Functional kirigami by exploiting elastic instabilities

Shape-morphing structures change their configurations in response to environmental stimuli. Their structural properties may also change as a consequence of the reconfiguration of their geometry and topology. Such reconfigurable structures are highly desired for their engineering functionalities in developing reprogrammable metamaterials with tunable properties, providing actuation and locomotion for soft robots, and performing material-based physical intelligence computations. For an elastic structure, shape-shifting can be achieved through reversible and controllable elastic instabilities. Among various types of structures designed for mechanical metamaterials exploiting elastic instabilities, architectures inspired by a paper cutting technique, kirigami, attracted tremendous attention due to its robust and straightforward ability to transform two-dimensional flat precursors into three-dimensional space structures. In this dissertation, using a combination of physical experiments, theoretical modeling, and numerical simulations, a novel shape-shifting kirigami architecture enabled by intrinsic multistability was developed. Harnessing the proposed multistable kirigami architecture as tunable mechanical metamaterials, soft robotic grippers, and mechanical logic computing units are investigated. The first part of this dissertation introduces a multistable kirigami architecture for mechanical metamaterials. By varying the spacing between adjacent cuts in the linear parallel kirigami cutting pattern, I obtain multistable kirigami lattice structures endowed with a bistable snap-through mechanism. I will demonstrate the precise control of material stiffness, along with the ability to tailor this property in-situ by locally and reversibly switching the unit cell configurations. In the second part of the dissertation, I will present a soft gripper based on the buckling-induced deformation of kirigami shells - thin elastic shells patterned with an array of cuts. The kirigami cut pattern is determined by evaluating the shell’s mechanics and geometry. This design strategy enables precise and rapid grasping, and can be miniaturized, modularized, and remotely actuated. I show that the kirigami shell gripper can be readily integrated with an existing robotic platform or remotely actuated using a magnetic field. The kirigami cut pattern results in a simple unit cell that can be connected together in series and in parallel, to create kirigami gripper arrays capable of simultaneously grasping multiple delicate objects. The third part demonstrates a kirigami-based strategy to design and fabricate mechanical logic computing system. Utilizing a deformed kirigami architecture with a triple-well energy landscape, mechanical binary bits could be stored (0 and 1) and transmitted (superposition of 0 and 1) between the three stable equilibrium states through limit-point instability. This dissertation seeks to provide an approach for the design of reconfigurable matter which would be applied in developing multifunctional metamaterials and soft robotics.

Author dc:creator

• Yang, Yi

Advisor dc:contributor.advisor

• Holmes, Douglas P.

• Mechanical engineering

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2144/43106

OAI identifier oai:identifier

oai:open.bu.edu:2144/43106