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Electro-responsive poly(lactic acid) filled with multi-walled carbon nanotubes

Sirivat A

The electroactive materials based on biopolymers have steadily received attentions for biomedical and actuator applications due to its biodegradability, biocompatibility and good mechanical properties. In this work, the multi-walled carbon nanotubes (MWCNTs), carbon-based nanoparticles, were used as an effective filler in the electro-responsive poly (lactic acid) fabrication. Dibutyl phthalate (DBP) was used as a plasticizer to improve flexibility and electromechanical response of the PLA composites. The effects of MWCNT concentration and electric field strength on electromechanical properties were investigated using a melt rheometer and by bending measurement. The highest storage modulus sensitivity (ΔGꞌ/Gꞌ0) of 1.56 belonged to the 0.1%v/v MWCNT/PLA/DBP composite at the electric filed strength of 1.5 kV/mm. At a MWCNT concentration higher than 0.8%v/v, the storage modulus response (ΔGꞌ) became negative, in which the storage modulus under electric field (G’) was lower than the initial storage modulus (Gꞌ0) without electric field. This behavior can be referred to as the negative electrostriction as similarly observed in the plasticized PLA embedded with graphene. All composites possessed the electromechanical reversibility in the temporal response experiments under applied electric field. In the bending measurement, the bending distances and dielectrophoresis forces of all specimens increased monotonically with increasing electric field strength. The MWCNT/PLA/DBP composite deflected towards the anode even at the low electric field strength of 25 V/mm. From the experimental data, the MWCNT/PLA/DBP nanocomposites provided good recoverability, high storage modulus sensitivity, and fast response time under applied electric fields. Thus, they can be potentially used as the electro active materials in soft actuator applications.