Beginning with a comprehensive survey of existing semiconductor-based chemical microsensors and microsystems, this book proceeds to describe in detail CMOS technology-based chemical microsensor systems. The benefits of using CMOS technology for developing chemical microsensor systems and, in particular, monolithically integrated sensor systems comprising transducers and associated circuitry are laid out. Several successful realizations of such microsensor systems are presented. First, the fundamentals of the chemical sensing process itself will be elucidated, followed by a short description of microfabrication techniques and the CMOS substrate. Thereafter, a comprehensive overview of semiconductor-based and CMOS-based transducer structures and their applications is given. It is shown that CMOS-technology can be successfully used as platform technology to integrate microtransducers with the necessary driving and signal conditioning circuitry, and, in a next step, to develop monolithic multisensor arrays and fully developed microsystems with on-chip sensor control and standard interfaces. The book concludes with a brief outlook to future developments, such as interfacing cells with CMOS microelectronics.

The two major areas of research described in this thesis are the design and fabrication of a chemical sensor for the detection of trace metals and a biosensor for iodide determination. The link connecting both areas is transduction technique, which is electrochemical in both instances. Chapter 1 serves as an introduction to some of the background theory necessary for the work carried out later in this thesis. It introduces the theory of electrochemistry, especially voltammetry and potentiometry, as well as providing an extensive literature review on work carried out to date on the development of reliable and reproducible reference electrodes. Chapter 2 describes work on the fabrication of miniaturised solid state silver/silver chloride reference electrodes on both plastic and silicon substrates. A study of two different types with respect to preparation and performance is then described. Chapter 3 focuses on the development of an environmental monitoring system for trace metals using anodic stripping voltammetry. The motivation behind this work was the increasing pressure on industry and regulatory bodies to monitor the discharge of trace metals into the acquatic environment. Chapter 4 contains work carried out into the preparation of an amperometric enzymatic biosensor, using the enzyme lactoperoxidase (LPOD) for the detection of iodide.

Silicon microelectrode arrays for in situ environmental monitoring have been successfully developed in this work. Meniscus etching was used to sharpen these cantilevered probes. Microelectrodes with solid tips were fabricated for oxidation-reduction potential (ORP) measurements. Microelectrodes with recessed tips were fabricated for future developments of ion selective electrodes. Both microelectrode types were fully characterized with standard and reference solutions as recommended by the American Society for Testing and Materials (ASTM). The silicon microelectrodes have substantially smaller sensing areas (m vs. cm) than their current commercial counterparts and exhibit significantly faster response times (milliseconds vs. minutes). Further, the sensors are robust due to redundant array configuration and the material strength of silicon. In the long term, we envision the use of these new sensors for field-based in situ monitoring in ground water quality and bioremediation applications.