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

A critical review of recent progress in mid-range wireless power transfer

Starting from Tesla’s principles of wireless power transfer a century ago, this critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into (i) the maximum power transfer and (ii) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the 2-coil systems, the 4-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the 2-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the 4-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (< 50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load.published_or_final_versio

Multi-megahertz IPT systems for biomedical devices applications

This paper investigates the main design constraints for the optimisation of an inductive power transfer (IPT) link for recharging implantable medical devices [1], and presents the potential advantages of operating in the multi-MHz range for such applications. The design proposed in this paper offers a fast charging solution, allowing patients to recharge their active medical implants every 4-5 years for 40% of its battery capability. The main challenge consists of obtaining good coupling and effective Q factor of the receiver coil, while minimizing the overall increase in size of the medical implant. Analysis obtained through electromagnetic simulations with CST Studio Suite for a 13.56 MHz, 1 W system suggests that it is possible to achieve a relatively high theoretical link efficiency of 66%, while keeping surface temperature increases and specific absorption rate (SAR) within the limits established in EN 45502 [2] and ICNIRP 1998 [3]. The experimental results show two feasible systems with different separation distances between the device's metallic case and the receiver coil, achieving transfer efficiencies [11] of 41% and 53% for separations of 1 mm and 7 mm, respectively

Applications of Wireless Power Transfer in Medicine : State-of-the-Art Reviews

Magnetic resonance within the field of wireless power transfer has seen an increase in popularity over the past decades. This rise can be attributed to the technological advances of electronics and the increased efficiency of popular battery technologies. The same principles of electromagnetic theory can be applied to the medical field. Several medical devices intended for use inside the body use batteries and electrical circuits that could be powered wirelessly. Other medical devices limit the mobility or make patients uncomfortable while in use. The fundamental theory of electromagnetics can improve the field by solving some of these problems. This survey paper summarizes the recent uses and discoveries of wireless power in the medical field. A comprehensive search for papers was conducted using engineering search engines and included papers from related conferences. During the initial search, 247 papers were found then non-relevant papers were eliminated to leave only suitable material. Seventeen relevant journal papers and/or conference papers were found, then separated into defined categories: Implants, Pumps, Ultrasound Imaging, and Gastrointestinal (GI) Endoscopy. The approach and methods for each paper were analyzed and compared yielding a comprehensive review of these state of the art technologies

Remote Powering and Communication of Implantable Biosensors Through Inductive Link

Nowadays there is an increasing interest in the field of implantable biosensors. The possibility of real-time monitoring of the human body from inside paves the way to a large number of applications and offers wide opportunities for the future. Within this scenario, the i-IronIC project aims to develop an implantable, low cost, health-care device for real-time monitoring of human metabolites. The contribution of this research work to the i-IronIC project consists of the design and realization of a complete platform to provide power, data communication and remote control to the implantable biosensor. High wearability of the transmitting unit, low invasivity of the implanted electronics, integration of the power management module within the sensor, and a reliable communication protocol with portable devices are the key points of this platform. The power is transmitted to the implanted sensor by exploiting an inductive link. Simulations have been performed to check the effects of several variables on the link performance. These simulations have finally confirmed the possibility to operate in the low megahertz range, where tissue absorption is minimum, even if a miniaturized receiving inductor is used. A wearable patch has been designed to transmit power through the body tissues by driving an external inductor. The same inductive link is used to achieve bidirectional data communication with the implanted device. The patch, named IronIC, is powered by lithium-ion polymer batteries and can be remotely controlled by means of a dedicated Android application running on smartphones and tablets. Long-range communication between the patch and portable devices is performed by means of Bluetooth protocol. Different typologies of receiving inductors have been designed to minimize the size of the implantable device and reduce the discomfort of the patience. Multi-layer, printed spiral inductors and microfabricated spiral inductors have been designed, fabricated and tested. Both the approaches involve a sensibly smaller size, as compared to classic “pancake” inductors used for remote powering. Furthermore, the second solution enables the realization of the receiving inductor directly on the silicon substrate hosting the sensor, thus involving a further miniaturization of the implanted device. An integrated power module has been designed and fabricated in 0.18 μm CMOS technology to perform power management and data communication with the external patch. The circuit, to be merged with the sensor readout circuit, consists of an half-wave voltage rectifier, a low-dropout regulator, an amplitude demodulator and a load modulator. The module receives the power from the implanted inductor and provides a stable voltage to the sensor readout circuit. Finally, the amplitude demodulator and the load modulator enable short-range communication with the patch

