Design and analysis of origami-inspired structures

This work focuses on creating novel structures by combining elements of common origami patterns. Multiple different types of physical and computer models are implemented to represent and analyze the structures. These structures have a broad range of potential applications, such as architecture, soft robotics, and aerospace. A combined Miura and EggBox pattern is presented. The combined unit cell for the sheet is parameterized, the Poisson ratio is calculated, and the sheets are 3D modeled using Solid Edge. Tubes constructed from the combined pattern are computer modeled and a static analysis is performed using the MERLIN2 software package in GNU Octave. These tubes can then be woven into cellular structures, some examples of which are 3D modeled and discussed. Also presented are many different combinations of the Miura and Resch unit cells. Crease patterns were drawn in Inkscape and computer folded using Origami Simulator. Some of these tessellations were found in literature but others were not. In addition to traditional origami paper folding, other fabrication methods for folded structures are presented, such as selective laser sintering (SLS) 3D printing and laser cutting of plastic sheets. Some software tools were developed and implemented to aid design.Includes bibliographical references

Plate-impact loading of cellular structures formed by selective laser melting

Porous materials are of great interest because of improved energy absorption over their solid counterparts. Their properties, however, have been difficult to optimize. Additive manufacturing has emerged as a potential technique to closely define the structure and properties of porous components, i.e. density, strut width and pore size; however, the behaviour of these materials at very high impact energies remains largely unexplored. We describe an initial study of the dynamic compression response of lattice materials fabricated through additive manufacturing. Lattices consisting of an array of intersecting stainless steel rods were fabricated into discs using selective laser melting. The resulting discs were impacted against solid stainless steel targets at velocities ranging from 300 to 700 m s-1 using a gas gun. Continuum CTH simulations were performed to identify key features in the measured wave profiles, while 3D simulations, in which the individual cells were modelled, revealed details of microscale deformation during collapse of the lattice structure. The validated computer models have been used to provide an understanding of the deformation processes in the cellular samples. The study supports the optimization of cellular structures for application as energy absorbers. © 2014 IOP Publishing Ltd

Bio Inspired Lightweight Composite Material Design for 3D Printing

Lightweight material design is an indispensable subject in product design. The lightweight material design has high strength to weight ratio which becomes a huge attraction and an area of exploration for the researchers as its application is wide and increasing even in every day-to-day product. Lightweight composite material design is achieved by selection of the cellular structure and its optimization. Cellular structure is used as it has wide multifunctional properties in addition to the lightweight characteristics. Applications of light weight cellular structures are wide and is witnessed in all industries from aerospace to automotive, construction to product design. In this thesis, the one-step and two-step approaches for design and prediction of cellular structure\u27s performance are presented for developing lightweight cellular composites reinforced by discontinuous fibers. The topology designs of a 2D honeycomb hexagon model, a 2D cuttlefish model, and a 3D octahedron model, inspired by bio material, are presented. Computer modeling based on finite element analysis was conducted on the periodic representative volume elements identified from the cellular structural models to characterize the designed cellular composites performance and properties. Additive manufacturing technique (3D printing) was used for prototyping the design, and experimental tests were carried out for validating the design methodology

Geometric Modeling of Cellular Materials for Additive Manufacturing in Biomedical Field: A Review

Advances in additive manufacturing technologies facilitate the fabrication of cellular materials that have tailored functional characteristics. The application of solid freeform fabrication techniques is especially exploited in designing scaffolds for tissue engineering. In this review, firstly, a classification of cellular materials from a geometric point of view is proposed; then, the main approaches on geometric modeling of cellular materials are discussed. Finally, an investigation on porous scaffolds fabricated by additive manufacturing technologies is pointed out. Perspectives in geometric modeling of scaffolds for tissue engineering are also proposed

Procedural function-based modelling of volumetric microstructures

We propose a new approach to modelling heterogeneous objects containing internal volumetric structures with size of details orders of magnitude smaller than the overall size of the object. The proposed function-based procedural representation provides compact, precise, and arbitrarily parameterised models of coherent microstructures, which can undergo blending, deformations, and other geometric operations, and can be directly rendered and fabricated without generating any auxiliary representations (such as polygonal meshes and voxel arrays). In particular, modelling of regular lattices and cellular microstructures as well as irregular porous media is discussed and illustrated. We also present a method to estimate parameters of the given model by fitting it to microstructure data obtained with magnetic resonance imaging and other measurements of natural and artificial objects. Examples of rendering and digital fabrication of microstructure models are presented

Bioprinting with live cells

Tissue engineering is an emerging multidisciplinary field to regenerate damaged or diseased tissues and organs. Traditional tissue engineering strategies involve seeding cells into porous scaffolds to regenerate tissues or organs. However, there are still some challenges such as difficulty in seeding different type of cells spatially into a scaffold, limited oxygen and nutrient delivery and removal of metabolic waste from scaffold and weak cell-adhesion to scaffold material need to be overcome for clinically successful results. Because of those challenges, novel scaffold-free approaches based on cellular self-assembly or three-dimensional (3D) bioprinting have been recently pursued. Bioprinting is a relatively new technology where living cells with or without biomaterials are printed layer-by-layer in order to create 3D living structures. In 3D bioprinting, cell aggregates and hydrogels are termed as bioink used as building blocks that are placed by the bioprinter into precise architecture according to developed computer models. In this chapter, we focus on the scaffold-free, self-assembly based bioprinting approaches and some of the novel developments in this field. This chapter will also discuss the importance as well as the challenges for 3D bioprinting using stem cells. We aim to highlight the importance of the continuous cell printing in order to fabricate 3D biological structures with predefined shapes as being the building blocks of large and complex tissues

Path planning and topology optimization for biomimetic three-dimensional bioprinting

Tissue engineering is a highly promising multi-disciplinary field for development of biological substitutes to replace or enhance the functions of damaged tissue or organs. Traditionally, highly porous scaffolds have been used for most of the tissue engineering applications. However, the challenges in seeding the cells into a scaffold and possible immunogenic reactions of scaffold materials have led to a new method of bioprinting with live cells. With the recent advancement in bio-additive manufacturing, cells with or without biological active molecules and biomaterials can be bioprinted layer-by-layer to form three-dimensional (3D) tissue constructs. In this research work, novel biomodeling and path planning methods for bioprinting are proposed so three-dimensional tissue structures could be biomimetically printed with live cells directly from medical images. First, the medical images of the targeted tissue are imaged and segmented to convert computer tomography (CT) or magnetic resonance imaging (MRI) images to a mesh model. For path planning and optimization, the generated mesh models need to be converted to computer-aided (CAD) models. The captured mesh models are converted into smooth parametric surfaces by developed novel biomodeling algorithms. Then, several bioprinting strategies are proposed to bioprint live multi-cellular aggregates using the created computer models. Because mechanically weak cellular aggregates need to be supported perfectly at each layer, several support structure generation algorithms are proposed. The proposed methods are used to make bioprinted cellular aggregates conserve their planned 3D form, while providing sufficient conditions for cell fusion. The proposed algorithms are implemented and several example tissue structures are bioprinted by directly controlling a bioprinter with the generated commands. The results show that multicellular aggregates and their support structures can be bioprinted biomimetically in the form of the biomodeled tissues