The goal of this project is creation of a material combining innovative actuation with integrated sensing. The actuation principle is based on a bistable electroactive polymer. This comprises an electrically insulating polymer sheet sandwiched between two flexible conductive layers. The polymer sheet exhibits a phase transition, with a large increase in compliance as temperature exceeds a transition value. In order to actuate the material, it is first heated above transition, then a potential is applied across the polymer. Electrostatic forces pull the conductive layers together, increasing the area of the sheet, possibly by several hundred percent. These high strains, combined with boundary constraints, cause large displacements of the actuator. Then the material is allowed to cool and transition back to the stiff form, locking in the new actuator position and allowing the electric potential to be removed. Thin film sensors measuring pressure or touch are integrated with the actuator sheets. The resulting high-strain, variable-compliance, self-sensing, device is well-suited for robotic manipulators with muscle-like dexterity. Such manipulators would have application to a wide variety of robotic systems, including prosthetic hands, patient rehabilitative equipment, compliant surgical instruments, artificial organs, and humanoid robots for assisted living. This project will provide summer research intern opportunities for minority high school students. Undergraduate and graduate students will also participate in the project, to gain hands-on research experience, and analytical, communication, and inter-personal skills.
This project investigates an artificial muscle material combining variable stiffness, large-strain actuation and sensing, and explores the application of the material for dexterous manipulation that is critically needed in a wide range of robotic applications. It differs from traditional robotics in that the manipulation is object-centered. The objects can have various different shapes, stiffness, surface texture, and weight. Artificial muscles combining sensing, actuation, and variable stiffness are desired to produce dexterous manipulations from gentle touch to firm gripping, with local controllability. Electroactive polymers have shown promise for reproducing both the active and structural properties of human muscles. Among these "artificial muscle" materials, dielectric elastomers exhibit low stiffness, high actuation strain and force output. Bistable electroactive polymers have stiffness variable up to 1000 times. In the softened state, the bistable polymer behaves like an elastomer and can be actuated like a dielectric elastomer. The combination of variable stiffness and large strain actuation will enable a new generation of artificial muscles for bioinspired robotic applications. A 6-finger manipulator will be demonstrated to grip and lift a variety of objects including eggs, golf balls, smartphones, and to squeeze a specified length of toothpaste out of the tube.
