The word piezo in greek means \to compress". Piezoelectric sensors work on the principle of direct piezoelectric effect, where a mechanical input generates a corresponding electric charge. The advantages of these sensors are wide fre-quency range of operation, high stiffness and small size. The main limitation of a piezoelectric sensor is that it cannot be used in measurements that are truly static. When a piezoelectric sensor is subjected to a static force, a fixed amount of charge is developed which would eventually decay at a rate dependent on the external impedance of the sensor circuitry. Operating sensors at resonance have been one of the methods to overcome the limitation of using piezoelectric sensors for static measurements. However, since both actuation and sensing are done by the same piezoelectric element, this results in a cross-talk of input and output signals. The drawback of using single piezoelectric element for actuation and sensing is overcome in this work by using two identical elements|one for actuation and one for sensing. The operating frequency is about 10 % of the natural frequency of the sensor, thus enabling to operate the sensor in non resonant mode. Since the actuation and sensing mechanisms are separated, static measurement can be carried out. The output signal from the sensing element is monitored by a Lock-in amplifier which works on the principle of phase sensitive detection. The advantage of this sensor design is high sensitivity along with narrow band detection. It can be shown that the voltage output of the sensor Vout / a1 + m(b1 + b2F + b3K) + c1F + d1K, where m and K are the external mass and interaction stiffness, respectively, F is the force acting on it. By maintaining any two of these three quantities constant, the remaining one can be measured without any difficulty. The non resonant mode of operation makes it possible to explore the potential of this sensor in investigating mechanics of solid-liquid (viscous), solid-solid (inelastic) and solid-tissue(viscoelastic) interactions. High sensitivity, wide range of measurement (1 g{1 g) and high resolutio(0.1 g) of the non resonant mass sensor makes it possible to use it in measure-ment of very small masses of the order 1 g. Typically, resonant sensors such as quartz crystal microbalance (QCM) are used for mass measurements at that range. However, since the performance of resonant sensors is controlled by damp-ing, a phenomenon known as `missing mass effect' arises. Operating a sensor in non resonant mode (stiffness controlled mode) is a way to overcome this problem, especially when the mass is viscous and/or viscoelastic in nature. Drosophila fly, egg and larvae are the viscoelastic masses that are measured using this non res-onant sensor. Evaporating sessile drops of water and Cetyl trimethylammonium bromide (CTAB) surfactant solution from nominally flat surfaces are monitored to characterize the sensor for viscous mass measurement. Evaporation rate per unit surface area remains more or less constant, during the initial stages of evap-oration. When the surfactant concentration is varied, evaporation rate per unit surface area is highest for solutions around critical miscelle concentration (CMC). A study is carried out to understand the effect of concentrations on spreading of ink over inkjet printing paper. It is found that the spreading is least around CMC, since spreading is dependent on the rate of evaporation. The non resonant piezoelectric sensor which has high stiffness and quick re-sponse is also capable of measuring very small frictional forces. This sensor is configured to work as an inertial slider. Friction measurement at micro scales is important for designing microsystems such as stick-slip actuators. At such length scales, experiments have to performed at low loads and high excitation frequencies. The support stiffness of such systems should be high and the force of friction generated during slipping, when displacements are smaller than the contact radius, are of the order of few N. The displacement during slipping (S) is dependent on the amplitude of the input voltage to the actuation element. The frictional force measured during slipping by the sensor element indicates that the co-efficient of friction ( ) is independent of the sliding velocity. The developed non resonant sensor in this work under small amplitude exci-tation, can measure force gradient (i.e. stiffness). The total force generated when a needle is inserted into a viscoelastic material is a sum of force due to stiffness of the material, friction and the cutting force at the tip. The force due to stiffness is dominant when the needle is bending the tissue before the puncture occurs. Use of the non resonant sensor in tandem with strain gauge force sensor enables distinguishing the three components of the total force. The slope of the force-displacement (F -d) curve during the initial stages of needle penetration into the viscoelastic material, before puncture, is indicative of the stiffness of