Tunable Permittivity Sensors

This thesis presents a novel electric permittivity sensor based on Bleustein- Gulyaev (BG) waves; waves that propagate along the surface of shear-poled piezoelectric materials. BG waves couple electromagnetic and acoustic waves, thereby reducing the speed of electromagnetic propagation to near acoustic speeds. Exploiting this property allows the development of permittivity sensors that feature several orders of magnitude reduction in size and operating frequency. This releases the limitations of RF complexity while reducing cost considerably. It also makes the sensor attractive for biological applications, as opposed to RF sensors that are limited by the water relaxation phenomenon at frequencies beyond 4 GHz. To date, sensors that used BG waves were limited to sensing mechanical properties, such as viscosity and density, which exploited the acoustic component of the wave only. To our best knowledge, this is the first attempt to probe and sense an electrical property acoustically using BG-waves. Towards that end, the nonlinear partial differential equations governing an electromechanical BG wave resonator are formulated. The permittivity of the medium-under-test was found to influence the sensor eigenvalues, enabling the implementation of a frequency-shift permittivity sensor. We also find that the sensor sensitivity is enhanced by increasing bias voltage to drive the sensor into the nonlinear regime, but this is limited by electrical breakdown. Sensor prototypes were fabricated on PZT4 and LiNbO3 shear-poled substrates. A novel method to characterize shear-horizontal surface acoustic waves, SHSAW, using a 1D Laser Doppler Vibrometer was developed to test the sensors. The method was also shown to be able to estimate the in-plane displacement field decay rate into the substrate. This technique provides researchers with a quick and effective method for the characterization of SH-SAW. The resonator model was validated using this experimental method. A Vector Network Analyzer was employed to observe the shift in the fundamental natural frequency of the fabricated permittivity sensors in the presence of various media-under-test. Measurements show deterministic and repeatable frequency shifts in the natural frequency in the presence of ethanol and deionized water compared to that of the bare surface, thereby demonstrating the permittivity sensor

Biosensors for Diagnosis and Monitoring

Biosensor technologies have received a great amount of interest in recent decades, and this has especially been the case in recent years due to the health alert caused by the COVID-19 pandemic. The sensor platform market has grown in recent decades, and the COVID-19 outbreak has led to an increase in the demand for home diagnostics and point-of-care systems. With the evolution of biosensor technology towards portable platforms with a lower cost on-site analysis and a rapid selective and sensitive response, a larger market has opened up for this technology. The evolution of biosensor systems has the opportunity to change classic analysis towards real-time and in situ detection systems, with platforms such as point-of-care and wearables as well as implantable sensors to decentralize chemical and biological analysis, thus reducing industrial and medical costs. This book is dedicated to all the research related to biosensor technologies. Reviews, perspective articles, and research articles in different biosensing areas such as wearable sensors, point-of-care platforms, and pathogen detection for biomedical applications as well as environmental monitoring will introduce the reader to these relevant topics. This book is aimed at scientists and professionals working in the field of biosensors and also provides essential knowledge for students who want to enter the field

Electrical and Electro-Optical Biosensors

Electrical and electro-optical biosensing technologies are critical to the development of innovative POCT devices, which can be used by both professional and untrained personnel for the provision of necessary health information within a short time for medical decisions to be determined, being especially important in an era of global pandemics. This Special Issue includes a few pioneering works concerning biosensors utilizing electrochemical impedance, localized surface plasmon resonance, and the bioelectricity of sensing materials in which the amount of analyte is pertinent to the signal response. The presented results demonstrate the potential of these label-free biosensing approaches in the detection of disease-related small-molecule metabolites, proteins, and whole-cell entities

Wideband Microwave Imaging Systems for the Diagnosis of Fluid Accumulation in the Human Torso

