A Review of Soft Actuator Motion: Actuation, Design, Manufacturing and Applications

Abstract

Compared with traditional rigid robots, soft robots have high flexibility, low stiffness, and adaptability to unstructured environments, and as such have great application potential in scenarios such as fragile object grasping and human machine interaction. Similar to biological muscles, the soft actuator is one of the most important parts in soft robots, and can be activated by fluid, thermal, electricity, magnet, light, humidity, and chemical reaction. In this paper, existing principles and methods for actuation are reviewed. We summarize the preprogrammed and reprogrammed structures under different stimuli to achieve motions such as bending, linear, torsional, spiral. and composite motions, which could provide a guideline for new soft actuator designs. In addition, predominant manufacturing methods and application fields are introduced, and the challenges and future directions of soft actuators are discussed.

Multimodal Soft Robotic Actuation and Locomotion

“…[119] While intricate and sophisticated motions produced by biological organisms appear to be complex, they can be broken down into elementary motions. [106] Breaking down the basic types of motion modalities that are c) 4D printing of anisotropic hydrogels for bending actuation after swelling in water. d) Millimeter-scale soft gripper, constructed from shape memory polymer, achieving distinct finger positions through selective folding using silver nanowire Joule heaters.…”

“…Crucially, the type of soft actuator material determines the external stimuli that can trigger deformation based on the actuation mechanism, including temperature, electrical field, pneumatic forces, magnetic field, and chemical solvents. [ 106 ] Strategies employed to convert energy into the necessary stimuli for actuation have significantly enhanced the convenience of this process. For example, resistive materials can be used for localized heating in temperature‐responsive materials, as running electrical currents in the resistive material generate heat via Joule heating.…”

“…[ 119 ] While intricate and sophisticated motions produced by biological organisms appear to be complex, they can be broken down into elementary motions. [ 106 ] Breaking down the basic types of motion modalities that are possible in actuators, these include linear, bending, torsional, and spiral motion. [ 106,120,121 ]…”

Conducting Polymer-based Biohybrid Materials : Towards Microphysiological Chips and Soft Actuators for Bone Tissue Engineering

“…[115] For instance, in nature, the flexible arms of octopus (a mollusk) without a bone inside can not only be moved/controlled to follow the motion trajectories, but be stiffened to catch prey or walk on the seabed. [116] Inspired by the locomotion behaviour of octopus, researchers have developed lots of novel variable stiffness actuators, [117] including reversible change variable stiffness and irreversible change variable stiffness actuators regulated by several proposed methods. In this chapter, the variable stiffness actuators are discussed in detail.…”

Nanocellulose‐based soft actuators and their applications

“…However, due to the limitations of manufacturing technologies and material property, traditional electro‐mechanical actuators are often composed of bulky and heavy subjects connected by complex structures, and thus show many disadvantages such as low work capacity, high voltage inputs, and poor flexibility, which significantly hinders their promising applications in biomedicine and other complex environments. Compared with the traditional electro‐mechanical actuators, soft actuators have received widespread attentions in recent years, because of their lightweight, high‐power density and good adaptability to multiple environments 6–8 . As flexible devices, soft actuators that inspired by living creatures from unicellular organisms to humans can achieve various actuation movements such as bending, contracting, rolling, and crawling, which have shown promising applications in the fields of soft robots, artificial muscles, and tissue engineering 8–11 .…”