Finding NEMO (novel electromaterial muscle oscillator): a polypyrrole powered robotic fish with real-time wireless speed and directional control

Abstract

This paper presents the development of an autonomously powered and controlled robotic fish that incorporates an active flexural joint tail fin, activated through conducting polymer actuators based on polypyrrole (PPy). The novel electromaterial muscle oscillator (NEMO) tail fin assembly on the fish could be controlled wirelessly in real time by varying the frequency and duty cycle of the voltage signal supplied to the PPy bending-type actuators. Directional control was achieved by altering the duty cycle of the voltage input to the NEMO tail fin, which shifted the axis of oscillation and enabled turning of the robotic fish. At low speeds, the robotic fish had a turning circle as small as 15 cm (or 1.1 body lengths) in radius.The highest speed of the fish robot was estimated to be approximately 33 mm s −1 (or 0.25 body lengths s −1 ) and was achieved with a flapping frequency of 0.6-0.8 Hz which also corresponded with the most hydrodynamically efficient mode for tail fin operation. This speed is approximately ten times faster than those for any previously reported artificial muscle based device that also offers real-time speed and directional control. This study contributes to previously published studies on bio-inspired functional devices, demonstrating that electroactive polymer actuators can be real alternatives to conventional means of actuation such as electric motors.

Evaluation of encapsulating coatings on the performance of polypyrrole actuators

“…Linear actuation in air of such PPy actuators under a 2 MPa applied stress was demonstrated, showing a considerable deterioration in actuation performance after a few cycles of actuation. In another study, Scotch tape and petroleum jelly were used for encapsulation of PPy tri-layer actuators operating in water [19]. It was found that the Scotch tape increased the stiffness of the actuators and resulted in a dramatic loss in tip displacement.…”

Enhancement of actuation ability of ionic-type conducting polymer actuators using metal ion implantation

“…1). As widely reported in the literature [3][4][5][6][7][8][9][10][11][12][13][14][15], if the conductivity of the contacts and the polymer is very good, there will be a small ohmic potential drop along the actuator length, and the charging rate will be high, which generate higher strains. The higher is the strain, the higher is the tip displacement of the actuators.…”

A stiffness enhancement methodology for artificial muscles

“…INTRODUCTION LECTROACTIVE conducting polymers have attracted the attention of many researchers since their discovery in mid 1970s. One reason for this interest is that the electroactive polymers are considered to be alternative to conventional actuator and sensor materials due to their small electrical energy consumption, light weight and compliant properties, biocompatibility, ability to operate in air and fluidic media, insensitivity to magnetic fields and simple fabrication [1][2][3]. When a small electrical potential or current is applied to the polymer actuators typified by PPy and appropriately engineered, this causes an electrochemical reaction for doping and undoping the polymer layer(s) [4][5].…”

“…Consequently, electroactive polymers, as unconventional actuators, can be used for a wide range of engineering applications such as in the growing area of biomimetics. Of these applications, the PPy actuator is employed as a propulsor in a swimming device (robot fish) [1,2]. There is a growing interest on the use of the polymer actuators in many other bio-inspired applications, [6][7].…”

“…With this in mind, the concept put forward in this study is comprehensive, yet simple to implement and extendable to other polymer actuators. As it has been reported in the literature [1][2][3][4][5][6], one way of increasing the force output is to apply a relatively higher input voltage. However, due to the increase in the energy consumption and possible damage to the polymer structure due to overoxidation, this cannot be a feasible solution.…”