Body Sensor Networks Guang-Zhong Yang (Ed.) Body Sensor Networks Foreword by Sir Magdi Yacoub With 274 Figures,32 in Full Color Guang-Zhong Yang,PhD Institute ofBiomedical Engineering and Department ofComputing, Imperial College London,UK British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library ofCongress Control Number:2005938358 ISBN-10:1-84628-272-1 ISBN-13:978-1-84628-272-0 Printed on acid-free paper © Springer-Verlag London Limited 2006 Apart from any fair dealing for the purposes of research or private study,or criticism or review,as permitted under the Copyright,Designs and Patents Act 1988,this publication may only be repro- duced,stored or transmitted,in any form or by any means,with the prior permission in writing of the publishers,or in the case ofreprographic reproduction in accordance with the terms oflicences issued by the Copyright Licensing Agency.Enquiries concerning reproduction outside those terms should be sent to the publishers. The use ofregistered names,trademarks,etc.,in this publication does not imply,even in the absence ofa specific statement,that such names are exempt from the relevant laws and regulations and there- fore free for general use. The publisher makes no representation,express or implied,with regard to the accuracy ofthe infor- mation contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. Printed in the United States ofAmerica (MVY) 9 8 7 6 5 4 3 2 1 Springer Science+Business Media springer.com Foreword Advances in science and medicine are closely linked; they are characterised by episodic imaginative leaps, often with dramatic effects on mankind and beyond. The advent of body sensor networks represents such a leap. The reason for this stems from the fact that all branches of modern medicine, ranging from prevention to complex intervention, rely heavily on early, accurate, and complete diagnosis followed by close monitoring of the results. To date, attempts at doing this consisted of intermittent contact with the individual concerned, producing a series of snapshots at personal, biochemical, mechanical, cellular, or molecular levels. This was followed by making a series of assumptions which inevitably resulted in a distortion of the real picture. Although the human genome project has shown that we are all “equal”, it confirmed the fact that each one of us has unique features at many levels, some of which include our susceptibility to disease and a particular response to many external stimuli, medicines, or procedures. This has resulted in the concept of personalised medicines or procedures promised to revolutionise our approach to healthcare. To achieve this, we need accurate individualised information obtained at many levels in a continuous fashion. This needs to be accomplished in a sensitive, respectful, non-invasive manner which does not interfere with human dignity or quality of life, and more importantly it must be affordable and cost-effective. This book about body sensor networks represents an important step towards achieving these goals, and apart from its great promise to the community, it will stimulate much needed understanding of, and research into, biological functions through collaborative efforts between clinicians, epidemiologists, engineers, chemists, molecular biologists, mathematicians, health economists, and others. It starts with an introduction by the editor, providing a succinct overview of the history of body sensor networks and their utility, and sets the scene for the following chapters which are written by experts in the field dealing with every aspect of the topic from design to human interaction. It ends with a chapter on the future outlook of this rapidly expanding field and highlights the potential opportunities and challenges. This volume should act as a valuable resource to a very wide spectrum of readers interested in, or inspired by, this multifaceted and exciting topic. Professor Sir Magdi Yacoub November 2005 London Acknowledgments I would like to