A SILICON FLOW CELL FOR OPTICAL-DETECTION IN MINIATURIZED TOTAL CHEMICAL-ANALYSIS SYSTEMS

The applicability of silicon micromachining to the fabrication of a small-volume flow cell for UV-visible absorption detection is demonstrated. With volumes ranging from 1 to 100 nl and lengths of 1 and 5 mm, this type of cell has a long path length relative to its volume. Light is transported through the cell by means of a series of reflections, so that the optical path length may be increased to values beyond the actual cell length, depending on the input angle of the light. Preliminary experiments using a 1 mm, 15 nl cell to measure dye-containing solutions demonstrate an application of multireflection to the measurement of absorbance.