Researchers from North Carolina State University created fast-moving soft robotics inspired by jellyfish. The new robot can outswim real jellyfish. The team's technique utilizes pre-stressed polymers to make soft robots more powerful.
Illustration of a soft robot jellyfish. Source: NC State University
Previous soft robotics were inspired by cheetahs. They were fast but had a stiff inner spine, which meant that the robots were not completely soft. The researchers wanted to make a completely soft robot that can move powerfully and quickly. In the end, the team didn’t make just one soft robot, they made three.
The new soft robots are made of two bonded layers of an elastic polymer. The first layer is pre-stressed, or stretched. The second layer is not stressed and contains an air channel. The robot flexes by pumping air into the air channel. The direction it moves is controlled by the relative thickness of the pre-stressed layer. Adding a third pre-stressed layer, an intermediate layer, allows the pre-stressed layer to move in a certain direction.
For example, a polymeric layer is pre-stressed by pulling it in two directions. It is then attached to the intermediate layer, resulting in a bilayer strip that wants to cure down. The thinner the strip is in relation to the air channel the more it will bend upwards. The thicker the layer, the more it will bend down. When air leaves the channel, the layer will snap into a resting state.
One of the soft robots created was a fast-moving soft crawler. This robot represents a larval insect. It curls its body to jump forward, exerting all of its stored energy. This is a simple robot.
The jellyfish bot was more complicated. This robot has a pre-stressed disk layer that was stretched in four directions. The channel layer is made of a ring-like air channel. The result of these parts ends up looking like a jellyfish. In a relaxed state, the jellyfish dome curves up. When air is pumped into the channel layer the dome quickly turns down. This robot had an average speed of 53.3 millimeters per second. A real jellyfish has an average speed of 30 millimeters per second.
The team also created a three-pronged gripper robot. Typical gripper roots hang open when relaxed and require energy to hold onto cargo as it moves. With the new robot, the team used the prestressed layers to create grippers where the default position is clenched shut. Energy is needed to open the grippers. Once in position to grab and hold an item, the robot returns to resting mode.
A paper on these new robots was published in Advanced Materials Technologies.
