Soft robots have a range of applications in sensing, object grasping and manipulation, but are largely still created by hand with manual casting, limiting the complexity of structures. The new method, described in Advanced Materials Technologies, integrates design and fabrication into a single automated workflow, allowing high performing soft robots to be built on bespoke 3D printers developed by the team at SUTD.
"Most fabrication approaches are predominantly manual due to a lack of standard tools," said SUTD Assistant Professor Pablo Valdivia y Alvarado, who led the study. "But 3D printing or additive manufacturing is slowly coming into play as it facilitates repeatability and allows more complex designs - improving quality and performance."
The team employed a technique called topology optimisation (TO), where mathematical models are used to design bespoke structures within a set of constraints. When developing an autonomous swimming robot inspired by batoids, they began by defining the robot's fin geometry, then used TO to generate the desired structure and properties within prescribed material and motion constraints.
This design was then translated into code, read by the team's custom-built printers, and fabricated. The soft robot with the optimised composite fins was 50 per cent faster than its counterpart with a traditionally casted soft fin, and marginally faster than a robot with a hard fin. It was also capable of turning roughly 30 per cent faster compared to the hand-casted fin and had the smallest turning circle of all three robots, making it better overall at manoeuvring through water.
According to Alvarado, the workflow for fabricating optimised, multi-material soft robots can be universally applied to design other soft robots.
"For example, if we're building a sensor, our objective in TO could be to tailor the electrical conductivity of certain portions of the structure," he said. "Customising optical, thermal, electrical, as well as other physico-chemical properties would also be interesting for other applications."