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The dielectrophoretic response of different solids is investigated in liquid media of various permittivities and resistivities. The solids investigated had a wide range of both relative permittivity (3.8 to 350) and resistivity (10-4 to 1016 Omega m). The use of dioxane and water solutions provided liquid media of controllable relative permittivity in the range 2.2 to 80. The response, which is found to be frequency dependent, is determined for various combinations of insulating and conducting materials at three frequencies: 102 Hz, 104 Hz and 2.55 MHz. The results show that the resistivities of the materials exercise a control over the response comparable to that of their relative permittivities. The correlation of the observed response with that predicted using a theory developed for non-insulating materials is discussed.

The behaviour of bubbles rising in AC isomotive electric fields of 50 Hertz frequency was investigated in several dielectric liquids. Isomotive electrodes were immersed in the sample liquids and aligned so that the motion of single bubbles of nitrogen rising in the interelectrode space was opposed by the dielectrophoretic force. The transit time of each bubble was timed over two set distances as a function of the voltage applied to the electrodes. The set distances were defined by three laser beams so that their interruption by a bubble could be detected optoelectronically and timed using a microcomputer. Analysis of the data presented indicates that the dielectrophoretic force on the bubbles is only position independent in the interior of the isomotive electric field.

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