A high power CMOS class-D amplifier for inductive-link medical transmitters

Powering of medical implants by inductive coupling is an effective technique, which avoids the use of bulky implanted batteries or transcutaneous wires. On the external unit side, class-D and class-E power amplifiers (PAs) are conventionally used thanks to their high efficiency at high frequencies. The initial specifications driving this work require the use of multiple independent stimulators, which imposes serious constraints on the area and functionality of the external unit. An integrated circuit class-D PA has been designed to provide both small area and enhanced functionality, the latter achieved by the addition of an on-chip phased-locked loop (PLL), a dead-time generator and a phase detector. The PA has been designed in a 0.18μm CMOS high-voltage process technology and occupies an area of 9.86 mm2. It works at frequencies up to 14 MHz and 30 V supply and efficiencies higher than 80% are obtained at 14 MHz. The PA is intended for a closed-loop transmitter system that optimises power delivery to medical implants

A Novel Power-Efficient Wireless Multi-channel Recording System for the Telemonitoring of Electroencephalography (EEG)

This research introduces the development of a novel EEG recording system that is modular, batteryless, and wireless (untethered) with the supporting theoretical foundation in wireless communications and related design elements and circuitry. Its modular construct overcomes the EEG scaling problem and makes it easier for reconfiguring the hardware design in terms of the number and placement of electrodes and type of standard EEG system contemplated for use. In this development, portability, lightweight, and applicability to other clinical applications that rely on EEG data are sought. Due to printer tolerance, the 3D printed cap consists of 61 electrode placements. This recording capacity can however extend from 21 (as in the international 10-20 systems) up to 61 EEG channels at sample rates ranging from 250 to 1000 Hz and the transfer of the raw EEG signal using a standard allocated frequency as a data carrier. The main objectives of this dissertation are to (1) eliminate the need for heavy mounted batteries, (2) overcome the requirement for bulky power systems, and (3) avoid the use of data cables to untether the EEG system from the subject for a more practical and less restrictive setting. Unpredictability and temporal variations of the EEG input make developing a battery-free and cable-free EEG reading device challenging. Professional high-quality and high-resolution analog front ends are required to capture non-stationary EEG signals at microvolt levels. The primary components of the proposed setup are the wireless power transmission unit, which consists of a power amplifier, highly efficient resonant-inductive link, rectification, regulation, and power management units, as well as the analog front end, which consists of an analog to digital converter, pre-amplification unit, filtering unit, host microprocessor, and the wireless communication unit. These must all be compatible with the rest of the system and must use the least amount of power possible while minimizing the presence of noise and the attenuation of the recorded signal A highly efficient resonant-inductive coupling link is developed to decrease power transmission dissipation. Magnetized materials were utilized to steer electromagnetic flux and decrease route and medium loss while transmitting the required energy with low dissipation. Signal pre-amplification is handled by the front-end active electrodes. Standard bio-amplifier design approaches are combined to accomplish this purpose, and a thorough investigation of the optimum ADC, microcontroller, and transceiver units has been carried out. We can minimize overall system weight and power consumption by employing battery-less and cable-free EEG readout system designs, consequently giving patients more comfort and freedom of movement. Similarly, the solutions are designed to match the performance of medical-grade equipment. The captured electrical impulses using the proposed setup can be stored for various uses, including classification, prediction, 3D source localization, and for monitoring and diagnosing different brain disorders. All the proposed designs and supporting mathematical derivations were validated through empirical and software-simulated experiments. Many of the proposed designs, including the 3D head cap, the wireless power transmission unit, and the pre-amplification unit, are already fabricated, and the schematic circuits and simulation results were based on Spice, Altium, and high-frequency structure simulator (HFSS) software. The fully integrated head cap to be fabricated would require embedding the active electrodes into the 3D headset and applying current technological advances to miniaturize some of the design elements developed in this dissertation