viii The danger is that the result so obtained may be an experimental artifact. Another approach is to examine in as much detail as possible the principles underlying the operation of a new device. This may not lead to a new sensor immediately, but those developed along these lines tend to be more reliable. The accent in this book is therefore on the principles behind the operation ("e;the trade"e;) rather than on a description of applications ("e;the tricks of the trade"e;) of individual sensors. In this respect it is written for students at both graduate and upper undergraduate levels. Approximately one semester's worth of material is presented. The book may also be useful for scientists and engineers involved in the development of new types of chemical sensors or for those who discover that "e;somebody else's sensor just does not work as it should"e; and wish to know why. The book is divided into five sections dealing with the four principal modes of transduction: thermal, mass, electrochemical, and optical, as well as a general introduction common to the four types. I have included five appendixes, which are intended as a quick reference for readers who may not possess sufficient background in some areas covered in the main text. I have run out of symbols in both the Latin and Greek alphabets. In order to avoid confusion and ambiguity I have confined the use of a set of symbols to each chapter and provided glossaries at the end of each chapter.

viii The danger is that the result so obtained may be an experimental artifact. Another approach is to examine in as much detail as possible the principles underlying the operation of a new device. This may not lead to a new sensor immediately, but those developed along these lines tend to be more reliable. The accent in this book is therefore on the principles behind the operation ("e;the trade"e;) rather than on a description of applications ("e;the tricks of the trade"e;) of individual sensors. In this respect it is written for students at both graduate and upper undergraduate levels. Approximately one semester's worth of material is presented. The book may also be useful for scientists and engineers involved in the development of new types of chemical sensors or for those who discover that "e;somebody else's sensor just does not work as it should"e; and wish to know why. The book is divided into five sections dealing with the four principal modes of transduction: thermal, mass, electrochemical, and optical, as well as a general introduction common to the four types. I have included five appendixes, which are intended as a quick reference for readers who may not possess sufficient background in some areas covered in the main text. I have run out of symbols in both the Latin and Greek alphabets. In order to avoid confusion and ambiguity I have confined the use of a set of symbols to each chapter and provided glossaries at the end of each chapter.