Session: S-03 Novel Structural Concepts

Paper Number: 171942

171942 - "Programming" Reconfigurable Origami Sheets With Bistable Hinges 

Multistable origami patterns have garnered increasing attention for their ability to transition between multiple stable configurations. This versatility has led to a wide range of applications, from mechanical logic systems to deployable shelters. Traditionally, multistability in origami sheets has mostly relied on crease patterns that involve stretching the creases or bending the faces during folding. In this study, we present a new approach to achieve multistability by incorporating buckled elastic shims at each crease.

Specifically, we fabricate our origami structures by laminating a piece of double-sided tape between two rigid 3D-printed PLA panels to form a hinge. Each hinge has a gap that allows for the insertion of a plastic shim. The length of the shims is chosen to be greater than the gap size so that the shim buckles upon insertion. This creates an asymmetric torque-angle profile that biases the folds in the origami pattern towards a mountain or valley state. The bias can be reprogrammed after fabrication by changing the buckling direction of the shim with respect to the origami sheet, switching the fold from a mountain to a valley state.

By coupling shims through origami sheets with multiple folds we unlock a rich space that is studied through experiment and simulation. We showcase that adding multiple shims at a single crease creates additional locked states, next to the mountain and valley states, when the shims are buckled in opposing directions. It is possible to target specific angles for each locked state based on the geometry of the shims. This allows for the creation of reprogrammable  6-vertex origami sheets that can switch between various fold patterns, such as the Miura and Yoshimura pattern. Furthermore, we observe that these sheets exhibit global multistable modes that are history dependent.

Multiple strategies to change the state of the hinges are developed. These allow the sheets to be reprogrammed through local and global inputs beyond pressing directly on the shims. Introducing asymmetries in the gap allows for an instability to arise that causes the shim to snap to its opposing state when it is folded in the dispreferred direction. We showcase that the angle at which this snap-through happens can be tuned through the geometry of the structure. Furthermore, we developed a strategy that allows a shim to snap when the origami is folded in its preferred direction. This enables the sheets to sequentially fold in different programmed configurations under the same loading conditions, which opens up the possibility to create mechanically intelligent structures that can fold into different shapes based on global force inputs. 

Presenting Author: Leon Kamp Harvard university

Presenting Author Biography: Graduate student in the Bertoldi group at Harvard university, studying reconfigurable structures, multistability and physical intelligence.