The interaction between electrorheological particles in AC electric field studied using optical tweezers

The dipole interaction between a pair of electrorheological (ER) particles under an external AC electric field was confirmed in a dynamic case using optical tweezers positioning and a system of high speed imaging and image processing. By measuring the interactions between two micron-sized ER particles with both central distance and structure forming time, the structure response time and the interaction strength were obtained for the particles under an AC electric field. The spacial resolution of the optical tweezers-high speed imaging-image processing system is 0.26mum. The sampling rate of the high-speed video recorder is up to 8000 frame/s with the corresponding time resolution being 0.125 ms.