Two methods of dielectric characterization are presented that offer quick and cost-effective solutions for screening complex dielectric material properties. Through Direct-Print Additive Manufacturing (DPAM) methods, a dielectric material of choice is dispensed into a capacitor structure and characterized through 1-port s-parameter measurements. The presented methods use fixtures that are modeled and validated through simulation then implemented in practice. Advanced simulations are performed to gain insights which are used to optimize the dielectric characterization performance of the fixtures. Additional investigations are performed which investigate the durability of the fixture and material within by exposing the combination to rough environmental conditions for an extended duration. The presented capacitor structures are investigated to characterize dielectric materials within the bandwidth of 0.1-15 GHz, saving the time and effort required in using multiple dielectric characterization methods that cover the same bandwidth. Both methods are compared based on the results for each method achieved in practice while considering the process required perform each method. The pros and cons of the presented characterization methods are weighed which highlights the key aspects for successfully characterizing dielectric materials with each method as well as revealing the potential limitations associated with each.

Electromechanical transducers based on elastomer capacitors are presently considered for many soft actuation applications, due to their large reversible deformation in response to electric field induced electrostatic pressure. The high operating voltage of such devices is currently a large drawback, hindering their use in applications such as biomedical devices and biomimetic robots, however, they could be improved with a careful design of their material properties. The main targets for improving their properties are increasing the relative permittivity of the active material, while maintaining high electric breakdown strength and low stiffness, which would lead to enhanced electrostatic storage ability and hence, reduced operating voltage. Improvement of the functional properties is possible through the use of nanocomposites. These exploit the high surface-to-volume ratio of the nanoscale filler, resulting in large effects on macroscale properties. This thesis explores several strategies for nanomaterials design. The resulting nanocomposites are fully characterized with respect to their electrical and mechanical properties, by use of dielectric spectroscopy, tensile mechanical analysis, and electric breakdown tests. First, nanocomposites consisting of high permittivity rutile TiO2 nanoparticles dispersed in thermoplastic block copolymer SEBS (poly-styrene-coethylene-co-butylene-co-styrene) are shown to exhibit permittivity increases of up to 3.7 times, leading to 5.6 times improvement in electrostatic energy density, but with a trade-off in mechanical properties (an 8-fold increase in stiffness). The variation in both electrical and mechanical properties still allows for electromechanical improvement, such that a 27 % reduction of the electric field is found compared to the pure elastomer. Second, it is shown that the use of nanofiller conductive particles (carbon black (CB)) can lead to a strong increase of relative permittivity through percolation, however, with detrimental side effects. These are due to localized enhancement of the electric field within the composite, which leads to sharp reductions in electric field strength. Hence, the increase in permittivity does not make up for the reduction in breakdown strength in relation to stored electrical energy, which may prohibit their practical use. Third, a completely new approach for increasing the relative permittivity and electrostatic energy density of a polymer based on 'molecular composites' is presented, relying on chemically grafting soft π-conjugated macromolecules to a flexible elastomer backbone. Polarization caused by charge displacement along the conjugated backbone is found to induce a large and controlled permittivity enhancement (470 % over the elastomer matrix), while chemical bonding, encapsulates the PANI chains manifesting in hardly any reduction in electric breakdown strength, and hence resulting in a large increase in stored electrostatic