Bonbons predict thin shell thickness

A simple fabrication technique derived by engineers at Massachusetts Institute of Technology, Cambridge, may help chocolate artisans create uniformly smooth shells and precisely tailor their thickness. The research could also have uses far beyond the chocolate shop. By knowing just a few key variables, engineers could predict the mechanical response of many other types of shells, from small pharmaceutical capsules to large airplane and rocket bodies.

The fabrication technique quickly creates thin, rubbery shells, in which a liquid polymer is drizzled over dome-shaped molds and spheres such as ping pong balls. Each mold was coated with liquid and cured over 15 minutes. The resulting shell was peeled off the mold and was smooth—virtually free of noticeable defects—with nearly uniform thickness throughout. Combining this simple technique with the theory they derived, the team created shells of various thicknesses by changing certain variables, such as mold size and polymer density.