This thesis analyzes the implementation of surface bonded piezoelectric actuators to control or minimize the deformation in elastic or viscoelastic cantilever beams due to simultaneous heat and moisture diffusion. The problem is addressed in the context of linearized elasticity and linearized viscoelasticity. The constitutive equations are derived from the balance laws for mass, linear and angular momenta, energy, entropy and the second law of thermodynamics. The constitutive equations for linearized elasticity are then obtained as a consequence of small deformation assumption. The temperature and moisture induced deformation is introduced through the coefficient of thermal expansion CTE and coefficient of moisture expansion CME. The constitutive equations for linearized viscoelasticity are obtained by correspondence principle. The coupled temperature and moisture diffusion equations are obtained as a consequence of Clausius-Duhem inequality. The extent of coupling between heat conduction and moisture diffusion phenomena is studied by varying the ratio of their diffusivities and a non-dimensional coupling parameter. The effect of coupled unsteady heat conduction and moisture diffusion phenomena on the short and long term response characteristics of the beam such as displacement, stress and strain fields is studied. Based on these response characteristics, the magnitude of external actuating voltage required to minimize deformation is predicted. This is followed by a comparative study of the field variables in cases of actuated and unactuated beams. Four materials are chosen for this study; aluminium, epoxy, carbon fiber reinforced polymer with fiber volume fraction of 60 percent, and an epoxy-like viscoelastic material. The viscoelastic material is assumed to be thermorheologically simple. The shift factor is assumed to be a linear function of temperature and moisture fields. To address this problem numerically, a finite difference formulation is presented for the field equations and boundary conditions. This numerical scheme is validated by solving the problem of uniformly loaded cantilever beam and comparing the results with the analytical solution known a priori. The results obtained numerically are validated by comparison with experimental results. It is observed that the under the effect of external actuation, the stress and displacement fields are largely minimized in all four cases chosen for study. The bending in the unactuated viscoelastic beam is more pronounced than bending in the unactuated elastic beam. This is due to the softening of the material with time due to evolving temperature and moisture fields. However, relatively lesser external actuating voltage is necessary to minimize bending in the former case compared to the latter. The magnitude of actuating electric field required in the piezoelectric layer suggests a need to address the problem with in a non-linear framework, no such attempt is made in this study.

Piezoelectric effect was discovered in the 19th century, but the applications of piezoelectric effect were realized until the 20th century. In this paper, piezoelectric actuators, which are made based on piezoelectric effect, are employed to establish a three-degree-of-freedom micro-manipulator. The mechanism of this micro-manipulator is designed as a parallel-type mechanism. The kinematics of the micro-manipulator is also analyzed. In addition, a remote control framework is implemented with a control system and this achievement can be a demonstration for future feasibility of application of this micro-manipulator to robotic systems.

By integrating Nanotechnology and MEMS technology, this thesis aims to research a flexural-plate wave (FPW) sensor for testing Immunoglobulin E (IgE) concentration in blood serum, a significant index for the diagnosis of allergies. The traditional methods of blood assay are time-consuming and costly, and its average accuracy of only 60-70 percent. After compare the major four kinds of acoustic sensor, the FPW sensor demonstrates a high accuracy, high sensitivity, low operation frequency, low diagnosis time and low cost. This thesis utilizes a reactive RF sputter system to deposite the piezoelectric ZnO thin film. To obtain the high C-axis orientation (002) characteristic of ZnO membrane, many parameters such as substrate temperature, Ar/O2 ratio and RF power have been adjusted and optimized during the sputtering process. The effects of varied parameters will be investigated and analysis by using SEM or XRD facilities. In this study, we combined the high figure-of-merits ZnO deposition techniques and single-side anisotropic silicon etch process to implement the process integration of FPW device. Finally, this research has demonstrated a 50-60MHz center frequency can be extracted from such silicon-based FPW microsensor.

This study has been carried out to develop and manufacture piezoelectric ceramic materials which are utilized for ultrasonic motor (USM) applications. For this purpose, the effect of compositional modifications on the dielectric and piezoelectric properties of lead zirconate titanate (PZT) based ceramics was investigated. PZT based powders were produced using the mixed oxide method. The base composition was selected as Pb(Zr0.54Ti0.46)O3. The samples in the proximity of morphotrophic phase boundary were doped with strontium, lanthanum, lead manganese niobate (PMnN) and lead manganese antimonate (PMS) in order to improve the structural characteristics and electromechanical properties which are very important for USM applications. The dielectric constant, planar coupling coefficient, mechanical quality factor, piezoelectric strain constant and tangent loss values were evaluated in accordance with standard IRE (Institute of Radio Engineers) test procedures. The results on dielectric and piezoelectric properties showed that piezoelectric ceramics with high mechanical quality factor, high piezoelectric strain constant and low tangent loss could be produced by using the aforementioned dopants. As a result, a new piezoelectric ceramic named as 0.97[PSLZT]-0.024[PMnN]-0.006[PMS] was produced with KT= 1913, Qm= 1240, d33= 540 pC/N, tan delta= 0.89%, kp= 0.57 and Tc= 235 &deg / C. This composition is a good candidate for high power applications. The ceramic samples with the developed compositions were used to produce an ultrasonic-wave type motor and the performance of the USM was evaluated in terms of speed, torque and efficiency.

