This thesis presents the utilisation of giant piezoresistance of carbon nanotubes (CNTs) for high resolution pressure sensing. The nanoscale diameter of CNTs, used as sensing elements, increases the resolution of piezoresistive sensing by three orders of magnitude to that of silicon based sensors. The design of the sensor is based on sensing the strain in CNTs induced by the flow of gas and can be adapted to benefit cross-disciplinary fields like; flow and pressure sensing, microfluidics, Lab-on-chip and NEMS (nano-electromechanical systems). CNTs were grown inside silicon micro-cavities so as to bridge the gap between two silicon substrates. The nickel catalyst coated silicon substrates act as electrodes connected to the two ends of CNTs. The CNTs grow on the nickel nanoparticles, thus self-anchoring on to the substrate. Diffusion of nickel in silicon provides low resistive NiSi contacts to CNTs. Growth of CNTs in this form have not been reported before and presents several merits including no chemical treatment or post-growth alignment of CNTs, thus keeping the process simple and robust. CNT growth parameters; temperature, time and methane flow rate, were optimised in a custom designed chemical vapour deposition (CVD) rig, to control the CNT diameter. CNT diameter directly affects its piezoresistive coefficient, πL, and Young’s modulus, E, the factors that define piezoresistance in any material. Thus, optimised growth conditions allowed the direct tuning of piezoresistance of the sensor. Piezoresistance sensing was performed by inducing strain in CNTs with an applied differential pressure across the microcavity. Pressure loadings of as low as 0.1 atm (limited only by the gauge resolution) and a piezoresistance of as high as 16% at a pressure loading of 1 atm, were achieved. This piezoresistance is at least one order higher and the resolution is three orders higher than commercially available polysilicon and GaAs membrane based sensors. Piezoresistance was modelled by applying Euler-Bernoulli beam theory, assimilating CNTs to rigid beams with special boundary conditions, accounting for self-anchoring to Ni islands. The resulting theory is found to be in good agreement with our experimental results and estimates the E, πL and the average radius of the CNTs. This modelling, to our knowledge, is an original attempt to modify Euler-Bernoulli beam theory with the assumed boundary conditions.

Imaging systems often make use of macroscopic lenses to manipulate light. Modern microfabrication techniques, however, have opened up a pathway to the development of novel arrayed imaging systems. In such systems, centimeter-scale areas can contain thousands to millions of micro-scale optical elements, presenting exciting opportunities for new imaging applications. We show two such applications in this thesis: pressure sensing in microfluidics and high throughput fluorescence microscopy for high content screening. Conversely, we show that arrayed elements are not always needed for three dimensional light field imaging. / Engineering and Applied Sciences

Piezoresistivity in conductive polymer nanocomposites occurs because of the disturbance of particle networks in the polymer matrix. The piezoresistance effect becomes more prominent if the matrix material is compliant making these materials attractive for applications that require flexible force and displacement sensors such as e-textiles and biomechanical measurement devices. However, the exact mechanisms of piezoresistivity including the relationship between the matrix polymer, conductive particle, internal structure and the composite’s piezoresistance need to be better understood before it can be applied for such applications. The objective of this thesis is to report on the development of conductive polymer nanocomposites for use as flexible sensors and electrodes. Electrically conductive and piezoresistive nanocomposites were fabricated by a scalable melt compounding process. Particular attention was given to elucidating the role of matrix and filler materials, plastic deformation and porosity on the electrical conduction and piezoresistance. These effects were parametrically investigated through characterizing the morphology, electrical properties, rheological properties, and piezoresistivity of the polymer nanocomposites. The electrical and rheological behavior of the nanocomposites was modeled by the percolation-power law. Furthermore, a model was developed to describe the piezoresistance behavior during plastic deformation in relation to the stress and filler concentration.

