Lateral flow profiles were measured using a 3D-printed set-up reported elsewhere (66), and imaged Here n is the number of electrons transferred, A the electroactive area (in cm 2 ), D = 0.6 × 10 -5 cm 2 s -1 the diffusion coefficient of ferro/ferricyanide (in cm 2 s -1 ), C the redox probe concentration (in mol cm - 3 ) and v the scan rate (in V s -1 ). The electrochemical porosity factor (η) was calculated by dividing the electroactive area by the geometric (projected) area of the design. Electron transfer rates were measured by electrochemical impedance spectroscopy (EIS) on a potentiostat (Vionic, Metrohm) using the same redox probe solution as above, and with the following parameters: DC offset of 0 V versus open circuit potential, 10 mV amplitude, frequency range from 1 Hz to 200 kHz . A Randles circuit was fitted to the high-frequency data in the EIS Nyquist plot using the Nova 2.1 software (Metrohm Autolab). The Randles circuit comprised a solution resistance, RΩ, followed by two components in parallel: a constant phase element for the double layer, CPEDL, and the charge transfer resistance, RCT. The electron transfer rate, k0, (in cm s -1 ) was calculated from (51):