Effect of Electrode Protrusions on Micro Object Manipulation using Grid Electrode Structure

A novel technique that manipulates tiny objects using electrostatic forces is proposed. This technique, which has grid-structure electrodes, potentially can drive multiple objects individually. One of the possible applications is precise sorting of small plastic pieces by materials or colors. The dielectrophoretic force that is generated by concentrated electric field is mainly utilized in this technique. In this study, the effect of a protrusion attached at the cross-point of the grid was investigated using a single-cross device which is a basic structure of this technique. A glass sphere with approximately 1.2 mm diameter was used as a model for target objects. The driving force exerted on the target was determined with high-speed photography of the trajectories, along with numerical simulation. It was elucidated that the electric field concentrated by the protrusion enhanced the forces directing to the cross point. At the same time, the comparison with the simulation of the dielectrophoretic force and the calculation of the field strength suggested that a little amount of charge generated by discharge affected the driving force. Moreover, the transfer of the glass sphere between two cross-points with the interval of 2 mm in approximately 300 ms was successful.