Characterization Of Commercially Available Conductive Filament And Their Application In Sensors And Actuators

The primary aim of this study is to contribute to the field of additives that would enable the fabrication of electrical sensors and actuators completely via Material Extrusion based Additive Manufacturing (MEAM). The second aim of the study is to provide the necessary characterization to facilitate the development of applications that predicts electrical part performance. The electrical characterization of two conductive poly-lactic acid (PLA) filaments, namely, c-PLA with carbon black and graphene PLA was performed to study the temperature coefficient of the resistance. Resistivity of carbon black filament was compared to a printed single layer and with that of a cube. The raw and printed c-PLA showed a positive temperature coefficient of resistance (α) ranging from ~0.03-0.01 ℃-1 while its counterpart in the study, graphene PLA, did not exhibit significant (α). Parts from graphene PLA with multilayer MEAM exhibited a negative α to a certain temperature before exhibiting positive α. The resistivity of the printed parts was 300 times higher for c-PLA and 1500 times for graphene PLA. However, no microstructural or chemical compositional changes were observed between the raw filaments and the printed parts. Due to the high α of the c-PLA, it was deemed as the better material for constructing electro thermal sensors and actuators using MEAM. First, c-PLA was used to fabricate and package a completely 3D printed flow meter that operates on the principle of Joule heating and hotwire anemometry. When the designed flowmeter was simulated using a finite element package, a flow sensitivity of -2.33 Ω sccm-1 and a relative change in resistivity of 0.036 sccm-1 was expected. For an operating voltage of 12-15 V, the experimental results showed a flow sensitivity within the range of 0.014-0.032 sccm-1 and the relative change in resistivity ranged from 0.039 – 0.065 sccm-1. Thus, a completely 3D printed flowmeter was demonstrated. Second, using the same principle of Joule heating, an actuator inspired from MEMS chevron grippers was designed, simulated, and fabricated. Simulation showed the feasibility of the structure and further predicted a displacement of a few hundred microns with a potential as low as 3 V with a cooling time as little less than 120 seconds. Experimentally, a displacement of 120.04, 97.05, and 88.96 μm were achieved in 15, 10, and 5 seconds with actuation potentials of 12.7, 13.8, and 17.9 V, respectively. As predicted by the simulation results, it took longer for the gripper to cool (close to 180 seconds) when compared to actuation times. During the above studies, we discovered the printing parameters altered the part resistance. Our final study examined how extrusion temperature and printing speed affects the impedance of the MEAM printed parts. Further, anisotropy in the impedance was observed and the influence of the interface to it was examined. From the experimental results, the anisotropy was quantified with a Z/F ratio and was found to be nearly constant, ~2.15±0.23. Impedance scaling with the number of interfaces was measured and showed conclusively that the interlayer bonding was the sole source for the observed Z/F ratio. Scanning electron microscope images shows the absence of air gaps at the interface, and energy dispersion spectroscopy shows the absence of oxidation at the interface. By investigating the role of print parameters and scaling of impedance with interfaces, a framework to model and predict electrical behavior of electro thermal sensors and actuators made via MEAM can be realized

Materials science of blood clot formation in insects: experimental methods for a multiscale in-situ investigation

This dissertation is structured around the development of a micro and nano-rheological instrument capable of measuring mPa·s-level viscosity of nanoliter droplets and micron thick films in a 10-20 second timeframe and using it to study the kinetics of formation of a blood clot in insects. To understand the materials science behind this clot formation, we enrich the microrheological study with studies of extensional rheology of various maturity stages of clots as well as studies of the surface tension isotherms, dynamic surface tensions, and surface rheology. To study the rapidly changing structure of the clots, we employ high magnification microscopy and scanning electron microscopy. Overall, we perform a detailed study of physical materials properties and structure of the material, which helps us better understand its outstanding performance. In Chapter 1, we introduce an engineering reader to the biological aspect of the problem and discuss the functionality of the material in an insect body. In Chapter 2, we discuss the importance of understanding multiscale rheology of the material and review the current methodologies available and their limitations with regards to the study of changing insect blood. In chapter 3, we discuss the principle of our methodology and the realization of the device with which we study the nanorheology with high precision and temporal resolution. In chapter 4, we present nanoscale viscosity measurements of blood of adult butterflies and moths: Manduca sexta, Vanessa cardui, and Danaus plexippus and discuss the significant deviations of the viscosities from the viscosity of water. In chapter 5, we present the nanorheological measurements of forming and maturing clots in the blood of M. sexta caterpillars and present the discovery of characteristic times of formation of these clots. In chapter 6, we present and discuss the fibrous and cellular structures of the forming blood clots of M. sexta caterpillars. In chapter 7, we study extensional rheology of forming blood clots of M. sexta caterpillars. In chapter 8, we discuss the structure formed in the clots in response to our extensional experiments and relate that to the functions of the clot constituents. Finally, in chapter 9, we study the materials properties of the surface of hemolymph of adult M. sexta, V. cardui, D. plexippus, and caterpillar M. sexta and relate them to the nano and microrheological measurements we performed on the material. We thus characterize the time-dependent structure-properties-performance triangles of blood and the forming blood clots in the studied insects

