(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.
When the engineers tested the battery, they found it will work theoretically for about 40 hours, said Robert Shepherd, director of Cornell's Organic Robotics Lab and senior author of the paper.
A possible new way to design robots
With the engineers' biology-inspired advancement, robots could become more autonomous and prevalent in our lives.
Currently, robots are limited because they require a lot of energy. But this study could lead to "increased energy density, autonomy, efficiency and multifunctionality in future robot designs," according to the study.
"You'll want (longer power) for search and rescue operations, to locate the source of failure in a nuclear reactor compound, finding people in a plane crash or exploration in space or underwater," Shepherd said. "These are places that having a robot that can operate for a long time would be important."
The battery design could also alter robot designs.
"This doesn't only increase the operating time of a robot but also potentially removes some of the need for wiring," Shepherd said. "You could distribute power throughout the robot rather than having a central location ... which means less electrical resistance and less weight from power wiring."