Octopus-inspired glove grips objects underwater

Underwater, the human hand is poorly equipped to hold onto things. Michael Bartlett, assistant professor at Virgina Tech and leader of the research, explained that there are critical times when this becomes a liability.

Rescue divers, underwater archaeologists, bridge engineers, and salvage crews all use their hands to extract people and objects from water. Human hands with less capability to hold slippery things must resort to using more force, and an iron grip can sometimes compromise those operations. When a delicate touch is required, it would be helpful to have hands made for water.

With this in mind, Bartlett and his team in the Soft Materials and Structures Lab adapted biological solutions into new technologies made from soft materials and robotics.

The octopus is equipped with eight long arms, covered with suckers controlled by the sea animal’s muscular and nervous systems. Each sucker, shaped like the end of a plunger, contributes a powerful snatching ability. 

After the sucker’s wide outer rim makes a seal with an object, muscles contract and relax the cupped area behind the rim to add and release pressure. When many of the suckers are engaged, it creates a strong adhesive bond that is difficult to escape.

“When we look at the octopus, the adhesive certainly stands out, quickly activating and releasing adhesion on demand,” said Bartlett. “What is just as interesting, though, is that the octopus controls over 2,000 suckers across eight arms by processing information from diverse chemical and mechanical sensors. The octopus is really bringing together adhesion tunability, sensing, and control to manipulate underwater objects.”

The team said its design focus was on re-imagining the suckers: compliant, rubber stalks capped with soft, actuated membranes. The design was created to perform the same function as an octopus’ sucker, activating a reliable attachment to objects with light pressure, which is ideal for adhering to flat and curved surfaces.

They also needed a way for the glove to sense objects and trigger the adhesion. For this, they brought in assistant professor Eric Markvicka from the University of Nebraska-Lincoln, who added an array of micro-LIDAR optical proximity sensors that detect how close an object is. 

The suckers and LIDAR were then connected through a microcontroller to pair the object sensing with the sucker engagement, mimicking the nervous and muscular systems of an octopus.

Using the sensors to engage the suckers also makes the system adaptable, researchers said. In a natural environment, an octopus winds its arms around crags in rocks and surfaces, attaching to smooth shells and rough barnacles. The team also wanted something that felt natural to humans and allowed them to pick things up effortlessly, adapting to different shapes and sizes as an octopus would. 

“By merging soft, responsive adhesive materials with embedded electronics, we can grasp objects without having to squeeze,” said Bartlett. “It makes handling wet or underwater objects much easier and more natural. The electronics can activate and release adhesion quickly. Just move your hand toward an object, and the glove does the work to grasp. It can all be done without the user pressing a single button.”    

In testing, researchers tried several gripping modes. To manipulate delicate and lightweight objects, they used a single sensor. They found that they could quickly pick up and release flat objects, metal toys, cylinders, the double-curved portion of a spoon, and an ultrasoft hydrogel ball. 

By reconfiguring the sensor network to utilise all sensors for object detection, they could also grip larger objects such as a plate, a box, and a bowl. Flat, cylindrical, convex, and spherical objects consisting of both hard and soft materials were adhered and lifted, even when users did not grab the object by closing their hands. 

Postdoctoral researcher Ravi Tutika said the capabilities, mimicking the advanced manipulation, sensing and control of cephalopods, provide a platform for synthetic underwater adhesive skins.

The team now envisions applications in soft robotics for underwater gripping, user-assisted technologies and healthcare, and manufacturing for assembling and manipulating wet objects.