**Meet the editor**

Mickaël Lallart graduated from Institut National des Sciences Appliquées de Lyon (INSA Lyon), Lyon, France, in Electrical Engineering in 2006, and received his Ph.D. in Electronics, Electrotechnics, and Automatics from the same university in 2008, where he worked for the Laboratoire de Génie Electrique et Ferroélectricité (LGEF). After working as a post-doctoral fellow in the

Center for Intelligent Material Systems and Structures (CIMSS) in Virginia Tech, Blacksburg, VA, USA in 2009, Dr. Lallart has been hired as an Associate Professor in the Laboratoire de Génie Electrique et Ferroélectricité. His current field of interest focuses on electroactive materials and their applications, vibration damping, energy harvesting and Structural Health Monitoring, as well as autonomous, self-powered wireless systems.

## Contents

#### **Preface** XI


Yu-Jen Wang, Sheng-Chih Shen and Chung-De Chen

X Contents


## Preface

The proliferation of low-power and ultralow-power electronics has enabled a rapid growth of autonomous devices that ranges from consumer electronics and nomad devices to autonomous sensors and sensor networks used in industrial and military environments. Hence, a wide range of application domains has been impacted by such technologies (aeronautic, civil engineering, biomedical engineering, home automation, etc.). Although batteries have initially promoted the spreading of these autonomous devices thanks to their relatively high energy capacity, they have become a break in the development of such systems especially when dealing with "left-behind" (or "place and forget") sensors or when these apparatus are deployed in large number (e.g., autonomous electrical switches). The main issues raised by primary batteries lie in the associated maintenance problems for replacement caused by their limited lifespan as well as environmental concerns as their recycling process is quite delicate. Therefore, an alternative solution has to be found.

Over the last decade, both the scientific and industrial communities have been interested in using ambient energy sources for supplying these low-power electronic systems, leading to the concept of "energy harvesting" or "energy scavenging", where the power is directly delivered by microgenerators that are able to convert ambient energy into electrical energy. Many sources from the near environment of the device can be found, for instance vibrations, electromagnetic radiations, photonic radiations, temperature gradients, heat fluctuations, and so on, and many conversion effects can be used with each of the above mentioned sources (piezoelectricity, electromagnetism, electrostatic, electrostriction, pyroelectricity, Seebeck effect…). However, dimension constraints are a challenging concern and the design of efficient microgenerators able to efficiently convert available energy from their environment and to provide enough power to the circuit is still an open issue.

Hence, the purpose of this book is to provide an up-to-date view of latest research advances in the design of efficient small-scale energy harvesters through contributions of internationally recognized researchers. The book covers the physics of the energy conversion, the elaboration of electroactive materials and their application to the conception of a complete microgenerator, and is organized according to the input energy source. Therefore, Section 1 covers the principles and application of energy harvesting from photonic through the use of fuel cells. Section 2 deals with thermal

#### XII Preface

energy harvesting, using either thermoelectric materials (Chapter 2) or dielectric approach featuring electroactive polymers (Chapter 3). Finally, Section 3 exposes the use of vibrations as energy input of the harvester. This section is subdivided into two subsections, the first one being devoted to the available conversion mechanisms for converting mechanical energy into electricity, using electrostatic coupling (Chapters 4- 5), piezoelectricity (Chapter 6), electromagnetism (Chapter 7) or electrostriction (Chapter 8). The second part of this section aims at presenting new techniques for efficiently harvesting mechanical energy, either by enlarging and/or matching the frequency band (Chapter 9-13) or by artificially increasing the coupling between the mechanical and electrical domains (Chapter 14), through the use of nonlinear approaches.

I sincerely hope you will find this book as enjoyable to read as it was to edit, and that it will help your research and/or give new ideas in the wide field of energy harvesting.

Finally, I would like to take the opportunity of writing this preface to thank all the authors for their high quality contributions, as well as the InTech publishing team (and especially the book manager, Ms. Silvia Vlase) for their outstanding support.

> **Dr. Mickaël Lallart** Laboratoire de Génie Electrique et Ferroélectricité, LGEF, INSA Lyon, France

**Section 1** 

## **Photonic**

**Chapter 1** 