energy. This is shown to lead to an improvement in the sensitivity of the measured electromechanical response (83 % reduction of the driving electric field) as well as in the maximum actuation strain (250 %). These results represent a large step forward in the understanding of the strategies which can be employed to obtain high permittivity polymer materials with practical use for electro-elastomer actuation. / Die Palette von elektro-mechanischen Aktuatoren, basierend auf dem Prinzip weicher dehnbarer Kondensatoren, scheint besonders für Anwendungen in der Medizin und für biomimetische Applikationen unbegrenzt. Diese Wandler zeichnen sich sowohl durch hohe Reversibilität bei großer mechanischer Deformation als auch durch ihre Flexibilität aus, wobei die mechanischen Deformationen durch elektrische Felder induziert werden. Die Notwendigkeit von hoher elektrischer Spannung zur Erzeugung dieser mechanischen Deformationen verzögert jedoch die technisch einfache und breite Markteinführung dieser Technologie. Diesem Problem kann durch eine gezielte Materialmodifikation begegnet werden. Eine Modifikation hat das Ziel, die relative Permittivität zu erhöhen, wobei die Flexibilität und die hohe elektrische Durchbruchsfeldstärke beibehalten werden sollten. Durch eine Materialmodifikation kann die Energiedichte des Materials bedeutend erhöht und somit die notwendige Betriebsspannung des Aktuators herabgesetzt werden. Eine Verbesserung der funktionalen Materialeigenschaften kann durch die Verwendung von Nanokompositen erzielt werden, welche die fundamentalen Eigenschaften der Nanopartikel, d.h. ein gutes Verhältnis von Oberfläche zu Volumen nutzen, um eine gezielte makroskopische Materialmodifikation zu bewirken. Diese Arbeit behandelt die Anwendung innovativer Strategien für die Erzeugung von Nanomaterialien mit hoher Permittivität. Die so erzeugten Materialien und deren relevante Aktuatorkenngrößen werden durch elektrische und mechanische Experimente vollständig erfasst. Mittels der klassischen Mischansätze zur Erzeugung von Kompositmaterialen mit hoher Permittivität konnte durch nichtleitendes Titaniumdioxid TiO2 (Rutile) in einem Thermoplastischen-Block-Co-Polymer SEBS (poly-styrene-co-ethylene-cobutylene-co-styrene) die Permittivität bereits um 370 % erhöht und die elektrische Energiedichte um 570 % gesteigert werden. Diese Veränderungen führten jedoch zu einem signifikanten Anstieg der Steifigkeit des Materials. Aufgrund der positiven Rückkopplung von elektrischen und mechanischen Eigenschaften des Kompositmaterials ermöglicht bereits dieser einfache Ansatz eine Verbesserung der Aktuation, bei einer 27 %-igen Reduktion der Aktuatorbetriebsspannung. Eine direkte Verwendung von leitfähigen Nanopartikeln kann ebenso zu einem Anstieg der relativen Permittivität beitragen, wobei jedoch die Leitfähigkeit dieser Nanopartikel bedeutende Wechselwirkungen verursacht, welche somit die Energiedichte des Materials negativ beeinflusst und die praktische Verwendung dieses Kompositsystems ausschließt. Als ein völlig neuer Ansatz zur Steigerung der relativen Permittivität und Energiedichte und abweichend vom klassischen Mischverfahren, wird die Herstellung eines "Molekularen Komposits", basierend auf einem chemischen Propfverfahren, präsentiert. In diesem Ansatz wird ein π-konjugiertes leitfähiges Polymer (PANI) an die Hauptkette des Elastomers der Polymermatrix gebunden. Die daraus resultierende Ladungsverteilung entlang der Elastomerhauptkette bewirkt eine 470 %-ige Steigerung der Permittivität des "Molekularen Komposits" im Vergleich zur Permittivität des unbehandelten Elastomermaterials. Aufgrund der Verkapselung der chemischen Bindungen der PANI-Kette entstehen kaum negative Rückwirkungen auf die elektrischen und mechanischen Eigenschaften des so erzeugten Komposits. Diese Materialeigenschaften resultieren in einem signifikanten Anstieg der Energiedichte des Materials. Das mittels dieses Verfahrens erzeugte Komposit zeigt sowohl eine Steigerung der Sensitivität der elektromechanischen Antwort (Reduktion des elektrischen Felds um 83 %) als auch eine bedeutende Steigerung der maximalen Aktuation (250 %). Die Ergebnisse und Ideen dieser Arbeit stellen einen wesentlichen Sprung im Verständnis zur Permittivitätssteigerung in Polymermaterialien dar und werden deshalb in der Erforschung und Entwicklung von Elastomeraktuatoren Beachtung finden.

