Molecular-dynamics simulations are utilized to simulate solvation and van der Waals forces between two nanoparticles immersed in a Lennard-Jones liquid. Three different sizes and shapes of nanoparticles with solvophilic and solvophobic properties are investigated. We compare different methods for calculating van der Waals forces. For solvophilic nanoparticles, the solvation forces oscillate between attraction and repulsion as the particle separation is increased. Solvophilic solvation forces are comparable to or stronger than van der Waals forces. In the solvophobic case, solvation forces are attractive. We find that surface roughness can significantly affect the solvation-force profile for solvophilic nanoparticles. Our results indicate that surface roughness can alter the balance between solvation and van der Waals forces in a solvophilic colloidal suspension and that a desirable force balance can be achieved by choosing nanoparticles with certain textures and/or shapes. (C) 2003 American Institute of Physics.