Future of smart cardiovascular implants

Cardiovascular disease remains the leading cause of death in Western society. Recent technological advances have opened the opportunity of developing new and innovative smart stent devices that have advanced electrical properties that can improve diagnosis and even treatment of previously intractable conditions, such as central line access failure, atherosclerosis and reporting on vascular grafts for renal dialysis. Here we review the latest advances in the field of cardiovascular medical implants, providing a broad overview of the application of their use in the context of cardiovascular disease rather than an in-depth analysis of the current state of the art. We cover their powering, communication and the challenges faced in their fabrication. We focus specifically on those devices required to maintain vascular access such as ones used to treat arterial disease, a major source of heart attacks and strokes. We look forward to advances in these technologies in the future and their implementation to improve the human condition

Design and Analysis of Printed Square Loop Antenna and Solenoidal Loop Antenna for Pill Shaped Bio-implants Object

This paper deals to design and investigated two proposed loop antenna for pill shaped bio-implants objects such as wireless capsule endoscopy. In additional it’s help in developing an understanding of how the fields decay with distance. The first proposed loop antenna is the planar printed square loop antenna with outer dimensions 9 mm and inner dimension 0.45 mm, 6 turns, width 0.5 mm and 0.25 mm of space which can be easily integrated with a system-on-chip technology. The second proposed loop antenna is the solenoidal loop antenna where the solenoid had 9 turns, a pitch of 1 mm and a radius of 5 mm and can be easily wound in the form of a coil and encased within the pill shaped object. For both antennas the electromagnetic field was solved at 1MHz. From the radiation patterns results it can be observe that the surrounding pattern gain around the antennas is constant and conform the omnidirectional pattern associated to such loop antennas that fit the capsule endoscopy randomly movement within the human body in different directions. The design simulations and results are performed and validated by using commercial High Frequency Structure HFSS software

Mid-range transformer based wireless power transfer system for low power devices

Wireless power transfer technique for biomedical devices has drawn great interest from many researchers in the biomedical domain. Biomedical devices can be powered up either by an external power cord or by batteries. However an external power cord may limit the mobility of a patient and batteries tend to have a very limited power capacity and these methods may pose a high risk of infection towards the patient. Therefore, a wireless power transfer system is proposed to solve the problem. This study attempts to develop a mid-range transformer based wireless power transmission system which is suitable to power biomedical devices. This includes the develop of a transmitter circuit, receiver circuit, a pair of transmitter and receiver coils and transformers. This study demonstrates that magnetic coupling technique is a reliable wireless charging technique biomedical devices due to its mid-range transmission and satisfactory efficiency. In order to reduce power loss, an impedance matching method which incorporates a step-up and step-down transformers in the transmitter and receiver circuit is proposed. This study also develops a wireless power charging system that does not emit harmful radiation towards the human body. The frequency for the system is within the range of 700 kHz to 900 kHz which is in accordance to the ICNIRP regulation. Three pairs of round-shaped transmitter and receiver coils pair have been designed and fabricated with the diameter size of 30cm, 40cm, and 50cm. The power supply and frequency generator are connected to the transmitter circuit and an oscilloscope is connected to the load of the receiver circuit. The performance results are recorded using a range from 4 centimeters to 110 centimeters and based on the tabulated results, the mid-range wireless power transfer system managed to supply a transfer efficiency of 60% at a distance of 35cm for the 30cm diameter coil, 62% at a distance of 43cm for the 40cm diameter coil and 46% at a distance of 50cm for the 50cm diameter coil

Design of High Efficiency Wireless Power Thansfer System With Nonlinear Resonator

