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There may come a day when humans take on the form of cyborgs with integrated, robotic parts to enhance our abilities. But long before then, a seemingly opposite type of integration may take place, with robots being equipped with human tissue or other living cells to make them more lifelike.

These "biohybrid" robots could be endowed with muscle cells to help them perform subtle movements. And on a microscopic scale, tiny robots could be merged with bacteria to ferry them through the body for precision medical procedures.

And the future, it seems, is happening now. [Super-Intelligent Machines: 7 Robotic Futures]

In a new review of studies, an international group of scientists and engineers described the state of biohybrid robotics — a field that is entering a "deep revolution in both [the] design principles and constitutive elements" of robots. The review was published today (Nov. 29) in the journal Science Robotics.

"You can consider this the counterpart of cyborg-related concepts," said lead author Leonardo Ricotti, of the BioRobotics Institute at the Sant'Anna School of Advanced Studies, in Pisa, Italy. "In this view, we exploit the functions of living cells in artificial robots to optimize their performances."

Scientists have created robots of all shapes and sizes with increasing complexity in recent decades. Some robots function well on assembly lines, tightening bolts or welding together sheets of metal. Miniaturized robots smaller than a millimeter are being developed to be placed in the body to kill cancer cells or heal wounds.

But what's lacking among all these fascinating robots is the range of fine movement and the energy efficiency found in living organisms, which evolved toward perfection over the course of millions of years, Ricotti told Live Science. That's why it's necessary to incorporate elements of living organisms into robots, he said.

If robot movement and efficiency are fine-tuned, scientists could be use them to explore the human body, monitor environments too small or intricate for current robots, or manufacture products with greater precision, the authors wrote in the review.

Actuation, or the coordination of movement, is a persistent hurdle in robotics, Ricotti said. For example, robots can be designed to easily lift heavy weights or make precision cuts, but they have difficulty coordinating actions as subtle as cracking an egg cleanly into a bowl or caressing a distressed individual. Their initial movements are jerky.

Animal movements, in contrast, start gently on a micro scale as a cascade of molecular machinery becomes activated inside nerve cells, and culminate in large-scale muscular motion, according to the review.

This raises the possibility that animal tissue, such as cardiac muscle or insect muscle, could provide precise actuation and steady movement in robots. For example, a group led by Barry Trimmer of Tufts University, a co-author of the Science Robotics paper, has developed worm-like biohybrid robots that move via the contraction of insect muscle cells.

Another problem in robotics is the power supply, particularly for micro-robots, in which the powering device can be bigger than the robot itself. Biohybrid robots can overcome this obstacle as well, Ricotti said. His colleague Sylvain Martel, of Polytechnique Montréal, also a co-author of the Science Robotics paper, is using magnetotactic bacteria, which naturally move along magnetic field lines, to transport medicine to hard-to-reach cancer cells. Martel's group can direct the bacteria with external magnets.

There are limits to what these biohybrid robots can achieve, though, Ricotti said. Living cells need to be nourished, which means that, for now, these robots tend to be short-lived. Also, biohybrid robots can operate only in the temperature range suitable for life, meaning that they can't be used in extreme heat or cold.

Despite these challenges, Ricotti and his colleagues said, the field of biohybrid robots is rapidly evolving from the "art of possible" to the science of "reliable manufacturing."

It may be that, in the near future, our cyborg descendants will be cured by biohybrid robotic medicine — administered, no doubt, by an android doctor.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.