Physical approaches for the performance optimization and investigation of organic batteries

The increasing awareness of the negative impacts humanity has on the global ecosystem resulted in an ever growing demand for a more sustainable energy and material consumption over the past decades. Environmentally benign electricity generation and energy storage represent two of the key technological approaches to address this issue. In this context, organic radical batteries (ORB) and redox flow batteries (RFB) possess significant advantages as energy storage technologies due to the sustainable material basis they rely on and the performance characteristics they offer. However, while material development is continuously advancing in this research field, methods for the proper characterization and performance optimization of ORBs and RFBs still need to keep pace with this development to exploit the full potential of these technologies. This thesis, therefore, aims to contribute with a physical perspective to the investigation and optimization of these novel energy storage systems. In particular, porous electrode morphologies in ORBs and special methods to produce them are investigated. Furthermore, non-conventional cell designs for the electrochemical reactors of RFBs are investigated and their impact on the performance parameters of the RFB are explored. Finally, two methods for the reliable and accurate measurement of the electrolytes' state-of-charge as one of the most important key parameters were developed and characterized

Viscoelasticity

This book contains a wealth of useful information on current research on viscoelasticity. By covering a broad variety of rheology, non-Newtonian fluid mechanics and viscoelasticity-related topics, this book is addressed to a wide spectrum of academic and applied researchers and scientists but it could also prove useful to industry specialists. The subject areas include, theory, simulations, biological materials and food products among others

Microscopy of spin hydrodynamics and cooperative light scattering in atomic Hubbard systems

