Study On Electroactuation Performance And Equivalent Circuit Model Of IPMC With Carbon Nanotubes Composite Electrode And Porous Membrane

Ionic polymer metal composite materials(IPMC,Ionic polymer metal composites)is a new type of intelligent material,which has low driving voltage,large swing,simple preparation,and good biocompatibility characteristics,etc.IPMC has great application prospects in artificial intelligence,military equipment,medical equipment,bionic equipment,and other fields.It is one of the hot fields of academic research.The MWCNT(multiwalled carbon nanotube)-Ag composite electrode was prepared by electrophoretic deposition and electroless plating method,and the effect of MWCNT-Ag composite electrode structure on IPMC electromotive property and its mechanism were studied,aiming at the problem that IPMC electrode materials are prone to crack and oxidizable,and the surface resistance of the electrode increases rapidly after electrification,which leads to the rapid deterioration of IPMC electroactuation performance.Porous Nafion membrane with high water content was prepared by particle leaching method,and the effect of porous Nafion membrane structure on the electroactuation performance of IPMC and its mechanism were studied,aiming at the problem that low moisture content of common IPMC base membrane leads to poor electroactuation performance of IPMC.An equivalent circuit model considering leakage current of MWCNT-Ag composite electrode/porous Nafion membrane IPMC was constructed which had simple structure,strong practicability,and high accuracy,aiming at the problem that the IPMC electrical model proposed by previous researchers has a large error.The main work and results were as follows.(1)The influence of MWCNT-Ag composite electrode structure on the electroactuation performance of IPMC was studied.MWCNT-Ag composite electrode structure was prepared using the electrophoretic deposition method.The influence of electrophoresis voltage and deposition time on the morphology of MWCNT-Ag composite electrode and the variation rule of IPMC output force and output displacement under different electrophoresis voltage and deposition time,and the influence of MWCNT-Ag composite electrode morphology on the electroactuation performance were obtained.The relationship among the key electrophoretic parameters,the microstructure of the composite electrode and the electroactuation performance of IPMC was given as follows.There was an obvious reunion in the MWCNT electrode layer prepared with excessive deposition time and electrophoresis voltages.The MWCNT electrode layer was easy to be incomplete due to too small deposition time and electrophoresis voltage.The glomerate and incomplete MWCNT electrode layer reduced the output performance of IPMC.Only under the suitable deposition time and electrophoresis voltage,can MWCNT electrode layer be formed with uniform coverage and IPMC give the best electroactuation performance.(2)The enhancement mechanism of electroactuation performance of MWCNT-Ag composite electrode structure IPMC was given.The IPMC multi-physical field model and the MWCNT-Ag composite electrode interface geometric model were established.The influence of interface morphology of MWCNT-Ag composite electrode on the potential distribution,nominal current density,nominal charge density and output displacement of IPMC by using COMSOL finite element analysis.The enhancement mechanism was given as follows.MWCNT-Ag composite electrode structure was responsible for the increasing double layer thickness,internal effective electric field intensity,electric field force on the hydrated cation,migration rate of hydrated cation,nominal current density,and nominal charge density,leading to the increasing output displacement.(3)The influence of porous Nafion membrane on the electroactuation performance and enhancement mechanism of IPMC was investigated.The porous Nafion membrane was prepared with particulate leaching method.The effect of pore forming agent concentration on average particle size,porosity and water content was studied.The output force,output displacement,strain energy density and stable working time of IPMC prepared by porous Nafion film with different pore forming agent concentrations were measured,and the effect of porous Nafion membrane structure on the electroactuation performance of IPMC was given.The enhancement mechanism was given as follows.There was many micro holes and pipes in the porous Nafion membrane,resulting in an increase in the number of hydrated cations,an increase in migration path,a decrease in migration resistance,an increase in the number of hydrated cations enriched at the cathode per unit time,and an increase in IPMC electroactuation performance.(4)Equivalent circuit model considering leakage current of MWCNT-Ag composite electrode/porous Nafion membrane IPMC was constructed.The type of IPMC internal current including leakage current was determined,and the equivalent circuit model considering leakage current was established according to MWCNT-Ag composite electrode/porous Nafion membrane IPMC electromotive mechanism,the microscopic ion movement,and the characteristics of IPMC electrode and base membrane structure.The rationality of the equivalent circuit model was verified by IPMC actual electrical data under different drive voltage amplitude,different drive voltage frequency and step voltage.The parameters of each element in the model were calculated by mathematical derivation and the accuracy of the equivalent circuit model was verified by experiments.In this paper,the relationship between IPMC preparation parameters and morphology structure,influence rule of morphology structure on IPMC electroactuation performance,enhancement mechanism of MWCNT-Ag composite electrode IPMC and porous Nafion membrane IPMC,and equivalent circuit model considering leakage current of IPMC provide an effective way for the theoretical study and the improvement of electroactuation performance of artificial muscle.