July 10, 2015 | By Alec

While some 3D printable filaments have been criticized for being too soft, that is exactly they quality a new robot from Harvard relies on. As a team of Harvard engineers described in the latest issue of the Science journal, they have developed a jumping robot with a rubbery 3D printed body that can jump up to six times its own height (or about 76 centimeters) and land without being damaged. This little robot could be a breakthrough for the field of soft robotics, where scientists have long since been challenged to encase hard objects in a soft, yet very durable outer body.

In a series of tests, the robot jumped two and a half feet (0.75 m) in height and half a foot (0.15m) laterally. In experiments, the robot jumped more than 100 times and survived an additional 35 falls from a height of almost four feet. Credit: Jacobs School of Engineering/UC San Diego/Harvard University

No this robot looks a little bit like one of those jumping toys from the nineties, but it is everything but safe to play with. For instead of being powered by a spring, it features a miniature combustion chamber that produces enough force to jump by igniting a mixture of butane and oxygen. This explosion easily carries the robot up into the sky, which is cool but not exactly the goal of this creation. After all, falling from great heights is remarkably easy to do; safely landing afterwards is what it’s all about.

And if you’ve ever dropped a robotic creation made from 3D printed ABS parts, you’ll know that 3D printed parts aren’t exactly made for landing. But the team from Harvard, led by Nicholas Bartlett, has developed a rubbery 3D printed exterior body for the robot easily capable of absorbing such impact. As you can see in the clip below, it can easily jump from point A to point B without being damaged along the way. In fact, it can do so at least a 100 times, while an earlier, harder iteration broke after five jumps. While the hard-bodied robot could jump higher, durability is far more efficient in the long run.

While this might not seem so special, it has been a longstanding challenge for roboticists. Mechanical engineer Michael Tolley, who co-led the study, emphasized that creating something soft enough to land, but with hard parts to enable jumping, has been particularly difficult. ‘Jumping seems like a challenging problem … that really, in my mind, showcases some of the benefits of a soft system,’ Tolley said. ‘It’s sort of well-known in material science that if you have a very rigid thing connected to a very soft thing, you get stress concentrations at that interface, and that can lead to all sorts of problems.’

Fortunately, that has been solved by looking at examples in nature. ‘For this particular application, this gradient of hard to soft, there are numerous examples in biology and in nature,’ the article’s lead author Bartlett tells reporters. ‘One in particular is an octopus, which has an almost entirely soft body except for a very rigid beak. The beak interfaces with the rest of the body not with a rigid, abrupt transition from hard to soft, but a gradient structure similar to what we used in this robot.’

Biological systems, they suggest, often outperform engineered creations because structural complexity comes at a far lower cost in the wild, than it does in laboratories. But fortunately, 3D printing has the potential to vastly improve that comparison. Like the octopus itself, this robot doesn’t just consist of hard materials covered in soft materials. Instead, Bartlett and company have used multi-layered acrylic to create a gradual transition from hard to soft materials, with the 3D printer creating multiple layers with differing levels of stiffness. This created an excellent surface for absorbing damage just like an animal would. At the heart of this multi-layered robot is thus a rigid central core – which houses the combustion chamber and electronics – with the layers on top of that becoming gradually harder and harder.

However, this 3D printed robotic creation also deals with another problem typically found in the soft robotics: speed. While numerous soft materials have been successfully tested, these usually slow robots down tremendously. Again, something which the jumping robot obviously doesn’t suffer from. As you can see in the clip, the robot features little ovular legs on one side, enabling it to tilt itself towards a particular direction before the combustion chamber is fired up.

Mimicking an invertebrate has thus opened up a whole new field of robotic movement with some interesting applications. In particular, this could be used in the future for robots deployed in disaster areas or other regions with harsh and unpredictable environments, or even out in space. ‘Something that's perhaps a little bit out there but is a fun potential application is in space,’ Bartlett speculated. ‘So on the moon or on Mars where there are obstacles to jump over or uneven terrain.’

At any rate, soft-skinned robots will be far more suitable for human interaction in the near future. ‘I imagine in the future more combinations will be possible and more materials in general will be possible,’ Tolley said.‘Now we have this freedom to fully design and determine how these things are arranged spatially, and that’s what I think is really exciting.’ And while a perfect iteration would involve 100% soft components – including the batteries and electronics – this is an excellent step in the right direction.

 

 

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