A report describes a size-sorting method to separate and concentrate micrometer-size dust from a broad size range of particles without using sieves, fluids, or other processes that may modify the composition or the surface properties of the dust.The system consists of four processing units connected in series by tubing. Samples of dry particulates such as lunar soil are introduced into the first unit, a fluidized bed. The flow of introduced nitrogen fluidizes the particulates and preferentially moves the finer grain sizes on to the next unit, a flat plate impactor, followed by a cyclone separator, followed by a Nuclepore polycarbonate filter to collect the dust.
By varying the gas flow rate and the sizes of various orifices in the system, the size of the final and intermediate particles can be varied to provide the desired products. The dust can be collected from the filter. In addition, electron microscope grids can be placed on the Nuclepore filter for direct sampling followed by electron microscope characterization of the dust without further handling.
This work was done by David McKay and Bonnie Cooper of Johnson Space Center. MSC-25264-1