Inchworm‐Like Soft Robot with Multimodal Locomotion Using an Acrylic Stick‐Constrained Dielectric Elastomer Actuator

Abstract

Several remarkable robots inspired by animals, such as fish, [1][2][3] inchworms, [4,5] annelids, [6,7] insects, [8][9][10] geckos, [11,12] and octopuses, [13,14] have attracted significant interest of researchers. These nature-based robots have been created for potential applications in search operations, inspection, cleaning, and manipulation. Among them, the inchworm has a soft and flexible body, simple and distinctive multimodal locomotion, including inverted climbing, vertical climbing, horizontal crawling, and turning, and high adaptability to complex natural environments. Over the decades, these characteristics have inspired the design of several robots with the morphology and locomotion patterns of inchworms. For instance, rigid inchworm-like robots capable of inverted climbing, vertical climbing, and horizontal crawling functions have been developed. [15,16] A study reported a crawling robot composed of servo motors, rigid linkages, and electromagnetic feet that could crawl on and climb pipes and flat surfaces. [5] An inchworm-like capsule robot with rigid expanders and extensors was developed that could crawl inside tubes. [17] However, these robots with rigid drivers and mechanical components were heavy, exhibited complex structures, and operated noisily. Furthermore, as opposed to actual inchworms, the rigid inchworm-like robots failed to adapt suitably to unstructured environments owing to the lack of resilience and flexibility of the components.To overcome the disadvantages of rigidity and endow the robots with flexible body characteristics, researchers have used soft actuator technology to design robots with inchworm-like structures and functions. [18][19][20][21] At present, pneumatics, magnetic fields, shape memory alloys (SMAs), twisted and coiled polymers (TCPs), liquid crystal elastomers (LCEs), ionic polymer-metal composites (IPMCs), and dielectric elastomers (DEs) are the major classes of soft actuators used for designing inchworm-like soft robots. In comparison with the conventional rigid robots, inchworm-like soft robots exhibit certain advantages, such as a simpler structure, higher flexibility, lighter weight, better mobility, and stronger adaptability. [22][23][24] Pneumatic actuators that can generate sufficient deformation and output force have been used to realize soft crawling robots, with vertical climbing and horizontal crawling motions, [25,26] and differential-drive soft robots capable of turning locomotion. [27] Alternatively, a versatile soft crawling robot comprising vacuum-actuated spring actuators and electrostatic footpads can accomplish vertical climbing and turning locomotion while carrying a payload that is 69 times its self-weight on a horizontal plane. [28] However, these robots are heavy, move slowly, and

Recent Advances in Electrically Driven Soft Actuators across Dimensional Scales from 2D to 3D

“…Generally, the dielectric elastomer actuator often needs several kilovolts for effective actuation and deformation. [ 100 ] In order to address this challenge, Ji et al [ 101 ] proposed a stacking strategy to develop dielectric elastomer actuators with a low operation voltage below 450 V (Figure 4c). Based on the low‐voltage dielectric elastomer actuator, an untethered insect‐sized soft robot was built and could run quickly with a speed of 30 mm s −1 .…”

Modeling of rigidly-constrained pure shear dielectric elastomer actuators: electromechanical coupling network method

“…The first approach enables uni-directional deformation of DE by arranging equalspacing nylon/glass fibers between two layers of DE films [19,20]. The second approach is by attaching rigid constraint elements on both sides of a single-layer DE film [21][22][23]. Compared with the first approach, in the second approach, the buckling instability that may occur during fiber constraint can be avoided due to the presence of a rigid constraint unit (although the deformation of the DE-film in the second approach is approximated as pure shear deformation instead of complete pure shear deformation).…”

“…Moreover, the preparation process is more convenient. Therefore, the second approach has been widely used in biomimetic muscle actuation, folded soft actuators, bistable mechanisms, and inchworm robots [21][22][23][24][25], demonstrating excellent actuation performance.…”

“…For the first type of pure shear DEA mentioned above [19,20], due to the intense arrangement of nylon fibers, the DE-film can only be deformed in the actuation direction, so the pure shear deformation theory is simplified and efficient to establish the analytical model. However, for the second type of pure shear DEA [21][22][23], it is incorrect to adopt the pure shear deformation theory directly since it neglects the inhomogeneous distribution of the elastomer film between rigidly constrained components [32,33]. In addition, it has been experimentally found that the lateral profile of DE films between neighboring rigidlyconstrained elements in rigidly-constrained pure shear DEA (PS-DEA) showed a necking deformation.…”

A self-loading suction cup driven by a resonant dielectric elastomer actuator

“…Compared with other switchable adhesion techniques, such as electro-adhesions (i.e. electrostatic forces) [4][5][6][7], dry adhesions (i.e. van der Waals forces) [8], and wet adhesions (i.e.…”