Bio-inspired physical intelligence for soft robotics

Abstract

<p indent="0mm">Biological organisms can efficiently move, prey, mate, and grow in complex, unstructured natural environments. These remarkable behaviors are endowed not only by the computational intelligence in the biological brains but also by the physical intelligence encoded in their bodies. Physical intelligence can be defined as encoding sensing, actuation, control, memory, logic, computation, adaptative material and structure, self-learning, self-healing, and self-decision-making into physical bodies of the biological or robotic agents. Physical intelligence can also be generated during the interaction between the agent’s body and the environment over time. The previous focus of intelligent robots is primarily focused on the computational intelligence. As a new paradigm, physical intelligence is expected to boost intelligent robots in real-world applications. Soft robots commonly use soft stimuli-responsive materials and intelligent structures and maintain high stretchability and considerable deformation, therefore, have intrinsic environmental conformable physical property. Thus, soft robots are essential platforms for testing the hypothesis of physical intelligence in nature. This review mainly focused on three key physical intelligence elements encoded in the natural organisms’ bodies: Material, structure, and morphology. Through bio-inspired design, smart soft materials, smart soft structures, and adaptable morphologies can be integrated into the robot’s body, thus introducing bio-inspired physical intelligence into the robots. By integrating bio-inspired physical intelligence, soft robots could reduce the cost of control, improve the response speed of the systems, enhance the robustness of robots in extreme environments, and embed intelligence into the micro- and small-scale robots. The research on bio-inspired physical intelligence may also promote the multi-disciplinary collaboration of biology, robotics, materials science, chemistry, computer science, etc. In this review, we first describe the characteristics and principles of physical intelligence in natural organisms’ material, structure, and morphology. Then we introduce the purposes and related key technologies and methods of realizing bio-inspired physical intelligence of soft robots. Furthermore, we enumerate the typical applications of bio-inspired physical intelligence of soft robots. Finally, we highlight the trends and challenges of bio-inspired physical intelligence of soft robots in the future. The research on bio-inspired physical intelligence for soft robots is still in the primary stage. There are several critical questions and challenges to be addressed. First, researchers should investigate the basic principles of physical intelligence in biomechanics and then apply the basic principles to guide the development of soft robots. Second, intelligent materials need to meet the challenges of fully integrating sensing, actuation, memory, computation, and communication in soft robots. To this end, an interesting approach is to use stimulus-responsive materials as the basic building blocks to rationally design and integrate different functions into a single composite material. Third, smart structures, like mechanical metamaterials can be a promising research direction in the field of intelligent structures for soft robots. Aided by artificial intelligence and 3D printing, mechanical metamaterials will boost the performance of soft robots in the foreseeable future. Fourth, the potential of adaptive morphology can be realized by endowing soft robots with the ability to self-optimize their morphologies in the environments. Finally, the integration of intelligent materials, structures, and morphologies in the soft robot system will significantly improve physical intelligence. We believe that bio-inspired physical intelligence for soft robotics will be an important research direction in the future.