Novel Electrostatic Actuator Uses Ferroelectrics to Boost Artificial Muscle Forces by 1,200 Times

Jul 06, 2023

Researchers from the Tokyo Institute of Technology and ENEOS Corporation have developed high-power electrostatic actuators that, they claim, could provide a means to scale the technology up for use in artificial muscles — while operating at a low driving voltage.

Electrostatic actuators, which move objects using electric fields, are simple enough to make, comprising as they do two oppositely-charge electrodes that generate a force through the application of electricity. They've even proven useful for making artificial muscles move, with one major drawback: Scaling the technology up to human-like musculature means having to drive the devices with far too high a voltage for reasonable safety.

It's this issue the researchers claim to have resolved, by switching from traditional paraelectric media to ferroelectrics — increasing the force available at lower voltages. "Ferroelectric media are superior to ordinary paraelectric media for use in electrostatic actuators in two respects," explains Suzushi Nishimura, professor at Tokyo Tech and lead on the project. "One is that they can generate a higher force by maintaining a large polarization even at low voltage, and the other is that their voltage response is almost linear, resulting in good device controllability."

Using a nematic liquid crystal that flows at room temperature, the team has been able to create forces across electrodes some 1,200 times higher than with traditional materials like insulating oil. A 3D-printed double-helical coil electrode proved the concept more than a theory, too: ""When we applied an electric field of 0.25MV m⁻¹, the device contracted by 6.3mm [around 0.25"], which is about 19 per cent of its original length," says Nishimura explains. "Visual observation showed that the device moves when a voltage of 20V is applied. This means that even a dry cell battery can power the present actuator."

The team's work has been published in the journal Advanced Physics Research, with an early view copy available on the Wiley Online Library under open-access terms.