Controlling the layout of elasticity in materials provides new opportunities for generating various functionalities such as shape-morphing capability, large stretchability, and elastic softening for aeronautics, drug delivery, soft robotics, and stretchable electronics applications. Recently, techniques building upon kirigami principles, the Japanese art of paper cutting, have been considered an effective strategy to control stiffness and deformation of materials by systemically integrating cut patterns into inextensible sheets. The performance of kirigami-inspired materials relies primarily on geometric features defined by cut patterns rather than chemistry of constituents, which can enable high compatibility with diverse material sets across a wide range of length scales. However, kirigami has been relatively unexplored to control adhesion and current challenges such as the intrinsic trade-off between high deformability and load-bearing capacity limits applications that require large shape change and structural strength. This thesis demonstrates that the kirigami approach is a powerful tool to control interfacial properties of adhesive films, and that composite approaches in kirigami-inspired material can overcome the deformation-strength trade-off. The kirigami principle is applied to adhesives to control adhesion through arrays of linear cut patterns (Chapter 2). The spatial layout of elasticity in the kirigami-inspired adhesive enhances adhesion over homogeneous adhesive systems and generates anisotropic adhesion. The utility of the proposed adhesive design criteria is further extended to complex non-linear cut patterns (Chapter 3). These non-linear patterns significantly enhance adhesion relative to linear patterns in adhesives and unpatterned films, while also enabling easy release and spatial control of adhesion across a sheet. The enhancement enabled by cut geometry remains effective in diverse adhesives, on various surfaces, and in wet and dry conditions. The adhesion dependence on cut geometry is further investigated to understand how arrays of sub-patterns adjacent to primary non-linear patterns affect adhesion performance (Chapter 4). Kirigami composites are also developed to overcome the trade-off between large deformability and load-bearing capacity (Chapter 5). A composite architecture is developed consisting of low melting point metal alloys incorporated into patterned elastomeric layers. This composite approach shows the ability to rapidly morph into complex, load-bearing shapes, while achieving reversibility and self-healing capability through phase change driven by embedded heaters. The utility of the multi-functional composite is demonstrated through a multimodal morphing drone which transforms from a ground to air vehicle and an underwater morphing machine which can be reversibly deployed to collect cargo. This thesis is then summarized by discussing key findings, contributions, and future perspectives (Chapter 6). / Doctor of Philosophy / Controlling stiffness across a material sheet provides new opportunities for emerging fields such as soft robotics and stretchable electronics. Recently, a technique based on kirigami principles, the Japanese art of paper cutting, has gained interest as an effective strategy for designing materials. This kirigami technique provides intriguing possibilities to create tunable and highly functional materials by adding cuts (e.g. controlling material geometry) without changing chemistry. This kirigami technique is also compatible with diverse materials from extremely small (e.g. nanoscale) to large scales (e.g. over millimeters to even beyond). However, engineered kirigami has been mostly used for creating deformable electronics and stretchable films. Further, although it makes the material soft and stretchable, it can reduce load-bearing capacity and strength. In this thesis, kirigami is utilized to engineer adhesives with unique properties and create multi-functional morphing materials that overcome extensibility-loading-bearing trade-offs. Inspired by the kirigami concept, an array of linear cut patterns is integrated into an adhesive strip, and adhesion is measured (Chapter 2). The kirigami adhesive shows stronger adhesion over an unpatterned adhesive, and it also shows high adhesion in one direction but low adhesion in the other direction. The utility of the adhesive design criteria is then extended to complex non-linear cut patterns (Chapter 3). This enables enhanced adhesion, easy release, spatial control of adhesion, and rapidly customized adhesive properties through a digital fabrication approach. The adhesion is strongly controlled by the cut size and density, thus this kirigami technique is applicable to diverse adhesives, on various surfaces, and in wet and dry conditions. The effects of non-linear patterns on adhesion are studied in further detail (Chapter 4). Diverse arrays of sub-patterns around original non-linear patterns are demonstrated to control the adhesion performance. Following the adhesion work in previous chapters, shape-changing materials are studied. Here, a kirigami approach is used to develop multi-functional, morphing composites (Chapter 5). The composite shows the ability to change into complex shapes while support loads through hard metal alloys and kirigami-inspired soft encapsulating layers, while achieving reversibility and self-healing capability through the phase change between solid and liquid states by an embedded heater. The utility of the multi-functional composite is demonstrated through a morphing drone which transforms from a ground to air vehicle and an underwater morphing machine which can be reversibly deployed to collect cargo. This thesis is then summarized by discussing key findings, contributions, and future perspectives (Chapter 6).

