Reconfigurable Kirigami Surfaces

Researchers

Description

Origami and its variants, such as kirigami (which allows cuts), provides a transformation from a flat sheet into a three-dimensional surface by folding. Typically, origami-inspired structures are designed to achieve a single target 3D surface. This work develops kirigami surfaces that can achieve multiple target configurations and explores multi-stability as a means of simplifying actuation between configurations. Among many potential applications, the primary motivation for this work is to enable morphing phased array antennas, which can manipulate properties such as field of view and aperture through geometric changes.

The first part of this work develops a computational framework to design new kirigami patterns capable of achieving several target surfaces. The video below shows a folding simulation of a pattern that can morph between six target surfaces (shown in blue), all with different curvature. A 3D printed prototype of the pattern is also shown below.

The pattern shown above exhibits a very rich configuration space, allowing it to morph between several surfaces. However, the tradeoff is that the patterns such as this have a large amount of kinematic freedom; the above pattern has 84 degrees of freedom. This introduces the challenge of how to actuate the structure between each configuration.

Multi-stability is a promising concept for simplifying actuation. By introducing springs throughout the structure (i.e., torsional springs on each fold), a design problem can be formulated to select spring parameters such that multiple target configurations are stable equilibrium configurations. If multiple configurations are stable, relatively simple actuation is required to snap the structure between stable configurations.

This design problem can be further extended to include mechanical stops (i.e., angle restrictions on each fold). Specified configurations can be made effectively rigid due to contact in the stops which is maintained by the spring forces. Below is a prototype of a morphing phased-array antenna that has two effectively rigid configurations that correspond to spherical and flat surfaces.

Publications:

Williams, D.E., Dorn, C., Pellegrino, S., Hajimiri, A., (2021). Origami-inspired shape-changing phased array. European Microwave Week Conference.
Li, Y. and Pellegrino, S. (2020). A theory for the design of multi-stable morphing structures. Journal of the Mechanics and Physics of Solids 136 (March): 103772.