Electrically Enhanced Self-Thermophoresis of Laser-Heated Janus Particles under a Rotating Electric Field

The motion of a laser-heated Janus particle is experimentally measured under a rotating electric field. Directionally circular motions of the Janus particle following or countering the direction of the rotating electric field are observed in the low-frequency region (from 1 to 6 kHz) depending on the direction of electrorotation. In the higher frequency region (>10 kHz), only pure electrorotation and electrothermal flow are observed. By measuring the dependence of the frequency, voltage, and laser heating power, we propose that the tangential component of circular motion is caused by electric field enhanced self-thermophoresis, which is proportional to the laser heating power and the electric field. This result indicates that thermophoresis could be modified by the induced zeta potential of the Janus particle tuned by the applied electric fields. By this mechanism, the intrinsic thermophoresis can be enhanced several times at a relatively low applied voltage (~3 Volt). Electrically tunable thermophoresis of a particle may bring new insights to thermophoresis phenomenon and also open a new direction for tunable active materials.