Plasma particle lofting : experimental investigation of dust removal force

Dust is everywhere. Sometimes it's harmless, but sometimes it needs to be removed. Especially in modern optical machinery, dust control can be of vital importance. In this research we look at dust on a surface. We focus on the behaviour under influence of a plasma.

The dust particles will stick to a surface due to the adhesive Van der Waals force. This force is hard to determine theoretically, as it highly depends on the local surface topology. Therefore, we have developed a method to experimentally measure this adhesive force. This method uses the inverse piezoelectric effect. We apply vibrations with increasing amplitude to the surface. This way we can observe which force is required for dust removal.

The required force is reduced when a plasma is applied over the surface. This may have different causes: the charging due to the plasma sheath may cause an additional force; the surface chemistry may change causing a lower adhesive force; the piezo vibrations may be influenced by the electrons. Current research is ongoing to find which of these effects causes the force reduction.