Light-activated skeletal muscle “blurs the boundary between nature and machines”

Light-activated skeletal muscle “blurs the boundary between nature and machines”
Muscle cell undergoing light activation (Image: MIT)
Muscle cell undergoing light activation (Image: MIT)
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Muscle cell undergoing light activation (Image: MIT)
Muscle cell undergoing light activation (Image: MIT)

In Sir Arthur C. Clarke’s 1972 novel Rendezvous with Rama, the explorers of a seemingly deserted alien spaceship passing through our Solar System encounter a strange three-legged creature that turns out to be an organic robot. In the ‘70s, this seemed so incredible that it could only be the product of an alien civilization thousands of years ahead of us. In 2012, scientists at MIT and the University of Pennsylvania are proving otherwise by starting work on organic robots here on Earth. Using genetically engineered muscle tissue that responds to light, they are blurring the line between animal and machine at the cellular level.

The basis of the MIT team’s approach is muscle tissue genetically engineered through the process of optogenetics. This is involves taking light-sensitive elements from other animals, usually invertebrates, and grafting them on to mammalian cells. Previously, this technique has been used to study cardiac muscles and to control the brains of monkeys, but here the researchers are creating cells that flex in response to light.

Their ambitions are high. The scientists regard this as the first step in their plan to build organic robots that move as fast and as gracefully as their biological equivalents.

The group’s design effectively blurs the boundary between nature and machines according to Harry Asada, the Ford Professor of Engineering in MIT’s Department of Mechanical Engineering.

“With bio-inspired designs, biology is a metaphor, and robotics is the tool to make it happen'" says Professor Asada. "With bio-integrated designs, biology provides the materials, not just the metaphor. This is a new direction we’re pushing in biorobotics.”

The researchers used skeletal muscle tissue as their starting point because it’s stronger and only flexes under external stimuli. This is normally done by neurons providing a tiny electric charge. Biologists use electric shocks as well, but this is as crude as getting your dog to move by kicking him.

The genetically modified muscle cells used by the MIT team were doped with a light-sensitive protein, cultivated and mixed with hydrogel to form three-dimensional muscle tissue. When exposed to 20-millisecond pulses of blue light, the cells, both individually and collectively, flexed. The scientists then tested the strength of the muscles by attaching them to tiny posts and gauging how much the muscles bent them.

Asda compared this to a training center for the tissue. “Like bedridden people, its muscle tone goes down very quickly without exercise.” He went on to say that the muscles showed a high degree of movement. “We can put ten degrees of freedom in a limited space, less than one millimeter. There’s no actuator that can do that kind of job right now.”

The purpose of all of this is to use the laser light as a way of activating the muscle tissues in order to control them like the switch on an electric motor. The MIT team sees the great flexibility of devices made out of engineered muscle as having applications in things like endoscopes, heart catheters or in drug monitors to detect substances that adversely affect muscle tissue, but the real goal is to make robots as fast, flexible and articulate as living beings.

Whether those organic robots would be as cute as Sir Arthur’s Raman tripods or something closer to the Terminator, we have yet to learn.

The video below shows muscle tissue responding to laser light.

Sources: MIT, Lab on a Chip

Light-activated skeletal muscles at MIT

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