Electroplating for three dimensional lab-on-a-chip electrodes and microstructures

A key issue in the development of microfabricated "lab-on-a-chip" (LOC) analysis systems has been the selection and implementation of appropriate detection systems. Electrochemical detection (ECD) offers several advantages such as a library of well-characterized electrode/analyte systems, precise control over electrode size, shape, type and material, and the ability to miniaturize. The purpose of this study was to explore the use of electroplating techniques to develop high aspect ratio, 3-D MEMS structures and utilize this technology to develop 3-D ECD electrodes for LOC devices. A simple surface micromachining process for fabricating high aspect ratio microstructures for MEMS devices and LOC electrodes using UV lithography, thick photoresist and nickel electroplating has been developed. High-aspect ratio molds (>10 μm) have been fabricated after optimizing the processing parameters for the thick photoresist. Nickel electroplating was characterized and used to translate the photoresist molds into nickel microstructures. This plating-through mask technology was then utilized to produce three-dimensional ECD electrodes for our current LOC research program.