Slender tube-shaped and square rod-shaped IPMC actuators with integrated sensing for soft mechatronics

Abstract

This paper describes the development of slender millimeter-size hollow (tube) and sub-millimeter-size solid (rod) shaped ionic polymer-metal composite (IPMC) actuators. The outer electrodes on the IPMC actuators are sectored to enable control for multiple degrees of freedom motion. Such small-size slender (high aspect ratio) IPMC actuators can be used to create active catheter devices, bio-inspired propulsion mechanisms in underwater autonomous systems, artificial cilia structures for micro-fluidic devices, and other emerging soft mechatronic systems. An experimental tube-shaped IPMC actuator is fabricated from Nafion polymer tube with inner and outer diameters of 1.3 and 1.6 mm, respectively. Likewise, the fabrication of a sub-millimeter size square cross-section rod IPMC actuator is described, with dimensions of 150 μm by 150 μm and 500 μm by 500 μm. The outer surface of the IPMC actuators are plated with platinum metal via an electroless plating process. The platinum plating is sectored into four isolated electrodes using a custom surface milling technique. Independent control of the patterned electrodes on the outer surface of the tube results in three-dimensional motion. A strain sensor is developed and integrated with the tube-shaped IPMC to sense the bending motion of the actuator as an example of its functionality. The integrated sensor is low cost and avoids the need for bulky external sensors such as lasers for measuring deflection. Thus, the sensor can be employed in practical applications including feedback control. The actuators are characterized and experimental results are presented to demonstrate performance.