This project set out to determine, by experimentation, what changes could be made to the material properties of paper-based strips by making different patterns of incisions. The purpose of the project was to evaluate the possibilities of paper-based strips as tourniquets in clinical use for venepuncture, in which a hypodermic needle is inserted into a vein. A tourniquet is required, at a site closer to the heart than where the needle is inserted, to exert a pressure small enough to allowblood to continue being pumped through the arteries, but large enough to stop blood flowing backthrough the veins. In this way the veins become visible and enable a needle to be inserted into one of them. The paper-based strips were each 50mm by 27mm, and their properties to be examined  were the tearing strength and the extension under a range of forces. Thirty one patterns were tested, four times each. This project has aimed to use force/extension graphs to assess different pattern types for their potential use as tourniquets during venepuncture procedures. / I det här arbetet undersöktes hur pappersremsors egenskaper förändras med olika utskurna mönster. Syftet var att ta fram och utvärdera en experimentell testmetod för att särskilja och utvärdera funktionen hos pappersremsorna med tillhörande mönster. Remsorna är tänkta användas som stasband när man ska ta blodprov i vården. Stasbandet ska ansätta ett trycktillräckligt lågt för att tillåta blodgenomströmning i artärer men tillräckligt högt för att stoppa blodgenomströmning i venerna. Om detta uppfylls blir venerna synliga och det blir lättare att sticka nålen i en ven, som annars kan vara svår att se. Remsorna, med area 128 x 27 mm2 där 50x 27 mm2 är täckt med mönster, utvärderades med avseende på sträckgräns och töjning vid olika laster. Trettioett mönster testades, varje prov upprepades fyra gånger. Resultaten visas i krafttöjningsdiagram. Den framtagana testmetoden kan användas som en första screening av olikamönster i pappersremsor för att studera hur de kan användas som stasband.

abstract: Origami and Kirigami are two traditional art forms in the world. Origami, from ‘ori’ meaning folding, and ‘kami’ meaning paper is the art of paper folding. Kirigami, from ‘kiri’ meaning cutting, is the art of the combination of paper cutting and paper folding. In this dissertation, Origami and kirigami concepts were successively utilized in making stretchable lithium ion batteries and three-dimensional (3D) silicon structure which both provide excellent mechanical characteristics. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2016

For origami-based designs to be functional, they need to be stable. Typically, stability is achieved through the introduction of exterior supports or members. This work focuses on incorporating stability into deployable origami-based engineering applications, including the development of deployable stiffeners or hard stops and generating concepts for stable origami-based systems in specific applications. Two types of deployable stiffeners are developed. Models for transcrease hard stops are presented, which can be directly implemented into origami-patterns to block motion at a specified angle. Thickness Utilizing Deployable Hard Stops (ThUDS), adapted from the transcrease hard stop models, can be implemented into thick materials for use in origami-based design. The application of self-deploying, self-locking ThUDS in an origami-based CubeSat reflectarray is shown, designed using optimization principles. Last, various multistable furniture concepts are presented, with stability incorporated into the concept design. These concepts focus on using composite wood as the base material, due to wood's abundance and commonality in furniture design.

