Strongly nonlinear waves in a chain of Teflon beads
  One dimensional "sonic vacuum" type phononic crystals were assembled from a chain of Teflon spheres with different diameters in a Teflon holder. It was demonstrated for the first time that this polymer-based "sonic vacuum", with exceptionally low elastic modulus of particles, supports propagation of strongly nonlinear solitary waves with a very low speed. 
C. Daraio, V. F. Nesterenko, E. Herbold, S. Jin