Elastogranular columns and beams.

String and grains can be combined to create structures capable of bearing significant loads. In this work, we prepare columns and beams through a layer-by-layer deposition of granular matter and loops of fiber strings, and characterize their mechanical properties. The loops cause the grains to jam, and the inter-grain contact leads to a Hertzian-like constitutive response. Initially, one force chain that propagates vertically through the column bears most of the compressive load. As the magnitude of the load is increased, more force chains form in the column, which act in parallel to increase its stiffness, akin to a "super-Hertzian" regime. Applying a compressive prestress enables the structures to withstand shear, enabling the fabrication of cantilevered beams. This work provides a mechanical framework to use elastogranular jamming to create rapid, reusable infrastructure components, such as columns, beams, and arches from inexpensive, commonplace materials, such as rocks and string.

Design and Computational Modeling of a 3D Printed Pneumatic Toolkit for Soft Robotics.

Soft and compliant robotic systems have the potential to interact with humans and complex environments in more sophisticated ways than rigid robots. The majority of the state-of-the art soft robots are fabricated with silicone casting. This method is able to produce robust robotic parts, yet its results are difficult to quantify and replicate. Silicone casting also limits design complexity as well as customization due to the need to make new molds. As a result, most designs are tailored for simple, individual tasks, that is, bending, gripping, and crawling. To address more complex engineering challenges, this work presents soft robots that are fabricated by using multi-material three-dimensional printing. Instead of monolithic designs, we propose a pneumatic modular toolkit consisting of a bending and an extending appendage, as well as rigid building blocks. They are assembled to achieve different tasks. We show that the performance of both appendages is (1) repeatable, that is, the same internal pressure results in the same rotation or extension across multiple specimens and repetitions, and (2) predictable, that is, the respective deformations can be modeled by using finite element analysis. Using multiple instances of both building blocks, we demonstrate the versatility of this toolkit by assembling and actuating a gripper and a crawling caterpillar. The reliability of the mechanics of the building blocks and the assembled robots show that this simple toolkit can serve as a basis for the next generation of soft robots.

Author Correction: Active Printed Materials for Complex Self-Evolving Deformations.

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Active printed materials for complex self-evolving deformations.

We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus.