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Treball final de màster oficial fet en col·laboració amb Universitat Autònoma de Barcelona (UAB), Universitat de Barcelona (UB) i Institut de Ciències Fotòniques (ICFO), [ANGLÈS] Optical Feedback Interferometry (OFI) and Double Optical Feedback interferometry (DOFI) are studied as non-invasive techniques for biomedical measurements. Due to its compactness and cost-effectiveness, both sensors provide a very interesting approach for sensing different biomedical parameters. After a brief introduction to the two techniques, a modified signal processing algorithm developed within this MSc Thesis is presented. DOFI is then discussed as a technique for arterial pulse wave shape reconstruction, showing its limitations in large amplitude measurements, which, nevertheless, enable an OFI sensor to accurately measure it. Experimental results on arterial pulse wave measurements will be presented. DOFI is then proposed as a candidate technique for monitoring the displacement of cantilevers in atomic force microscopy which enhances the performance of present cantilever sensing solutions due to its robustness., [CASTELLÀ] Las técnicas conocidas como Optical Feedback Interferometry (OFI) y Double Optical Feedback Interferometry (DOFI) han sido estudiadas como técnicas no invasivas para medidas biomédicas. Ambos sensores son propuestas interesantes para medir parámetros biomédicos debido al hecho de ser compactos y con un bajo coste para su alta efectividad. Tras una breve introducción a las dos técnicas, se presenta un algoritmo de procesamiento de señal modificado que se ha desarrollado dentro de esta tesis de Máster. Luego se discuten las posibilidades de usar DOFI como una técnica capaz de reconstruir la forma de las ondas de pulso arterial, mostrando las limitationes de la técnica para medidas de larga amplitud aunque, pese a todo esto, permite el desarrollo de un sensor basado en OFI que puede medirlo con gran exactitud. Se presentarán resultados de medidas de la forma de la onda de presión arterial. Finalmente, se propone DOFI como técnica para controlar el desplazamiento de un cantilever en microscopía de fuerza atómica mejorando las prestaciones de las soluciones actuales para esta aplicación gracias a su robustez., [CATALÀ] Les tècniques conegudes com Optical Feedback Interferometry (OFI) i Double Optical Feedback Interferometry (DOFI) han estat estudiades com tècniques no invasives per a mesures biomèdiques. Tots dos sensors són propostes interessants per mesurar paràmetres biomèdics a causa del fet de ser compactes i amb un baix cost per la seva alta efectivitat. Després d'una breu introducció a les dues tècniques, es presenta un algorisme de processament de senyal modificat que s'ha desenvolupat dins d'aquesta tesi de màster. Després es discuteixen les possibilitats d'usar DOFI com una tècnica capaç de reconstruir la forma de les ones de pols arterial, mostrant les limitationes de la tècnica per a mesures de llarga amplitud encara que, malgrat tot això, permet el desenvolupament d'un sensor basat en OFI que pot mesurar amb gran exactitud. Es presentaran resultats de mesures de la forma de l'ona de pressió arterial. Finalment, es proposa DOFI com a tècnica per controlar el desplaçament d'un cantilever en microscòpia de força atòmica millorant les prestacions de les solucions actuals per a aquesta aplicació gràcies a la seva robustesa.

We demonstrate the feasibility of intravascular ultrasound (IVUS) chirp imaging as well as chirp reversal ultrasound contrast imaging at intravascular ultrasound frequency. Chirp excitations were emitted with a 34?MHz single crystal intravascular transducer and compared to conventional Gaussian-shaped pulses of equal acoustic pressure. The signal to noise ratio of the chirp images was increased by up to 9?dB relative to the conventional images. Imaging of contrast microbubbles was implemented by chirp reversal, achieving a contrast to tissue ratio of 12?dB. The method shows potential for intravascular imaging of structures in and beyond coronary atherosclerotic plaques including vasa vasorum, IST/Imaging Science and Technology, Applied Sciences

We demonstrate the feasibility of intravascular ultrasound (IVUS) chirp imaging as well as chirp reversal ultrasound contrast imaging at intravascular ultrasound frequency. Chirp excitations were emitted with a 34?MHz single crystal intravascular transducer and compared to conventional Gaussian-shaped pulses of equal acoustic pressure. The signal to noise ratio of the chirp images was increased by up to 9?dB relative to the conventional images. Imaging of contrast microbubbles was implemented by chirp reversal, achieving a contrast to tissue ratio of 12?dB. The method shows potential for intravascular imaging of structures in and beyond coronary atherosclerotic plaques including vasa vasorum, IST/Imaging Science and Technology, Applied Sciences

