Reconfigurable laminates enable multifunctional robotic building blocks

Abstract

Folding and assembling of two-dimensional laminated materials have greatly facilitated robot fabrication by creating robots with lightweight body frames, articulated joints, and embedded actuators and sensors. The combinations of rigid laminates bridged by thin-film flexures, often called rigid-flex linkages, have been extensively used in micro- and macro-scale robots to achieve complex joint motions with simplified kinematic and dynamic properties. Much like traditional robots these rigid-flex laminate robots are designed with a fixed body-plan, and thus may face challenges when environments require mechanical reconfiguration such as stiffening joints for load support or changing appendage morphologies for navigating confined spaces. Recent advances in adaptive materials and smart actuators have highlighted the features that robots with morphable geometries and tunable mechanical properties can provide, such as self-folding joints and variable stiffness and damping mechanisms. However, incorporation of these reconfigurable elements into laminate robots has been limited. In this paper, we present a new method for creating quasi two-dimensional structures for robotics, called reconfigurable laminates, that use geometric reconfiguration of laminate layers to alter passive mechanical properties and actuate joints. Unlike traditional rigid-flex linkages with single-layered flexures, here we create laminate joints with dual-layered soft hinges and rigid channels allowing a multitude of reconfiguration opportunities including: sliding-layer laminates for passive stiffness control, snapping-hinge locks for reconfigurable joints, and buckle-bend joints for bending actuation. Through experimental characterization we demonstrate the capabilities of these multifunctional robotic building blocks.

Piece‐By‐Piece Shape‐Morphing: Engineering Compatible Auxetic and Non‐Auxetic Lattices to Improve Soft Robot Performance in Confined Spaces

“…Yet, to our knowledge, anti‐tetrachiral patterns have not been used in soft robotics. While honeycomb and reentrant patterns have been used in mobile robots, [ 53,54 ] we hope that here by showing that metamaterials quantitatively improve performance in a challenging environment will encourage further use of these types of materials in new and innovative ways—perhaps using our analysis to create multi‐stiffness materials ( E A ≠ E N ) for layer jamming, [ 61 ] smoothly varying Poisson's ratio within 3D‐printable biomaterials, or design mechanisms that amplify local actuation with material‐scale FEA.…”

Development of a Stiffness‐Adjustable Articulated Paddle and its Application to a Swimming Robot

“…[21][22][23] A sliding laminate mechanism could adjust the stiffness of a flexural joint by displacing a thin laminate kept insides that joint. [24] An underwater flapping tail using this mechanism was built, and its stiffness state had a huge effect when swimming in open water and confined channel.…”

“…First, a novel stiffness-adjustable paddle cascaded with dozens of passive flaps for aquatic rowing is developed. Although three main components of the proposed paddle 1) sliding laminatebased variable stiffness, [24,32] 2) film flexural joint with mechanical stopper; [8] and 3) passive flap for extra drag reduction during recovery stroke) [25,26,29] were already addressed from previous studies, this article newly introduced the fabrication method of integrating all these components into a monolithic structure. Secondly, a non-tethered swimming robot propelled by a bilateral pair of paddles is developed to demonstrate the advantage of stiffness change in frequency-varying swimming.…”

“…[8]. Furthermore, the stiffness of flexural joint was adjusted by adopting the sliding laminate‐based approach [ 24 ] owing to ease of integration with a film joint‐based mechanism. So far, no previous aquatic rowing robots driven by stiffness‐adjustable propulsors had demonstrated both enhancement of swimming speed and efficiency upon active stiffness change.…”

Bi-Directional Origami-Inspired SMA Folding Microactuator

“…The concept presented here uses the technique of self-folding, following the ancient art of paper folding, known as origami, by which flat sheets transform into numerous three-dimensional (3D) shapes. The shape change can be achieved by bimorph structures [1], smart composites [2,3], or smart materials such as shape memory alloys (SMAs), responding to an external stimulus such as the environmental temperature or an electrical current. The advantage of origamiinspired designs in engineering is their compact and deployable setup, which has proven its versatility in various macroscopic applications, e.g., airbags [4], wings [5], or tools for minimally invasive surgery [6].…”