This robotic ray, developed at Zhejiang University in Hangzhou, China, is propelled by soft flapping wings made of dielectric elastomers, which bend when electricity is applied to them. Dielectric elastomers respond very quickly with relatively large motions, but they require very high voltages (on the order of 10 kilovolts) to get them to work. Traditionally, dielectric elastomers are covered in insulation, but for this aquatic application the researchers instead just submerged everything insulation free, relying on the water to act as both electrode and electric ground.
via IEEE Spectrum
