Ultrasonic actuators: Remote strain measurements, high strain horns and ultrasonic chromatography

In this thesis, optical diffraction strain measurement, silicon-based ultrasonic horn actuators for thin film testing, and μfluidic assay systems are presented.; Optical ultrasonic strain measurement: Using optical diffraction gratings integrated on a PZT/silicon laminate actuator, the strain on the actuator was optically and remotely measured. The methodology, limitations, analytical and numerical (ANSYS) analysis are presented. This technology of diffraction grating for ultrasonic strain measurements could lead to an instrument useful for remote monitoring of strain on MEMS sensors.; Design of high efficiency silicon-based ultrasonic horn, and their fabrication for thin film testing under cyclic load: A detailed ultrasonic horn design and its analysis are resented. For this application a Gaussian horn is utilized. Most ultrasonic horns have a single point maximum strain point along the horn resulting in strain gradient at all points. For the purpose of straining thin films it is desirable to have areas of spatially constant strain fields. Remarkably, the Gaussian horn has a constant strain area suitable for thin film testing. High strain values can lead to testing not only fatigue, but also fracture of thin films. We feel that the ability to generate constant ultrasonic strain areas on silicon is a technique suitable for industrial and academic material characterization.; A portable high-intensity ultrasonic actuator for μfluidic separation (ultrasonic chromatography): Micro-particle manipulation in a liquid using ultrasonic fields in a micro-channel, principle of operation, and analysis are presented. Beads of different sizes could be separated within an optically viewable aperture (∼100 μm). It is found that the separation occurs due to ultrasonic radiation force and a new inertial force, acting on the beads. The key mechanism of focusing beads at the nodes of ultrasonic standing waves, and the origin of the inertial force for the separation are described. The capability of separating beads by size using CMOS circuits and in a rapid manner could result in fast portable biomedical assays utilizing beads coated with different antibodies or receptor molecules.