Artificial muscles based on conducting polymers

Abstract

Natural muscles have mechanical properties that conventional actuators do not possess. These natural machines show large strain, moderate stress, high efficiency and stability, fast response time, high power/weight ratio, long lifetime, etc. In the last years a great interest has arisen to develop materials that mimic natural mechanisms. Conducting polymers have an array of potential applications as artificial muscles since they are capable to produce a moderate displacement when submitted to an electrochemical reaction. This property has been used to fabricate actuator devices that imitate and even improve the performance of natural muscles. For example, conducting polymers show stresses 15 times higher than those generated by mammalian muscles, a high power/weight ratio and a high degree of compliance. However, there are also several responses that need improvement in the actuators based on conducting polymers. Strains are still c. 50% lower than in natural muscles. Most of this kind of actuators only work in liquid media. It is necessary to increase the response time and obtain more durable actuators with longer lifetime and higher stability. In spite of these disadvantages, the first actuators based on conducting polymers are being commercialized. This paper presents a brief summary of some of the actuators based on these polymers, focusing on their design, performance and actuation mechanism.

Soft Robotics: Biological Inspiration, State of the Art, and Future Research

“…Actuators developed by using conducting polymers (Cortés and Moreno 2003) have been used to build many biologically inspired robots. Nie et al (2006), for example, developed a tortoise-like flexible microrobot that can crawl and swim underwater by using four legs actuated by ionic conducting polymer film (ICPF).…”

“…EAP gels (Cortés and Moreno 2003) have been used to fabricate a hand with gel fingers (Shiga et al 1989) and gel robots (Otake et al 2002). The gel robots are made entirely of EAP gel that changes shape under spatially varying electric fields.…”

“…EAPs suffer from several shortcomings that make their extensive use in soft robots difficult. Most ionic EAPs can work only in aqueous media (Bar-Cohen 2000), conjugated polymers and ionic polymer-metal composites have short lifecycles due to creep and material degradation (Shahinpoor et al 1998), EAP gels require very high voltage for actuation (up to 150 MV/m) (Cortés and Moreno 2003) and most actuators made of EAPs are not significantly scalable. In spite of these challenges, EAPs remain a popular material for soft robots.…”

Intelligent control of a highly flexible robotic structure with hundreds of motor elements

“…One likely candidate for a fundamental constituent, following the lead of Yoseph Bar-Cohen [5] of the Jet Propulsion Laboratory, is the electro-active polymer (EAP). Developers of EAP technology have made great progress in the last decade [6][7][8][9][10][11][12][13]. Electroactive polymers are appearing as sensors, actuators, computing elements, and even as batteries and energy transducers [13].…”

Computational Modeling of Electrochemical-Poroelastic Bending Behaviors of Conducting Polymer (PPy) Membranes

“…They produce large forces and deformations in a narrow space as the generated force and strain per unit volume are large. They are paid attention in the fields of MEMS and biomedical engineering requiring downsizing as various mechanical designs realizing the motions of expansion/contraction, bending and torsion are possible (1), (2) . When the polypyrrole membrane is subjected to an electric voltage, the ions in the electrolyte liquid or the solid electrolyte gel get connected with and separated from the conducting polymers by the oxidation and the reduction, causing an internal volume change.…”