Additive manufacturing (AM) of regenerated biomaterials is in its infancy despite the urgent need for alternatives to fuel -based

KEYWORDSBiomimetics, bio-inspired design, computational design, hierarchical computation, adaptation, mesh data structure, multi-functional, natural exoskeletons HIGHLIGHTS• MetaMesh is a hierarchical computational construct to generate articulated armored surfaces • The ancient armored fish Polypterus senegalus provides source of bio-inspiration • Local, regional and global levels of organization embed functional differentiation • Articulation of scale units is preserved by neighborhood morphing techniques • The model is adaptable to a wide array of complex hosting surfaces GRAPHICAL ABSTRACT ABSTRACTMany exoskeletons exhibit multifunctional performance by combining protection from rigid ceramic components with flexibility through articulated interfaces. Structure-to-function relationships of these natural bioarmors have been studied extensively, and initial development of structural (load-bearing) bioinspired armor materials, most often nacremimetic laminated composites, has been conducted. However, the translation of segmented and articulated armor to bioinspired surfaces and applications requires new computational constructs. We propose a novel hierarchical computational model, MetaMesh, that adapts a segmented fish scale armor system to fit complex "host surfaces." We define a "host" surface as the overall geometrical form on top of which the scale units are computed. MetaMesh operates in three levels of resolution: (i) locally -to construct unit geometries based on shape parameters of scales as identified and characterized in the Polypterus senegalus exoskeleton, (ii) regionally -to encode articulated connection guides that adapt units with their neighbors according to directional schema in the mesh, and (iii) globally -to generatively extend the unit assembly over arbitrarily curved surfaces through global mesh optimization using a functional coefficient gradient. Simulation results provide the basis for further physiological and kinetic development. This study provides a methodology for the generation of biomimetic protective surfaces using segmented, articulated components that maintain mobility alongside full body coverage. 2 INTRODUCTIONStructural materials in nature achieve diverse functions such as toughness, flexibility and strength, through spatial variation in material properties and morphometry across organizational hierarchies with precise interfacial control [1][2]. Biologically inspired engineering, or the translation of design schema in nature, being chemical, physical, genetic, or geometric, to synthetic systems requires complex models that both capture the intricacies of biological models and adapt their multi-scale design principles to new operative constraints. The process of mapping functional requirements between design solutions presents several theoretical and technical challenges to ensure continuity and coherence of all components. With the advent of high resolution materials characterization methods, powerful computational simulation capabilities, and increasingly precise digital ...

Structural hierarchy and material organization in design are traditionally achieved by combining discrete homogeneous parts into functional assemblies where the shape or surface is the determining factor in achieving function. In contrast, biological structures express higher levels of functionality on a finer scale through volumetric cellular constructs that are heterogeneous and complex. Despite recent advancements in additive manufacturing of functionally graded materials, the limitations associated with computational design and digital fabrication of heterogeneous materials and structures frame and limit further progress. Conventional computer-aided design tools typically contain geometric and topologic data of virtual constructs, but lack robust means to integrate material composition properties within virtual models. We present a seamless computational workflow for the design and direct digital fabrication of multi-material and multi-scale structured objects. The workflow encodes for and integrates domainspecific meta-data relating to local, regional and global feature resolution of heterogeneous material organizations. We focus on water-based materials and demonstrate our approach by additively manufacturing diverse constructs associating shape-informing variable flow rates and material properties to mesh-free geometric primitives. The proposed workflow enables virtual-to-physical control of constructs where structural, mechanical and optical gradients are achieved through a seamless design-to-fabrication tool with localized control. An enabling technology combining a robotic arm and a multi-syringe multi nozzle deposition system is presented. Proposed methodology is implemented and full-scale demonstrations are included.

The Massachusetts Institute of Technology (MIT) Mediated Matter Group is honing its research into robotic swarm printing by focusing its efforts on material sophistication, or ‘tunability’, and communication or coordination between fabrication units. Here, the group's Neri Oxman, Jorge Duro‐Royo, Steven Keating, Ben Peters and Elizabeth Tsai illustrate this by describing three case studies that investigate robotically controlled additive fabrication at architectural scales.

Despite recent advancements in digital fabrication and manufacturing, limitations associated with computational tools are preventing further progress in the design of non-standard architectures. This paper sets the stage for a new theoretical framework and an applied approach for the design and fabrication of geometrically and materially complex functional designs coined Fabrication Information Modeling (FIM). We demonstrate systems designed to integrate form generation, digital fabrication, and material computation starting from the physical and arriving at the virtual environment. The paper reviews four computational strategies for the design of custom systems through multi-scale trans-disciplinary data, which are classified and ordered by the level of overlap between the modeling media and the fabrication media: (1) the first model takes as input biological data and outputs 3D printed digital materials organized according to functional constraints; (2) the second model takes as input geometry and environmental data and outputs robotically wound fibers organized according to functional constraints; (3) the third model takes as input material and environmental data and outputs CNC deposited pastes organized according to functional constraints; (4) the forth model takes as input biological, material and environmental data and outputs robotically deposited polymers organized according to functional constraints. The analysis of these models will demonstrate the FIM approach and point towards its value to designers who seek to inform their work through multi-scale transdisciplinary data, a capability that is currently missing from standard design-to-fabrication workflows.