Creating a soft robot that can mimic this motion requires special materials — rigid skeletal structures can't replicate the graceful flexing of an invertebrate. To do this, lead researcher Yonas Tadesse of UT Dallas and colleagues used nickel-titanium shape memory alloys, which can revert back to their original shapes after being contorted. They coated multi-walled carbon nanotubes in a nano-platinum catalyst powder, which creates heat when exposed to hydrogen and oxygen. Then the nanotubes were wrapped around the shape memory alloy. The exothermic reaction between the metal and the water sparks the shape memory alloy to change its shape, contracting and moving forward. As the artificial muscles relax, the shape memory alloy reverts back to its original form — in this case, one of eight bell segments.