Thesis (Ph. D.)--Drexel University, 2003. / Includes abstract and vita. Includes bibliographical references (leaves 140-146).

Wireless micro-sensors can enjoy popularity in biomedical drug-delivery treatments and tire-pressure monitoring systems because they offer in-situ, real-time, non-intrusive processing capabilities. However, miniaturized platforms severely limit the energy of onboard batteries and shorten the lifespan of electronic systems. Ambient energy is an attractive alternative because the energy from light, heat, radio-frequency (RF) radiation, and motion can potentially be used to continuously replenish an exhaustible reservoir. Of these sources, solar light produces the highest power density, except when supplied from indoor lighting, under which conditions the available power decreases drastically. Harnessing thermal energy is viable, but micro-scale dimensions severely limit temperature gradients, the fundamental mechanism from which thermo piles draw power. Mobile electronic devices today radiate plenty of RF energy, but still, the available power rapidly drops with distance. Harvesting kinetic energy may not compete with solar power, but in contrast to indoor lighting, thermal, and RF sources, moderate and consistent vibration power across a vast range of applications is typical. Although operating conditions ultimately determine which kinetic energy-harvesting method is optimal, piezoelectric transducers are relatively mature and produce comparatively more power than their counterparts such as electrostatic and electromagnetic kinetic energy transducers. The presented research objective is to develop, design, simulate, fabricate, prototype, test, and evaluate CMOS ICs that harvest ambient kinetic energy in periodic and non-periodic vibrations using a small piezoelectric transducer to continually replenish an energy-storage device like a capacitor or a rechargeable battery. Although vibrations in surrounding environment produce abundant energy over time, tiny transducers can harness only limited power from the energy sources, especially when mechanical stimulation is weak. To overcome this challenge, the presented piezoelectric harvesters eliminate the need for a rectifier which necessarily imposes threshold limits and additional losses in the system. More fundamentally, the presented harvesting circuits condition the transducer to convert more electrical energy for a given mechanical input by increasing the electromechanical damping force of the piezoelectric transducer. The overall aim is to acquire more power by widening the input range and improving the efficiency of the IC as well as the transducer. The presented technique in essence augments the energy density of micro-scale electronic systems by scavenging the ambient kinetic energy and extends their operational lifetime. This dissertation reports the findings acquired throughout the investigation. The first chapter introduces the applications and challenges of micro-scale energy harvesting and also reviews the fundamental mechanisms and recent developments of various energy-converting transducers that can harness ambient energy in light, heat, RF radiation, and vibrations. Chapter 2 examines various existing piezoelectric harvesting circuits, which mostly adopt bridge rectifiers as their core. Chapter 3 then introduces a bridge-free piezoelectric harvester circuit that employs a switched-inductor power stage to eliminate the need for a bridge rectifier and its drawbacks. More importantly, the harvester strengthens the electrical damping force of the piezoelectric device and increases the output power of the harvester. The chapter also presents the details of the integrated-circuit (IC) implementation and the experimental results of the prototyped harvester to corroborate and clarify the bridge-free harvester operation. One of the major discoveries from the first harvester prototype is the fact that the harvester circuit can condition the piezoelectric transducer to strengthen its electrical damping force and increase the output power of the harvester. As such, Chapter 4 discusses various energy-investment strategies that increase the electrical damping force of the transducer. The chapter presents, evaluates, and compares several switched-inductor harvester circuits against each other. Based on the investigation in Chapter 4, an energy-investing piezoelectric harvester was designed and experimentally evaluated to confirm the effectiveness of the investing scheme. Chapter 5 explains the details of the IC design and the measurement results of the prototyped energy-investing piezoelectric harvester. Finally, Chapter 6 concludes the dissertation by revisiting the challenges of miniaturized piezoelectric energy harvesters and by summarizing the fundamental contributions of the research. With the same importance as with the achievements of the investigation, the last chapter lists the technological limits that bound the performance of the proposed harvesters and briefly presents perspectives from the other side of the research boundary for future investigations of micro-scale piezoelectric energy harvesting.

