Earlier last week, a team of US scientists, from Florida Atlantic University (FAU) and the US Office of Naval Research published a paper on five jellyfish robots that they have manufactured. The paper is titled Thrust force characterization of free-swimming soft robotic jellyfish. The prime motive of the scientists to build such robotic jellyfish is to track and monitor fragile marine ecosystems without causing unintentional damage to them.
These soft robots can swim through openings narrower than their bodies and are powered by hydraulic silicon tentacles. These so-called ‘jelly-bots’ have the ability to squeeze through narrow openings using circular holes cut in a plexiglass plate.
The design structure of ‘Jelly-bots’
Jelly-bots have a similar design to that of a moon jellyfish (Aurelia aurita) during the ephyra stage of its life cycle before they becoming a fully grown medusa. To avoid the damage to fragile biological systems by the robots, soft hydraulic network actuators are chosen. To allow the jellyfish to steer, the team uses two impeller pumps to inflate the eight tentacles.
The mold models for the jellyfish robot were designed in SolidWorks and subsequently, 3D printed with an Ultimaker 2 out of PLA (polylactic acid). Each jellyfish has varying rubber hardness to test the effect it has on the propulsion efficiency.
What this study was about?
These jelly robots will help the scientists in determining the impact of the following factors on the measured thrust force:
- Actuator material Shore hardness
- Actuation frequency
- Tentacle stroke actuation amplitude
The scientists found that all three of these factors significantly impact mean thrust force generation, which peaks with a half-stroke actuation amplitude at a frequency of 0.8 Hz.
- The material composition of the actuators significantly impacted the measured force produced by the jellyfish, as did the actuation frequency and stroke amplitude.
- The greatest forces were measured with a half-stroke amplitude at 0.8 Hz and a tentacle actuator-flap material Shore hardness composition of 30–30.
- In the test, the jellyfish was able to swim through the narrow openings than the nominal diameter of the robot and demonstrated the ability to swim directionally.
- The jellyfish robots were tested in the ocean and have the potential to monitor and explore delicate ecosystems without inadvertently damaging them.
One of the scientists, Dr. Engeberg said to Tech Xplore:
“In the future, we plan to incorporate environmental sensors like sonar into the robot’s control algorithm, along with a navigational algorithm. This will enable it to find gaps and determine if it can swim through them.”