Manipulation of single particles by utilizing electrostatic force

Because manipulation of single particles is of great importance in the fields of electronics and biology, the author has been investigating an electrostatic manipulation system. The manipulation probe consisted of dipole pin electrodes. When voltage was applied between the electrodes, the dielectrophoresis and coulombic force generated in the non-uniform electrostatic field was applied to the particle near the tip of the electrode. The particle was captured by the application of voltage and then it is released from the probe by turning off the voltage application. It was possible to manipulate not only insulative but also conductive particles. However, if a particle was charged, the Coulomb adhesion force prevented the release of the particle even when the voltage application was turned off. This condition was generally observed for small particles. Asymmetric and coaxial electrode systems were developed so that the release of the attached particle was independent of the position of the probe. Instead of turning off the voltage application, high voltage was applied to the electrodes to blow off the particle by the ionic wind generated in a corona discharge field, and the applicability of this system was demonstrated. Further, a vibration separator was developed. A three-dimensional field calculation was conducted to calculate the dielectrophoretic force by using the finite difference method and the calculated force was compared to the measured force. It was deduced that the predominant force for the particle adhesion was not dielectrophoresis but Coulomb force generated due to triboelectrification.