Draping Films:  A Wrinkle-to-Fold Transition

D.P. Holmes and A.J. Crosby. In Preparation. 2009.

A polymer film draping over a point of contact will wrinkle due to the strain imposed by the underlying substrate.  The wrinkle wavelength is dictated by a balance of material properties and geometry, and scales with film thickness to the three-fourths power.  At a critical strain, the stress in the film will localize, causing hundreds of wrinkles to collapse into several discrete folds.  

Delamination Folding

D.P. Holmes, A.Davis, and A.J. Crosby. In Preparation. 2009.

In this paper we present the delamination and folding of a thin polymer film from a rigid substrate under a uniaxial compression stress.  The width of the delaminated regions scale linearly with the film thickness, and at a critical compressive strain, the polymer yields in the delaminated regions going from a structure with a constant curvature to a sharp fold.

Crumpled Surface Structures [PDF]

D.P. Holmes, M. Ursiny, and A.J. Crosby. "Crumpled Surface Structures" Soft Matter, 2008, 4, 82.

We present a scalable patterning method based on surface plate buckling, or crumpling, to generate a variety of topographies that can dynamically change shape and aspect ratio in response to stimuli.

Snapping Surfaces [PDF]

D.P. Holmes and A.J. Crosby. "Snapping Surfaces" Advanced Materials, 2007, 19(21), 3589.

We present a simple, robust, responsive surface based on controlled elastic instabilities using an array of microlens shells as a surface geometry.  The snap-through transition is dictated by geometry, length-scale, and materials properties, thus the transition time, sensitivity, and magnitude change are highly tunable.