Extrusion printing parameters were changed with each ink to attempt to keep the printing results as similar as possible. For example, higher printing pressure was used with more viscous inks so that gaps would not be left in the lattice that was printed. An electrolyte solution was mixed using 100 mM hexacyanoferrate (II), 100 mM hexacyanoferrate (III), and 1 M KCl. Hexacyanoferrate has a very low redox potential, making it an ideal candidate for measuring ionic conductivity. This solution was absorbed into a graphite felt and a platinum wire was used as a current collector to connect to a Keithley 2450 source meter (Tektronix, USA) for conductivity characterization. To ensure that no resistance was contributed by the electrodes themselves, the resistance was measured at two different lengths (8 mm and 4 mm) and subtracted to get the resistance of a 4 mm length of hydrogel. In this process, we found the resistance contributed by the electrodes was negligible.