TABLE OF CONTENTS In this chapter, we come to the very purpose of biochips. So far, we have dealt with the principles of microfluidic transport of macromolecules or microparticles, and we have shown how these principles are used to displace and manipulate these objects inside microsystems. It is recalled here that the approach has been done in two steps: first, the study of the microfluidic flow as a carrier fluid; second, the study of the behavior of macromolecules and microparticles in such microfluidic flows. Up to now, we have dealt only with tools to perform a task. And the essential question is: What task are we going to perform with such tools and what have all these techniques been developed for? This brings us to the purpose of biochips or bioMEMS.
Basically, the main purpose of biochips is the analysis and recognition of macromolecules DNA, proteins, and such. Ultimately, recognition processes should be fast, sensitive, and reliable, with the less possible false results, and largely parallelizable, allowing for simultaneous samples recognition.
We will see in this chapter that biorecognition is based on a mechanism of key lock [1], which is in reality a biochemical reaction. This leads us to present the kinetics of chemical and biochemical reactions, with a special attention to some key reactions, like enzyme-catalyst reactions for proteins and adsorption reactions for DNA hybridization. Because in biochip technology, the targets to analyze are immersed and carried by a buffer fluid, recognition times depend not only on the biochemical reaction...
