Electrorotation of a metallic coated Janus particle under AC electric fields

Electrorotations (EROTs) of the Pt-silica Janus particles are measured in different conditions under rotatingelectric fields. Unlike simple particles, we find that the rotation direction of a Janus particle is mainly opposite to the direction of theelectric field (counter-field), which is similar to the metallic particles, while the rotation direction may reverse from counter-field to co-field at the low-frequency region (1 MHz), depending on the thickness ofmetallic coating and conductivities of solutions. We also find that EROT of a Janus particle reaches a maximum angular speed at acharacteristic frequency, which increases with the thickness ofmetallic coating and can be one order higher than that of a fully metalliccoated particle. These results suggest that the EROT responses of a Janus particle have bothdielectric and metallic features and these responses are not simply averaged responses of its both sides. Half sidemetallic coating reduces the time ofpolarization due to the lack of fullyelectric field screening ability comparing with the metallic particles. The specialproperties ofpolarization of a Janus particle underelectric fields may provide a method to create designable micro-rotors or active particles for applications.

Source: Applied Physics Letters - November 9, 2016 Category: Physics Authors: Yu-Liang Chen and Hong-Ren Jiang Source Type: research