Quality Ultralight Ensuring the light-weight and high-strength properties of carbon-fiber composite materials is costly. Cheung and Gershenfeld (p. 1219 , published online 15 August; see the Perspective by Schaedler et al. ) have mass-produced cross-sectional parts that can be assembled into strong, ultralight lattices. Carbon-fiber composites are sliced into cross-shaped pieces that can be independently tested and reliably assembled into rigid and reversible cuboctahedral lattices.

We describe an approach for the discrete and reversible assembly of tunable and actively deformable structures using modular building block parts for robotic applications. The primary technical challenge addressed by this work is the use of this method to design and fabricate low density, highly compliant robotic structures with spatially tuned stiffness. This approach offers a number of potential advantages over more conventional methods for constructing compliant robots. The discrete assembly reduces manufacturing complexity, as relatively simple parts can be batch-produced and joined to make complex structures. Global mechanical properties can be tuned based on sub-part ordering and geometry, because local stiffness and density can be independently set to a wide range of values and varied spatially. The structure's intrinsic modularity can significantly simplify analysis and simulation. Simple analytical models for the behavior of each building block type can be calibrated with empirical testing and synthesized into a highly accurate and computationally efficient model of the full compliant system. As a case study, we describe a modular and reversibly assembled wing that performs continuous span-wise twist deformation. It exhibits high performance aerodynamic characteristics, is lightweight and simple to fabricate and repair. The wing is constructed from discrete lattice elements, wherein the geometric and mechanical attributes of the building blocks determine the global mechanical properties of the wing. We describe the mechanical design and structural performance of the digital morphing wing, including their relationship to wind tunnel tests that suggest the ability to increase roll efficiency compared to a conventional rigid aileron system. We focus here on describing the approach to design, modeling, and construction as a generalizable approach for robotics that require very lightweight, tunable, and actively deformable structures.

Abstract-Understanding how linear strings fold into 2-D and 3-D shapes has been a long sought goal in many fields of both academia and industry. This paper presents a technique to design self-assembling and self-reconfigurable systems that are composed of strings of very simple robotic modules. We show that physical strings that are composed of a small set of discrete polygonal or polyhedral modules can be used to programmatically generate any continuous area or volumetric shape. These modules can have one or two degrees of freedom (DOFs) and simple actuators with only two or three states. We describe a subdivision algorithm to produce universal polygonal and polyhedral string folding schemas, and we prove the existence of a continuous motion to reach any such folding. This technique is validated with dynamics simulations as well as experiments with chains of modules that pack on a regular cubic lattice. We call robotic programmable universally foldable strings "moteins" as motorized proteins.

A novel origami cellular material based on a deployable cellular origami structure is described. The structure is bi-directionally flat-foldable in two orthogonal (x and y) directions and is relatively stiff in the third orthogonal (z) direction. While such mechanical orthotropicity is well known in cellular materials with extruded two dimensional geometry, the interleaved tube geometry presented here consists of two orthogonal axes of interleaved tubes with high interfacial surface area and relative volume that changes with fold-state. In addition, the foldability still allows for fabrication by a flat lamination process, similar to methods used for conventional expanded two dimensional cellular materials. This article presents the geometric characteristics of the structure together with corresponding kinematic and mechanical modeling, explaining the orthotropic elastic behavior of the structure with classical dimensional scaling analysis.S Online supplementary data available from stacks.iop.org/sms/23/094012/mmedia

Architected lattice materials are some of the stiffest and strongest materials at ultra‐light density (<10 mg cm−3), but scalable manufacturing with high‐performance constituent materials remains a challenge that limits their widespread adoption in load‐bearing applications. We show mesoscale, ultra‐light (5.8 mg cm−3) fiber‐reinforced polymer composite lattice structures that are reversibly assembled from building blocks manufactured with a best‐practice high‐precision, high‐repeatability, and high‐throughput process: injection molding. Chopped glass fiber‐reinforced polymer (polyetherimide) lattice materials produced with this method display absolute stiffness (8.41 MPa) and strength (19 kPa) typically associated with metallic hollow strut microlattices at similar mass density. Additional benefits such as strain recovery, discrete damage repair with recovery of original stiffness and strength, and ease of modeling are demonstrated.

Ultralight materials present an opportunity to dramatically increase the efficiency of load-bearing aerostructures. To date, however, these ultralight materials have generally been confined to the laboratory bench-top, due to dimensional constraints of the manufacturing processes. We show a programmable material system applied as a large-scale, ultralight, and conformable aeroelastic structure. The use of a modular, lattice-based, ultralight material results in stiffness typical of an elastomer (2.6 MPa) at a mass density typical of an aerogel 5.6 mg cm 3 (). This, combined with a building block based manufacturing and configuration strategy, enables the rapid realization of new adaptive structures and mechanisms. The heterogeneous design with programmable anisotropy allows for enhanced elastic and global shape deformation in response to external loading, making it useful for tuned fluid-structure interaction. We demonstrate an example application experiment using two building block types for the primary structure of a 4.27 m wingspan aircraft, where we spatially program elastic shape morphing to increase aerodynamic efficiency and improve roll control authority, demonstrated with full-scale wind tunnel testing.

We describe a robotic platform for traversing and manipulating a modular 3D lattice structure. The robot is designed to operate within a specifically structured environment, which enables low numbers of degrees of freedom (DOF) compared to robots performing comparable tasks in an unstructured environment. This allows for simple controls, as well as low mass and cost. This approach, designing the robot relative to the local environment in which it operates, results in a type of robot we call a "relative robot." We describe a bipedal robot that can locomote across a periodic lattice structure, as well as being able to handle, manipulate, and transport building block parts that compose the lattice structure. Based on a general inchworm design, the robot has added functionality for travelling over and operating on a host structure.

We present a material-robot system consisting of mobile robots which can assemble discrete cellular structures. We detail the manufacturing of cuboctahedral unit cells, termed voxels, which passively connect to neighboring voxels with magnets. We then describe "relative" robots which can locomote on, transport, and place voxels. These robots are designed relative to and in coordination with the cellular structure--the geometry of the voxel informs the robot's global geometric configuration, local mechanisms, and end effectors, and robotic assembly features are designed into the voxels. We describe control strategies for determining build sequence, robot path planning, discrete motion control, and feedback, integrated within a custom software environment for simulating and executing single or multi-robot construction. We use this material-robot system to build several types of structures, such as 1D beams, 2D plates, and 3D enclosures. The robots can navigate and assemble structures with minimal feedback, relying on voxelsized resolution to achieve successful global positioning. We show multi-robot assembly to increase throughput and expand system capability using a deterministic centralized control strategy.