Analysis systems for the detection of ammonia based on micromachined components modular hybrid versus monolithic integrated approach

This paper presents two miniaturized analysis systems for measurement of the ammonia concentration in aqueous solutions. Both systems are based on identical micromachined components. In the first system the components are integrated on one chip, thus literally forming a "lab-on-a-chip". The second system uses the components as separate dies assembled in or on a printed circuit board (PCB) and connected via a micromachined fluidic channel plate. The latter modular system provides easy replacement of components, either to replace a malfunctioning component or to upgrade a component to an improved version. Additionally, replacement of modules enables a change in the functionality of the system in order to perform a different chemical analysis. With the monolithic and the modular system measurement of concentrations in the range 10-20 mM, respectively, 5.6-560 muM were demonstrated. With this paper, the authors intend to show that both the integrated as well as the modular approach of making a micromachined analytical system can result in working systems. Though the chemical behavior of both systems were not fully explored, it is made clear that both approaches can successfully be used for chemical analysis purposes. (C) 2003 Elsevier Science B.V. All rights reserved.