Researchers at the Massachusetts Institute of Technology have created a theory and a fabrication technique that could help chocolatiers perfect their confections, and also could help engineers determine what kind of mechanical response they can achieve from thin coatings.

Chocolate inspires a theory for coatings. Image Credit: Melanie Gonick/MIT NewsThe researchers created a technique to make thin, rubbery shells on dome-shaped molds similar to ping-pong balls. Using a liquid polymer that was drizzled, they let the molds cure and solidify. They then observed that the coating was smooth and virtually uniform. They then determined that changing the variables, such as the size of the mold or the density of the polymer, could create shells of various thicknesses and density.

The fabrication technique and theory can predict a shell’s final thickness based on the shape and geometry of the mold, as well as the rheology of the original material. The theory calculates the viscosity of the liquid, the radius of the mold, density of the fluid, gravity and curing time, then derives the shell’s ultimate thickness. The technique could be used to create artificial vesicles, smart skins and packaging films. The researchers say they hope their discovery will reignite interest in shell mechanics.