Layered electroactive polymers for robust and reliable variable-stiffness suspensions in robotics, prosthetics and autonomous vehicles

Engineers in Prof. Mark Cutkosky's laboratory have developed patented electrostrictive elements that can support high loads over a long lifetime when used as variable suspension systems for robots, autonomous vehicles or prosthetics. Variable suspension systems can help mimic an important characteristic of animals: controlling the stiffness of their limbs through their muscles. This feature can be electrically manipulated and tuned through electroactive polymer suspensions (see Stanford Docket S12-067). To improve the basic suspension technology, the inventors developed manufacturing methods to easily fabricate uniform thin layers of electroactive polymer films on an expandable and contractible electrode. The multiple layers of the resulting electrostrictive element reduce stress concentration which then increases the overall force and stiffness of the suspension system while also improving reliability and lifetime. This technology could be used to control joints that can rapidly vary their stiffness to improve the capabilities of robots, prosthetics and other dynamically controlled devices.

Stage of Research
Elastomeric polymer suspension prototype: The inventors previously demonstrated the elastomeric polymer suspension with a prototype that changes stiffness by a factor of 10 in less than 10 milliseconds with a signal between 0 and 10 volts. (Stanford Docket S12-067)

Layered electrostrictive element prototype: The inventors fabricated a 20-layer device that supported a load of over 15 N at minimum stiffness and maximum voltage for displacements of +/- 7 mm and up to 138 N at maximum stiffness with a displacement of 20 mm. The multilayer devices have demonstrated 3 million mechanical load cycles (charging and discharging) and hundreds of thousands of stiffness variations.