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Dissertation
Synthesis, fabrication, and characterization of self-exciting, self-sensing PZT/SiO₂ piezoelectric micro-cantilever sensors
Doctor of Philosophy (Ph.D.), Drexel University
Nov 2006
DOI:
https://doi.org/10.17918/etd-1227
Abstract
A piezoelectric cantilever (PEC) consists of a piezoelectric layer, e.g., leadzirconate titanate (PZT) bonded to a non-piezoelectric layer, e.g., silica. Compared to other current biosensing technologies, PEC's ability to withstand damping in water and its all-electric, self-exciting, self-sensing features make it stand out for in-liquid biosensing applications that is in-situ, real-time, multiplexed, and high throughput. The scaling analysis of PECs shows that reducing a PEC's dimension can increase its mass sensitivity dramatically. The goal of the thesis study is to fabricate miniaturized piezoelectric micro-cantilever sensors (PEMS) with femtogram mass detection sensitivity (10-15 gram/Hz) for biological and chemical sensing applications. To achieve the goal, the thesis study encompasses three major components: (1) fundamental studies on the sensor physics to allow an optimal sensor design, (2) lead zirconate titanate (PZT) sol-gel thin film development, (3) microfabrication of the PZT PEMS. For the fundamental study, the effects of the sensor's geometry on its detection sensitivity were examined both theoretically and experimentally to show that a proper nonpiezoelectric extension enhances a PEMS detection sensitivity. Using a unique sol-gel method using ethylene glycol as the solvent, dense, smooth, and defect-free PZT thin films were obtained with superb dielectric and ferroelectric properties, an intrinsic dielectric constant [epsilon]int=2100 and a saturation polarization Ps=55 [mu]C/cm2. Integrating with silicon based micro-fabrication technologies, PZT/SiO₂ PEMS 300 to 40 m long were successfully fabricated exhibiting resonance peaks with high quality factors ranging from 120 to 320. Mass detection sensitivities of 6.7 x10⁻¹⁶ g/Hz and 9.1 x10⁻¹⁶ g/Hz (mass of a single virus or a fraction of a single cell) were obtained with 40 m and 60 m PZT/SiO₂ PEMS, respectively, in humidity detection--the smallest and most sensitive PZT based PEMS ever reported.
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Details
- Title
- Synthesis, fabrication, and characterization of self-exciting, self-sensing PZT/SiO₂ piezoelectric micro-cantilever sensors
- Creators
- Zuyan Shen - DU
- Contributors
- Wan Y. Shih (Advisor) - Drexel University (1970-)Wei-Heng Shih (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 1227; 991014632332204721