Manipulation by dipole probe

A dipole probe is fabricated to manipulate millimeter- to submillimeter-sized objects. A tungsten needle, an alumina tube and a stainless tube are arranged concentrically in order inside the probe. The tip of the stainless tube is ground to form a needle. They are embedded in an epoxy resin and the tip of the probe is shaped hemispherically. The probe has two electrodes, a tungsten needle and a stainless steel needle, inside it. The probe can attract objects by gradient force like a bipolar electrostatic chuck. The attraction force is measured as a function of the applied voltage, and they are compared with those calculated by a 3D FEM. Both the experimental values and the calculated values are proportional to the square of the applied voltage. The determined values are, however, three times greater than those by the calculated values. The difference is ascribed to the incomplete shape of the probe model and the difference of dielectric constants of materials. The probe can attract both conductive gold particles and dielectric foam styrene particles. The probe is placed above the particle and a voltage supplier is turned on. The particle jumps up and adheres at the tip of the probe. The adhesive position is not on the center axis of the probe but the opposite side to the stainless needle against the center of the probe. The distances from the center of the probe are at a range of 0.4–1.05 mm for 20 experiments. The FEM calculation shows that maximum attraction force is for the particle placed at the opposite side to the stainless needle. Release is possible only by turning the voltage supplier off. The particle moves to the bottom of the probe, and falls after 1–2 s. The delay is due to the attenuation period of electrons accumulated at the surface of the probe.