Mechanical Iris Stretcher for Electroactive Polymers

An electroactive polymer is a material capable of changing its size and shape when an electric field is present. It is composed of a thin film of dielectric elastomer and two electrodes placed on the top and bottom of the dielectric material. Since the rediscovery of their capabilities, electroactive polymers have been proposed as novel materials for use in numerous fields such as in bioengineering, electronics, hydraulics, and aerospace. It has been demonstrated that the actuation potential of electroactive polymer dielastomers can be significantly enhanced by mechanically pre-straining the material prior to application of an electric field. Application of uniform pre-strain is critical for uniform actuation and is challenging to achieve. This research details methods for constructing an automated uniform stretcher that resulted in the production of a LabView controlled iris stretcher for flexible materials. The high torque stretcher was capable of pre-straining materials with a minimum diameter of 1 inch mm) to a maximum diameter of 16 inches. The stretcher calculates the percent strain and has adjustable speed control through a high torque micro-stepper motor and controller. The stretcher’s capabilities were demonstrated on materials within varying tensile strengths up to 725 psi.