Experimental study on the motions of prolate spheroidal particles under electric field

This paper presents a study on the electromechanics of prolate spheroidal conducting particles on a conducting plane. The objective of the study is to clarify the fundamental role of the non-spherical shape of particles on their behavior under electric field. We used two sizes of particles having the same major axial length but different diameter (minor axes) for the experiments. The electric field EM initiating particle motion was measured, and we found that EM was slightly higher than the theoretical field strength of the particle for rotation. The lift-off behavior of the particles at EM was different from the theoretical prediction as the particles departed from the conducting plane at significantly larger angles than the theoretical prediction. The discrepancy of the departing angle was possibly due to the predominant rotating motion of particles. With higher electric field than EM, the experimental results showed that the linear vertical motion of particles became dominant, resulting in virtually parallel lift-off of the particles. However, re-contact might occur after lift-off between the particles and the lower electrode, and increase the particle charge as a result. Charge estimation based on the lying cylindrical model is found appropriate only when a particle has a small aspect (length-to-diameter) ratio or when the field is much higher than the critical field for particle rotation.