Puzzles in Surface Force Apparatus (SFA) Experiments

Since Frantz and Salmeron (1998) found that the surface energy of recleaved mica is 50{\%} higher than that cleaved using conventional cleaving method detailed in Israelachvili et al. (2004), there is concern in the SFA community on how the mica surface preparation influences observations. In addition, mica's surface condition might be responsible for the divergence between experiments and computer simulation in this area. Our group has been working on mica cleaved based on the ``Salmeron method.'' While some differences in results were obtained from mica prepared by different methods, the underlying cause for such discrepancy is not well understood. In addition, it is not clear if mica preparation affects all SFA results performed in different experimental conditions equally. This presentation will give a comparison on results obtained using mica with different cleaving methods. Experimental parameter(s) that renders mica surface condition an important consideration will be discussed.