Developing Biosensor Technology to Monitor Biofilm Formation on Voice Prosthesis in Throat Cancer Patients Following Total Laryngectomy

Voice prostheses (used to replace an excised larynx in laryngectomy patients) are often colonised by the yeast Candida albicans, yet no monitoring technology for C. albicans biofilm growth until these devices fail. With the current interest in smart technology, understanding the electrical properties of C. albicans biofilm formation is necessary. There has been great interest in Passive Radio Frequency Identification (RFID) for use with implantable devices as they provide a cost-effective approach for sensing. The main drawback of RFID sensors is the need to overcome capacitive loading of human tissue and, thus, low efficiency to produce a high read range sensor design. This is further complicated by the size restriction on any RFID design to be implemented within a voice prosthesis as this medical device is limited to less than 3 cm in overall size. In order to develop such a voice prosthesis sensor, we looked at three separate aspects of C. albicans colonisation on medical devices within human tissue. To understand if it is possible to detect changes within a moist environment (such as the mouth), we developed a sensor capable of detecting minute dielectric changes (accuracy of ± 0.83 relative permittivity and ± 0.05 S·m-1 conductivity) within a closed system. Once we understood that detection of dielectric changes within a liquid solution were possible, to overcome human tissue capacitive loading of RFID sensors. Adjusting backing thickness or adding a capacitive shunt into the design could limit this tissue effect and even negate the variability seen between human tissues. Without developing these methods, implementation of any RFID device would be difficult as human tissue variability would not be compensated for properly. Finally, biofilm growth in terms electrical properties. As C. albicans biofilm matures, there is a loss in capacitance (the biofilm becomes increasingly hydrophobic) prior to 24 hours after which the biofilm thickness shifts the resonance leading to a slow gain in capacitance. Understanding all of these aspects allowed us to develop two final voice prosthesis sensors producing read ranges above 60 cm and 10 cm within a tissue phantom. Ultimately, this showed the possibility of developing cost-effective passive RFID sensor technology for monitoring microbial biofilm formation within human tissue, leading to more effective real-time clinical care

New autonomous sensor system for the continous monitoring of the composting process from the inside

The composting process is Nature's way of recycling organic wastes with a good quality organic fertilizer as a result. This process, though, needs of a thoroughly monitoring of temperature and humidity for a good resulting material. During this Ph.D thesis we developed a wireless temperature and humidity autonomous system that monitored from the inside of compost. The fact of measuring and transmitting from the inside implies the need of a protection for the circuit and an issue in the measure. Temperature suffers delays when measuring from the inside of a protection and, as such, we developed an algorithm, implementable on microcontrollers, to counteract the effects of first order step responses. The conditioning has been optimized in terms of components and consumption, obtaining a theoretical and experimental comparative between the classic conditioning and the use of direct interfaces. Commercial humidity sensors need to be in direct contact with the environment they are measuring, but that is not possible in compost since they can get damaged. That is why we designed a humidity sensor based on coplanar capacitive electrodes that can measure through a protection layer. Some theoretical models have been obtained for the physical optimization of both the sensor and the influence of the protective layer. Compost has never been characterised as a transmission environment, and as such, communications in compost are innovative. The heterogeneity of the material and its changes in humidity, temperature and density made the transmission complex. We found the proper frequency band to commercially work in compost and the RF transmission model in compost to estimate attenuation vs distance.El procés de compostatge és la forma que té la natura de reciclar els residus orgànics amb un fertilitzant orgànic de bona qualitat com a resultat. Aquest procés, però, necessita d’una monitorització de la temperatura i la humitat per a obtenir un bon material resultant. Durant aquesta tesi doctoral s'ha desenvolupat un sistema autònom sense fils de mesura de temperatura i humitat des de dins del compost. El fet de que la mesura i la transmissió s’hagin fet des de dins comporta la necessitat d’un material protector per l’electrònica, la qual cosa esdevé un problema en la mesura. La temperatura pateix retards quan es mesura des de dins d’un material protector, i per això, s’ha desenvolupat un algoritme implemetanble en microcontroladors per contrarestar els efectes de respostes esglaó de primer ordre. S'ha optimitzat el condicionament des del punt de vista de components i consum, obtenint una comparativa teòrica i experimental entre els mètodes de condicionament clàssic i l'ús d'interfícies directes. Els sensors de humitat comercials necessiten estar en contacte directe amb l’ambient a mesurar. Això no és possible en el compost ja que es poden malmetre. Per això s’ha dissenyat un sensor d’humitat basat en elèctrodes capacitius plans que poden mesurar a través de capes de protecció. S'han extret models teòrics per l’optimització física tant del sensor com de la influencia de la capa protectora El compost no ha estat mai caracteritzat com un medi de transmissió, i per tant, les comunicacions dins del compost suposen una novetat. La heterogeneïtat del material i els seus canvis en temperatura, humitat i densitat fan de la transmissió un tema complex. S’ha trobat, a més, la banda de freqüència òptima per treballar comercialment i el seu model de transmissió RF estimant l’atenuació en funció de la distànciaPostprint (published version

