Scaled particle theory is used to calculate depletion interactions between a hard wall and a single hard sphere solute in a hard sphere solvent. By determining the work required to insert and grow a cavity of a given size, it is possible to capture the qualitative and some quantitative behaviour of the entropie potential between the solute and the wall for separations less than the solvent diameter. The method is based upon simple geometric arguments (statistical geometry) and does not require knowledge of the internal structure of the solvent. As the diameter of the solute particle is increased, the method predicts the entropie potential with greater accuracy. However, for packing fractions in excess of 0.2, it begins to underestimate the entropie potential, although for large solute diameters the predicted barrier heights and force profiles are reasonably accurate. Possible improvements in the theory are discussed. Besides capturing the qualitative (and some quantitative) behaviour more accurately than the simple Asakura-Oosawa ideal gas approximation, the method can be extended readily to the determination of depletion forces between the solute and a hard wall of arbitrary curvature.
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Corti et al. (1998) studied this question.