Glowing Sucker Octopus (Stauroteuthis syrtensis)-Inspired Soft Robotic Gripper for Underwater Self-Adaptive Grasping and Sensing

Abstract

A soft gripper inspired by the glowing sucker octopus (Stauroteuthis syrtensis)' highly evolved grasping capability enabled by the umbrella-shaped dorsal and ventral membrane between each arm is presented here, comprising of a 3D-printed linkage mechanism used to actuate a modular mold silicone-casting soft suction disc to deform. The soft gripper grasp can lift objects using the suction generated by the pump in the soft disc. Moreover, the protruded funnel-shaped end of the deformed suctorial mouth can adapt to smooth and rough surfaces. Furthermore, when the gripper contacts the submerged target objects in a turbid environment, local suctorial mouth arrays on the suction disc are locked, causing the variable flow inside them, which can be detected as a tactile perception signal to the target objects instead of visual perception. Aided by the 3D-printed linkage mechanism, the soft gripper can grasp objects of different shapes and dimensions, including flat objects, objects beyond the grasping range, irregular objects, scattered objects, and a moving turtle. The results report the soft gripper's versatility and demonstrate the vast application potentials of self-adaptive grasping and sensing in various environments, including but are not limited to underwater, which is always a key challenge of grasping technology.

Keywords: bioinspiration; glowing sucker octopus; self-adaptive grasping; soft gripper.

Figure 1

Glowing sucker octopus (Stauroteuthis syrtensis)‐inspired suction disc. A) Morphology structure of the Stauroteuthis syrtensis. Suctorial mouth arrays are distributed on the soft arms, and membranes connect the arms to form a disc. B) CAD model of the biomimetic soft gripper. The suction disc can be opened and closed under the drive of the tubular bellow. C) CAD model of the suction disc. Suctorial mouth arrays with funnel‐shaped ends are distributed on the suction disc. D) Schematics of the suction disc.

Figure 2

Fabrication and finite element analysis simulations of the suction disc. A) CAD model of the modular molds. The mold is designed into six parts for the integrated pouring of the suction disc. B) Schematic of the assembly of the modular mold. C) Biomimetic prototype photographs of the suction disc. The suction disc is fabricated according to the prototype of Stauroteuthis syrtensis. The photo of a single suctorial mouth can be seen in the picture. D) The flexibility of the suction disc. It remains unfolded in the initial state and can be closed when external force acts. E) Finite element analysis simulations of the suction disc. Hyperelastic FEM simulation on the suction disc was conducted through COMSOL and the simulation results are remarkably similar to the physical testing.

Figure 3

Suction test of the suction disc. A,B) When the peeling position is in the center, the suction is generated by the suction disc on A) the plane and B) the ring surface. C,D) When the peeling position is at the edge, the suction is generated by the suction disc on C) the plane and D) the ring surface. Gray represents the suction cup and blue represents the disc used to block the suction disc, which is used to test the suction. The arrow represents the position of the peeling obstacle (center or edge). E) The simulation shows the speed distribution on the inner of the suction disc. F) The simulation shows the velocity distribution inside the mouth. The inner pressure shows a decreasing trend from the inside to the outside.

Figure 4

Sensing function of mouth disc in a turbid underwater environment. A) The working mechanism and working environment of mouth disc. B) When the mouth disc faces discs of different areas, the showed flow rate changes. C) Sensing test of material objects. The type of object can be distinguished based on the flow rate.

Figure 5

Capabilities and finite element analysis simulations of tubular bellows. A) Shrinking distance of tubular bellow under negative pressure. B) The pulling force of the tubular bellow under negative pressure. C) Hyperelastic FEM simulation of tubular bellows through COMSOL under negative pressure. D) Extend the distance of tubular bellow under positive pressure. E) The pushing force of the tubular bellow under positive pressure. F) Hyperelastic FEM simulation of tubular bellows through COMSOL under positive pressure.

Figure 6

Grasping of the soft gripper in the air. A) Assembly of the soft gripper. The opening and closing of the suction disc are controlled by the expansion and contraction of the tubular bellows to realize the grasping of the object. B) The suction disc uses suction to grasp the object. The suction disc can grasp large flat objects under the negative pressure of the pump. C) Grasping of small irregular objects. Driven by the tubular bellows and assisted by the suction disc membranes, the soft gripper can hold various small objects firmly in a wrap‐around style. It is worth mentioning that the gripper could grasp multiple objects. D) Grasping of large irregular objects. Because of the large force output by the tubular bellows, the soft gripper can grasp large objects from the edge, especially an empty bulky water bottle.

Figure 7

Underwater grasping performance of soft gripper. A) Grasping performance when soft gripper faces flat‐concave and convex structure objects. B) In the face of irregular objects such as water bottles and printed samples, the soft gripper can directly and firmly grasp. C) The combination of suction and adaptive grasping allows the soft gripper to grasp scattered multiple objects (scallops) at once.

Figure 8

Living body grasping experiment of the soft gripper. A) The experimental object is a live turtle with small protrusions on its convex back. Its back has high roughness. B) Performance of the process of grasping moving turtle with soft grippers. Figures (B1) to (B4) show the grasping process. C) The umbrella‐shaped suction cup and suctorial mouth of the gripper can control the small fish not to escape after being caught. Figures (C1) to (C4) show the grasping process. D) The gripper uses suction to control and grasp the turtle. Figures (D1) to (D4) show the grasping process.