In this study, we discuss AlGaN/GaN high electron-mobility heterostructs grown by metal organic chemical vapor deposition technique. We analyzed the samples by optical and magnetoelectrical experiments to probe the dependence of the piezoelectric effect on the structural difference. We hope our results may be useful for the design of nitride heterostructures. The E-beam evaporator operation manual given in this thesis may be useful for future users.

Veeco Applied EPI 930 molecular beam epitaxy system equipped with a radio frequency plasma assisted nitrogen source has been introduced and the growth procedure and some specialized measurements are also described. The GaN thin films grown by RF-MBE have been talked about nitridation, low temperature GaN buffer layer, and GaN epilayer. The nitridation is a necessary for grown GaN on c-sapphire. From the result of the HRXRD symmetric (002) rocking curve, the magnitude of the FWHM of the GaN films without nitridation was larger than the films with nitridation. The growth temperature of the LT GaN buffer layer was the major factor on the quality of GaN epilayer which grown on the almost without nitridated sapphire substrate. The growth condition of high growth temperature, thin, low growth rate, and low N/Ga ratio of the LT GaN buffer layer can improve the sequent GaN epilayer quality. On the other hand, in the N/Ga flux ratio of GaN epitaxy layer experiment, we have found three interesting results. First, the narrowest peak width of PL spectrum appeared in a slight Ga-rich condition. Second, the smallest of HRXRD FWHM appeared in the nearly stoichiometry condition. Third, the highest electron mobility and less overall dislocations appeared in a slight N-rich condition. Finally, we report the results about AlGaN/GaN heterostructure grown by metalorganic chemical vapor deposition. The piezoelectric effect on the Alx-£_In£_Ga1-xN/GaN heterostructures was investigated and we found that a little In atom in the spacer (£_< 0.01 %) will substantially reduce the strain at interface due to the much larger size of the In atom in comparison to Al and Ga atoms. The electric field at the interface is reduced one order of magnitude smaller than that of the heterostructure without In atom. Two SdH oscillations beat each other due to the population of the lowest two subbands was been seen. Another two SdH oscillations beating have been observed in modulation-doped AlxGa1-xN/GaN heterostructures caused by the finite zero-filed spin splitting due to the inversion-asymmetry-induced bulk k3 term.

Coupling between the electric field, magnetic field, and strain of composite materials is achieved when electro-elastic (piezoelectric) and magneto-elastic (piezomagnetic) particles are joined by an elastic matrix. Although the matrix is neither piezoelectric nor piezomagnetic, the strain field in the matrix couples the E field of the piezoelectric phase to the B field of the piezomagnetic phase. This three-phase electro-magneto-elastic composite should have greater ductility and formability than a two-phase composite in which E and B are coupled by directly bonding two ceramic materials with no compliant matrix. A finite element analysis and homogenization of a representative volume element is performed to determine the effective electric, magnetic, mechanical, and coupled-field properties of an elastic (epoxy) matrix reinforced with piezoelectric and piezomagnetic fibers as functions of the phase volume fractions, the fiber (or particle) shapes, the fiber arrangements in the unit cell, and the fiber material properties with special emphasis on the symmetry properties of the fibers and the poling directions of the piezoelectric and piezomagnetic fibers. The effective magnetoelectric moduli of this three-phase composite are, however, less than the effective magnetoelectric coefficients of a two-phase piezoelectric/piezomagnetic composite, because the epoxy matrix is not stiff enough to transfer significant strains between the piezomagnetic and piezoelectric fibers.

This thesis consists of two subjects of research: eliminating, by avoidance or removal, the effects of different types of interference on small signal recording, and a body-sensor transmitter application utilizing piezo sensors. The first topic demonstrates ECG signal and noise signal recording in the presence of various types of interference. A low-pass filter is proposed to remove power-line interference of ECG signals, and a switch between high-pass filters before amplification is proposed to avoid motion artifacts in the ECG signal. Finally, a low-cost noise recording system for educational uses that can record and analyze the noise of resistors and amplifiers in the LabVIEW program is proposed. The second topic concerns the application of a body-sensor transmitter. The sensor uses piezo film and combines the characteristics of piezo film with the characteristics of the human body and can exchange information by capacitor coupling. The signal used in the body-sensor transmitter is designed for a fixed frequency using narrow band-pass filters and is received by receivers via four methods as confirmation. Finally, the charge amplifier designed to detect signals is fabricated using a 0.35£gm 2P4M CMOS process.

Dissertation (Ph.D.)--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references.

Thesis (doctoral)--Helsinki University of Technology, 2009. / Includes bibliographical references. Also available on the World Wide Web.