Spiral tearing of thin films

Controlling the fracture propagation in a film is an important element in the design of better packaging seals that must resist handling and yet provide a tearing mechanism for easy opening. Here we show that under simple initial setup conditions a divergent tear can be obtained that follows the path of a logarithmic spiral over two decades in length scale. We study the general rules leading to the spiral growth of a tear and connect its geometry to the specific material properties of the film.