Electrochemical nanofluidics: The mesoscopic limit

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.