Soft robots composed of elastic materials can exhibit nonlinear behaviors, such as variable stiffness and adaptable deformation, that are favorable to cooperation with humans. These characteristics enable soft robots to be used in multiple applications, ranging from minimally invasive surgery and search and rescue in emergency or hazardous environments to marine or space exploration and assistive devices for people with musculoskeletal disorders. Although soft actuators composed of smart materials have been proposed as a control strategy for soft robots, most studies have focused on traditional actuators using hydraulic or pneumatic pressure. Over the years, these have made a lot of progress, but they have not been able to overcome the limitations of the complex configuration of the system and the expansion of the cross-section of the actuator when contracted. This paper merges the actuator design methodology for smart materials with the mechanical analysis of auxetic structures to present an electrically driven soft actuator architecture that achieves reliable actuation displacements. This novel soft actuator, constructed with contractile SMA springs and flexible auxetic metamaterials (FAM), has a spontaneous recovery of the shape after a contraction, a negative Poisson’s ratio, and over 90% of consistency with the performance predictions at the design stage. Our research presents a methodology for the design of a new electrically driven soft actuator, describes the manufacture of SMA springs and FAM, and concludes with the validation of the design by experimental analysis using the 2D planar soft actuator prototype. Finally, our study revealed that the application of the extraordinary characteristics of smart materials and structures together into a single architecture can be a strategy to overcome the limitations of existing soft actuator studies.
Shape‐morphing capabilities of metamaterials can be expanded by developing approaches that enable the integration of different types of cellular structures. Herein, a rational material design process is presented that fits together auxetic (anti‐tetrachiral) and non‐auxetic (the novel nodal honeycomb) lattice structures with a shared grid of nodes to obtain desired values of Poisson's ratios and Young's moduli. Through this scheme, deformation properties can be easily set piece by piece and 3D printed in useful combinations. For example, such nodally integrated tubular lattice structures undergo worm‐like peristalsis or snake‐like undulations that result in faster speeds than the monophasic counterpart in narrow channels and in wider channels, respectively. In a certain scenario, the worm‐like hybrid metamaterial structure traverses between confined spaces that are otherwise impassable for the isotropic variant. These deformation mechanisms allow us to design shape‐morphing structures into customizable soft robot skins that have improved performance in confined spaces. The presented analytical material design approach can make metamaterials more accessible for applications not only in soft robotics but also in medical devices or consumer products.
- NSF-PAR ID:
- 10371951
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 24
- Issue:
- 9
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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