Pressure within the esophagus arises from two mechanisms: intrabolus pressure, which is a hydrodynamic phenomenon, and esophageal occlusion pressure, which is a contact phenomenon. Current esophageal manometers are sensitive to both hydrodynamic and contact pressures and cannot distinguish between the two measurements in the absence of other information. It has been shown that measurement of intrabolus pressure is a clinically relevant parameter in esophageal manometry. There is no single device available that can obtain this measurement directly. This work presents a novel fibre optic-based flexible catheter for high resolution manometry with sensing pods that can be selectively sensitized to either hydrodynamic pressure alone, or contact and hydrodynamic pressure, offering sensing schemes not possible with existing high resolution manometers. The catheter is designed to be used with a time division multiplexing interrogation technique, yielding a system capable of exceeding the 36-sensor count limit of current solid state manometers. The device consists of rigid sensing pods connected by flexible tubing with in-fiber Bragg gratings acting as sensing elements within each of the pods. Absent in each sensing pod are rigid anchor points, representing a novel departure from comparable designs and resulting in increased sensitivity and decoupling from axial loading. Device functionality is demonstrated through bench top trials. A pressure sensitivity of 1.8 pm/mmHg and axial sensitivity of 11 mmHg/N of applied load is demonstrated. Crosstalk between individual sensors is characterized and a compensation scheme is developed and validated. Temperature response is demonstrated to be linear such that its confounding can be corrected for procedurally. Sensing schemes afforded by this design may yield clinically relevant parameters not achievable by any single existing device. / Graduate

<p>Glaucoma is the leading cause of irreversible blindness worldwide effecting more than 2.7 million people in the U.S alone. Treatments exist in the form of both pharmaceutical and surgical options, but often do not provide the desired efficacy. For example, the failure rate of a trabeculectomy procedure is 39% within 5 years. Additionally, none of the current glaucoma treatments allow for closed loop monitoring of pressure, therefore requiring more frequent doctor visits. Glaucoma management can be improved through the use of a closed loop application of electroceutical treatment. The goal is to develop an implantable device that will be inserted into the eye to monitor intraocular pressure (IOP) and provide responsive therapeutic stimulation to the eye. I designed a discrete pressure monitoring system that interacts with a bare die piezoresistive pressure sensor. The system is based on a Wheatstone bridge design which translates the input resistances of the pressure sensor into a voltage output. This system has an average accuracy of 0.53 mmHg and draws 295 µW of power. I then combined this pressure system with data processing code and Howland current pump stimulation circuitry. This simulation system can output up to 1.05 mA of current for electroceutical intraocular stimulation to lower IOP. Future work will involve miniaturizing the circuitries in the form of an ASIC and packaging the entire system into an ocular implant. This implant can wirelessly monitor IOP and provide therapeutic stimulation to lower IOP. A reliable, closed loop method of lowering IOP would greatly benefit the ever-growing population affected by glaucoma.</p>

Scaling down operations and functions into the fascinating micro world not only improve performance, lower costs, and enable easier integration, but also opens the door to new functionalities. This truly multidisciplinary thesis presents novel solutions to current and relevant challenges in the areas of 1) on-chip liquid manipulation which has applications in micro total analysis systems, medical diagnostics, and drug discovery and 2) pressure sensing which has an established market in the automotive and industrial processes industry. Especially in the area of liquid manipulation, the aim was to take advantage of forces and properties dominating on the micro scale whenever possible, rather than compensating for these effects, and to create solutions with universal appeal and application areas. In the area of liquid manipulation, this thesis discusses a novel method of passively synchronizing liquid movement on-chip based on liquid surface tension and device geometry. This technique has potential applications in timing independent processes, liquid-liquid interactions, and digitizing liquid movement. A fast and passive discrete sample micromixer is also presented based on the same principles. A unique way of direct access, bubble tolerant sample interfacing with flow-through microfluidics using a closed-open-closed channel is also introduced. This method can be used to regulate flow on-chip without the need for any moving parts or electrical contact. Moreover, work is presented on two types of out-of-plane electrospray ionization mass spectrometry (ESI-MS) emitter tips which mimic ideal mass spectrometry tips. Fabrication of these tips is uncomplicated and results in robust structures with good performance. In the field of pressure sensing, this thesis investigates a form based resonating principle. The Q factor of the sensor is improved by low pressure encapsulation and structure design. A novel technique for excitation and detection of resonant microsensors using 'burst' technology is also demonstrated. This method involves temporally separating excitation and detection, thereby eliminating crosstalk and the need for electrical feedthroughs. It also allows high voltages to be used with sensitive circuitry and a single electrode to be used for both excitation and detection.