Wechselwirkungen zwischen quantenmechanischen Teilchen können zu kollektiven Phänomenen führen, deren Eigenschaften sich vom Verhalten einzelner Teilchen stark unterscheiden. Während solche Quanteneffekte im Allgemeinen schwierig zu beobachten sind, haben sich ultrakalte, in optischen Gittern gefangene atomare Gase als vielseitige experimentelle Plattform zur Erforschung der Quantenvielteilchenphysik erwiesen. In dieser Arbeit setzten wir ein Gitterplatz- und Einzelatom-aufgelöstes Quantengasmikroskop für bosonische Rb-87 Atome ein, um Vielteilchensysteme im und außerhalb des Gleichgewichts zu untersuchen. Zunächst betrachteten wir den quantenmechanischen Phasenübergang zwischen dem suprafluiden und dem Mott-isolierenden Zustand im Bose-Hubbard-Modell, das nativ durch kalte Atome in optischen Gittern realisiert wird, und zeigten, dass sich die Brane-Parität eignet, um nichtlokale Ordnung im konventionell als ungeordnet erachteten zweidimensionalen Mott-Isolator zu identifizieren. Mithilfe eines mikroskopischen Ansatzes zur Realisierung einstellbarer Gittergeometrien und programmierbarer Einheitszellen implementierten wir Quadrats-, Dreiecks-, Kagome- und Lieb-Gitter und beobachteten die Skalierung des Phasenübergangspunkts mit der mittleren Koordinationszahl des Gitters. In einem eindimensionalen Gitter untersuchten wir zudem den Hochtemperatur-Spintransport im Heisenberg-Modell, das durch Superaustausch in der Mott-isolierenden Phase eines zwei-Spezies Bose-Hubbard-Modells realisiert wurde. Durch Betrachten der Relaxationsdynamik eines als Domänenwand präparierten Anfangszustandes fanden wir eine superdiffusive Raum-Zeit-Skalierung mit einem anomalen dynamischen Exponenten von 3/2. Anschließend untersuchten wir die theoretisch vorhergesagten mikroskopischen Voraussetzungen für Superdiffusion, indem wir reguläre Diffusion im nicht-integrablen, zweidimensionalen Heisenberg-Modell und ballistischen Transport für SU(2)-Symmetrie-gebrochene magnetisierte Anfangszustände nachwiesen. Weiterhin maßen wir die Zählstatistik der durch die Domänenwand transportierten Spins; die sich daraus ergebende schiefe Verteilung deutete auf einen nichtlinearen zugrundeliegenden Transportprozess hin, der an die dynamische Kardar-Parisi-Zhang Universalitätsklasse erinnert. Mittels Mott-Isolatoren im Limit tiefer Gitter konnten wir darüber hinaus die durch Photonen vermittelten Wechselwirkungen in einem Spinsystem untersuchen, das aus zwei über einen geschlossenen optischen Übergang gekoppelten Zuständen besteht. Durch spektroskopische Untersuchung der Reflexion und Transmission konnten wir die direkte Anregung einer subradianten Eigenmode und kohärente Spiegelung beobachten, was auf die Realisierung einer effizienten, im freien Raum operierenden, paraxialen Licht-Materie-Schnittstelle hindeutet.The interplay of quantum particles can give rise to collective phenomena whose characteristics are distinct from the behavior of individual particles. While quantum effects are generally challenging to observe, ultracold atomic gases trapped in optical lattices have emerged as a versatile experimental platform to study quantum many-body physics. In this thesis, we employed a site– and single-atom–resolved quantum gas microscope of bosonic Rb-87 atoms to explore many-body systems in and out of equilibrium. We first considered the ground-state quantum phase transition between the superfluid and Mott-insulating state in the Bose–Hubbard model, natively realized by cold atoms in optical lattices, for which we found brane parity to be suitable for detecting nonlocal order in the conventionally unordered two-dimensional Mott insulator. Using a microscopic approach to realizing tunable lattice geometries and programmable unit cells, we implemented square, triangular, kagome and Lieb lattices, and observed the mean-field scaling of the phase transition point with average coordination number. In a one-dimensional lattice, we furthermore studied high-temperature spin transport in the Heisenberg model, realized by superexchange in the Mott-insulating phase of a two-species Bose–Hubbard model. By tracking the relaxation dynamics of an initial domain-wall state, we found superdiffusive space–time scaling with an anomalous dynamical exponent of 3/2. We then probed the predicted microscopic requirements for superdiffusion, verifying regular diffusion for the integrability-broken two-dimensional Heisenberg model and ballistic transport for SU(2)-symmetry–broken net magnetized initial states. Subsequently, we measured the full counting statistics of spins transported across the domain wall; the resulting skewed distribution implied a nonlinear underlying transport process, reminiscent of the Kardar–Parisi–Zhang dynamical universality class. Moving to Mott insulators in the deep-lattice limit, we could moreover study photon-mediated interactions on a subwavelength-spaced, array-ordered spin system consisting of states coupled by a closed optical transition. By spectroscopically probing the reflectance and transmittance, we demonstrated the direct excitation of a subradiant eigenmode and observed specular reflection, indicating the realization of an efficient free-space paraxial light–matter interface

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals

Novel bottom-up sub-micron architectures for advanced functional devices

This thesis illustrates two novel routes for fabricating hierarchical micro-to-nano structures with interesting optical and wetting properties. The co-presence of asperities spanning the two length scales enables the fabrication of miniaturised, tuneable surfaces exhibiting a high potential for applications in for instance, waterproof coatings and nanophotonic devices, while exploiting the intrinsic properties of the structuring materials. Firstly, scalable, superhydrophobic surfaces were produced via carbon nanotubes (CNT)-based electrohydrodynamic lithography, fabricating multiscale polymeric cones and nanohair-like architectures with various periodicities. CNT forests were used for manufacturing essential components for the electrohydrodynamic setup and producing controlled micro-to-nano features on a millimetre scale. The achieved high contact angles introduced switchable Rose-to-Lotus wetting regimes. Secondly, a cost-effective method was introduced as a route towards plasmonic bandgap metamaterials via electrochemical replication of three-dimensional (3D) DNA nanostructures as sacrificial templates. A range of sub-30nm 3D DNA polyhedrons, immobilised onto conductive and insulating surfaces, were replicated with gold via electrochemical deposition and sputtering. Microscopic characterisation revealed detailed gold replicas preserving both edges and cavities of the DNA nanostructures. Accurate tuning of both polyhedrons’ dimensions and gold plating conditions finally enabled sub-100nm structures which show promising optical properties such as, birefringence for potential applications in photonics, metamaterials and sensing