Contact between swabs and surfaces during explosives detection

The ability to remove residual explosives from surfaces is crucial to detecting the presence of explosives in a variety of settings. Trace amounts adhere to the hands and equipment of those handling explosives and are subsequently transferred to clothing, parcels, vehicles, or other surfaces. Improved methods to remove detectable amounts of these explosives from surfaces will allow more effective detection of explosives in a range of environments. Current collection methods can be classified as either contact or non-contact. Contact sampling dislodges explosive particles through physical contact with a swab and collects particles that adhere more strongly to the swab than to the original surface. Non-contact sampling relies on momentum transfer between a moving fluid (typically air) and the explosive residue to dislodge the particles from the surface. This research focuses on contact sampling between an explosives detection swab and a variety of surfaces often encountered by transportation security. The adhesion forces between selected explosives and surfaces are first measured to determine the explosives\u27 adhesion ability. Then the contact between selected swabs and surfaces is simulated and analyzed to determine the percentage of the surface in which a particle of an approximate size could remain undetected when the swab is placed against the surface. This value can be used as a first-generation ranking tool to describe the swab\u27s ability to interrogate the surface