Depletion forces near curved surfaces

Based on density functional theory the influence of curvature on the deplet ion potential of a single big hard sphere immersed in a fluid of small hard spheres with packing fraction eta(s) either inside or outside of a hard sp herical cavity of radius R-c is calculated. The relevant features of this p otential are analyzed as a function of eta(s) and R-c. There is a very slow convergence towards the Flat wall limit R-c --> infinity. Our results allo w us to discuss the strength of depletion forces acting near membranes both in normal and lateral directions and to make contact with recent experimen tal results.