitable for integrating ZnO thin film for sensing applications. Chapter 4: The development of a novel gas flow sensor for the flow rate measurement in the range of L min-1 is presented in this chapter. The sensing element is a Phynox alloy cantilever integrated with piezoelectric ZnO thin film. A detailed theoretical analysis of the experimental set–up showing the relationship between output voltage generated and force at a particular flow rate has been discussed. The flow sensor is calibrated using an in-house developed testing set-up. Chapter 5: This chapter is divided into two sections. Section 5.1 reports on the development of a novel packaged piezoelectric thin film impact sensor and its application in non-destructive material discrimination studies. Different materials (Iron, Glass, Wood and Plastic) were successfully discriminated by using the developed impact sensor. The output response of impact sensor showed good linearity and repeatability. The impact sensor is sensitive, reliable and cost-effective. Section 5.2 reports on the development of a Thin Film Senor Array (TFSA) for monitoring the location and magnitude of the impact force. The fabricated TFSA consists of evenly distributed ZnO thin film sensor array. Chapter 6: It consists of two sections. Section 6.1 reports on the fabrication of micro actuator using piezoelectric ZnO thin film integrated with flexible Phynox substrate. A suitable concave Perspex mounting was designed for the actuator element. The actuator element was excited at different frequencies for the supply voltages of 2V, 5V and 8V. The developed micro actuator has the potential to be used as a micro pump for pumping nano liters to micro liters of fluids. Section 6.2 reports the design and development of a portable ready to use Thin Film Micro Vibrator (TFMV). The TFMV is capable of providing the vibration amplitude in the range of nanometer to micrometer. A thin silicon diaphragm was used as a test specimen for its vibration testing studies using the developed TFMV. The TFMV is light-weight and have internal battery, hence no external power supply is required for its functioning. Chapter 7: The first section summarizes the salient features of the work presented in this thesis. In the second section the scope for carrying out the further work is given.