fig3

Figure 3. Electrochemistry of the PEDOT/alginate interface. (A) Cyclic voltammograms (normalised by area and Q_{electrodeposition}) for bare gold wire (black), PEDOT:SDS (control without alginate, grey) and PEDOT/alginate structures electrodeposited with step potential (red), pulsed RPI protocol (green) and OCPI protocol (blue) in PBS (pH = 7.4) as supporting electrolyte and scan rate of 50 mV s^-1. (B) Bode plots showing impedance modulus (left axis, continuous line) and phase angle (right axis, dashed line) for PEDOT:SDS (control without alginate, grey) and PEDOT/alginate hydrogel electrodeposited with step potential (red), RPI protocol (green) and OCPI protocol (blue). (C) Charge storage capacity (CSC) measured in PBS for bare gold wire (black), PEDOT:SDS (control without alginate, grey) and PEDOT/alginate hydrogel electrodeposited with step potential (red), RPI protocol (green) and OCPI protocol (blue). Experiment was performed in triplicate over different gold wire electrodes. Error bars indicate one standard deviation of the mean. Statistical significance is determined by one-way analysis of variance (ANOVA)/Tukey correction, n.s. is non-significant P > 0.05, *P < 0.05 and **P < 0.001. (D) Equivalent circuit (top) and schematic (bottom) of the proposed molecular distribution in the core-shell structure. In the equivalent circuit, R_S represents solution resistance, CPE represents a constant phase element representing the doped PEDOT core and C is the capacitance of the alginate hydrogel shell. CPE elements are used for inhomogeneous or imperfect capacitance, comprising the parameters Y₀ and n, where Y₀ is a pseudocapacitance constant and n is the deviation from ideal capacitor behaviour (n = 1 for a pure capacitor and n = 0 for a pure resistor,). (E) Table with values for all circuit components extracted from fitting experimental impedance spectra. R_PEDOT represents the electronic resistance due to PEDOT (see methods section) obtained from CPE where n < 0.3. χ² statistically represents the approximation between theoretical and experimental data.