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This dissertation presents the first reported systematic investigation on the implementation of multilayer patch antennas over Fe3O4-based polymer nanocomposite (PNC) magneto-dielectric substrates. The PNC substrate is created by the monodispersion of Fe3O4 nanopthesiss, with mean size of 7.5nm, in a polymeric matrix of Polydimethylsiloxane (PDMS). Recently, magneto-dielectric substrates have been proposed by several researchers as a means for decreasing the size and increasing the bandwidth of planar antennas. Nevertheless, factors such as high loss and diminished control over magnetic and dielectric properties have hindered the optimal performance of antennas. In addition, the incompatibility and elevated complexity prevents integration of conventional magnetic materials with antennas and standard fabrication processes at printed circuit boards (PCBs) and wafer levels. Additionally, the low hysteresis losses exhibited by uniformly embedded superparamagnetic nanopthesiss complemented by the ease of integration of polymer nanocomposites in standard fabrication processes, offer promising solutions to resolve any of the complications and concerns foresaid. Towards this dissertation work, one multilayer antenna was constructed over a molded PDMS substrate along with three similar antennas built on PDMS-Fe3O4 PNC substrates with different Fe3O4 nanopthesis loading concentrations in the PDMS matrix of 80%, 50% and 30% by weight. This pioneering work in the experimental implementation and characterization of magneto-dielectric PNC antennas has not only resulted in antennas with different operational frequencies in the 3-5GHz band, but also expanded our knowledge base by correlating the concentration of magnetic nanopthesiss to key antenna performance metrics such as antenna bandwidth, antenna efficiency and miniaturization factors. Among the most significant results a magneto-dielectric antenna with maximum miniaturization factor of 57%, and a 58% increase in bandwidth, whilst retaining an acceptable antenna gain of 2.12dBi, was successfully demonstrated through the deployment of molded PDMS-Fe3O4 PNC substrate under external DC bias magnetic fields. This dissertation also presents a versatile process for constructing flexible and multilayer antennas by the seamless incorporation of a variety of materials such as PDMS, Liquid Crystal Polymer (LCP) laminates, metal clads and molded magneto-dielectric polymer nanocomposites with evenly embedded magnetic nanopthesiss.

The continuous scaling of microelectronic devices requires high permittivity (high-k) dielectrics to replace SiO₂ as the gate material. HfO₂ is one of the most promising candidates but the crystallization temperature of amorphous HfO₂ is too low to withstand the fabrication process. To enhance the film thermal stability, HfO₂ is deposited using atomic layer deposition (ALD), and incorporated with various amorphizers, such as La₂O₃, Al₂O₃, and Ta₂O₅. The incorporation is achieved by growing multiple ALD layers of HfO₂ and one ALD layer of MO[subscript x] (M = La, Al, and Ta) alternately (denoted as [xHf + 1M]), and the incorporation concentration can be effectively controlled by the HfO₂-to-MO[subscript x] ALD cycle ratio (the x value). The crystallization temperature of 10 nm HfO₂ increases from 500 °C to 900 °C for 10 nm [xHf + 1M] film, where x = 3, 3, and 1 for M = La, Al, and Ta, respectively. The incorporation of La₂O₃, and Ta₂O₅ will not compromise the dielectric constant of the film because of the high-k nature of La₂O₃, and Ta₂O₅. Angle resolved X-ray photoelectron spectroscopy (AR-XPS) reveals that when the HfO₂-to-MO[scubscript x] ALD cycle ratio is large enough (x > 3 and 4 for La and Al, respectively), periodic structures exist in films grown by this method, which are comprised of repeated M-free HfO₂ ultrathin layers sandwiched between HfM[subscript x]O[scubscript y] layers. Generally, the film thermal stability increases with thinner overall thickness, higher incorporation concentration, and stronger amorphizing capability of the incorporated elements. When the x value is low, the films are more like homogeneous films, with thermal stabilities determined by the film thickness and the amorphizer. When the x value is large enough, the periodically-repeated structure may add an extra factor to stabilize the amorphous phase. For the same incorporation concentration, films with an appropriately high periodicity may have an increased thermal stability. The manner by which the periodic structure and incorporated element affect thermal stability is explored and resolved using nanolaminates comprised of alternating layers of [scubscript y]HfO₂ and [xHf + 1M] × n, where y varied from 2 to 20, x varied from 1 to 2, and n varied from 4 to 22. / text

