Soft and highly responsive multi-walled carbon nanotube/pullulan hydrogel composites as electroactive materials

Abstract

Pullulan is a polysaccharide as obtained from the black yeast fermentation. Soft and flexible pullulan hydrogels and multi-walled carbon nanotube/pullulan hydrogel composites were fabricated by a solvent casting method. The effects of crosslinking agent, MWCNT content, and electric field strength on the electromechanical behaviours were investigated. The storage modulus (G′) or the elasticity monotonically increased with increasing crosslinking agent and electric field strength. The MWCNT/pullulan hydrogel composite with 0.01%v/v MWCNT provided the highest storage modulus sensitivity of 71.2 at the applied electric field strength of 800 V/mm, relative to other hydrogel composites previously reported. The storage and loss moduli were further transformed to the creep compliance through the relaxation spectrum and the retardation spectrum, respectively. The creep compliance of the pristine hydrogels and composites decreased with increasing crosslinking agent amount and electric field strength. The 01MWCNT/Pullulan_5STMP hydrogel composite yielded the lowest creep compliance function, illustrating the ability to resist deformation through electric field. The dielectrophoresis force density of the MWCNT/pullulan hydrogel composite with 0.01%v/v MWCNT was the highest obtained at 0.2258 mN/mm3, suggesting as the most suitable for practical actuator applications.