Wireless power transfer technology (WPT) has been rapidly developed in recent years. The primary benefit of WPT is that it replaces the traditional wire charging with a cordless charging method. WPT technology has been applied in many fields, such as bio-implants, electric vehicles, and wirelessly charging systems. According to the different energy transmission mechanism, WPT technology can be divided into magnetic field coupling (includes magnetically coupled inductive and magnetically-coupled resonant), microwave radiation, laser emission, electrical-field coupling, and ultrasonic transmission type. Among these technologies, the magnetic resonance coupling method has a better promise because of its long transfer distance and high efficiency. However, there are some questions that need to be resolved, among which the most prominent is that the technology has a low tolerance to the variations of the coupling factor because of the frequency splitting phenomenon, which would lead to transmission efficiency degradation of magnetic resonance coupling WPT systems. Hence, based on reviewing the research status and trend of WPT technology, this paper analyses the frequency splitting phenomenon of the wireless power transfer system, discusses the duffing resonator circuit and its properties, and designs a kind of high-efficiency wireless power transfer inductive system with both non-linear inductors and non-linear capacitors. The main research works of this paper are as follows: Firstly, aiming at the frequency splitting problem during magnetic coupled resonance wireless power transmission, the frequency splitting phenomenon for the wireless power transfer system is studied by an electric circuit model method. The expression of the relationship between the load voltage, transmission efficiency, and coupling factor was derived, and the law of frequency splitting is discussed. Furtherly, an analysis of frequency splitting based on simulation also presented. Finally, the frequency splitting suppression method is proposed. The above research work provides a theoretical basis for solving the problem of frequency splitting and designing a kind of high-efficiency WPT system. Subsequently, a duffing resonator circuit with a nonlinear capacitor, which can eliminate the frequency splitting and keep the high transmission efficiency and power delivered to the load is developed. With the help MATLAB software, the properties of the duffing resonance circuit are discussed furtherly. The results show that the duffing resonance circuit has significantly wider bandwidth than the conventional linear resonance circuit while achieving a similar amplitude level. Finally, the high efficiency non-linear wireless power transfer system based on non-linear inductors with ferromagnetic thin film core and non-linear capacitors with ferroelectric thin film dielectrics is designed. Moreover, the system\u27s performance is improved, the range of coupling factors significantly extended while both load power and high PTE were maintained. The reason for the high efficiency of the system is furtherly discussed, and the research result shows that non-linear inductor with ferromagnetic thin film core has variable inductance which can be synchronously changed along with the current through the inductor in the circuit. The non-linear capacitor with ferroelectric thin film dielectrics can also have variable capacitance, which can be synchronously changed along with the voltage applied to the capacitor. However, the voltage across the capacitor and current through the inductors are different initially, high power transmission efficiency can be achieved by self-tuning capability of inductance and capacitance from the film based non-linear resonators. Research results of this paper can lay the solid foundations for the application of WPT technology in the fields of bio-implants, electric vehicles, wirelessly charging systems, etc

Power Management in Wireless Sensor Networks (WSNs)

This thesis was submitted for the award of Master of Philosophy and was awarded by Brunel University LondonThe wireless sensor network (WSN) is increasingly used in many areas nowadays. It can be applied to provide the solutions to environmental problems, help increasing security and safety systems, and make the detection of the problems more efficient, e.g. the earthquake or tidal wave, which will harmful to humans. The WNS is durable and resistant to all types of terrain and climate, but while the WSN system is more and more widespread, one of the obstacles hindering the growth of this technology and the demand for WSN applications is the limited battery lifespan. Consequently, there is a significant requirement for techniques for prolonging the battery’s lifespan. Therefore, one potential solution is to use alternative energy sources combined with the sensor nodes in WSN, specifically energy harvesting from existing environmental sources. This research project reviews the characteristics of each kind of energy harvesting, understanding the various energy sources (solar energy, vibration energy and wind power), including wireless power transfer (WPT) by using electromagnetic (EM) radiation energy transfer or RF radio-frequency emission and magnetic coupled energy transfer. They are adopted for extending node’s life in the WSN, based on published information. Then it compares these diverse alternative energy methods and identifies for the most suitable energy harvesting method for application to wireless sensor nodes in order to prolong the lifespan of the battery. The major findings from the researcher include that wireless power transfer energy harvesting (WPT) using the magnetic field is the most appropriate tool for extending the lifespan of the WSN system. In addition, the author also designed an experiment to test this alternative energy, achieving by modelling the wireless power transfer with four coils. From the experimental results, it can be seen that the WPT technique using energy harvesting with magnetic inductive source can be applied to prolong the lifespan of the WSN system

A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors

Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the <em>in vitro</em> part, including the energy transmitting circuit and resonant transmitter coils, and <em>in vivo</em> part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm<sup>3</sup>

Lokalisierung und freie Positionierung unter Verwendung eines kooperativen Multi-Spulensendesystems für die drahtlose Energieübertragung