Ces travaux de thèse ont consisté à mener une étude approfondie des propriétés physico-chimiques duparylène C, qui est un polymère chloré, en lien avec ses propriétés électriques et diélectriques. Ces dernièresont cerné principalement le comportement de la constante diélectrique et des pertes diélectriques enfonction de la température (de l’azote jusqu’à 300 °C) sur une plage de fréquence étendue (10-4 Hz – 1 MHz).Les analyses par diffraction des rayons X ont montré que ce polymère présentait une structure cristalline a-monoclinique avec un taux de cristallinité de 45 % après élaboration. Ce taux est faiblement dépendant del’épaisseur pour des couches d’épaisseurs supérieures à 50 nm. Des recuits spécifiques appliqués sur leparylène C au dessus de la température de transition vitreuse ont permis de modifier le taux de cristallinité etdes valeurs de 30% à 75 % ont pu être obtenues. Une relation linéaire entre le taux de cristallinité et latempérature de recuit a été proposée. Les analyses diélectriques ont permis de mettre en évidence troismécanismes principaux de relaxation : La relaxation b, la relaxation g et la relaxation a. Par ailleurs, unmécanisme de polarisation interfaciale de type Maxwell-Wagner-Sillars (MWS) a été identifié à hautetempérature (au-delà de la transition vitreuse). La mobilité moléculaire des chaînes autour de la températurede transition vitreuse a été analysée en profondeur et les résultats (indice de fragilité, paramètresthermodynamiques…) ont été positionnés par rapport aux données de la littérature concernant d’autrespolymères. / This work of thesis consisted in undertaking a thorough study of the physicochemical properties of theparylene C, which is a chlorinated polymer, in relationship with its electric and dielectric properties. These lastdetermined mainly the behavior of the permittivity and the dielectric losses according to the temperature (ofnitrogen up to 300 °C) on a wide frequency range (10-4Hz – 1 MHz). The analyses by x-rays diffraction showedthat this polymer had a a - monoclinical crystalline structure with a rate of crystallinity of 45 %. This rate isslightly depending on the thickness for layers thicknesses higher than 50 nm. Specific annealing applied to theparylene C made it possible to modify the rate of crystallinity and values from 30% to 75 % of crystallinitycould be obtained. A linear relation between the rate of crystallinity and the temperature of annealing wasproposed. The dielectric analyses made it possible to highlight three principal mechanisms of relaxation: b, g,a. In addition, a mechanism of interfacial polarization (Maxwell-Wagner-Sillars) was identified at hightemperature (beyond the glass transition). The molecular mobility of the chains around the glass transitionwas analyzed in-depth and the results (index of fragility, thermodynamic parameters...) were positionedcompared to the data of the literature concerning of other polymers.

abstract: Estimation of complex permittivity of arsenic-doped silicon is the primary topic of discussion in this thesis presentation. The frequency that is of interest is 2.45 GHz, frequency typically used in conventional microwave ovens. The analysis is based on closed-form analytical expressions of cylindrical symmetry. A coaxial/radial line junction with the central conductor sheathed in dielectric material, which is As-doped silicon in this case, are analyzed. Electrical and magnetic field equations governing the wave propagation in this setup are formulated by applying the necessary boundary conditions. Input admittance is computed using the fields in the device and reflection coefficient is calculated at the input. This analytical solution is matched to the reflection coefficient acquired by experiments conducted, using VNA as the input source. The contemplation is backed by simulation using High Frequency Structural Simulator, HFSS. Susceptor-assisted microwave heating has been shown to be a faster and easier method of annealing arsenic-doped silicon samples. In that study, it was noticed that the microwave power absorbed by the sample can directly be linked to the heat power required for the annealing process. It probes the validity of the statement that for arsenic-doped silicon the heating curve depends only on its sheet properties and not on the bulk as such and the results presented here gives more insight to it as to why this assumption is true. The results obtained here can be accepted as accurate since it is known that this material is highly conductive and electromagnetic waves do not penetrate in to the material beyond a certain depth, which is given by the skin depth of the material. Hall measurements and four-point-probe measurements are performed on the material in support of the above contemplation. / Dissertation/Thesis / M.S. Electrical Engineering 2014

