Pneumatic Extension Actuators With Kirigami Skins

Abstract

Soft pneumatic actuators have found many applications in robotics and adaptive structures. Traditionally, these actuators are constructed by wrapping layers of reinforcing helical fibers around an elastomeric tube. This approach is versatile and robust, but it suffers from a critical disadvantage: cumbersome fabrication procedures. Wrapping long helical filaments around a cylindrical tube requires expensive equipment or excessive manual labor. To address this issue, we propose a new approach towards designing and constructing pneumatic actuators by exploiting the principle of kirigami, the ancient art of paper cutting. More specifically, we use “kirigami skins” — plastic sleeves with carefully arranged slit cuts — to replace the reinforcing helical fibers. This paper presents an initial investigation on a set of linear extension actuators featuring kirigami skins with a uniform array of cross-shaped, orthogonal cuts. When under internal pressurization, the rectangular-shaped facets defined by these cuts can rotate and induce the desired extension motion. Through extensive experiments, we analyze the elastic and plastic deformations of these kirigami skins alone under tension. The results show strongly nonlinear behaviors involving both in-plane facet rotation the out-of-plane buckling. Such a deformation pattern offers valuable insights into the actuator’s performance under pressure. Moreover, both the deformation characteristics and actuation performance are “programmable” by tailoring the cut geometry. This study lays down the foundation for constructing more capable Kirigami-skinned soft actuators that can achieve sophisticated motions.

Pneumatic Soft Actuators With Kirigami Skins

“…As a result, the kirigami skin is forced to deform in-plane and buckle out-of-plane. While it is well-understood that a stretched kirigami skeet can develop out-of-plane deformations ( Rafsanjani and Bertoldi, 2017 ; Iannucci and Li, 2020 ), the kirigami skin’s deformation in this study is uniquely different. Due to the presence of the internal balloon, the skin can only buckle radially outwards (aka.…”

“…Therefore, this study aims to build upon our proof-of-concept preliminary study in ( Iannucci and Li, 2020 ) and uncover the linkage between the kirigami skin design and the corresponding actuation motion characteristics. To this end, we formulate a new kinematics model that introduces “virtual folds” to the kirigami skin at locations showing the most concentrated deformation.…”