Healing surface defects with nanoparticle-filled polymer coatings: Effect of particle geometry

One of the current challenges in designing "smart" materials is to create coatings that effectively heal defects in the underlying surface. Such coatings would significantly extend the life-time and utility of manufactured components. Due to the push to fabricate nano-scale devices, there is a particular need to create materials for healing the nano-scale defects that arise in these devices. What is needed is a "responsive" coating that can be readily applied to the system, such that when a defect appears, the coating effectively senses its presence and then causes the repair of the damaged area. Through molecular dynamics, we examine how a molten polymer coating containing nanoparticles could be utilized to repair a nano-scale crack on a surface. Particles are driven into the crack by a purely entropic depletion attraction. This effect can be enhanced by using rod-like particles.

Snapshots of filled polymer coatings near a surface notch with (a) spherical and (b) rod-like particles. Coatings filled with rod-like particles significantly reduce the stress concentrations at the notch. The application of such nanocomposite coatings could potentially yield defect-free surfaces that exhibit enhanced mechanical properties.
Stress profile for a surface notch subjected to strain when coated with (a) pure polymer and (b) polymer filled with rod-like particles.

^{Updated: Nov 16, 2010}