The purpose of this research was to design a blood glucose sensing system based on the induced shift in the resonant frequency of an antenna patch operating in the ISM band (5.725 – 5.875 GHz). The underlying concept is the fact that when a person has variations in their blood glucose levels, the permittivity of their blood varies accordingly. This research analyzed the feasibility of using an antenna patch as a blood glucose sensing device in three configurations: 1) as an implantable active sensor, 2) as an implantable passive antenna sensor, and 3) as a non-invasive sensor. In the first arrangement, the antenna is to be implanted inside the body as an active antenna, requiring that its power supply and internal circuitry to be implanted. In the second arrangement, the antenna is also implanted, but would not require a power supply or internal circuity since it would be passive. For the third arrangement, the non-invasive sensing approach, the antenna is placed facing the upper arm while mounted outside the body. In order to evaluate the best approach all the three approaches were simulated using the electromagnetic field tool simulator ANSYS EM15.0 HFSSTM, along with a human tissue model. The tissue model included physiological and electrical characteristics of the human abdomen for simulating the active and passive approaches, and the upper arm for the non-invasive approach. The electromagnetic boundaries were set with perfectly matched layers to eliminate any reflections which would cause a non-physical resonance in the results. Simulation of the active sensing configuration resulted in a resonant frequency shift from 5.76 to 5.78GHz (i.e., a 20 MHz shift) for a simulated blood permittivity variation of 62.0 to 63.6. This corresponds, theoretically, to an approximate glucose shift of 500 mg/dL. The passive configuration simulations did not yield conclusive variations in resonant frequency and this approach was abandoned early on in this research. Thirdly, the non-invasive approach resulted in a simulated shift of resonant frequency from 5.797 to 5.807 (i.e., a 10MHz shift) for simulated blood permittivity variation of 51.397 to 52.642 (an approximate variation of 2000 mg/dL in glucose). In the literature planar, continuous blood-rich layers are used to simulate RF sensing of glucose, which is not applicable when measuring glucose in actual human veins, which are tubular in geometry and of finite extent. Therefore the model employed assumed a 1.8 mm diameter blood vessel, buried under a fatty layer that was capped with skin. The above results, both simulated and verified experimentally, used this more realistic model which is further proof that a practical non-invasive blood glucose measurement system should be possible. The non-invasive approach was tested experimentally by using oil in gel phantoms to mimic the electrical properties of skin, fat, blood and muscle. A fat phantom was placed over a muscle phantom, with a strip of blood phantom within and a skin phantom was placed on top. The blood phantom had a 2000mg/dL variation of D-glucose in the phantom mixture which decreased the relative permittivity from 52.635 to 51.482 and resulted in a shift of resonant frequency from 5.855 to 5.842 (i.e., a 13MHz shift). This is consistent with the non-invasive simulated results thus validating our model of the non-invasive sensing approach. While this variation in blood glucose is non-physical (typical human glucose range can range in the extremes from 30 to 400 mg/dL, where healthy glucose levels vary from 70mg/dL to 180mg/dL) it was necessary to provide a high confidence fit between the simulated and experimental data. This is because the level of precision with which the physical phantoms could be fabricated with was insufficient to match the highly precise simulated data. Analysis on the effect of lateral displacement of the antenna from the blood vessel, its elevation above the skin and variations caused by different skin thickness, and blood vessel depth were evaluated. A calibration technique to correct physical misalignment by the user is proposed in which two additional antennas, located diagonally with respect to the sensing antenna, serve as reference point for placement over the upper arm in line of sight with the blood vessel. Once the non-invasive sensor approach was shown to be viable for continuous glucose monitoring, a sensor platform was designed whereby an RF generator was used to drive the antenna with a frequency sweep between 5.725 to 5.875GHz. A fraction of its output power was coupled to both the antenna and the system analysis circuitry through a directional coupler. The transmitted and received power were then processed with demodulating logarithmic amplifiers which convert the RF signal to a corresponding voltage for downstream processing. Both inputs were then fed into a microcontroller and the measured shift in resonant frequency, fO, converted to glucose concentration which was displayed on glucose meter display.

