Sensors - Overview

Sensor research has always been a very dynamic area. We have gone a long way since the primary form of sensor, litmus paper, was first made for crude pH measurements. Since the mid-1980s, there has been an explosion of research interests in sensor development as witnessed by the overwhelming amount of papers published during this period. Sensor research has always been driven by commercial needs. It is also an area that crosses over several developing areas, and has benefited by the advances in material sciences, engineering, and affordable computer technology. Consequently, in recent years, there is huge diversity of sensors available in the market place that covers industrial, environmental, and clinical applications. Yet, despite the large amounts of capital and human resources invested in the development of new devices, the best sensor commercially available is probably still the pH glass electrode in terms of its selectivity, sensitivity, dynamic range, response time, robustness, and ease of manufacture. The big successes in commercial terms since the late 1950s have been, in the chemical sector, the oxygen electrode based on the Clark cell, the fluoride electrode and ion-selective electrodes (ISEs) used in clinical analyzers, and the solid-state oxygen sensors based on zirconium oxide (ZrO₂) and titanium oxide (TiO₂) used in automobile air-to-fuel control; whereas more recently in the biosensor sector, the various glucose sensors based on glucose oxidase and the pregnancy test strips have been successful. There are clear advantages in using sensors in field (or in vitro) applications compared to conventional analytical....