A modular strategy for distributed, embodied control of electronics-free soft robots

Abstract

Robots typically interact with their environments via feedback loops consisting of electronic sensors, microcontrollers, and actuators, which can be bulky and complex. Researchers have sought new strategies for achieving autonomous sensing and control in next-generation soft robots. We describe here an electronics-free approach for autonomous control of soft robots, whose compositional and structural features embody the sensing, control, and actuation feedback loop of their soft bodies. Specifically, we design multiple modular control units that are regulated by responsive materials such as liquid crystal elastomers. These modules enable the robot to sense and respond to different external stimuli (light, heat, and solvents), causing autonomous changes to the robot’s trajectory. By combining multiple types of control modules, complex responses can be achieved, such as logical evaluations that require multiple events to occur in the environment before an action is performed. This framework for embodied control offers a new strategy toward autonomous soft robots that operate in uncertain or dynamic environments.

Free-Form Liquid Crystal Elastomers via Embedded 4D Printing

“…Many unique methods for regulating LCE mesogen alignment by modifying printing parameters have been explored in the literature ,, and can be implemented to generate further complexity during LCE actuation. Further 3D geometries should be explored to harness the unique shape transformation of LCE structures for more complex actuations such as snapping, jumping, or crawling …”

“…AM is most well known for on-demand fabrication of geometrically complex 3D shapes, some of which are impossible to create by using traditional manufacturing techniques. Meanwhile, advances in stimulus-responsive materials such as hydrogels, shape memory polymers, magneto-active materials, and liquid crystal elastomers (LCEs) have demonstrated unique promise for the fabrication of smart, responsive structures that have found widespread applications in biomedical devices, − soft robots, − and deployable structures. − When 3D-printed, smart materials can transform as a function of time, leading to a new paradigm of printing called 4D printing …”

Mechanical metamaterials and beyond

“…Active mechanical metamaterials are generally created with various functional materials such as shape memory polymers (SMPs) 22 , shape memory materials (SMMs) 13 , etc. Using functional and self-adaptive materials enables realizing active metamaterials that can automatically respond to different external stimuli 33 , 131 , 142 , 143 . Programmable mechanical metamaterials often refer to tunable mechanical characteristics (e.g., stiffness 99 , 100 , Poisson’s ratio 29 , 45 , 47 and elastic wave propagation 31 ), or overall tunable characteristics (e.g., the ability to adapt in response to external excitations 139 and self-stimulated under certain stimuli 13 ).…”

“…It is desirable to minimize the complexity associated with integrating numerous electronic pieces into robotic systems, and to move beyond form factor limitations imposed by traditional electronics. Some decision-making capabilities of robots (e.g., trajectory control in response to environmental cues 142 ) may be able to be embodied as metamaterial-based multifunctional devices, to increase reliability, robustness, and maintainability. However, this emerging direction is still in its infancy, and it remains to be fully explored.…”

Engineering Kirigami Frameworks Toward Real‐World Applications

“…The ability to tailor mechanical properties based on these design parameters makes kirigami a highly versatile and promising tool to engineer materials with desired characteristics and applications. Considerable efforts have been made to investigate and optimize kirigami designs, with the aim to unleash their full potential across diverse fields, including soft robotics, [15][16][17][18][19][20] flexible electronics, [21][22][23][24][25][26][27][28] medical devices, [29,30] and energy storage. [31][32][33][34] Owing to its profound relevance across a multitude of applications, there are several recent reviews that have surveyed this ever-evolving topic, providing a foundation for understanding kirigami designs.…”