City Research Online

Abstract

Currently, a rapid development of point of care technologies can be observed, mainly due to the alternative they offer to traditional complex laboratory equipment, not only saving costs, but also improving patients convenience, delivering quick and reliable measurement results, increasing the confidence in clinical decisions and most importantly, improving patient care. Phononic crystals were recently introduced, and their unique capabilities to control the transmission of waves has paved the way for the development of many applications, including the development of acoustic sensors. Phononic crystal sensors offer a fundamentally different measurement principle to the development of point of care technologies by enabling the measurement of the acoustic properties of small liquid samples. So far, various phononic crystal sensors have been proposed to be used as liquid sensors. However, they are still in very early stages of development and suffer several drawbacks like high analyte consumption, complex manufacturing procedures, highly dependent on ambient variables and no portability, making it impossible to implement them in point of care devices. The main objective of this study is to evaluate the potential implementation of multi-layered phononic crystals as liquid sensors for biomedical applications, especially for developing point of care technologies. Theoretical and experimental studies were performed in order to evaluate the behaviour of the designed structures. For computing the frequency response of phononic crystals, the transmission line model and the finite element method were used. Different liquid analytes were utilised during the experimental realisations to corroborate the results obtained during the theoretical studies. Variations in the acoustic properties of small liquid samples, resulted in measurable changes in the transmission coefficient of the phononic crystal, specifically shifting the frequency of relevant transmission peaks located inside bandgaps, which provide boundary conditions for eliminating noise and enhancing their quality factor. The introduction of multiple defect modes showed to be a feasible alternative to generate differential measurements in phononic crystals and compensate the effect of temperature. Furthermore, the use of biorecognition agents was also utilised and discussed to enhance the detection capabilities of this new sensors.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	Doctoral Theses School of Science & Technology > School of Science & Technology Doctoral Theses School of Science & Technology

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