In stamping operations, sheet metal is formed into a desired shape by pressing it in a hydraulic or mechanical press between suitably shaped dies. As a predominant manufacturing process, sheet metal forming has been widely used for the production of automobiles, aircraft, home appliances, beverage cans and many other industrial and commercial products. A major effort till date on stamping processes monitoring has been focused on investigating variations in the press force. Given that the press force itself is an integral of the contact pressure distribution over the die and binder contact interfaces, it is conceivable that defects may be better identified by analyzing the contact pressure distribution directly at the tooling-workpiece interface, instead of measuring the press force, which is less reflective of the localized forming process due to its nature as a secondary effect. It is thus desirable that a new, integrated sensing method capable of directly assimilating forming pressure distribution in the tooling structure be devised for improved stamping process monitoring. Designing such a distributed sensing scheme and analyzing the feasibility of its structural integration into a stamping tooling structure is the objective of this reported work. In this context, four research tasks have been identified and examined during the course of this work: 1) Devising a New, Embedded Sensing Method The new sensing method monitors stamping processes by means of an array of force sensors structurally integrated into the stamping tooling. The ability to directly measure local forming events by means of such an integrated and distributed sensing provides a new means of performing defect detection and process monitoring. Such a distributed sensing system overcomes the limitations of traditional tonnage and acceleration sensing systems which are focused on the measurement of indirect, global parameters. The new method is based on the evaluation of spatially continuous pressure surfaces from spatially discrete sensor measurements that are directly related to the local events at the stamping interface. To evaluate the effectiveness of this method, a panel stamping test bed equipped with an array of embedded force sensors has been designed, modeled and fabricated. Data obtained from experiments conducted on the test bed indicates that the new sensing method can be highly effective in process monitoring of stamping operations. 2) Reconstruction of Spatio-Temporal Distribution of Contact Pressure Structurally integrating sensors under tooling surfaces reduces the surface rigidity of the tool, thus limiting the number of sensors and the locations at which they can be embedded. This in turn affects the reconstruction of contact pressure distribution on the tooling surface. Numeric surface generation methods, such as Bezier surfaces and Thin Plate Spline surfaces offer a method for estimating the contact pressure distributions on the tooling surfaces from a sparse distribution of sensors. The concept of interpolating force distributions using surfaces has been investigated by researchers previously. However, selection of the surface generation method has remained largely an ad hoc process. The work presented here addresses this issue by using tooling interface contact pressure distribution information obtained from FE simulations as the basis for evaluating the accuracy of two commonly employed surface methods mentioned above. In order to reach a generic conclusion, the mathematical background of these schemes has been examined in light of the purpose at hand. The results indicate that an interpolative scheme such as the Thin Plate Spline surfaces (TPS), which can estimate the contact pressure distributions more accurately in a multi-sensor environment. The local and global accuracies of the Thin Plate Spline surface modeling technique have been experimentally evaluated using a sensor embedded stamping test bed designed for the purpose. 3) Modeling of Contact Pressure Distribution at the Sheet Metal-Tooling Interface Information about the contact pressure distribution at the tooling interface is critical to identifying the accuracy of numeric schemes that estimate by interpolation or approximation the contact pressure at any point on the tooling surface, based on a limited number of spatially distributed sensors. Furthermore, such knowledge is valuable in identifying operational parameters for the sensors to be integrated into the stamping tooling structure. In the absence of a tractable analytic method of determining the contact pressure distribution on stamping tooling surfaces, Finite Element models of a stamping operation have been created. Furthermore the drilling of sensor cavities under the working surfaces of the dies adversely affects the working life of stamping dies and their strength. The accuracy of analytic fatigue failure mechanics in evaluating the effect of parameters, such as embedding depth and sensor rigidity, on the operational life of the die, suffers from uncertainty in the estimation of stress concentrations around sharp geometric features of the sensor cavity. This shortcoming has been circumvented by the creation of FE models of the sensor cavity for more accurate estimation of stress concentrations around sharp geometries. The effect of different embedding materials on the sensitivity of embedded sensors has also been evaluated based on these models. 4) Defect Detection in Stamping Operation The ultimate goal of this thesis research was to study the feasibility of identifying defects in a stamping process based on the contact pressure distribution surfaces. This was achieved in this reported work by spatio-temporal decomposition of ‘parameters’ derived from the contact pressure distribution surfaces. Here ‘parameters’ refers to quantities such as the minimum, maximum, and mean contact pressures. These parameters have a time-varying spatial location as well as magnitude value associated with them. The feasibility of defect detection in stamping operations based on such parameters has been investigated. In addition to these focal areas, the design and implementation of a stamping test bed equipped for distributed contact pressure sensing has also been researched. This test bed was utilized for experimental verification of the developed theories and numerical models. Design of the proposed test bed required research into additional topics like the design of a protective package for embedded sensors and the effect of sensor embedding depth on contact pressure measurements. These issues have been addressed in this work, culminating in the experimental demonstration of the embedded pressure sensing system for process monitoring in the sheet metal stamping processes.