Toward biomaterial-based implantable photonic devices

Optical technologies are essential for the rapid and efficient delivery of health care to patients. Efforts have begun to implement these technologies in miniature devices that are implantable in patients for continuous or chronic uses. In this review, we discuss guidelines for biomaterials suitable for use in vivo. Basic optical functions such as focusing, reflection, and diffraction have been realized with biopolymers. Biocompatible optical fibers can deliver sensing or therapeutic-inducing light into tissues and enable optical communications with implanted photonic devices. Wirelessly powered, light-emitting diodes (LEDs) and miniature lasers made of biocompatible materials may offer new approaches in optical sensing and therapy. Advances in biotechnologies, such as optogenetics, enable more sophisticated photonic devices with a high level of integration with neurological or physiological circuits. With further innovations and translational development, implantable photonic devices offer a pathway to improve health monitoring, diagnostics, and light-activated therapies. Keywords: biomaterials; biocompatible; biodegradable; optics; photonicsUnited States. Department of Defense (Award FA9550-13-1-0068)National Institutes of Health (U.S.) (Award P41-EB015903)National Institutes of Health (U.S.) (Award R01-CA192878)National Science Foundation (U.S.) (Award CBET-1264356)National Science Foundation (U.S.) (Award ECCS-1505569

Review of recent microwave planar resonator-based sensors: Techniques of complex permittivity extraction, applications, open challenges and future research directions

Recent developments in the field of microwave planar sensors have led to a renewed interest in industrial, chemical, biological and medical applications that are capable of performing real-time and non-invasive measurement of material properties. Among the plausible advantages of microwave planar sensors is that they have a compact size, a low cost and the ease of fabrication and integration compared to prevailing sensors. However, some of their main drawbacks can be considered that restrict their usage and limit the range of applications such as their sensitivity and selectivity. The development of high-sensitivity microwave planar sensors is required for highly accurate complex permittivity measurements to monitor the small variations among different material samples. Therefore, the purpose of this paper is to review recent research on the development of microwave planar sensors and further challenges of their sensitivity and selectivity. Furthermore, the techniques of the complex permittivity extraction (real and imaginary parts) are discussed based on the different approaches of mathematical models. The outcomes of this review may facilitate improvements of and an alternative solution for the enhancement of microwave planar sensors’ normalized sensitivity for material characterization, especially in biochemical and beverage industry applications

Radiotaajuisen säteilyn altistuksen arviointi kauneudenhoidon sovelluksissa

The aim of this Master’s Thesis was to assess the radiofrequency exposure of beauty care appliances and to be able to evaluate the safety of the devices according to the limits issued in the regulations for the exposure of electromagnetic fields. The treatments with radiofrequency beauty care appliances are usually associated with some degree of local tissue heating, thus the effects of excessive heating might cause some thermal damage in tissues. In the literature survey of this Thesis, the principles of radiofrequency (RF) radiation and its interaction mechanisms with biological tissue, the properties of human tissues, the structure and operation of RF beauty care appliances and different dosimetric assessment methods of radiofrequency radiation exposure are studied. To study the operation and output power of the RF beauty care appliances, a moveable power measurement set-up was developed. In this set-up the RF power, which connects to resistors representing human body and its impedance, was determined from the output signal with an oscilloscope. A model simulating a human forearm made of cylindrical container and tissue simulating liquid was fed with radiofrequency power of RF beauty care device under review. The temperature increase in the liquid was measured below the RF treatment electrode. An output power of the device, which was obtained from the temperature increase measurements, was used as an output power when assessing the exposure in numerical simulations with Finite Difference Time Domain (FDTD) method in homogeneous and heterogeneous human models. The numerical simulation model was successfully validated with the temperature increase measurements. The dosimetry of the RF exposure was based on simulations with heterogeneous model. The simulations showed that the distribution of the specific absorption rate (SAR) in the heterogeneous tissue model was really superficial, and maximum 10 g average SAR value might exceed the public exposure limit values. This value was determined to be 650 W/kg ± 38 % (k=2), meaning that when considering the public exposure limits, the treatment electrode can be held in one place for 1,1 seconds in head and trunk area and 2,2 seconds in limbs. The power measurement set-up can be used for getting more information on the appliances for surveillance use, but it still needs to be developed further to obtain more reliable estimations on the exposure of the device being measured