Electrophysiological signal acquisition such as ECG and EEG play an important part in modern medical monitoring and diagnostics. The measurement of these very low-level, low-frequency signals are normally made from the skin with a directly coupled sensor utilizing a conductive gel to create a low resistance path for the charge. The application of the gel is tedious and time consuming as well as requiring a clinical environment and prevents long period measurements. In this paper, a contact-less, capacitively coupled sensor — without any need for gel — together with an electronic readout circuit using a PCB is presented. A design with a very high input impedance allows for measurements of signals with amplitudes down to a few tens of microvolts and at frequencies between a few hertz to tens of hertz. Measurements show that the circuit could detect an input signal of 25 μV at 10 Hz with an SNR of 9.7 dB.

The development and optimization of medical ultrasound transducers and imaging modalities require a computational method that accurately predicts the nonlinear acoustic pressure field. A prospective method should provide the wide-angle, pulsed field emitted by an arbitrary planar source distribution and propagating in a three-dimensional, large scale domain holding a nonlinear acoustic medium. In this paper, a method is presented that is free of any assumed wavefield directionality. The nonlinear acoustic wave equation is solved by treating the nonlinear term as a contrast source. This formulation leads to an iterative scheme that involves the repetitive solution of a linear wave problem through Green’s function method. It is shown that accurate field predictions may be obtained within a few iterations. Moreover, by employing a dedicated numerical convolution technique, the method allows for a discretization down to two points per wavelength or period of the highest frequency of interest. The performance of the method is evaluated through a number of nonlinear field predictions for pulsed transducers with various geometries. The results demonstrate the directional independence of the method. Moreover, comparison with results from several existing methods shows that the method accurately predicts the nonlinear field for weak to moderate nonlinearity., Telecommunications, Electrical Engineering, Mathematics and Computer Science

The development and optimization of medical ultrasound transducers and imaging modalities require a computational method that accurately predicts the nonlinear acoustic pressure field. A prospective method should provide the wide-angle, pulsed field emitted by an arbitrary planar source distribution and propagating in a three-dimensional, large scale domain holding a nonlinear acoustic medium. In this paper, a method is presented that is free of any assumed wavefield directionality. The nonlinear acoustic wave equation is solved by treating the nonlinear term as a contrast source. This formulation leads to an iterative scheme that involves the repetitive solution of a linear wave problem through Green’s function method. It is shown that accurate field predictions may be obtained within a few iterations. Moreover, by employing a dedicated numerical convolution technique, the method allows for a discretization down to two points per wavelength or period of the highest frequency of interest. The performance of the method is evaluated through a number of nonlinear field predictions for pulsed transducers with various geometries. The results demonstrate the directional independence of the method. Moreover, comparison with results from several existing methods shows that the method accurately predicts the nonlinear field for weak to moderate nonlinearity., Telecommunications, Electrical Engineering, Mathematics and Computer Science

"Cell Clinics," CMOS/MEMS hybrid microsystems for on-chip investigation of biological cells, are currently being engineered for a broad spectrum of applications including olfactory sensing, pathogen detection, cytotoxicity screening and biocompatibility characterization. In support of this effort, this research makes two primary contributions towards designing the cell-based lab-on-a-chip systems. Firstly it develops CMOS capacitance sensors for characterizing cell-related properties including cell-surface attachment, cell health and growth. Assessing these properties is crucial to all kinds of cell applications. The CMOS sensors measure substrate coupling capacitances of anchorage-dependent cells cultured on-chip in a standard in vitro environment. The biophysical phenomenon underlying the capacitive behavior of cells is the counterionic polarization around the insulating cell bodies when exposed to weak, low frequency electric fields. The measured capacitance depends on a variety of factors related to the cell, its growth environment and the supporting substrate. These include membrane integrity, morphology, adhesion strength and substrate proximity. The demonstrated integrated cell sensing technique is non-invasive, easy-to-use and offers the unique advantage of automated real time cell monitoring without the need for disruptive external forces or biochemical labeling. On top of the silicon-based cell sensing platform, the cell clinics microsystem comprises MEMS structures forming an array of lidded microvials for confining single cells or small cell groups within controllable microenvironments in close proximity to the sensor sites. The opening and closing of the microvial lids are controlled by actuator hinges employing an electroactive polymer material that can electrochemically actuate. In macro-scale setups such electrochemical actuation reactions are controlled by an electronic instrument called potentiostat. In order to enable system miniaturization and en