Fig. 2: Microfabrication, electrochemical and structural assessment of microelectrodes based on EGNITE.

a, Layers involved in the microfabrication of flexible arrays of microelectrodes of EGNITE. b, Designs of epicortical and intraneural arrays used in this work. c, Photograph of flexible implants based on EGNITE. d, Detailed micrograph of an EGNITE microelectrode of 25 µm diameter. e, Representative CV at 100 mV s⁻¹ of an EGNITE microelectrode. f, EIS of EGNITE microelectrodes, showing the module (blue line) and phase (yellow line) of the impedance versus frequency. n = 18 electrodes. g, Voltage response to current-controlled biphasic pulses of 1 ms per phase (dashed lined) applied through EGNITE electrodes, corresponding to charge injection values of 2 and 4 mC cm⁻². h, Map of the cathodic capacitive voltage excursion occurring at the interface between EGNITE microelectrodes and the electrolyte during the injection of current pulses at different levels of injected charge and pulse widths. i, Evolution of impedance at 1 kHz throughout continuous stimulation with 15 µA (3 mC cm⁻²) biphasic pulses of 1 ms per phase. g–i, n = 3 electrodes. j, Images of EGNITE electrodes fabricated in a PI device before and after 15 min of ultrasonication. k, Left: schematic and cross section of the bending set-up, indicating the pressure of a cylindrical bar of 700 µm diameter producing bending angles of 131°. Centre: impedance magnitude at 1 kHz for three different devices, each with 18 microelectrodes, measured before and after 10 and 20 bending cycles. Right: impedance spectrum for a device before and after 10 and 20 cycles of bending. Line represents the mean and shading the s.d. In f,g,i,k, data are mean (solid lines) ± s.d. (shaded area). In boxplots, the median, quartile box and minimum and maximum values (excluding outliers) are presented.