Direct quantification of Aspergillus niger spore adhesion to mica in air using an atomic force microscope

An atomic force microscope (AFM) has been used to quantify directly the adh esion between single Aspergillus niger spores and freshly cleaved mica surf aces in air, a system that is relevant to the removal of spores by filtrati on. The measurements used 'spore probes' constructed by immobilising a sing le spore at the end of a tipless AFM cantilever. It was found that adhesion was reproducible at a relative humidity of 64%, but that it showed substan tial variability at a relative humidity of 33%, findings that are consisten t with capillary forces playing a dominant role in the adhesion process. Th e technique should prove useful both in the evaluation of different types o f filter materials and in assessing the effect of environmental conditions on spore removal efficiency. (C) 2000 Elsevier Science B.V. All rights rese rved.