the mate-rial. The peak force measured during penetration is higher for needles with larger diameters and lower insertion velocities. The viscoelastic response (relaxation) of the material remains independent of the insertion velocity, for a given thickness of the material and a constant needle diameter. In summary, the sensor designed and developed in this work operates in stiffness controlled mode to eliminate the `missing mass effect' encountered dur-ing resonant mode of operation, has been clearly highlighted. Mass, force and stiffness measurements are possible over a wide range just by varying the ampli-tude of the input signal to the actuator element. The advantages such as high stiffness, small size and high response makes it advantageous to carry out in-situ micro scale studies in scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Based on productivity maps and data analysis it is possible for the producer to check and act over the low yielding areas, maximizing the final productivity that way. This paper intents to show the importance of the usage of precision agriculture maps on farms in order to help farmers to determine low yielding areas and act over it, improving productivity. This paper and the generated maps referred during the text were made using John Deere equipment and AMS (Agricultural Management Solutions). The studied area is a 19ha (190.000m²) total area, located at Faxinal, Paraná state. Five maps were analyzed totaling a 3 years range period of samples that were used later for interpolation. The interpolations and adjustments done were made using Apex® and CR Campeiro® software. The output of this interpolation is a single map that shows some tendencies for some areas to present low, medium and high yield. Those regions represent 5,95%, 86,25% and 7,80% respectively. This map is a base for the final analysis that will provide information to develop and increase productivity in low yielding areas. / Com base nos mapas de produtividade e as análises realizadas dos locais proporciona ao produtor rural agir pontualmente nestas áreas de baixa produtividade para maximizar sua produção. Este trabalho demonstra a importância da agricultura de precisão em utilizar os mapas de produtividade nas propriedades rural para ajudar a determinar pontos de baixa produtividade nas áreas colhidas, desta forma possibilita ser realizada análise destes locais para determinar qual é o fator que está gerando esta baixa produtividade. Para o desenvolvimento deste trabalho e geração dos mapas de produtividade foi utilizado o sistema de Solução em Gerenciamento Agrícola (AMS) e equipamentos da John Deere. A área do estudo é de 19 ha (190.000 m²) localizados no município de Faxinal - PR obteve-se desta área, mapas de produtividade de um período de três anos totalizando cinco mapas, que foram utilizados para realizar a interpolação. Para a realização da interpolação e ajustes dos mapas utilizaram-se os programas Apex® e CR Campeiro®, o resultado final desta interpolação foi a geração do mapa mostrando as zonas de manejo da área de estudo onde, no decorrer deste período, a produtividade manteve uma tendência nas regiões de baixa, média e alta produtividade do talhão, estas regiões representaram 5,95%, 86,25% e 7,80% respectivamente. Com base no mapa com as áreas de zona de manejo possibilitará a análise das regiões menos produtivas do talhão para maximizar a produção.

The field of coupled resonant systems is a rich research area with enumerable real-world applications, including the fields of neural computing and pattern recognition, energy harvesting, and even modeling the behavior of certain types of biological systems. This work is primarily focused on the study of the behaviors of two subsets of this field: large networks of globally coupled resonators (which, in this work, refers to passive, damped resonant elements which require external stimulus) and smaller networks of oscillators (referring to active devices capable of self-sustained motion), which are coupled through a network of light-sensitive resistive elements. In the case of the former, we begin by developing an analytical and experimental framework to examine the behaviors of this system under various conditions, such as different coupling modalities and element-level parametric mistunings. Once a proper understanding of the dynamics of these systems has been established, we go on to develop the system into a single-input, single-output, multi-analyte volatile organic compound sensor. For the study of oscillator networks, we begin by building a device which utilizes a network of Colpitts oscillators, coupled through a series of color-filtered CdSe photocells. We then establish that through the analysis of particular emergent behaviors (most notably, frequency locking within the network), this type of system may show promise as a threshold color sensor. By exploiting these behaviors, this type of system may find applications in neuromorphic computing (particularly in optical pattern recognition).