A Three – tier bio-implantable sensor monitoring and communications platform

One major hindrance to the advent of novel bio-implantable sensor technologies is the need for a reliable power source and data communications platform capable of continuously, remotely, and wirelessly monitoring deeply implantable biomedical devices. This research proposes the feasibility and potential of combining well established, ‘human-friendly' inductive and ultrasonic technologies to produce a proof-of-concept, generic, multi-tier power transfer and data communication platform suitable for low-power, periodically-activated implantable analogue bio-sensors. In the inductive sub-system presented, 5 W of power is transferred across a 10 mm gap between a single pair of 39 mm (primary) and 33 mm (secondary) circular printed spiral coils (PSCs). These are printed using an 8000 dpi resolution photoplotter and fabricated on PCB by wet-etching, to the maximum permissible density. Our ultrasonic sub-system, consisting of a single pair of Pz21 (transmitter) and Pz26 (receiver) piezoelectric PZT ceramic discs driven by low-frequency, radial/planar excitation (-31 mode), without acoustic matching layers, is also reported here for the first time. The discs are characterised by propagation tank test and directly driven by the inductively coupled power to deliver 29 μW to a receiver (implant) employing a low voltage start-up IC positioned 70 mm deep within a homogeneous liquid phantom. No batteries are used. The deep implant is thus intermittently powered every 800 ms to charge a capacitor which enables its microcontroller, operating with a 500 kHz clock, to transmit a single nibble (4 bits) of digitized sensed data over a period of ~18 ms from deep within the phantom, to the outside world. A power transfer efficiency of 83% using our prototype CMOS logic-gate IC driver is reported for the inductively coupled part of the system. Overall prototype system power consumption is 2.3 W with a total power transfer efficiency of 1% achieved across the tiers

Development of sensors and non-destructive techniques to determine the performance of coatings in construction

The primary objective of this work was to examine and develop techniques for monitoring the degradation of Organically Coated Steel (OCS) in-situ. This included the detection of changes associated with the weathering to both the organic coating and metallic substrate. Initially, a review of current promising techniques was carried out however many were found to be unsuitable for this application and the adaptation of current techniques and the development of new techniques was considered. A brief concept investigation, based on initial testing and considerations, was used to determine a number of sensing techniques to examine. These included embedded, Resonant Frequency Identification (RFID), Magnetic Flux Leakage (MFL) and dielectric sensing. Each of these techniques were assessed for the application, prototyped, and tested against a range of samples to determine the accuracy and sensitivity of degradation detection provided. A range of poorly and highly durable coated samples were used in conjunction with accelerated weathering testing for this aim. Track based electronic printed sensors were presented as both a cut edge corrosion tracking and coating capacitance measurement method. While suffering somewhat from electrical paint compatibility issues both concepts showed merit in initial trials however the capacitive sensor ultimately proved insufficiently responsive to coating changes. The embedded, progressive failure-based, cut edge corrosion sensor was produced and tested in modern coating systems with moderate success. Novel applications of RFID and MLF techniques were considered and proved capable of detecting large changes in substrate condition due to significant corrosion. However, there was a lack of sufficient sensitivity when considering early-stage corrosion of durable modern OCS products. Finally, it was shown that a chipless antenna could be designed and optimised for novelly monitoring the changes to the dielectric properties of a paint layer due to degradation. However, ultimately this test, due to equipment requirements, lent itself more to lab testing than in-situ. Due to some of these limitations a different approach was considered in which the environmental factors influencing degradation were examined with the aim of relating these to performance across a building. It was observed that a combination of high humidity and the build-up of aggressive natural deposits contributed to high degradation rates in sheltered regions, such as building eaves, where microclimates were created. The build-up of deposits and their effect was presented as a key degradation accelerant during in-use service. A unique numerical simulation approach was developed to predict the natural washing, via rain impact and characteristics of the building analysed. This approach showed promise for determining areas unlikely to be naturally washed, and therefore subjected to a degradation accelerating, build-up of deposits. Given these understandings coated wetness sensors were considered as a realistic live-monitoring device capable of determining deposit build up and ultimately OCS lifetime

Microfluidic microwave resonant sensors

Matter can be identified by its interaction with electromagnetic fields. This can be described by its dielectric and magnetic properties, which typically vary with respect to frequency in the microwave region. Microwave-frequency spectroscopy is capable of making non-contact, non-destructive, non-invasive and label-free measurements with respect to time. It can be used to characterise all states of matter and combinations thereof, such as colloids and microparticulate suspensions. Sensors based upon this technology therefore have great potential for (bio)chemical and industrial point-of-sampling applications where existing measurement techniques are insufficiently portable, low-cost or sensitive. Microfluidics is the manipulation of fluids within microscale geometries. This gives rise to phenomena not observed at the macroscale that can be exploited to achieve enhanced control of fluid flow. This means that microfluidic techniques can be used to perform complex chemistry in a completely sealed environment with minimal reagent consumption. Hence, microfluidics offers an ideal sample interfacing method for a microwave-frequency sensor. This work is concerned with developing novel, low-cost and highly sensitive probes that be easily integrated into a microfluidic device for performing on-chip sample preparation and diagnostics for generic (bio)chemical and industrial point-of-sampling applications. To this end, several novel microwave resonant structures were designed, optimised and integrated into microfluidic devices in order to characterise a variety of liquid-phase samples.EThOS - Electronic Theses Online ServiceGBUnited Kingdo