Dielectric elastomers, popular materials in robotic hands, soft robots, tunable lenses, and pneumatic valves, may now be used to create flapping robotic wings.

Researchers from the Harbin Institute of Technology in Weihai, China and the University of California, Los Angeles (UCLA), have discovered a new resonance phenomenon in a dielectric elastomer rotary joint. By applying alternating voltages to the electro-active polymer, the joint continuously bends at different angles. When the rotational inertia of the joint or the applied voltage is large enough, the joint deforms beyond 90 degrees to 180 degrees.

The new phenomenon makes the dielectric elastomer joint a good candidate for creating a soft and lightweight flapping wing for robotic birds. The development would be more efficient than bird wings based on electrical motors due to the higher energy conversion efficiency (60 to 90 percent) of the dielectric elastomer.

Made by sandwiching a soft insulating elastomer film between two compliant electrodes, dielectric elastomers can be squeezed and expanded in a plane when a voltage is applied between electrodes. In contrast to actuators based on rigid materials such as silicon, dielectric elastomers reach a very large extent of stretch, enabling new possibilities in many fields, including soft robotics, tunable optics, and cell manipulation.

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