Les sondes de permittivité sont des instruments de prospection géophysique non destructifs qui donnent accès aux propriétés électriques, aux basses fréquences (10 Hz-10 kHz), de la proche subsurface. Ce faisant, elles renseignent sur la composition, porosité, température et éventuelle hétérogénéité des premiers mètres sous la surface.Utilisant généralement 4 électrodes, le principe des sondes de permittivité est simple : il consiste à injecter un courant sinusoïdal de phase et d’amplitude connues entre deux électrodes (dipôle émetteur) et à mesurer l'impédance mutuelle (le rapport complexe entre la tension et le courant injecté) entre ce dipôle émetteur et un dipôle récepteur. La permittivité complexe du matériau de surface, à savoir sa constante diélectrique et sa conductivité électrique, sont alors déduites de la mesure de l’amplitude et de la phase de cette impédance mutuelle. Les fréquences d’opération des sondes de permittivités sont basses là où l’approximation quasi-statique s’applique. A ce jour, les propriétés électriques de seulement deux surfaces planétaires extraterrestres ont été étudiées par des sondes de permittivité : celle de Titan par l’instrument PWA-MIP/HASI/Huygens/Cassini-Huygens et celle du noyau de la comète 67P/Churyumov–Gerasimenko par SESAME-PP/Philae/Rosetta.Nous présentons la première analyse des données obtenues par SESAME-PP à la surface de la comète 67P/Churyumov–Gerasimenko. Grâce à un travail précis (1) de modélisation numérique de l’instrument et de son fonctionnement, (2) de campagne de mesures (en laboratoire et dans des grottes de glace) afin de valider la méthode d’analyse et (3) d’hypothèses réalistes sur l’environnement proche de la sonde, nous avons pu contraindre la composition et surtout la porosité des premiers mètres du noyau cométaire montrant qu’ils étaient plus compacts que son intérieur. Nous avons également travaillé à une nouvelle analyse des données obtenues en 2005 par PWA-MIP proposant notamment de nouveaux scénarios pour le changement brutal de propriétés électriques observé 11 min après l’atterrissage de Huygens. Ces nouveaux scénarios s’appuient, entre autres, sur les mesures de caractérisation électrique menées au LATMOS sur des échantillons de composés organiques (tholins), analogues possibles des matériaux recouvrant la surface de Titan. / Permittivity probes are non-destructive geophysical prospecting instruments that give access to the low frequency (10 Hz – 10 kHz) electrical properties of the close subsurface. This provides us with information on the composition, porosity, temperature, and heterogeneity of the first meters of the subsurface.Using 4 electrodes, the technique consists in injecting a sinusoidal current of known phase and amplitude between two electrodes (transmitting dipole) and measuring the mutual impedance (complex ratio of measured potential over injected current) between this dipole and a receiving dipole. The complex permittivity (i.e. dielectric constant and conductivity) of the subsurface material is derived from the measured phase and amplitude of the mutual impedance. The frequency range of operation of permittivity probes is low, therefore the quasi static approximation applies. To this day the electrical properties of only two extra-terrestrial surfaces have been studied by permittivity probes, the surface of Titan by the instrument PWA-MIP/HASI/Huygens/Cassini-Huygens and the surface of the nucleus of comet 67P/Churyumov–Gerasimenko by SESAME-PP/Philae/Rosetta.We present a first analysis of the data collected by SESAME-PP at the surface of the comet 67P/Churyumov–Gerasimenko. With the help of (1) precise numerical models of the instrument, (2) field measurements (in a controlled and natural environment) in order to validate the analysis method, and (3) realistic hypothesis on the close environment we were able to constrain the composition and porosity of the first meters of the comet’s nucleus, showing that the subsurface is more compact than its interior. We also reanalysed of the data collected in 2005 by PWA-MIP, offering new explanations for the abrupt change in the electrical properties observed 11 minutes after the landing of Huygens. These new scenarios were built in the light of lab measurements performed at LATMOS on samples of organic matter (tholins), possible analogue of Titan’s surface material.

This thesis deals with the dielectric relaxation spectroscopy applied to samples of an epoxy slip filled by grounded mica with granularity of 40 m. The changes of dielectric properties were investigated depending on the fulfillment of grounded mica, temperature, the relative air humidity, and the frequency between 100 Hz and 1MHz.