Introduction – Implantable Sensor Systems for Medical Applications

Introduction

Andreas Inmann, PhD, MBA,     Cleveland, Ohio, USA

Diana Hodgins, PhD, MBE,     Codicote, UK

The rapid changes we are seeing in society today regarding sophisticated medical treatments using active implantable medical devices would not be achievable without important recent developments. Implantable systems to restore function and for monitoring medical conditions are made possible by new material compositions, advancements in processing technologies at the micro- and nanoscale, and greater knowledge of how the human body reacts to implanted foreign bodies. As we live longer and expect to maintain sight, hearing, movement and other body functions, medical technology development needs to keep advancing to meet the ever-increasing demand. Consequently, there is considerable amount of research and development worldwide in the area of implantable systems. Much of this work is done by small and medium-sized companies who are often specialists in one area and do not have the knowledge of all related topics and fields necessary to produce a fully implantable system. Furthermore, information produced by academic programmes or within various research groups is often not published and, therefore, not easily accessible.

Implantable systems need to be small, lightweight and sealed from the harsh environment of the human body. These systems should also consume very little power to allow for long-term operation, and they need to provide for data transmission to and from the implanted device. Developing such sophisticated implantable systems requires an incredible amount of in-depth knowledge and expertise in a multitude of fields such as materials, electronics, signal processing, chemistry, biology, physiology, etc.

This book contains a series of individual monographs providing a wide-ranging overview of important aspects, challenges and recent developments in the area of implantable systems, focusing on sensor-based systems. To provide a comprehensive review, we have asked experts in both academia and industry to contribute. The book is organised into three parts discussing first the fundamentals and then the challenges of developing implantable systems, concluding with examples of current and novel medical applications of implantable sensor systems.

Part I provides an overview of the core technologies that are fundamental to implantable systems, applicable for both sensor and actuator systems. This part describes how the appropriate choice of materials dictates device reliability and the human body’s interaction with the implanted device. Various newly developed materials are discussed, and assembly, coating and packaging techniques for implantable devices, particularly at the micro- and nanoscale, are reviewed. Further, fabrication methods for complex multi-electrode arrays and novel implantable power sources fuelled by glucose are presented.

Part II discusses challenges that one faces during the development of implantable systems, critical aspects during operation, considerations of the regulatory framework and the pathway to the market. Rigorous measures have to be implemented to ensure that the foreign-body reaction of an implantable device is minimised, the device is sterilised properly and data is transmitted securely to and from the implant. Further, the implantable system needs to be developed and tested according to national and worldwide standards and conform to regulatory restrictions that ensure safe operation of the device and that no harm is done to the user.

Part III reviews various applications of implantable systems, concentrating on how all the materials, technologies and processes are integrated and tested, as well as how challenges can be overcome. In vivo MEMS sensors/actuators, electrodes for recording of nerve signals, use of sensors for control and feedback in motor neuroprostheses, implantable device networks and a complete system replacing a very important physiological sensor – the retina of the eye – are discussed in great detail. Many of these applications have seen recent, dramatic development, and they represent some of the most promising implementations of implantable technology.

An incredible amount of knowledge has been amassed in the field of implantable systems; this extraordinarily multidisciplinary field provides for challenging development and has experienced exciting progress. With this book, we aim to provide those interested in developing implantable systems, particularly sensor-based systems, with information on materials and processes that are suitable for implants, how to address the issue of biocompatibility and how to navigate the challenges of product development. The book discusses some of the R&D activities in current and emerging areas carried out with European and American funding, and it provides concrete examples for the different components, processes and total system solutions. Each chapter of the book contains a large number of specific references and other sources to provide further guidance and information for all aspects of implantable systems.

We would like to express our sincerest gratitude and appreciation to the contributing authors and the staff at Woodhead Publishing without whom this book would not have been possible.