Lowering of Electrostatic Actuator Driving Voltage and Increasing Generated Force Using Spontaneous Polarization of Ferroelectric Nematic Liquid Crystals

Abstract

Although electrostatic actuators have a simple structure and are lightweight, their range of application is limited because a high applied voltage of more than several kilovolts is required for practical use. Since the force acting between the electrodes of an electrostatic actuator is determined by the electric charge accumulated at the electrode/dielectric interface, the focus is on spontaneous polarization of ferroelectrics to increase the charge. As the ferroelectric material, a nematic liquid crystal material with a spontaneous polarization of 5 µC cm −2 is used. It is demonstrated that a force of 1.3 N is generated at an applied electric field of 0.5 MV m −1 . This force is 1200 times higher than that for standard paraelectric materials with a dielectric constant of ten. Further, the generated force responds linearly to the applied voltage, whereas it is proportional to the square of the applied voltage for paraelectric materials. The actuator function of this ferroelectric is examined using a double‐helical coil electrode fabricated using a 3D printer. It can be successfully operated at a voltage of several tens of volts. Under an electric field of 0.25 MV m −1 , a remarkable contraction of 6.3 mm occurs, corresponding to 19% of the original length.