Traditional industrial robots are rigid — mostly metal — as well as fast, precise, and powerful. Their speed and accuracy come at the cost of complexity and can often pose a danger to humans who get too close. Soft robots are adaptable and resilient but slow, difficult to fabricate, and challenging to make autonomous because most motors, pumps, batteries, sensors, and microcontrollers are rigid.
But Harvard engineers have developed 3D printed soft robots that moves autonomously. This design combines the autonomy and speed of a rigid robot with the adaptability and resiliency of a soft robot and, because of 3-D printing, is relatively cheap and fast. They have published their paper in the July 10 issue of the journal Science.
The robot’s body transitions from soft to hard, reducing the stress where the rigid electronic components join the body and increasing the robot’s resiliency. With no sliding parts or traditional joints, the robot isn’t victim to dirt or debris like its more intricate cousins, making it a good candidate for use in harsh terrains.
The vision for the field of soft robotics is to create robots that are entirely soft. But for practical reasons, this soft robots typically have some rigid components — things like batteries and control electronics. This robot is a demonstration of a method to integrate the rigid components with the body of the soft robot through a gradient of material properties, eliminating an abrupt, hard-to-soft transition that is often a failure point.
The combustion-powered robot — reminiscent of a toy rubber popper — is constructed of two main parts: a soft plungerlike body with three pneumatic legs and the rigid core module, containing power and control components and protected by a semisoft shield created with a 3-D printer.
To initiate movement, the robot inflates its pneumatic legs to tilt its body in the direction it wants to go. Then butane and oxygen are mixed and ignited, catapulting the robot into the air. It’s a powerful jumper, reaching up to six times its body height in vertical leaps and half its body width in lateral jumps. In the field, the hopping motion could be an effective way to move quickly and easily around obstacles.
The robot’s stiffness gradient allows it to withstand the impact of dozens of landings and to survive the combustion event required for jumping. Consequently, the robot not only shows improved overall robustness but can locomote much more quickly than traditional soft robots.
The robot’s jumping ability and soft body would come in handy in harsh and unpredictable environments or disaster situations, allowing it to survive large falls and other unexpected developments.
This new design demonstrates the potential of 3-D printing in soft robotics. Traditional methods of fabrication — custom molds and multistep assembly — are costly and slow. The ever-increasing variety of materials compatible with 3-D printers is allowing engineers to prototype new designs faster. Increased complexity does not necessarily lead to increased cost.
Boston Dynamics created a jumping robot called “Sand Flea” which is an 11 pound robot that drives like an RC car on flat terrain, but can jump 30 ft into the air to overcome obstacles.
