Eq. 1 -3 effectively show a simplified mechanism for the oxygen reduction reaction. A more detailed discussion of this reaction is included in the supplementary information (SEq. . This method permits facile, interference-free DO quantification, without the need for an oxygen permeable membrane, consequently enabling miniaturisation. The detection of hydrogen peroxide during oxygen reduction has classically been achieved using a rotating ring disc electrode (RRDE) configuration. , , in this method, hydrogen peroxide produced at the disc is pushed to the outer ring electrode by convection forces, ensuring maximum collection of the produced hydrogen peroxide. Typically, the collection efficiencies are quite low by comparison with generator-collector experiments which utilise a redox couple. Collection efficiencies of 15-25% are considered high for the RRDE with quite complex instrumentation which is unsuitable for miniaturised or portable sensing applications. An alternative to the RRDE for the detection of produced hydrogen peroxide is the use of IDEs. In this approach, detection is governed by diffusion of hydrogen peroxide from the generator to the collector rather than by convection. This has been shown to be a viable approach by Postlethwaite et al, using IDEs with 10 µm width and 10 µm gaps. The major drawback being a lower observed collection efficiency; by comparison to ring-disc approaches. While low collection efficiencies are expected for this reaction, the IDE method shown by Postlethwaite had a hydrogen peroxide collection efficiency of just 5%. However, by developing IDEs having smaller electrode gaps and widths, such as 1 µm for both dimensions, it should be possible to increase the efficiency significantly in line with ring-disc approaches. The IDE approach also has the major benefit in that it permits redox cycling, i.e., where the same molecule can be reduced and oxidised a number of times. , , In the RRDE setup, at the ring collector electrode the product of oxidised hydrogen peroxide (i.e., oxygen) is pushed away by the prevailing convection forces from the disc electrode. In the IDE set-up, it can diffuse back to the generator electrode to be reduced again, thus improving sensitivity.