Researchers building soft robots have been hampered by finding alternatives for control systems and electric power for the robots. Circuit boards and batteries are rigid and previous models of soft robots have either had these hard components rigged, or have been tethered to an off-board system.
A team of researchers from Harvard University has built a soft robot that has no electronics. The robot is powered by a chemical reaction controlled by microfluidics. The team consisting of members with experience in mechanical engineering, microfluidics and 3D printing, affectionately call their creation the octobot. Octopuses have no internal skeleton, yet they can perform incredible feats of dexterity and strength. This has made them a long-standing inspiration for soft robotics.
Octobot is small and has been created through 3D printing. It is not tethered to any external hardware and is entirely soft. Researchers believe it will be the forerunner of a new generation of completely autonomous, soft machines. The research has proven that key components of a simple, entirely soft robot can easily be manufactured and that rigid components like electronic controls and batteries can be replaced by equivalent soft systems. The foundation for more complex designs has now been laid.
The team used a hybrid assembly approach and 3D printed each of the functional components including actuation, power and fuel storage. This approach allows for rapid production time. Octobot’s creation demonstrates that the strategy of integrated design and additive fabrication is feasible for embedding autonomous functionality.
Michael Wehner, a postdoctoral fellow in the Wood lab and co-first author of the paper notes that soft robots have always relied on rigid components for fuel sources. Octobot is driven by pneumatics, i.e. it uses pressurized gas. A small amount of liquid fuel (hydrogen peroxide) is transformed into a large amount of gas by a reaction that takes place inside the robot. The gas then flows into the octobot’s arms and inflates them. Rigid power sources have therefore been replaced by a simple reaction between hydrogen peroxide and platinum.
The reaction is controlled by the soft equivalent of a simple electronic oscillator. A microfluidic logic circuit inside the octobot controls when hydrogen peroxide transforms to gas. Ryan Truby, a graduate student in the Lewis lab and co-first author of the paper, explains that three fabrication methods were used to manufacture the complete system – 3D printing, soft lithography and molding.
As the assembly process is very simple, it paves the way for more intricate designs. The Harvard team plans to next design an octobot that can interact with its environment, crawl and swim. Truby hopes that this proof of concept will inspire roboticists, researchers focused on advanced manufacturing and material scientists.