6.1. Introduction

The world in which we live is rapidly becoming dominated by digital information. Initially, the digital revolution primarily involved stand-alone computers that gradually became networked. More recently, the merging of computing with wireless communications systems has led to an enormous growth in accessibility to, and hence demand for, this information. At present, this demand is dominated by a mixture of text, audio and image-based data driven mainly by almost ubiquitous accessibility to the internet. However, the "web" communications that has been assembled over the past decade will fuel demand for more sources of information and data about important aspects of our lives - our health, our environment, our food, our work. Sensors provide portals between the "real" or analogue world in which we live, and the digital world of computers and modern communications systems. They make it possible for us to obtain real time information about things we can see, touch, smell and hear, and about other things that we cannot detect - things that can be harmful or beneficial to us.

A chemical or biological sensor works by emitting a signal (typically a voltage or current) in response to an event such as binding between two molecules. This event typically involves a chemo- or bio-receptor (e.g. macrocyclic ligand, enzyme or antibody) binding with a specific target molecule in a sample, known as the "analyte". The electronic signal is passed to a circuit where it is digitized by an analog-to-digital converter or ADC...