Mechanical metamaterials are becoming an emerging frontier in scientific research and engineering innovation due to its unique properties, arising from innovative geometrical designs rather than constituent materials. Reconfigurable metamaterials can change their shapes and structures dramatically under external forces or environmental stimuli. It offers an enhanced flexibility in performance by coupling dynamically changing structural configuration and tunable properties, which has found broad potential applications in 3D meso-structures assembly and programmable machines. Despite extensive studies on harnessing origami, the ancient paper folding art, for design of mechanical metamaterials, the study on utilizing its close cousin, kirigami (“kiri” means cut), for programmable reconfigurable mechanical metamaterials and machines remains largely unexplored. In this dissertation, I explore harnessing the uniqueness of cuts in kirigami for achieving extraordinary mechanical properties and multifunctionalities in krigami-based metamaterials, as well as its potential applications in programmable machines and soft robotics. I first exploit the design of hierarchical cuts for achieving high strength, high stretchability, and tunable mechanical properties in hierarchical rotation-based kirigami mechanical metamaterials. Hierarchical line cuts are introduced to a thin sheet composed of non-stretchable materials (copy paper), less stretchable materials (acrylics), and highly stretchable materials (silicone rubber, PDMS), to explore the role of constituent material properties. The cut unit in the shape of solid rectangles with the square shape as a special case was demonstrated for achieving the extreme stretchability via rigid rotation of cut units. It shows that a higher hierarchical level contributes to a higher expandability and lower stiffness to constituent material. However, when such kirigami structure is applied onto less-stretchable materials (e.g. acrylics), its stretchability is almost eliminated regardless of the hierarchical level, because severe stress concentration at rotation hinges leads to the structure failure at the very beginning stage of pattern transformation. To address this challenge, I propose a hinge design which can significantly reduce the stress concentration at cut tips and enable high stretchability for rotation-based kirigmai structure, even on acrylic thin sheet. I also study the tunable photonic behavior of proposed hierarchical kirigami metamaterial by simple strain-induced structural reconfiguration. I then explore the programmability of kiri-kirgami structures by introducing notches to the simplest kirigami structure patterned with parallel line cuts for breaking its deformation symmetry. Engraving the flat-cut kirigami structure enables programmable control of its out-of-plane tilting orientation, thus generating a variety of inhomogeneous structural configurations on demand. I find that compared to the its counterpart without engraving notches, the introduced notches have a negligible effect on both the stress-strain curve over the large strain range and the extreme stretchability, however, they reduce the critical buckling force largely. Furthermore, I demonstrate the adaptive kiri-kirigami structure through local actuation with its tilting directions to be programmed and switched in response to the change of environmental temperature. Lastly, I demonstrate the potential promising outcome of kiri-kirigami structures as adaptive building envelope in energy efficient buildings, especially in electric saving for lighting and cooling load saving through numerical simulation. In addition to kirigami based soft metamaterials, I also investigate the utilization of soft materials and soft structures for robotics functions. First, I explore the design of soft doming actuator upon pneumatic actuation and its implications in design of multifunctional soft machines. I propose a novel bilayer actuator, which is composed of patterned embedded pneumatic channel on top for radial expansion and a solid elastomeric layer on bottom for strain-limiting. I show that both the cavity volume and bending angle at the rim of the actuated dome can be controlled by tuning the height gradient of the pneumatic channel along the radial direction. I demonstrate its potential multifunctional applications in swimming, adhesion, and gripping. I further explore harnessing doming-based bilayer doming actuator for developing soft climbing robot. I characterize and optimize the maximum shear adhesion force of the proposed soft adhesion actuator for strong and rapid reversible adhesion on multiple types of smooth and semi-smooth surfaces. Based on the switchable adhesion actuator, I design and fabricate a novel load-carrying amphibious climbing soft robot (ACSR) by combining with a soft bending actuator. I demonstrate that it can operate on a wide range of foreign horizontal and vertical surfaces, including dry, wet, slippery, smooth, and semi-smooth ones on ground, as well as under water with certain load-carrying capability. I show that the vertical climbing speed can reach about 286 mm/min (1.6 body length/min) while carrying over 200g object (over 5 times the weight of ACSR itself) during climbing on ground and under water. / Mechanical Engineering

No description available.