Integration of ring nanoelectrodes into microwells for the bioelectrochemical analysis in sub-picolitre volumes

In this work, we report the fabrication and the electrochemical characterization of recessed disk micro-electrodes (DME) and ring nanoelectrodes (RNE) integrated in microwell arrays. Such configurationhas all advantages of microelectrodes arrays but is more suitable for electrochemical measurementin sub-picolitre volumes (∼0.3 pL). The technological process based on the reactive ion etching of a SiO₂/Ti/Pt/Ti/SiO₂stack is optimized in order to integrate RNE arrays on transparent glass substrate. Mul-tiphysic simulations and electrochemical characterizations are conducted in order to study and improvethe amperometric behaviour of recessed ring nanoelectrodes according to their geometry. A good fitis shown between experimental, theoretical and simulation results, allowing full understanding of theelectrochemical detection properties of RNE-based microwell arrays. Then, a “generation − collectionmode” chronoamperometric approach is proposed to evaluate experimentally the collection ratio of RNEarrays and compare it with simulation results. Finally, first electrochemical characterizations in sub-picolitre volumes are conducted with anti-oxidant species. All these results demonstrate that recessedring nanoelectrode arrays are fitted to the detection of bio-electrochemical species at the microscale and,consequently to single mitochondrion or single sub-cellular organelle analysis.