Thesis (Ph.D.) - Simon Fraser University, 2005. / Theses (Dept. of Chemistry) / Simon Fraser University.

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2008 / In recent years, due to rapid advances in technology there has been an increasingly high demand for large displacement and large force, precise positioning, fast response, low power consuming miniature piezoelectric actuators. In certain smart structure applications, the use of curved piezoelectric actuators is necessary. The present work extends the earlier investigations on the C- shape actuator by providing a detailed investigation on the influence of geometric and material properties of the individual layers of the C-shape piezocomposite for its optimal performance as an actuator. Analytical models have. been used to optimize the geometry of the actuator. Experimental and finite element analyses (using general purpose finite element software i.e. CoventerWare and MSC. Marc) have been used for validation. The present work has established that, by maintaining the thickness of the substrate and piezoceramic layers constant; changing the external radius, for example increasing it, the stiffness of the structure decreases and thus yielding large displacement This has a negative effect on the force produced by the actuator. With fixed thickness of the substrate and varying the thickness of the piezoceramic (for fixed external radius) the result is as follows: Increasing the thickness of the piezoceramic layer has the effect of decreasing the displacement while the force increases. With fixed PZT thickness as well as the external radius, varying the substrate thickness has the following effect: As the thickness of the substrate increases the displacement increases reaching a maximum. Subsequent increase in the thickness of the substrate the displacement is reduced. The force continues increasing at least for the ratios up to 1.0, further increase of the substrate, subsequent decrease of force is also noted. In addition to changing the thickness of the substrate, the choice of different material for the substrate has the following effect: For substrate/PZT ratios of up to 0.6. an actuator with substrate material having higher elastic modulus will produce larger displacement while for ratios beyond this ratio the situation is reversed. The causes for this kind of behaviour have been addressed. In all cases both force and displacement are found to be directly proportional to applied voltage.

Biological cells are naturally exposed to a wealth of stimuli that influence their function and behaviour. In fields where the focus is on artificially growing biological material, such as tissue engineering and regenerative medicine, it is important to consider this array of senses to ensure correct cell signalling and tissue development. For decades, however, research has targeted only the chemical aspects of these stimuli. Mechanical and electrical signals are also fundamental in the development of our biology. Piezoelectric materials offer a promising solution to the electrical stimulation issue, and have drawn much attention recently as `active' cell culture scaffolds. However, little thought has been given to the mechanical properties of these materials and how they align with the requirements of cellular systems. Furthermore, the composition of many piezoelectric materials raises questions about biocompatibility. In this thesis, nanostructures of the piezoelectric bio-polymer poly-\textsc{l}-lactic acid (PLLA) have been fabricated, characterised and implemented in cell culture devices to investigate their potential for electromechanical stimulation of living tissue. Novel variations on the template-wetting method have been developed to create the nanostructures. PLLA nanowires were fabricated for the first time using temperature-controlled solution template-wetting. The nanowires were characterised using Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD) and Piezo-response Force Microscopy (PFM) combined with Finite Element Analysis (FEA). The results indicated that the nanowires were highly crystalline (up to 45 %) with a degree of molecular alignment, and that the nanowires displayed shear piezoelectricity with an estimated piezoelectric coefficient d₁₄ = 8 pC/N. This was the first observation and quantification of shear piezoelectricity in PLLA at the nanoscale. FEA was used to show that hollow nanotube structures would more closely align with the requirements for an active cell culture platform - namely, a greatly enhanced direct piezoelectric response compared to an equivalent wire. Therefore, melt template wetting was subsequently used to create PLLA nanotubes. Crystallisation induced by heat treatment was investigated using XRD, DSC and polarised light optical microscopy (POM). The results indicated that crystallisation in the confined nanotube environment leads to molecular alignment with the polymer chain parallel to the nanotube axis. No significant changes in crystal structure were observed between bulk PLLA and PLLA nanotubes. Various Scanning Probe Microscopy (SPM) modes were used to characterise the PLLA nanotubes at the nanoscale. PeakForce Quantitative Nanomechanical Mapping (PF-QNM) revealed the mechanical properties and lamellar structure of the polycrystalline polymer, although rigorous quantitative analysis proved challenging, as verified by FEA simulations. Kelvin Probe Force Microscopy (KPFM) highlighted the difference in surface potential between amorphous and crystalline nanotubes. PFM data also demonstrated the piezoelectric activity of both crystalline and amorphous nanotubes. The interaction between PLLA nanotubes and Human Dermal Fibroblast (HDF) cells was also investigated. Cell attachment was found to be significantly higher for nanotubes in comparison to bulk films, and a further increase in attachment was observed between amorphous and crystalline nanotubes. Electrodes embedded into the nanotube devices allowed for electrical stimulation to be applied during cell growth. Preliminary observations suggest that this stimulation improves cell attachment and/or proliferation, and the use of Aerosol Jet Printing (AJP) to pattern the electrodes can lead to directed cell growth.

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Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaves 207-220).

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Logging While Drilling (LWD) instruments used in oil and gas exploration are subjected to extreme environmental conditions that make reliable operation a major challenge. The sensors directly exposed to this environment experience accelerated aging and may suffer physical damage leading to failure. The cost of drilling and rig operations is very high magnifying any failures or issues with LWD tools. The goal of this report is to present a built-in self-test for an instrument sensor that provides a means to evaluate sensor functionality. The sensor is a piezoelectric ultrasonic transducer. A brief review of the sensor physics will be given. I will review some methods for characterizing piezoelectric ceramic materials and transducers. The application of sensor test methods is applied in an ultrasound pulse-echo application. A brief review of the application circuit will be covered including state of the art in commercial ultrasound integrated circuit design. A prototype of the BIST method is evaluated using test transducers to verify the circuit provides indication of a transducers ability to function correctly. The prototype is achieved through the AD5933 demo board and MATLAB is used for data processing. / text

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