EHD with mobile electrodes propulson

What is it about?

Conduction Electrohydrodynamics refers to a physical mechanism that directly converts electrical energy into mechanical energy of a fluid, through the interaction between a high-voltage electrostatic field and the ions in a dielectric fluid. We report the idea, design and testing of a novel system for propelling millimeter-scale untethered robots in fluids using Conduction Electrohydrodynamics (EHD) in combination with mobile electrodes. Through the use of mobile electrodes, instead of using a fluid as the actuation medium, we exploit the reaction forces exerted by the fluid on the electrodes. The robot is designed as an inverted sail-boat, with the thrust generated on the sail submerged in the liquid. The performance of the robot in terms of speed, acceleration and produced thrust is experimentally measured, showing a relative speed of a ~1.28 bl/s at 2263 V, among the highest recorded for robots propulsion in liquids using smart actuator technologies. The response is also fast and shows a power law correlation with the produced thrust.

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Why is it important?

Actuators are surely among the most critical technologies for achieving mobile, untethered and soft-bodied robots. Conventional rigid robots are actuated almost entirely by electromagnetic motors and rigid pneumatic cylinders. Since robots bodies are becoming lighter and more compliant and their application fields are increasing in number, novel actuation technologies, able to face the new challenges posed by the changes in the field, are required. Conduction EHD with mobile electrodes, which we report in this work, is based on reaction body forces so it is an actuator system that does not require any moving structure . It can be easily miniaturised since, unlikely magnetic fields, the area of activation does not depend on the size of the electrodes. Additionally absorbed powers (≈10 mW) and currents (≈10 µA) are extremely small.

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