ABSTRACT Amperometric detection is an attractive detection scheme for mico- and nanofluidic systems as it directly yields an electrical signal. However, this scheme is not often utilized because of its limited sensitivity. We overcome this limitation by employing a nanofluidic device consisting of a solution-filled cavity bounded by two closely spaced parallel electrodes that can amplify the current by repeatedly reducing and oxidizing electroactive species. Here we demonstrate the utility of such a device to measure enzyme kinetics in real time. We compare the conversion of p-cresol into methylquinone by tyrosinase using our nanofluidic device against a standard UV-Vis spectroscopic protocol. KEYWORDS: Electrochemistry, Redox Cycling, Enzyme Kinetics, Nanofluidics@en

ABSTRACT We have developed a lithography-based nanofluidic device for sensitive electrochemical detection applications. The device consists of a solution-filled channel bounded by parallel electrodes that are separated by ~50 nm. Redox cycling at the two electrodes is used to amplify the electrochemical signals from molecules in the volume between the electrodes, and can lead to dramatic improvements in sensitivity and/or selectivity. Interestingly, an important limit to sensitivity is placed by statistical fluctuations in the number of molecules present in the device, a consequence of its extremely small volume (a few femtolitres). In this Proceedings article, we focus on the consequences of these statistical fluctuations on the signal-to-noise ratio of electrochemical sensors based on redox cycling. KEYWORDS: Nanofluidics, electrochemistry, sensing, number fluctuations, mesoscopic.@en