In the past few years, we have covered many bio-inspired robots here. This electrohydraulic Arachno-bot is also worth a look. A team of researchers of the Robotic Materials Department at the Max Planck Institute for Intelligent Systems and the University of Colorado Boulder were inspired by spiders’ joints to develop robots without bulky components and connectors. As they explain:
they built a flexible pouch made of thin plastic films (either polyester or polypropylene will do) which they filled with a liquid dielectric—a vegetable-based oil. They then placed electrodes on each side of the pouch. These liquid-filled pockets serve as actuators, in which the hydraulic power is generated through electrostatic forces. The pouch is attached to a rotary joint. When a high voltage is applied between the electrodes, the electrostatic forces cause the liquid dielectric to shift inside the pouch and the joint to flex.