Friction between cellulose surfaces measured with colloidal probe microscopy

Colloidal probe microscopy was employed to study sliding friction between model cellulose surfaces in aqueous solutions. Regardless of scan size, friction exhibits irregular stick–slip behavior related to surface roughness. At small scan sizes (∼10 nm), the coefficient of friction decreases with increasing load. Above a critical scan size of about 100 nm — corresponding to the average size of asperities on one of the model surfaces — friction forces are independent of scan size, but depend on the load. Hydrodynamic forces contribute little to friction. Small amounts of high molecular weight, polyelectrolytes decrease significantly sliding friction between cellulose surfaces.