(CNN) Robots are taking a step closer to resembling us.

To tackle an energy problem in robots, engineers at Cornell University and the University of Pennsylvania turned to human bodies for inspiration.

They designed a robotic lionfish decked out with a system that mimics a human's vascular system, which transports blood and other nutrients throughout the body.

However, this synthetic vascular system distributes "robot blood," or energy-dense battery fluid to power the robot, according to the engineers' study, published Wednesday in science journal Nature

The soft robot is built from flexible silicon materials, which allow it to bend.

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