Multigait soft robot

Abstract

This manuscript describes a unique class of locomotive robot: A soft robot, composed exclusively of soft materials (elastomeric polymers), which is inspired by animals (e.g., squid, starfish, worms) that do not have hard internal skeletons. Soft lithography was used to fabricate a pneumatically actuated robot capable of sophisticated locomotion (e.g., fluid movement of limbs and multiple gaits). This robot is quadrupedal; it uses no sensors, only five actuators, and a simple pneumatic valving system that operates at low pressures (< 10 psi). A combination of crawling and undulation gaits allowed this robot to navigate a difficult obstacle. This demonstration illustrates an advantage of soft robotics: They are systems in which simple types of actuation produce complex motion.

Fig. 1.

(A) Schematic representation of the soft PN channels, formed by bonding an elastomeric layer (layer 1) to the strain-limiting layer (layer 2). The independent PNs are labeled PN 1, 2, 3, 4, and 5; black arrows indicate the location at which we insert tubing, and the dashed arrow indicates the bonding of layer 2 to layer 1. (B) A cross section of a portion of PN 2 is schematically illustrated at atmospheric pressure (P₀; Left) and actuated at PN pressure (P₁ > P₀; Right). (Inset, Left) Top view of the robot and the section removed from PN 2. (C) An optical micrograph with PN 2 at atmospheric pressure (Left) and at 7.0 psi (0.5 atm; Right). The rest states (Left) of PNs 1 and 2 are curved away from the surface. The scale bar is 3 cm.

Fig. 2.

(A–G) Cycle of pressurization and depressurization of PNs that results in undulation. The particular PN(s) pressurized in each step are shown (Insets) as green, and inactive PN(s) are shown (Insets) as red. The scale bar in A is 4 cm.

Fig. 3.

(A–F) Cycle of pressurization and depressurization of PNs that results in crawling. The particular PN(s) pressurized in each step are shown (Insets) as green, and inactive PN(s) are shown (Insets) as red. The scale bar in A is 4 cm.

Fig. 4.

PN actuation sequence (Left) and snapshots (Right) of a soft robot crawling to a short gap, undulating underneath it, then crawling again on the other side. (A) The robot starts unpressurized and (B) we pressurize the central channel and (C) actuate the legs to crawl toward the gap. (D) The central channel is depressurized and (E–G) we undulated the robot under the gap. (H) Finally, we repressurized the central channel and crawled on the other side of the gap. PN(s) actuated in each step are shown (Insets) as green, inactive PN(s) are shown (Insets) as red, and partially pressurized PNs are shown (Insets) as orange. The height of the gap is indicated by an overlaid dashed white line. The scale bar in A is 4 cm.