EBL/NIL fabrication and characterization of interdigitated electrodes for potential application in combinatorial studies.

Electrochemical transducers are frequently used to electrochemically deposit, synthesize and/or sense chemical compounds in material science, chemistry and biology. Traditionally this is done in fairly large volumes; generally several milliliters to even full production scale tanks, however, for high throughput measurements and combinatorial experiments smaller volumes are generally preferred. To probe small volumes small electrodes with preferable high density are needed. Presented in this paper is how to fabricate interdigitated electrodes by electron beam lithography (EBL) and also how to make large quantities by nanoimprint lithography (NIL) to enable combinatorial studies of cells or materials in microsystems (Lab-on-a-Chip Systems).Interdigitated electrodes are shown to have additional advantages compared to simple disk or rod electrodes, such as being able to perform redox cycling experiments. The collection efficiency for the electrodes with pitch of 400 nm and width of 200 nm fabricated by EBL has been found to be round 87% when characterized electrochemically using ferro-/ferricyanide. The shape of the cyclic voltammograms for the electrodes are also in good agreement with the theoretical expectations for ultramicroelectrodes. Hence, these electrodes should be ideal candidates for combinatorial and high-throughput studies based on electrochemical methods.Furthermore, a fabrication process based on nanoimprint lithography (NIL) is demonstrated, this could potentially ease fabrication and reduce cost of devices. The NIL process is based on thermal imprinting in PMMA 950k and LOR 0.7A.