Popcorn May Hold Secret for Biodegradable Robots

At the IEEE International Conference on Robotics and Automation (ICRA) in Brisbane, Australia, in May, six researchers from Cornell University presented a paper offering an insight into the potential use of popcorn as the energetic component of biodegradable robots. Popcorn-Driven Robotic Actuators, by Steven Ceron, Aleena Kurumunda, Eashan Garg, Mira Kim, Tosin Yeku and Kirstin Petersen, suggests that popcorn, at around U$5/kg, could become a very cost-effective and environmentally friendly solution to one of the conundra being addressed by the robotics community seeking biodegradable components – DARPA among them.

“Popcorn kernels are a natural, edible, and inexpensive material that has the potential to rapidly expand with high force upon application of heat. Although this transition is irreversible, it carries potential for several robotic applications. As kernels can change from regular to (larger) irregular shapes, we examine the change in inter-granular friction and propose their use as granular fluids in jamming actuators, without the need for a vacuum pump. Furthermore, as a proof-of-concept, we also demonstrate the use of popcorn-driven actuation in soft, compliant, and rigidlink grippers. Serving as a first introduction of popcorn into robotics, we hope this paper will inspire novel mechanisms for multi-functional designs,” the paper postulates.

Unpopped kernels are essentially tiny storehouses of mechanical energy, transformed into useful motion when heated. Over 900kPa of internal pressure causes an explosion of content from the kernel, which then expands and dries to a rigid structure in very short order. The expansion factor varies between 5 and 15 times the original volume of the kernel, depending on type, heating protocols and circumstances.

Applications the paper suggests for popcorn-powered robotics include:

• Jamming actuator: using just 36 kernels, researchers managed to lift a 100g weight;
• Elastomer actuator: researchers used three actuators to form a three-fingered grip;
• Origami actuator: dimensionally constrained actuators using 80g of popped kernels were able to lift a 4kg weight;
• Rigid-link gripper: popped kernels force plates apart, actuating a gripper.

As an alternative to air (or vacuum) as an energetic source, popcorn is simple, cheap and requires no additional (and normally non-degradable) infrastructure. The idea is far from a ‘silver bullet’ solution and it is perfectly obvious that a great deal more work needs to be done. But, no matter how ‘off the wall’ the concept may seem on first glance, there is definitely the germ of a good and exploitable idea here. A kernel, even!