Directional Roll-up of Nanomembranes Mediated by Wrinkling

Abstract

We investigate the relaxation of rectangular wrinkled thin films intrinsically containing an initial strain gradient. A preferential rolling direction, depending on wrinkle geometry and strain gradient, is theoretically predicted and experimentally verified. In contrast to typical rolled-up nanomembranes, which bend perpendicular to the longer edge of rectangular patterns, we find a regime where rolling parallel to the longer edge of the wrinkled film is favorable. A nonuniform radius of the rolled-up film is well reproduced by elasticity theory and simulations of the film relaxation using a finite element method.

Stretchable Magnetoelectronics

“…Furthermore, the specimens are peeled along the stripe structure, which favors the wrinkling perpendicular to it. The aligned wrinkling of the metal film, with the stress being relaxed along the sensor stripe, makes it more stiff in the orthogonal direction 178 , which prevents the perpendicular stress relaxation and associated wrinkling in most regions. Instead, a slight bending across the GMR stripe could be observed on the peeled sensor elements.…”

Shapeable magnetoelectronics

“…159,165 Furthermore, the specimens are peeled along the stripe structure, which favors the wrinkling perpendicular to it. The aligned wrinkling of the metal film, with the stress being relaxed along the sensor stripe, makes it stiffer in the orthogonal direction, 166 which prevents the perpendicular stress relaxation and associated wrinkling in most regions. Instead, a slight bending across the entire GMR stripe could be observed on the peeled sensor elements.…”

Nature‐Inspired Stimuli‐Responsive Self‐Folding Materials

“…Li et al [20] and Schmidt [21] experimentally demonstrated the opposite scenario, namely a preference for longside rolling, in the case where bilayers are progressively etched from a substrate. They observed that when the tube circumference was much larger than the width or the aspect ratio of the rectangle was high, rolling always occurred from the long side.…”

“…Control of rolling/folding direction is very important for programmed folding. For example, Schmidt demonstrated that introduction of wrinkles allows switching to short-side rolling [21].…”