Silk fibroin/polycarbazole composite as artificial muscle

Abstract

Pure silk fibroin (SF) hydrogel and composites of polycarbazole/silk fibroin (PCZ/SF) hydrogel were fabricated by solvent casting technique to investigate electromechanical properties, dielectric properties, and deflection properties as functions of SF concentration, glutaraldehyde concentration, and particle concentration in the blends electric field strength. Electromechanical properties were characterized using oscillatory shear mode over a frequency range from 0.1 to 100 rad/s under various electric field strengths from 0 to 600 V/mm at a temperature of 27 ºC. For both pristine SF hydrogel and the composites, the storage modulus response (∆G´) and the storage modulus sensitivity ((∆G´/ G´₀) increase dramatically with increasing electric field strength; the pristine hydrogel possesses the highest storage modulus sensitivity value of 5.87, a relatively high value when compared with other electroactive polymers. With increasing incorporation of conductive polycarbazole into the SF hydrogel, the storage modulus sensitivity and the relative dielectric constant decrease; the conductive polymer thus provides a softening effect. In a deflection experiment with using a cantilever fixture, for both the pure SF hydrogel and the composites, the dielectrophoresis force and deflection distance increase monotonically with electric field strength, with the pure SF hydrogel showing the highest deflection distance and dielectrophoresis force.