If you’ve ever been a kid at some point in your life, chances are you’ll know the true joys of playing around with bubbles. Soapy water and a couple of necessary tools can make an afternoon quite enjoyable, blowing up air contained within liquid that’s held together by surface tension.
Interestingly enough, the field of robotics has now taken a shot at utilizing our kid-friendly bubble-casting technologies to make “soft” robotics that we may soon find in special applications—well, at the very least, if you ask the likes of scientists like assistant professor of chemical and biological engineering Pierre-Thomas Brun from Princeton University, who led this kind of study with a team of researchers. Their study on “bubble-casting” robotics was published in the journal Nature.
Brun and team realized that while soft robotics already exists, the technologies required to produce them usually come with a hefty price tag; these include technologies like soft actuators and soft batteries, which require the use of 3D printers and laser cutters. Thus, the team responded by looking into less expensive ways of creating the next generation of soft robots.
In a statement by Brun in a news release by Princeton University: “[Traditional rigid robots have multiple uses, such as in manufacturing cars,] but they will not be able to hold your hands and allow you to move somewhere without breaking your wrist. They’re not naturally geared to interact with the soft stuff, like humans or tomatoes.”
Instead, Brun and the team looked into how bubbles are cast—leading to their development of their “bubble-casting” technique to make soft robotics parts. In this case, the robot itself needs no internal powered mechanism, and simply relies on the way materials behave when inflated like balloons.
First, Brun and team shot a liquid elastomer through a mold, then proceeded to pass air through the mold itself. In doing so, the liquid elastomer forms a somewhat “unequal” bubble, where a thin layer of the material now rises on the upper half of the mold, while most of the material now lies at the bottom half.
Afterwards, the liquid elastomer is cured; this leads to a sort-of unequal, rubbery “bubble,” where the top half is thinner than the bottom half. As it turns out, thicker material tends to stretch less compared to those of the same type but thinner; thus, when inflated, the rubbery bubble naturally curves towards the thicker side, giving it a predisposed curvature once inflated with air.
“If [the elastomer is] allowed more time to drain before curing, the film at the top will be thinner. And the thinner [the] film, the more it will stretch when you inflate it and cause greater overall bending,” said first author and chemical and biological engineering graduate student Trevor Jones to Princeton University’s news release.
Brun and team used this predisposition of the rubber piece to create a “soft” robot that can grasp items like berries with just air and some rotation at the base to allow the robot to orient itself. Alongside this, the team also managed to create vascular structures that bend in one way or another, like a mock-up of a fish tail and long appendages.
An equation was devised in order to be able to predict how the soft robot would bend when inflated; this equation was found using computer simulations of the robot, and was determined by co-author and postdoctoral researcher Etienne Jambon-Puillet, who worked together with Jones.
Said Jambon-Puillet: “We can predict what will happen using a simple equation that anyone can use. We understand quite well now what happens when we inflate these tube-like materials.”
Next steps for Brun and team include devising ways of producing even longer soft robot tubing, as well as creating more complex designs. Doing so will allow the team to think of even more applications that may benefit from the help of soft robots. They will also have to address several issues with the process along the way, including ways of preventing the “popping” of the bubble appendages when overinflated.
In closing, Jones noted to Princeton: “We understand this problem at a physics level pretty strongly, so now the robotics can really be explored.”
(For more on robotics, check out the new robot with “rolling fingers” developed by a collaboration of scientists. Afterwards, read on how ultrasound helps in designing the next generation of assistive exoskeletons.)
References
- Coxworth, B. (2021, November 12). “Bubble casting” tech used to create soft actuators for soft robots. New Atlas. https://newatlas.com/robotics/bubble-casting-soft-actuators-robotics/
- Jones, T. J., Jambon-Puillet, E., Marthelot, J., & Brun, P.-T. (2021). Bubble casting soft robotics. Nature, 599(7884), 229–233. https://doi.org/10.1038/s41586-021-04029-6
- Waldron, P. (2021, November 11). Tiny bubbles help create soft robotics. Princeton University School of Engineering and Applied Science. https://engineering.princeton.edu/news/2021/11/11/tiny-bubbles-help-create-soft-robotics
