ABSTRACT
Developments over the last decade in particular have made it possible to perform chemical and biochemical analyses in microfabricated devices. The concept of micro total analysis system (~LTAS), or "lab-on-a-chip," was first introduced by Manz et al. some 10 years ago [ 1 ], and an increasing number of applications has been discussed and explored since then. Generally, such analysis systems consist of micrometer-sized reservoirs and flow channels fabricated in a planar substrate. For the traditionally open systems, such as micro plates, evaporation becomes a severe problem when working in nanoliter scale. Potentially, miniaturized systems offer a number of advantages, the first one being the inherently small scale itself. This implies that very small quantities of analytes and reagents are required, provided, of course, that the actual analysis and detection methods provide the necessary sensitivity. Also, the small dimensions in such systems yield short diffusion lengths, which translate into faster mass transport, and hence also in faster reaction times, which may be of significant interest, e.g., in clinical assays. Second, microanalysis systems generally refer to integrated systems, capable of several processing unit operations in sequence within the device, thereby reducing the need for intermediate robotic steps. These systems are also well suited for automation, e.g., of sample handling, analysis, and data processing. Altogether, 11-TAS offers interesting opportunities in high throughput applications. A particularly interesting area in this context is development of (bio)pharmaceuticals where thousands of substances are frequently screened for biological activity prior to even selecting a candidate drug for clinical trials.
