Electrorotation of Janus Particles and Particle-Particle Interaction under Self-Generated Thermal Gradient

• Main Authors: Cheng-Xiang Yang, 楊承翔
• Other Authors: Hong-Ren Jiang
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6pg284

碩士 === 國立臺灣大學 === 應用力學研究所 === 105 === The responses of colloidal particles under electric fields have been intensively studied. This technique can be applied to drug delivery, self-assembly and cell separation. The movement of particles under the electric field is mainly determined by polarizability which can be obtained by using the electrorotation method. The characteristic frequency of electrorotation can be changed by the solution properties or the size of particles. However, these reports did not consider the influence of temperature. Therefore, we apply a defocused laser on the Janus particles under the rotating electric field. The metal-coated side of Janus particles absorb the laser and create local temperature gradient which propulses the particles. However, the scientists have not fully understood the motions of particles under the electro-thermal coupling field, so we measure the motions of laser-heated Janus particles under a rotating electric field. In this study, a new active circular motion of Janus particles is observed at low frequency. The propulsive velocity of Janus particles, rotation radius and rotation direction of this circular motion can be controlled by voltage, laser power and frequency. At the high frequency, electrothermal flows occur around the Janus particles. Besides, the Janus particles in the system can be used to concentrate the negative dielectrophoresis particles and exclude the positive dielectrophoresis particles. These special phenomena can be applied to solution mixing and cell collection on microchips.