A team of Harvard and UC San Diego scientists believes the perfect robot is neither rigid nor soft -- instead, it's a combination of both. To prove that, the group (led by Michael Tolley from UCSD and Nicholas Bartlett from Harvard) has created a hybrid robot capable of over 30 untethered jumps without breaking into pieces. It's also faster than completely squishy ones, which are typically slow. The top half composed of nine layers 3D printed in one piece has a soft exterior that gradually becomes more rigid as you get to the inner core. On the other hand, the bottom's entirely flexible, with a cavity where you can inject a mixture of butane and oxygen. After being ignited, the gases swell and cause the robot to jump.