The problem: Batteries are made out of hard materials, which are obstructive and limit a robot’s range of motion. But making batteries out of a flexible or stretchy material usually makes them less conductive.
The solution: Scientists made a flexible, stretchy battery by mimicking electric eels, which discharge electricity using special layered muscle cells that run down their bodies. When the brain sends a signal, the connections between the layers open, creating a current that’s not unlike what happens when you have a bunch of AAs connected in a remote. Scientists recreated this system using hydrogels — flexible materials that are 60% water — with salt inside to carry a charge.
What’s next: These kinds of designs are especially useful in soft robotics, where machines are also made out of flexible materials. But they could also be used for medical implants because the batteries can move with the human body, and soft materials are less likely to be rejected by the body than hard ones.