According to the World Health Organization (WHO), cardiovascular diseases (CVDs) are the leading causes of death worldwide, with one third of deaths attributed to CVDs in 2012. Pulmonary oedema and pleural effusion are the most apparent symptoms of many diseases categorized under CVDs such as heart failure and lung cancer, at which fluid (mainly with high water content) is accumulated in or around the lungs. Therefore, constant monitoring of fluid levels inside the lungs is one of the most efficient ways of early detection of CVDs. Chest X-Rays and computational tomography (CT)-scans are the most widely used devices for fluid detection; however, they suffer from lack of sensitivity and ionizing radiation, respectively, that makes them unsuitable for long term monitoring purposes. Currently, magnetic resonance imaging (MRI) is the most reliable device that can be utilized for fluid accumulation detection. However, considering the fact that more than 75% of the CVDs occur in countries with low or middle income, it is not widely available. Moreover, due to their bulky structures, the abovementioned devices lack the capability of being used in mobile emergency units such as ambulances or clinics at rural areas. To that end, this thesis is dedicated to design and fabrication of a low cost, portable and non-invasive device that can be used as an initial decision making tool for medical staff to pursue further investigations to define the exact cause of the oedema. First chapter of the thesis is allocated to introduction of the cardiovascular diseases and their effects on the dielectric properties of the tissues inside the lungs. A complete literature review on various alternative methods for replacing the conventional devices is performed. The obtained results by these systems and their advantages as well as their limitations are discussed. Microwave imaging technique is then presented in chapter two as a robust method which can both provide information about the presence and location of the accumulated fluid. This is specifically of great importance for cases where biopsy is required to remove or take sample of the accumulated fluid for saving the life of the patient. Chapter two is also allocated to the introduction of microwave-based medical diagnostic and monitoring systems for different applications such as breast cancer detection and brain imaging. A prospect of the possible realizable systems is investigated and existing scanning approaches are discussed. The main contributions of the thesis that are the design of several complete platforms, design of novel and unidirectional microwave sensors (antennas), promotion of novel scanning and detection methods are clarified in these chapters. In chapter three, firstly the optimum operating frequency for torso imaging is defined. By applying a circuit model that models different layers of torso as circuit elements, it is shown that a wide operating bandwidth at lower ultra-high frequency (UHF) band provides a reasonable compensation between the resolution of the obtained images and signal penetration inside the body. It is explained that due to the limited allowed microwave power for safety considerations unidirectional antennas are required. Then, it is explained that due to the large wavelengths at lower UHF band the sizes of the prospective antennas are expected to be large. To that end, novel miniaturization techniques are proposed to reduce the sizes of the conventional antennas in chapters three and four. These antennas are categorized under three dimensional (3-D) and planar structure. A folding technique is introduced and used in the proposed 3-D structures and it is shown that by using this technique both size and directivity/back radiation suppression is improved. 3-D slot-antenna and cubic monopole-fed antennas are also proposed that wide operating bandwidth is achieved using slot impedance transformer, and multiple resonance-merging techniques, respectively. Regarding the planar structures that are presented in chapter four, it is shown that by combining the loop-dipole modes, both wide-operating bandwidth and directivity enhancement is achievable. Capacitive-loading of a loop antenna is the other proposed technique in which a loop antenna is partially and/or non-uniformly loaded with capacitors in the forms of simple slots and mu-negative (MNG) metamaterial-unitcells that help miniaturizing the size of the antenna by lowering its first resonance frequency. In chapters five and six, several platforms using single and multiple antennas with linear and circular configurations are presented and the utilized imaging technique for data processing is explained. The platforms are presented in a systematic progressive manner in which each system is covering the limitations of its previous prototype. Two final clinical platforms in the shape of clinical bed and doughnut-shaped chamber are proposed and the obtained test results on artificial phantom, animal lungs and human tests are presented. Based on the obtained results on healthy human beings it is shown that the scattered-field from torso of people with different body sizes vary in a reasonably limited range that is a welcoming result for building a global-database to define a threshold for healthy range. Chapter seven concludes the discussions made throughout the thesis and explains future works that can be carried out to further improve the reported systems

Microfluidics for Biosensing

There are 12 papers published with 8 research articles, 3 review articles and 1 perspective. The topics cover: Biomedical microfluidics Lab-on-a-chip Miniaturized systems for chemistry and life science (MicroTAS) Biosensor development and characteristics Imaging and other detection technologies Imaging and signal processing Point-of-care testing microdevices Food and water quality testing and control We hope this collection could promote the development of microfluidics and point-of-care testing (POCT) devices for biosensing

Sonocytology: dynamic acoustic manipulation of particles and cells

Separating and sorting cells and micro-organisms from a heterogeneous mixture is a fundamental step in biological, chemical and clinical studies, enabling regenerative medicine, stem cell research, clinical sample preparation and improved food safety. Particle and cell manipulation by ultrasound acoustic waves provides the capability of separation of cells on the basis of their size and physical properties. Offering the advantages of relatively large microfluidic volumes in a label-free, contactless and biocompatible manner. Consequently, the discovery of alternative methods for precise manipulation of cells and particles is of highly demand. This thesis describes a novel approach of ultrasound acoustic manipulation of particles and cells. The principle of operation of the dynamic acoustic field method is described accompanied with acoustic separation simulations. Furthermore, the complete fabrication and characterisation of two types of ultrasound devices is given. The first one is a bulk acoustic wave (BAW) device and the second is a surface acoustic wave (SAW) device. Successful experiments using the BAW device for sorting different diameter particles with a range from 5 to 45 μm are demonstrated, also experiments for sorting particles depending on their density are presented. Moreover, experiments of the proposed method for sorting porcine dorcal root ganglion (DRG) cells from a heterogeneous mixture of myelin debris depending on their size are displayed. Experimental results of sorting cells depending on their stiffness are demonstrated. Experiments using the fabricated SAW device for sorting different diameter particles in a constant flow with a range from 1 μm to 10 μm are presented. Furthermore, experiments of the proposed method for sorting live from dead Htert cells depending on their mechanical properties, i.e. stiffness are displayed. As a side project a new idea for dynamic acoustic manipulation by rotating the acoustic field is demonstrated. The basic principles of this method and the simulations for verifying this concept are displayed. Experiments for sorting 10 μm from 3 μm polystyrene particles are presented, with two different types of the dynamic acoustic rotating field being examined

Use of microwave techniques in medical diagnostics and therapy

The main original contribution in this thesis is the novel application of microwave open-ended coaxialprobes in the characterisation of the electrical properties of normal and cancer tissues, and their use for cancer therapy. In terms of the cancer diagnosis part, thisthesis showsthe design, analysisand realization of new open-ended microwave sensors with a needle aperture to assess their sensitivity and usefulness for microwave characterizations of materials. These needle-type sensors are capable of penetrating easily into semi-solid and multilayered material. This is very important in cancer diagnosis since they permit non-destructive measurement, with the advantage of using them as medical needles that have higher sensitivity at low frequencies than the usual flat aperture probes. Moreover, the sensors have been developed to measure properties of normal and cancer tissues for early cancer detection applications. In terms of the cancer treatment part, a novel non-thermal microwave irradiation technique has been adapted and developed for complete annihilation of cancer cells with a limited peak temperature of 42°Cand short treatment time of 5 minutes