Military Investigates Invertebrates as Model for 3D Printed Active Materials for Robots

The octopus is an amazing creature. While most invertebrates are known for their ability to writhe helplessly on a sidewalk after a rainstorm, go squish when accidentally stepped on, or otherwise fail to act in a professional manner, the octopus is a gung-ho, go-getter of an animal, as any of the millions of people who watched a video of one escaping through a tiny hole can attest. In addition to their abilities to squeeze through tight spaces, they can change color, use tools, and strategize to capture prey. Their amazing flexibility is due to the fact that the only hard part of their bodies is their beak, and so they are able to fit through any space larger than that beak with an ease that should amaze anyone who has ever tried to go around a coffee table without banging their shins.

The valuable nature of this corporeal flexibility has not been lost on the military, which has become interested in producing robots that, while not as agile as the octopus, demonstrate less structural rigidity than traditional robots. The idea is that if robots could be produced with more giving materials, they would be more useful when performing maneuvers in congested areas, rather than simply pushing their way through them. Joining together with a team at the University of Minnesota (UMN), the researchers worked to create an autonomous freeform fabrication platform that is able to create soft robots. This advanced 3D printer has been named the Solider. Army Research Laboratory’s Dr. Ed Habtour described the benefits of emulating invertebrates and the research that is being undertaken to benefit from current understanding of invertebrate movement:

(a) Schematic of a soft actuator device (left) and exploded view of the device and constituent material layers (right). (b) Schematic of depositing (3D printing) hydrogel on the surface of a silicone layer after surface treatment and under UV light exposure. (c) Printing of the ionic hydrogel on the passive layer after surface treatment (left), final 3D printed DEA (middle), and microstructure image of the device cross-section (right). [Image: US Army illustration]

“Successful stealthy maneuvering requires high structural flexibility and distributive control to sneak into confined or restricted spaces, operate for extended periods, and emulate biological morphologies and adaptability…The research findings represent an important stepping stone towards providing the Solider, an autonomous freeform fabrication platform – next-generation 3D printer, which can print functional materials and devices – to generate soft actuators and potentially tether less soft robots on demand, on the fly, and at the point of need.”

This is only the beginning of the investigation that needs to be undertaken in order to ready such soft robots for deployment in the field, but is a vital step in that direction. Professor Michael McAlpine of UMN outlined the approach that they took when beginning their investigation:

“In the initial phase of the project, our team began by investigating new methods for emulating the location of invertebrates, which provided fundamental insights into the machineries of their soft distributed actuation circuitries that allow for high bending motions without skeletal support.”

Ghazaleh Haghiashtiani, fellow researcher and lead author on the paper titled “3D Printed Electrically-Driven Soft Actuators” recently published in Extreme Mechanics Letters (EML) describing the investigation, highlighted that this new method of printing allows the machine to “take advantage of the unique actuation properties of soft DEAs [dielectric elastomer actuators] at the fundamental materials level” and is highly advantageous because it does not require the typical post-processing steps. Habtour explained the next steps for pushing this research forward:

“The intriguing interactions among the materials’ micro mechanical properties and various nonlinearities may provide new scientific opportunities to emulate the symbiotic interactions in biological systems. If we can understand these interactions, then we can use those insights to fabricate dynamic structures and flexible robots which are designed to be self-aware, self-sensing, and capable of adjusting their morphologies and properties in real time to adapt to a myriad of external and internal conditions.”

After all, nature does bumble around, it blends in and moves through environments. The rigidity of robotic structures has made them more akin to heavy machinery than a participant in the environment. This research hopes to learn from some of nature’s simpler creatures, in order to create some of the world’s most complex, as 3D printing and soft robotics continue to converge.

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[Source: US Army]