As one reader points out on the comments board of a related Design News article, combining living tissue with mechanical components sounds like Mary Shelley's Frankenstein story written almost 200 years ago. But the Medusoid jellyfish-like creature described in that article, which combines engineered rat heart muscle tissue with a silicone muscle structure, isn't alone. Researchers at the Massachusetts Institute of Technology and the University of Pennsylvania have engineered skeletal muscles they will use to build robots that move like animals -- or people.
The team has genetically engineered muscle cells that flex in response to light. They plan to use these to create small, lightweight robots that are highly articulated, and that can move with the strength, flexibility, and fine motor movements of living creatures. The researchers are among the still small number of engineers in the emerging field of biorobotics.
Harry Asada, a professor of engineering in MIT's department of mechanical engineering, along with postdoc Mahmut Selman Sakar and professor Roger Kamm, chose skeletal muscle for their robot design because it's stronger than cardiac or smooth muscle. Using electricity to stimulate the muscle tissue to make it move -- a technique used for the Medusoid as well as Frankenstein's monster -- could bog down small robots with electrodes and their required power supply. Instead, the researchers turned to optogenetics, which involves genetically modifying neurons so they respond to short light pulses.
To date, optogenetic techniques had been used to stimulate cardiac muscle with laser light, but not skeletal muscle. The MIT team cultured skeletal muscle cells and genetically modified them to express a light-activated protein. After fusing the cells into long muscle fibers, they exposed them to blue light in 20-millisecond pulses, making them contract, both individually and together. When a beam of light shone on one fiber, only that fiber contracted. Larger beams directed to multiple fibers made them all contract simultaneously. Asada then expanded the technique to three-dimensional muscle tissue, with similar results. Watch a video demonstrating the genetically engineered skeletal muscles here.
The MIT team worked with Christopher Chen, a professor in Penn's department of bioengineering, who designed a micromechanical chip to test static and dynamic stresses on the light-sensitive skeletal tissue. The engineered tissue is capable of a wide range of motions, making it useful for a number of applications besides robotics, such as medical devices and navigation. One medical robotic device might be a robotic endoscope, said Asada. "We can put 10 degrees of freedom in a limited space, less than one millimeter," he said. "There's no actuator that can do that kind of job right now."
The researchers describe their results in an article (subscription only) in the journal Lab on a Chip. Other team members include MIT's Devin Neal, Yinqing Li and Ron Weiss, and Penn's Thomas Boudou and Michael Borochin. The research was supported by the National Science Foundation, the National Institutes of Health, the RESBIO Technology Resource for Polymeric Biomaterials, the Center for Engineering Cells and Regeneration of the University of Pennsylvania, and the Singapore-MIT Alliance for Research and Technology.