Abstract

Demonstrations of microfabricated chemical instrumentation initially focused on chemical separations, first in the gas phase and later in condensed phase using capillary electrophoresis. It soon became clear that microfabrication could be extended to include a much larger portion of the chemical measurement problem and the concept of the Lab-on-a-Chip resulted[1,2,3]. The realization of the Lab-on-a-Chip requires the development of a number of functional elements or unit processes that can eventually be integrated to solve chemical and biochemical measurement problems. As the field of micromachined chemical instrumentation continues to grow, more sophisticated devices with increased functionality are being fabricated and tested. Functional elements that have been demonstrated for chemical and biochemical analysis include free solution electrophoresis [4,5,6,7,8,9], electrophoretic sizing of DNA fragments [11,12], and methods for isolation of neutral species [13,14,15]. In addition, initial levels of monolithic integration have been demonstrated by coupling chemical separations with chemical and enzymatic reactions [16,17,18,19,20]. Quantification tools used for detection of materials on or from microchips have primarily included fluorescence which is particularly applicable due to its extreme sensitivity[21] and electrospray ionization for off-chip analysis using mass spectrometry [22]. In addition to these more conventional chemical analysis methods, electrokinetically driven fluidics have been used to perform electrokinetically focused flow cytometry [23] and homogeneous enzyme reaction kinetics [24]. These latter two capabilities are described in greater detail below.

© 1998 Optical Society of America