Interface And Material Design, Mechanical And Electrical Model And Bionic Application Of Ionic Polymer Metal Composite Artificial Muscle

Distributed Actuation(muscle actuation) of animals contributes to their high flexibility, high degree of redundancy and high bearing capacity to weight ratio. The actuator like muscle plays a significant role on development of high-performance robot and MEMS system. It shows that precise control of gecko’s toe movement and the combination of size effect from micro-nano scale seta of gecko’s toe can contribute to gecko’s leap onto roofs and over walls. Therefore, it is necessary to imitate the locomotion of gecko’s toe, in order to develop a kind of controllable adhesive mechanism. Ionic polymer metal composite(IPMC) is an ionic electro-active polymer(EAP) actuator, composed of a perfluorinated polymer membrane coated with a noble metal such as platinum(Pt) or gold(Au) on both sides. Compared with piezoelectric ceramics and shape memory alloy materials, IPMC, also termed “artificial muscle”, has several advantages such as a relatively large stroke with low driving voltage, light weight, low noise, flexibility and high driving energy density. The controlled oscillation produced by an IPMC is similar to the actuation style of the gecko’s toes, which can realize the attachment and detachment of toe for simple, effective and precise actuation.This dissertation mainly focuses on interface and material design, mechanical and electrical modeling of IPMC artificial muscle, its application in imitating the locomotion of gecko’s toe, and novel adhesive material.The effect of interfacial surface texture between the polymer matrix and electrode on the actuator was studied. It was found that the larger electrode interfacial surface area is beneficial to the actuation behavior of IPMC, which is attributed to the larger electrical double layer capacitance. Two stainless steel templates were fabricated using electric-spark machining, and a hierarchical surface texture of ionic polymer was produced using both polishing and replication methods, which produced microscale and nanoscale groove-shaped microstructures at the surface of the polymer. Compared with sandblasted Nafion-based IPMC, the blocking force, displacement, and electric current of the replicated Nafion-based IPMC were 4.39, 2.35, and 1.87 times higher, respectively, and the effective air-operating time prolongs 5 times.Cationic surfactant cetyl trimethyl ammonium bromide(CTAB) was employed to disperse multi-walled carbon nanotubes(MWCNTs) in the Nafion matrix, forming a homogeneous and stable dispersion of nanotubes. The processing did not involve any strong acid treatment and thus effectively preserved the excellent electronic properties associated with MWCNT. Furthermore, a novel Nafion membrane containing a primary Nafion/tetraethyl orthosilicate(TEOS) layer sandwiched between two outer Nafion/MWCNT nanocomposite layers was prepared by consecutive casting of liquid solutions. The multilayered IPMC exhibited a significantly improved blocking force of 6.5 gf as well as a long effective air-operating life time of 300 s under the sinusoidal voltage of 3 V at 0.1 Hz.We develop an ionic polymer metal-carbon nanotube composite(IPMCC) actuator composed of a MWCNT/Nafion membrane sandwiched between two hybrid electrodes, composed of palladium, platinum and MWCNTs. MWCNT layer can adhere very well with the platinum-palladium metal electrode, fill the cracks in the metal surface, prevent the oxidation of nanoscale platinum particles, and maintain the stability of electrode property. An equivalent circuit is used to model the nonlinear current of the IPMCC, in which the leakage current was taken into account and analyzed.The Nafion membranes with different thickness were prepared by casting from liquid solution. By employing these Nafion membranes, IPMCs with varying thickness were fabricated by electroless plating. The effects of the thickness on the performance of IPMC were analyzed with an electromechanical model. Results show that as the thickness increases, the blocking force of IPMC increase, however, the current and the displacement decrease.A newly developed ionic electro-active actuator composed of an ionic electrolyte layer sandwiched between two graphene film layers was investigated. Scanning electron microscope(SEM) observation, x-ray diffraction(XRD) analysis and four probe tester were used to study graphene film. Contact angle measurement was employed to measure the surface energy of the ionic electrolyte polymer. We report that this ionic actuator exhibits stable bending strain, ranging from 0.032 to 0.1%(305 to 945 μm) as functions of voltage.IPMC is use for actively actuating an adhesive array to imitate the locomotion of gecko’s toes., which can effectively actuate an artificial gecko’s toe to attach and detach from a surface. A novel polydimethylsiloxane(PDMS) material enhanced with two types of crosslinkers, carbon nanotubes and graphene sheets, was fabricated. It exhibits excellent adhesion, sufficiently high elastic modulus and high repeatability at low preloads.