Les capteurs résonants de type M/NEMS sont largement utilisés dans l’environnement biologique pour la mesure de masse de biomolécules en raison de leur grande précision combinée à une taille réduite. Classiquement, la détection et la quantification se basent sur le décalage fréquentiel induit par la masse ajoutée. Toutefois, ce décalage devient très faible et difficile à distinguer du bruit de mesure lorsque les masses considérées sont très petites. Il est théoriquement possible de gagner encore un ou plusieurs ordres de grandeur en résolution avec ces méthodes fréquentielles en diminuant encore les tailles et/ou en augmentant le rapport signal sur bruit, c’est-à-dire en actionnant de manière plus importante les résonateurs. Mais, dans ces conditions, les nanorésonateurs ont un comportement très fortement non-linéaire, source d’instabilités et de mixage de bruit basses et hautes fréquences susceptibles de dégrader la fiabilité et la précision des mesures. C’est pourquoi cette thèse a pour objectif de définir des principes de détection alternatifs basés sur l’exploitation des phénomènes non-linéaires, tels que les comportements hystérétiques et les bifurcations des courbes de réponse en fréquence. Pour cela, un modèle réduit de micro/nano-poutre résonante avec actionnement électrostatique est considéré. Les résultats numériques montrent que les brusques sauts d’amplitude à proximité des points de bifurcation permettent la détection de masses très faibles. Contrairement à la détection fréquentielle, ces sauts sont d’autant plus grands que la masse additionnelle est petite, ce qui rend cette technique particulièrement intéressante. De plus, le seuil de détection peut être ajusté avec la valeur de la fréquence de fonctionnement. Un mécanisme de réinitialisation est toutefois indispensable pour rendre la détection à nouveau possible après un saut d’amplitude. Afin d’automatiser la réinitialisation et ainsi permettre la détection en temps réel, un concept totalement innovant de détection de masse par balayage en fréquence des cycles d’hystérésis est proposé, qui permet de détecter, quantifier et localiser la masse ajoutée sur la poutre résonante. La mise en réseau de plusieurs poutres résonantes est également traitée et constitue un premier pas vers la mise en oeuvre de réseaux de milliers de capteurs. Pour cela, des architectures efficaces sont proposées et les modèles numériques sont adaptés en conséquence. Sur des configurations symétriques, l’exploitation des bifurcations de type brisure de symétrie permet là-encore d’améliorer la détection de masse. / Resonant M/NEMS mass sensors are widely used in biological environment for measuring the mass of biomolecules due to their high accuracy combined with a reduced size. Usually, the detection and the quantification are based on the frequency shift induced by an added mass. However, this shift becomes very small and difficult to distinguish from the noise of measurement as the considered masses are tiny. It is theoretically possible to increase further one or several orders of magnitude in resolution with these frequency methods by further reducing size and/or by increasing the signal-to-noise ratio, that is to say by operating more importantly the resonators. But in these conditions, the nanoresonators have a strongly nonlinear behavior, a source of instability and noise mix of low and high frequencies likely to degrade the reliability and the accuracy of measurements. Therefore, the thesis’s objective is to define alternative principles of detection based on exploiting the nonlinear phenomena, such as the hysteretic behavior and the bifurcations of frequency-response curves. To this end, a reduced model of resonant micro/nano-beam with electrostatic actuation is considered. The numerical results show that the sudden jumps in amplitude close to bifurcation points allow the detection of very small masses. Unlike the frequency detection, the smaller the added mass, the larger the increase of the jump, which makes this technique particularly interesting. In addition, the detection threshold can be adjusted with the value of the operating frequency. However, a mechanism of reinitialization is mandatory to make the detection possible again after a jump in amplitude. In order to automate the reinitialization and allow the detection in real-time, a completely innovative concept of mass detection by the frequency sweep of the hysteretic cycles is proposed to detect, quantify and locate the added mass on the resonant beam. An array of several resonant beams is also considered and constitutes a first step toward the implementation of arrays of thousands of sensors. Efficient architectures are proposed for this purpose and the numerical models are adapted accordingly. On symmetric configurations, exploiting the bifurcations of symmetry-breaking type allows here again to improve the mass detection.