What happens when you drop a piece of rubber? Simple: it bounces, an effect caused when the rubber deforms, and then reforms rapidly upon impact. This quality of rubber, and similar so-called viscoelastic materials, makes it great for superballs and the like, but the bounciness has drawbacks when you use it as a dampening material, like in an iPhone case. Sure, the deforming qualities of rubber will protect your iPhone on the first bounce, but subsequent bounces can increase the odds of you breaking your device, especially if it lands wrong. If only there was a way to "program" that rubber to cushion, but to not unpredictably bounce, right?
That's just what researchers at MIT's Computer Science and Artificial Intelligence Laboratory (or CSAIL) have figured out. They've developed a technique to 3D print soft, viscoelastic materials—like rubber and plastic—which deform in predictable ways, essentially allowing MIT to control how they bounce. But CSAIL isn't just pitching this as a way to design better iPhone cases. They see it as a method of protecting robots, drones, and even professional athletes, as well.
MIT calls the technique "Programmable Viscoelastic Materials," or PVMs. The basic idea is this: instead of using existing injection-moulding processes, which are normally used to shape custom parts out of materials like rubber, the researchers 3D print them instead. The fine-grained printing process allows them to control the exact distribution of elasticity in the finished part. As they print, they can build a sort of skeleton inside a viscoelastic part, controlling the exact way in which it will deform and reform by mixing solid materials, liquid, and a flexible rubber-like material called TangoBlack+ in the same design. The result? Objects which bounce in completely predictable ways—or not at all, if you prefer.
The researchers think the technique could have a diverse range of applications, especially for robots and drones. To test it, they 3D-printed a cube robot that moves by bouncing. Then, they fit it with shock-absorbing skins, printed using their technique. Those skins ended up reducing the amount of energy the robot transferred to the ground with every bounce by around 250%. "That reduction makes all the difference for preventing a rotor from breaking off of a drone or a sensor from cracking when it hits the floor," says CSAIL director Daniela Rus, who also points out that this material could extend the lifespan of delivery drones, like the ones being developed by Amazon.
There are other innovative uses for these programmable viscoelastic materials, too—and plenty that could end up making their way into our everyday lives. Take running shoes, which could be designed to better absorb shocks and cushion your joints. PVMs could even potentially be used in helmets, perhaps getting us one step closer to that mythical concussion-proof NFL helmet. But for many of us, the most obvious innovation is clear: they could end up making their way into the nigh-invulnerable Otterboxes of the future, which bounce in such a way that your iPhone lands safely, with its screen pointing up, every time.
Read MIT's paper on programmable viscoelastic materials here.
[Photos: Jason Dorfman/MIT]