Electro-rotation in octopole micro cages

Abstract

We have developed a new design for a three-dimensional (3D) micro electrode octopole, driven by rotating electric fields in the MHz range. It allows simultaneous caging and rotation of single cells or particles with a size between 5 and 30 µm. The conflict between particle caging and the induction of particle rotation has been solved by breaking the symmetry of the electrode arrangement. The octopole consists of two layers of planar electrodes processed on glass and separated by a 40 µm thick polymer spacer, which forms a flow channel. Unlike planar four-electrode devices, the 3D octopole electrode cage can trap micro objects in free suspension. In addition, we have developed a new method for the automatic detection of single particle dynamics (MOSPAD). We also give calculations for dielectric forces and torque moments and a comparison of differences to four electrodes structures.