Pneumatic Soft Actuators With Kirigami Skins

Abstract

Soft pneumatic actuators have become indispensable for many robotic applications due to their reliability, safety, and design flexibility. However, the currently available actuator designs can be challenging to fabricate, requiring labor-intensive and time-consuming processes like reinforcing fiber wrapping and elastomer curing. To address this issue, we propose to use simple-to-fabricate kirigami skins—plastic sleeves with carefully arranged slit cuts—to construct pneumatic actuators with pre-programmable motion capabilities. Such kirigami skin, wrapped outside a cylindrical balloon, can transform the volumetric expansion from pneumatic pressure into anisotropic stretching and shearing, creating a combination of axial extension and twisting in the actuator. Moreover, the kirigami skin exhibits out-of-plane buckling near the slit cut, which enables high stretchability. To capture such complex deformations, we formulate and experimentally validates a new kinematics model to uncover the linkage between the kirigami cutting pattern design and the actuator’s motion characteristics. This model uses a virtual fold and rigid-facet assumption to simplify the motion analysis without sacrificing accuracy. Moreover, we tested the pressure-stroke performance and elastoplastic behaviors of the kirigami-skinned actuator to establish an operation protocol for repeatable performance. Analytical and experimental parametric analysis shows that one can effectively pre-program the actuator’s motion performance, with considerable freedom, simply by adjusting the angle and length of the slit cuts. The results of this study can establish the design and analysis framework for a new family of kirigami-skinned pneumatic actuators for many robotic applications.

Engineering by Cuts: How Kirigami Principle Enables Unique Mechanical Properties and Functionalities

“…There have been many successful implementations on very stiff constitutive materials like graphene, [ 4 , 55 , 56 ] boron nitride (h‐BN) nano‐sheets, [ 57 ] MoS2 monolayer, [ 58 , 59 ] metal, [ 60 ] and 2D phosphorene. [ 61 ] As a result, super‐stretchable kirigami materials have shown broad application appeals, such as architectures, [ 62 ] shape‐morphing systems, [ 63 , 64 ] flexible electronics, [ 65 , 66 , 67 , 68 , 69 ] sunlight tracking and wearable solar cell, [ 18 , 70 ] robotic actuators, [ 14 , 71 ] optics, [ 72 ] stretchable heaters, [ 73 ] energy harvester, [ 74 , 75 ] bioprobe, [ 76 ] artificial skin, [ 77 ] telecommunication devices, [ 78 ] and adaptive transparent surfaces. [ 79 ] We will detail some of these applications in Section 3 .…”

“…Other self‐actuation strategies for kirigami involve using shape memory alloy (SMA) actuators, [ 137 , 138 ] or soft pneumatic actuators. [ 14 , 139 , 140 ] Integrating the design and self‐actuation methods can provide a simple yet powerful method to program morphing surfaces.…”

“…Reproduced under the terms of the Creative Commons CC‐BY license. [ 14 ] Copyright 2021, The Authors. Published by Frontiers Media, S.A. e) A micrometer‐scale kirigami spring based on graphene.…”

Configuration detection and external force tuning for soft-bending actuators under position constraint

“…6 Moreover, soft robots have greater conformity with the environment and the behavior of the human body and provide much greater freedom of action compared to traditional rigid robots. 7,8 Soft fiber-reinforced bending actuators (SBAs), 9 having a monolithic structure and being made of flexible materials such as elastomers, 10,11 hydrogels, 12 and shape memory alloys 13,14 are a key component in the design and construction of soft robots. Their actuation can be achieved in a variety of ways by using electric charges, 15 chemical reactions, and pressurized fluids.…”

Phononic Bandgap Programming in Kirigami

“…On the other hand, kirigami -the ancient art of paper cutting -has become a versatile engineering framework for designing and constructing multi-functional material systems [17]. Careful cutting can impart stretchability to thin sheet materials like metal alloys, graphene [18], and electronics [19], thus fostering new designs of flexible sensors [20], robots [21,22], and metamaterials [23][24][25]. In particular, a stretched kirigami sheet can buckle out-of-plane and exhibit multi-stability [26].…”