Brillouin scattering has been verified to be an effective mechanism in temperature and strain sensing. This kind of sensors can be applied to civil structural monitoring of pipelines, railroads, and other industries for disaster prevention. This thesis first presents a novel fiber sensing scheme for long-span fully-distributed pressure measurement based on Brillouin scattering in a side-hole fiber. After that, it demonstrates that Brillouin frequency keeps linear relation with temperature up to 1000°C; Brillouin scattering is a promising mechanism in high temperature distributed sensing. A side-hole fiber has two longitudinal air holes in the fiber cladding. When a pressure is applied on the fiber, the two principal axes of the fiber birefringence yield different Brillouin frequency shifts in the Brillouin scattering. The differential Brillouin scattering continuously along the fiber thus permits distributed pressure measurement. Our sensor system was designed to analyze the Brillouin scattering in the two principal axes of a side-hole fiber in time domain. The developed system was tested under pressure from 0 to 10,000 psi for 100m and 600m side-hole fibers, respectively. Experimental results show fibers with side holes of different sizes possess different pressure sensitivities. The highest sensitivity of the measured pressure induced differential Brillouin frequency shift is 0.0012MHz/psi. The demonstrated spatial resolution is 2m, which maybe further improved by using shorter light pulses. / Master of Science

From computation to sensing, two-dimensional materials are revolutionizing the field of nanoscale electronics and devices. They enable the engineering of membranes, circuits and coatings with tailored electronic properties at ultimate, atomic thinness. Yet, the manufacturing processes to obtain these materials are not sufficiently advanced to meet industrial demands. The next step for them to push into the consumer market is the successful, large-scale integration with existing silicon technology. For many two-dimensional materials, this proves challenging due to high synthesis temperatures or low mechanical stability in transfer processes. Not so for two-dimensional noble-metal chalcogenides: PtSe2 is an exemplary candidate because it can be grown at temperatures below 500 ℃, rendering it suitable for facile integration at the back end of the line. Additionally, it features very high stability with respect to moisture, irradiation, and mechanical strain, high carrier mobilities, and electronic properties that can be fine-tuned with the number of layers. These properties collectively make it a very promising material for free-standing nanoelectromechanical sensors, such as piezoresistive pressure sensors and motion detectors for the Internet of Things. Unfortunately, one cannot have their cake and eat it too: The broadly tunable properties of PtSe2 lead to challenges in fabricating devices with reproducible performance. This issue can be overcome with sufficient understanding and control of the nanostructure of PtSe2 thin films. The aim of this thesis is to study these nanostructures in depth, employing state-of-the-art density-functional theory and a machine learning approach to get closer to modelling PtSe2 under realistic conditions. Firstly, the family of noble-metal dichalcogenides is introduced and discussed. Secondly, the role of stacking disorder in PtSe2 is taken into account and its impact on electromechanical properties is analyzed. Lastly, a machine learning approach is employed to study edges and surfaces of nanoplatelets of PtSe2, which are the building blocks of polycrystalline thin films. Through these studies, crucial parameters have been identified that need to be controlled during the manufacturing process of PtSe2, and the groundwork to built up large-scale models has been laid out.