express my sincere thanks to all contributing authors to this volume. Without their enthusiasm, support, and flexibility in managing the tight publishing schedule, this book would not have become possible. I am grateful to members of the pervasive computing team of the Department of Computing, and the Institute of Biomedical Engineering of Imperial College London for all their help throughout the preparation of this book. In particular, I would like to thank Su-Lin Lee, Benny Lo, Surapa Thiemjarus, and Fani Deligianni for all their hard work in providing essential editorial support, as well as being actively involved in the preparation of some of the chapters. My special thanks go to James Kinross and Robert Merrifield for their kind help with the graphical illustrations. I would also like to thank the editorial staff of Springer, the publisher of this volume. In particular, I am grateful to Helen Callaghan and her colleagues in helping with the editorial matters. This work would not have been possible without the financial support from the following funding bodies: • The Department of Trade and Industry, UK • The Engineering and Physical Sciences Research Council, UK • The Royal Society • The Wolfson Foundation Their generous support has allowed us to establish and promote this exciting field of research – a topic that is so diversified, and yet brings so many challenges and innovations to each of the disciplines involved. Guang-Zhong Yang November 2005 London About the Editor Guang-Zhong Yang, BSc, PhD, FIEE Chair in Medical Image Computing, Imperial College London, UK Guang-Zhong Yang received PhD in Computer Science from Imperial College London and served as a senior and then principal scientist of the Cardiovascular Magnetic Resonance Unit of the Royal Brompton Hospital prior to assuming his current full-time academic post at the Department of Computing, Imperial College London. The department was rated 5* at the last RAE (research quality assessment) and has been placed among the top ten departments worldwide by several academic surveys. Professor Yang’s main research interests are focussed on medical imaging, sensing, and robotics. He received a number of major international awards including the I.I. Rabi Award from the International Society for Magnetic Resonance in Medicine (ISMRM) and the Research Merit Award from the Royal Society. He is a Fellow of the IEE, Founding Director of the Royal Society/Wolfson Medical Image Computing Laboratory at Imperial College, co- founder of the Wolfson Surgical Technology Laboratory, Chairman of the Imperial College Imaging Sciences Centre, and Director of Medical Imaging, the Institute of Biomedical Engineering, Imperial College London. Contents Foreword v Acknowledgments vii About the Editor ix Contributors xix List of Acronyms xxi 1 Introduction 1 Omer Aziz, Benny Lo, Ara Darzi, and Guang-Zhong Yang 1.1 Wireless Sensor Networks 1 1.2 BSN and Healthcare 4 1.2.1 Monitoring Patients with Chronic Disease 6 1.2.2 Monitoring Hospital Patients 7 1.2.3 Monitoring Elderly Patients 9 1.3 Pervasive Patient Monitoring 10 1.4 Technical Challenges Facing BSN 13 1.4.1 Improved Sensor Design 13 1.4.2 Biocompatibility 14 1.4.3 Energy Supply and Demand 15 1.4.4 System Security and Reliability 16 1.4.5 Context Awareness 18 1.4.6 Integrated Therapeutic Systems 19 1.5 Personalised Healthcare 20 1.6 Finding the Ideal Architecture for BSN 22 1.7 The Future: Going from “Micro” to “Nano” 27 1.8 The Scope of the Book 30 References 34 2 Biosensor Design and Interfacing 41 Bhavik A. Patel, Costas A. Anastassiou, and Danny O’Hare 2.1 Introduction 41 2.1.1 What Is a Biosensor? 