fig2

Figure 2. Characterization of ICH. (A) ICH chemical interaction mechanism. Tyramine binds to deprotonated sulfonate of PSS by hydrogen bonding, while glycerol covalently binds with deprotonated sulfonate of PSS; (B) FT-IR spectra of HATYR (blue), 0.5% HATYR/PEDOT:PSS (red), 1% HATYR/PEDOT:PSS (gray), 2% HATYR/PEDOT:PSS (black), and PEDOT:PSS (green); (C) FT-IR spectra of HATYR/PEDOT:PSS hydrogel (black) and addition of glycerol (ICH) (red); (D) Photograph of gelation of HATYR/PEDOT:PSS and ICH; (E) Oscillation frequency sweep measurements of HA/PEDOT:PSS (black) and HATYR/PEDOT:PSS (red) hydrogels. The filled circles represent the storage modulus (G'), and the empty circles represent the loss modulus (G"); (F) Viscosity with increasing shear rates (0.01-100 s^-1) of HA/PEDOT:PSS (black) and HATYR/PEDOT:PSS (red) hydrogels (injectability of HATYR:PEDOT:PSS in 30 G needle, inset photo); (G) 3D printing of electrode array design using ICH; (H) LED demonstration of ICH: photograph (top) and circuit model (bottom); (I) Reversible electrical reliability of the ICH during cyclic stretching/releasing tests (at a speed of 0.3 mm/s and strain of 100%) on one hundred times (inset images represent initial and final 5 peaks); (J) Real-time monitoring of EMG signal from repeated open-clenching, based on ICH-electrode; (K) ECG signals with typical P-Q-R-S-T wave monitoring via ICH-electrode without filtering. ECG: electrocardiogram; EMG: electromyogram; FT-IR: fourier transform infrared; HATYR: tyramine-conjugated hyaluronic acid; ICH: injectable conductive hydrogel; PEDOT:PSS: poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate); PSS: poly(styrenesulfonate).