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Light-Activated Muscle: Biology Meets Robotics
Think of an eagle flying: soaring on currents of air, swooping down from the heights into a meadow to snatch up its tiny prey. This execution of precise movement requires an impressive coordination of systems. Importantly, none of it would be possible without the mechanics of skeletal muscle.
Hoping to engineer robots that achieve the dexterity of skeletal muscle tissue, researchers at MIT and the University of Pennsylvania have recently published an article in the journal Lab on a Chip showing, for the first time, engineered muscle tissue that can accurately be activated by light.
These experiments used optogenetics, where specific cell types are genetically modified to express a light-activated protein. Exposure to light can then be used to activate the cell whenever and wherever needed, including individual muscle fibers or an entire muscle tissue.
In this study, mouse skeletal muscle cells were modified to express membrane Channelrhodopsin-2, an ion channel naturally expressed in green alga and activated by light. The cells then self-assembled into functional three-dimensional muscle fibers. Individual muscle cells or entire swaths of tissue were made to contract simply by shining focused light on the desired area. (For a movie of this occurring, click here.) In addition to the activation of muscle cells with light, the engineered muscle tissues were attached to a micromechanical chip that enabled measurement of forces generated by the tissue in real-time.
Currently, electrodes can be used to activate muscle tissue, but the spatial resolution is limited and the device can be bulky and imprecise. With optical stimulation of muscle tissue, minimally invasive, targeted and real-time results can be achieved. With a robot made of light-activated muscle, quick and dexterous movements could be made with “controlled, graded tension.” This study represents the first time that skeletal muscle has been activated using a light stimulus. The technology has potential applications in endoscopy, drug screening, and many robotics applications.
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Sakar MS, Neal D, Boudou T, Borochin MA, Li Y, Weiss R, Kamm RD, Chen CS, Asada HH. (2012). Formation and optogenetic control of engineered 3D skeletal muscle bioactuators. Lab Chip. Dec 7;12(23):4976-85.