42 xii Body Sensor Networks 2.2 How Do Electrochemical Devices Work? 44 2.2.1 Potentiometric Devices 45 2.2.2 Amperometry and Voltammetry 53 2.3 Instrumentation 65 2.3.1 Potentiometry 65 2.3.2 Amperometry and Voltammetry 66 2.3.3 Reference and Counter Electrodes 68 2.4 Photoelectrochemistry and Spectroelectrochemistry 69 2.5 Biocompatibility 71 2.5.1 Sensor Fouling 71 2.5.2 Tissue Damage 73 2.6 Novel Approaches to Handling Sensor Data 73 2.7 Conclusions 80 Acknowledgments 82 References 82 3 Protein Engineering for Biosensors 89 Anna Radomska, Suket Singhal, and Tony Cass 3.1 Introduction 89 3.1.1 Electrochemical Sensors 90 3.1.2 Optical Sensors 91 3.1.3 Gravimetric Sensors 92 3.1.4 Consuming and Non-Consuming Biosensors 92 3.2 Protein Engineering 93 3.2.1 The Signal Transduction Module 95 3.2.2 The Recognition Site Module 97 3.2.3 Immobilisation Module 100 3.3 Biocompatibility and Implantation 102 3.4 Conclusions 109 References 109 4 Wireless Communication 117 Henry Higgins 4.1 Introduction 117 4.2 Inductive Coupling 118 4.3 RF Communication in Body 119 4.4 Antenna Design 121 4.5 Antenna Testing 125 4.5.1 Antenna Impedance and Radiation Resistance Measurement 125 4.5.2 Quarter Wave Line Impedance Measurement 126 4.6 Matching Network 128 4.6.1 Transmitter Tuning 128 Contents xiii 4.6.2 The L Network 130 4.6.3 The (cid:652) Network 131 4.6.4 The T and (cid:652) -L Networks 132 4.6.5 Parasitic Effects 133 4.6.6 Network Choice 134 4.6.7 Radio Frequency Losses in Components and Layout Issues 135 4.6.8 Receiver Tuning 135 4.6.9 Base Station Antennas 136 4.7 Propagation 136 4.8 Materials 137 4.9 Environment 138 4.10 External Transceiver (Base Station) 138 4.11 Power Considerations 139 4.11.1 Battery Challenges 140 4.12 Defibrillation Pulse 141 4.13 Link Budget 142 4.14 Conclusions 142 References 143 5 Network Topologies, Communication Protocols, and Standards 145 Javier Espina, Thomas Falck, and Oliver Mülhens 5.1 Network Topologies 145 5.2 Body Sensor Network Application Scenarios 148 5.2.1 Stand-Alone Body Sensor Networks 148 5.2.2 Global Healthcare Connectivity 149 5.2.3 Pervasive Sensor Networks 150 5.3 Wireless Personal Area Network Technologies 152 5.3.1 Overview 152 5.3.2 The Wireless Regulatory Environment 153 5.3.3 Wireless Communication Standards 155 5.3.4 IEEE 802.15.1: Medium-Rate Wireless Personal Area Networks 155 5.3.5 IEEE P802.15.3: High-Rate Wireless Personal Area Networks 158 5.3.6 IEEE 802.15.4: Low-Rate Wireless Personal Area Networks 160 5.3.7 ZigBee 164 5.3.8 Comparison of Technologies 168 5.4 Practical Experiences with IEEE 802.15.4 169 5.5 Healthcare System Integration 174 5.5.1 Existing Interoperability Standards 174 5.5.2 Wireless Interoperability Standards Under Development 176 5.6 Conclusions 177 References 180 xiv Body Sensor Networks 6 Energy Scavenging 183 Eric Yeatman and Paul Mitcheson 6.1 Introduction 183 6.1.1 Sensor Node Power Requirements 184 6.1.2 Batteries and Fuel Cells for Sensor Nodes 185 6.1.3 Ambient Energy Sources 186 6.2 Architectures for Inertial Energy Scavenging 187 6.2.1 Energy Extraction Mechanisms for Inertial Generators 187 6.2.2 Performance Limits 191 6.3 Fabrication and Testing 195 6.3.1 Device Fabrication and Structure 195 6.3.2 Device Testing 197 6.4 Module Design and Simulation 200 6.4.1 System Modelling 200 6.4.2 Integrated Simulation 204 6.5 Power Electronics and System Effectiveness 205 6.5.1 Power Electronics Requirements and Trade-Offs 205 6.5.2 Semiconductor Device Design 209 6.5.3 Coherent Simulation 211 6.6 Discussion and Conclusions 213 6.6.1 What Is Achievable in Body-Sensor Energy Scavenging? 213 6.6.2 Future Prospects and Trends 215 References 216 7 Towards Ultra-Low Power Bio-Inspired Processing 219 Leila Shepherd, Timothy G. Constandinou, and Chris Toumazou 7.1 Introduction 219 7.2 Bio-Inspired Signal Processing 220 7.3 Analogue vs Digital Signal Processing 221 7.3.1 Quantised Data/Time vs Continuous Data/Time 221 7.3.2 Analogue/Digital Data Representation 222 7.3.3 Linear Operations 223 7.3.4 Non-Linear Operations 224 7.3.5 Hybrid System Organisation 224 7.4 CMOS-Based Biosensors 225 7.4.1 Ion-Sensitive Field-Effect Transistor (ISFET) 227 7.4.2 ISFET-Based Biosensors 229 7.4.3 Towards Biochemically Inspired Processing with ISFETs 230 7.5 Applications of Ultra-Low Power Signal Processing for BSN 234 References 236