Self-sustained Levitation of Dust Aggregate Ensembles by Temperature Gradient Induced Overpressures

In laboratory experiments we observe dust aggregates from 100 \mu m to 1 cm in size composed of micrometer sized grains levitating over a hot surface. Depending on the dust sample aggregates start to levitate at a temperature of 400 K. Levitation of dust aggregates is restricted to a pressure range between 1--40 mbar. The levitating is caused by a Knudsen compressor effect. Based on thermal transpiration through the dust aggregates the pressure increases between surface and aggregates. Dust aggregates are typically balanced 100 \mu m over the surface. On a slightly concave surface individual aggregates are trapped at the center. Ensembles of aggregates are confined in a 2D plane. Aggregates are subject to systematic and random translational and rotational motion. The levitated aggregates are well suited to study photophoretic or thermophoretic forces on dust aggregates or the mutual interaction between dust aggregates.