L'objectif de cette thèse est l'étude des interactions mécaniques entre la langue et le palais dans la production de parole et la déglutition. Cette interaction est cruciale car elle détermine la morphologie de la langue et son évolution dans le temps avant et après les contacts. Elle ne peut cependant pas être étudiée avec des approches cinématiques conventionnelles, car l'amplitude des mouvements est trop faible. La première partie de la thèse est consacrée à la conception d'un dispositif expérimental permettant de mesurer ces interactions sans perturber l'appareil vocal. La première particularité est que le dispositif est utilisé sur des patients édentés appareillés. Nous utilisons un duplicata de la prothèse complète maxillaire pour insérer des capteurs miniatures à jauges de contrainte dont les caractéristiques de réponse sont optimisées et qui permettent de mesurer la pression mécanique exercée par la langue sur le palais. La seconde particularité est qu’il existe une procédure d'étalonnage, associée aux capteurs, qui utilise une Colonne d’Eau Sèche. Elle applique une pression sur le capteur via une membrane en latex déformable, capable de simuler le comportement visco-élastique de la langue sur le palais. La deuxième partie de la thèse décrit le protocole de recherche clinique visant à (1) caractériser l'interaction langue-palais au cours de la prononciation et de la déglutition normales sur des individus édentés que nous considérons adaptés à leur prothèse complète (Cohorte 1), (2) observer l'adaptation dans une étude longitudinale des patients édentés nouvellement appareillés (Cohorte 2). Ce projet comprend, pour les deux cohortes, la description des objectifs, le protocole expérimental, la description fine des paramètres pertinents et la méthode statistique de traitement des données. Toutefois, le processus de rédaction et de soumission de ce protocole à un Comité de Protection des Personnes (CPP) a été plus long que prévu et l’étude clinique n’a pu être menée dans le cadre de cette thèse. C’est pourquoi, dans la troisième partie de la thèse, nous avons utilisé les données enregistrées dans l’étude de faisabilité, auprès d'un adulte édenté francophone. Les résultats montrent que notre dispositif permet d'explorer des hypothèses théoriques cruciales dans la parole comme l'existence de cibles virtuelles au-dessus du palais ou le rôle du palais dans la mise en forme du conduit aérien des consonnes fricatives. Les résultats des données enregistrées lors de la déglutition sont moins clairs, mais l'enchaînement temporel précis des contacts peut être décrit, ce qui permet de préciser comment les mouvements ondulatoires de la langue pendant la phase orale de la déglutition exploitent les contacts avec le palais. Les retombées cliniques de cette thèse permettent une meilleure connaissance du rôle fonctionnel des prothèses complètes et d’envisager la conception de prothèses qui seraient adaptées aux spécificités de chaque patient, notamment pour la rééducation des sujets traités chirurgicalement après des cancers de la langue, dans le cadre des taches de production de parole et de déglutition / The aim of the thesis is the study of the mechanical interaction between tongue and palate in speech production and swallowing. This interaction is crucial since it determines the shape of the tongue and its time evolution before and after contacts occur. Yet it cannot be studied with conventional kinematic approaches, since magnitude of movements is too small. The first part of the thesis was devoted to the design of an experimental setup to measure this interaction without perturbing the vocal tract. The first specificity is that the setup is used on subjects who are edentulous and wear a complete denture. We use a duplicate of the complete denture to insert miniature strain gauge sensors with enhanced response characteristics, that enable the measure of the mechanical pressure exerted by the tongue in different locations of the palate, without altering the shape of the palatal arch. The second specificity is that the calibration procedure uses a Dried Water Column (DWC) that applies pressure on the sensor via a deformable latex membrane, that simulates the way tongue touches the palate. The second part of the thesis enabled the design of an experimental protocol aiming at (1) providing a characterization of the tongue-palate interaction in normal speech production and swallowing based on edentulous subjects whom we consider to have adapted to their complete denture (cohort 1), (2) observing the adaptation process in a longitudinal study of edentulous subjects who are new users of complete denture (cohort 2). This work includes for two cohorts the design of the subject inclusion criteria, the motor tasks and the statistical method for the data analysis. However, unforeseen long delays were faced in the application process for the ethical approval and no data were collected in this context. Hence the third part of the thesis used data recorded in our most recent pilot study, with a French speaking edentulous adult. It is shown that our setup makes possible to tackle crucial theoretical questions in speech production such as the existence of virtual targets above the palate in stops or the role of the palate in the air channel shaping in fricatives. Results of swallowing tasks are less clear, but it is shown that precise time sequencing of contacts can be described, making possible the specification of how the ondulatory movements of the tongue in the oral phase of swallowing takes advantage of palatal contacts. In conclusion implications of this thesis are presented for a functional assessment of complete dentures, and the design of dentures that would be adapted to each subject’s specificities