Effects of clinorotation and positive dielectrophoresis on suspensions of heavy particles

Experiments in both microgravity (aboard the NASA research aircraft KC-135) and ground-based environments were conducted in a clinostat (a channel slowly rotated around its horizontal axis to simulate "weightlessness") in which a dilute suspension of heavy, positively polarized spheres was exposed to a high-gradient strong ac electric field. While dielectrophoresis is shown to provide a powerful method for the manipulation and concentration of particles in clinostats, we find that clinorotation does not simulate the zero gravity morphology of the aggregation pattern due to an unexpectedly pronounced effect of a relatively weak, rotating gravity. This effect imposes certain limitations on the use of ground-based tests for predicting the operation of electrotechnologies for the control and manipulation of suspensions in microgravity.