Coefficient of restitution for bouncing nanoparticles

We demonstrate the measurement of the coefficient of restitution, e, for nanoparticles, through observations of the final distribution of bismuth particles that have bounced within silicon V-grooves. The experiments, taken together with complementary molecular-dynamics simulations, show that e is generally smaller for liquid than for solid nanoparticles, and that macroscopic theories underestimate the velocity dependence of e. Hence, while nanoparticles are harder than bulk materials, once they have begun to yield the rate of increase of the inelastic deformation is greater.