Directional microphones, which suppress noise coming from unwanted directions while preserving sound signals arriving from a desired direction, are essential to hearing aid technology. The device presented in this paper abandons the principles of standard pressure sensor microphones, dual port microphones, and multi-chip array systems and instead employs a new method of operation. The proposed device uses a lightweight silicon micromachined structure that becomes “entrained” in the oscillatory motion of air vibrations, and thus maintains the vector component of the air velocity. The mechanical structures are made as compliant as possible so that the motion of the diaphragm directly replicates the motion of the sound wave as it travels through air. The microphone discussed in this paper achieves the bi-directionality seen in a ribbon microphone but is built using standard semiconductor fabrication techniques and utilizes piezoelectric readout of a circular diaphragm suspended on compliant silicon springs. Finite element analysis and lumped element modeling have been performed to aid in structural design and device verification. The proposed microphone was successfully fabricated in a cleanroom facility at The University of Texas at Austin. Testing procedures verified that the resonant frequency of the microphone, as expected, was much lower than in traditional microphones. This report discusses the theory, modeling, fabrication and testing of the microphone. / text

Due to the high affinity and selectivity of aptamer selected from DNA library towards target proteins, the use of specific protein biomarkers to assist early diagnosis, and the recent rapid development of piezoelectric quartz crystal (PQC) biosensor technology, the research reported is focused on developing PQC biosensor using aptamers selected from a DNA library as selective coating for the detection of albumin in urine, two protein biomarkers for malaria in sera, and the determination of trace amount of SCV helicase protein from SAR in sera. Three new aptamer-PQC biosensors are developed with research conducted on aptamer selection, optimization of coating methods for aptamers on PQC, and coupling paramagnetic nanoparticle technology with PQC biosensor in flow injection analysis (FIA) to enrich analyte and eliminate sample matrix interference. A new approach for aptamer selection is successfully attempted in the development of the first aptamer-PQC biosensor with an aim to offer an early detection of microalbuminuria enabled by an increase in detection sensitivity with aptamer selected by its actual binding with albumin-PQC biosensor. The aptamer-PQC sensor developed has shown to give a working range between 0.1 to 10 ug/mL, a detection limit (S/N = 3, n=3) of 0.048 μg/ml, repeatability of RSD = 6.8% (n=3), a response time of 1 minute and a throughput of 60 samples/hour. The developed piezoelectric aptamer sensor is shown to have sufficient sensitivity to detect microgram quantities of albumin in urine. Aptamer-PQC biosensors are developed for the detection of two protein biomarkers, PfLDH for general diagnosis and PfHRP-2 for a specific diagnosis of Plasmodium falciparum malaria parasitemia, in sera. The results show satisfactory working range from 10-100 ng/mL for both PfLDH and PfHRP-2 protein biomarker, low detection limit of 1.8 and 4.7 ng/mL and satisfactory repeatability (%RSD, n = 3) of 7.4% and 9.2% for PfHRP-2 and PfLDH respectively. It is first report for aptamer based PQC biosensor to detect malarial PfHRP-2 and PfLDH at ppb range to meet the requirement for their diagnosis. To meet the highly demanding challenge for detecting protein biomarkers at pg/mL level in high-protein sera sample, the coupling of paramagnetic nanoparticle technology with aptamer-PQC biosensor was attempted for developing aptamer-PQC biosensor for selective detection of SCV helicase protein produced from SARS CoV replication. The coupling of aptamer coated paramagnetic nanoparticles for sample pretreatment to aptamer-PQC biosensor has shown to detect helicase protein in one-minute assay with a detection limit of 350 pg/mL. The aptamer-coated crystal exhibits a frequency shift linearly proportional to the concentration of SARS helicase from 1 to 1000 ng/mL with a correlation coefficient of 0.9975 and a repeatability of 6.8% (%RSD, n=3). After the enrichment procedure, recoveries of 102% and 119% were achieved using samples spiked with SARS helicase at concentrations of 10 ng/mL and 1.0 ng/mL respectively. It is the first report to detect for SCV helicase protein using PQC biosensor at pg/mL level after magnetic bead enrichment. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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<p>To compare the use of a piezoelectric with a standard surgical handpiece in third molar surgery. Thirty patients requiring removal of third molars were included in the study. Panoramic radiographs were used to assess the third molars. The patients were randomly subdivided and the split-mouth technique applied. In split-mouth design, divisions of the mouth, such as right (upper and lower) and left (upper and lower) quadrants constitute the experimental units, which are randomly assigned to two treatment groups. Each patient serves as his or her own control, which increases statistical efficiency (Siddiqi et al. 2010). Each side was operated with either a piezoelectric or a conventional handpiece. All aspects of preoperative care, general anaesthesia, surgery and postoperative care were standardized for the groups.</p>

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