Atomic force microscopy analysis of wool fibre surfaces in air and under water

Wool fibre surfaces have been treated by solvent cleaning which leaves the native covalently bound surface lipid layer intact, and by alcoholic alkali which removes the lipid layer. The resultant surfaces have been analysed b y atomic force microscopy (AFM), with particular emphasis on force-distance (F-d) methods. Methodologies were developed for investigation in situ in w ater of both the surface topography and the characteristics of the lipid la yer. Longitudinal surface texturing was resolved in images of wool fibre su rfaces in air; the texturing remained prominent after exposure to water. Hi gh resolution F-d curves revealed features associated with the lipid layer. A simple formalism was used to show that the layer had a thickness of a fe w nm, and an effective stiffness of some 0.12 +/- 0.01 N/m. Strong adhesive interactions, equivalent to a pressure of 0.1 MPa, acted on the tip at the tip-to-substrate interface. The methodology and formalism are likely to be relevant in the broad field of thin-film analysis and for fibre technology . (C) 2000 Elsevier Science Ltd. All rights reserved.