Transport effects in biochip sensors with redox cycling amplification

We report a study of transport effects on a microfluidic sensor-chip in which electrochemical sensing is amplified by redox cycling using an interdigitated electrode array (IDA). A full three-dimensional simulation-based model and a simple one-dimensional model for the transition velocity between the two regimes is presented. These models indicate that there exist two dominant regimes: one which is limited by redox cycling diffusion—a unique feature of IDAs— and another which is limited by convection and has dominant flow effects. The transition velocity between the two sensing regimes was found to be vflow[mmsec]=0.335L[μm]+0.04 which is similar to the prediction of vflow∝1L, obtained from the one-dimensional model.