Publications by authors named "Theodosia Stratoudaki"

Ultrasonic imaging, using ultrasonic phased arrays, has an enormous impact in science, medicine and society and is a widely used modality in many application fields. The maximum amount of information which can be captured by an array is provided by the data acquisition method capturing the complete data set of signals from all possible combinations of ultrasonic generation and detection elements of a dense array. However, capturing this complete data set requires long data acquisition time, large number of array elements and transmit channels and produces a large volume of data.

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Laser ultrasonics is a technique where lasers are employed to generate and detect ultrasound. A data collection method (full matrix capture) and a post processing imaging algorithm, the total focusing method, both developed for ultrasonic arrays, are modified and used in order to enhance the capabilities of laser ultrasonics for nondestructive testing by improving defect detectability and increasing spatial resolution. In this way, a laser induced ultrasonic phased array is synthesized.

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A dual frequency mixing technique has been developed for measuring velocity changes caused by material nonlinearity. The technique is based on the parametric interaction between two surface acoustic waves (SAWs): The low frequency pump SAW generated by a transducer and the high frequency probe SAW generated and detected using laser ultrasonics. The pump SAW stresses the material under the probe SAW.

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Article Synopsis
  • The paper presents a new optically powered MEMS transducer capable of generating ultrasonic bulk waves efficiently using laser excitation.
  • It features a two-mask-level design, with a microdisk and microstem, where the disk's resonant motion creates narrowband ultrasound through thermomechanical interactions.
  • Experimental results confirm that this transducer produces ultrasound with significantly higher amplitude and better signal-to-noise ratio than traditional methods, while being cost-effective and compact.
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This paper presents the analysis, design, and experimental study of a microcantilever optically-activated ultrasonic detection transducer. An analytical model was derived using 1-D cantilever structural dynamics, leading to the optimization of the transducer design. Finite element modeling enabled dynamic simulation to be performed, with results in good agreement with the analytical model.

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