With the continuous development of communication technology there are more and more portable devices requiring periodic charging with a cable and power socket. Wireless power transfer (WPT) technology provides a promising solution to overcome the inconvenience, potential safety hazard and unsightliness of power supply cables. The result of this thesis is a conceptual design for an optimized 100 kHz WPT system having a large charging pad allowing free placement of the device to be charged. The system has high efficiency and is Electromagnetic Compatibility friendly. The three-coil system, composed of a single transmitter coil and two coils in the receiver, is operating in series resonance and has been optimized by synthesis of the coupling coefficient and quality factor to provide maximum efficiency and power simultaneously. Unique to the proposed design is that the single transmitter coil is replaced with 4-coil structure which enables field forming to strengthen the field in the center of the 4-coil structure and reduce it at the margins. A transmitter matrix consisting of cooperative multiple coils is proposed to increase the charging pad area and reduce the external magnetic field. A 16 coils system is selected as most cost efficiency. The transmitter coil radius is optimized using the criterion of weighted overall efficiency, which results in high efficiency with minimal emission to the surroundings. During charging, the appropriate 4-coil structure is activated, depending on the device location, with the other coils turned off. Several algorithms are presented that enable localization of the receiver position including: grid search, Gauss-Newton and reflected impedance for combined coils. COMSOL simulation is used to investigate the effects of using ferrite, aluminum loading and a reactive resonant coil to improve system efficiency and reduce external fields below specified human exposure limits. This thesis provides a WPT solution for charging mobile and portable devices that has many advantages. The proposed 100 kHz 16 coils transmitter matrix WPT system, consisting of individually activated 4-coil sub structures, allows free placement within the charging area, more than 65% transfer efficiency at 10 cm transmission distance and electromagnetic field emission considerably less than required by guidelines.Mit fortschreitender Entwicklung der Kommunikationstechnik steigt die Anzahl tragbarer Geräte, die einen wiederholten Ladevorgang über ein Kabel benötigen, kontinuierlich. Drahtlose Energieübertragung (Wireless Power Transfer, WPT) umgeht die damit verbundenen Sicherheitsrisiken sowie die Unbequemlichkeiten und Unansehnlichkeit, die eine große Zahl an Ladekabeln mit sich bringt. Im Rahmen dieser Arbeit ist ein konzeptueller Entwurf für ein optimiertes 100 kHz WPT-System entstanden, welcher einen großen Ladebereich mit der Möglichkeit zur freien Platzierung des zu ladenden Gerätes erlaubt. Das System zeichnet sich durch eine hohe Effizienz und elektromagnetische Verträglichkeit aus. Ein Dreispulensystem, bestehend aus einer Sendespule und zwei Empfängerspulen in Serienresonanz, wird hinsichtlich Kopplungsfaktor und Gütefaktor optimiert. Die Sendespule wird durch eine 4-Spulen Struktur ersetzt, die eine Feldformung ermöglicht, so dass eine Verstärkung des Feldes im Zentrum der Struktur erreicht wird bei gleichzeitiger Abschwächung an den Rändern. Sendermatrizen aus kooperativen Mehrspulensystemen werden untersucht mit dem Ziel, die Fläche des Ladefeldes zu vergrößern und das externe magnetische Feld zu reduzieren. Ein System aus 16 Spulen wird als das mit dem besten Kosten-Effizienz Verhältnis identifiziert. Der Radius der Senderspulen wird nach einem Kriterium der gewichteten Gesamteffizienz optimiert. Ziel ist eine hohe Effizienz bei gleichzeitig minimalen Emissionen in die Umgebung. Beim Ladevorgang wird in Abhängigkeit von der Position des zu ladenden Geräts die passende 4-Spulen Struktur aktiviert während die übrigen deaktiviert bleiben. Zur Lokalisierung des Empfängers werden die Algorithmen Rastersuche, Gauss-Newton und reflektierte Impedanz für kombinierte Spulen vorgestellt. Zur Untersuchung der Effekte von Ferriten und Aluminium sowie reaktiver resonanter Spulen wurden Simulationen mit COMSOL durchgeführt, mit dem Ziel die Effizienz zu erhöhen und die externen Felder zu reduzieren, so dass die Grenzwerte für die menschliche Exposition unterschritten werden. Diese Arbeit liefert eine WPT-Lösung für das Laden mobiler und portabler Geräte welche zahlreiche Vorteile bietet. Das vorgeschlagene 100 kHz 16-Spulen Matrixsystem, bestehend aus individuell aktivierbaren 4-Spulen Teilstrukturen, ermöglicht eine freie Platzierung auf dem Ladebereich, mehr als 65 % Übertragungseffizient im Abstand von 10 cm sowie deutlich geringere Elektromagnetische Feld Emissionen als in den Richtlinien gefordert