It may be more termite than Terminator, but a team of bioengineers has grown mammal muscle on a silicon skeleton to create a microscopic robot that can crawl. This "microrobot" represents the most advanced synthesis yet of machines and living organisms.
One of the biggest challenges facing nano-engineers is powering the motion of their tiny machines. One solution is to look to biology and exploit enzymes such as kinesin and myosin as biomolecular motors. But these enzymes make weak motors on their own, so engineers must get billions of such motors to work collectively. Here, biology offers another clue: muscles, in which molecules move in unison. Researchers have already tried attaching muscles to micro-machines called MEMS (microelectromechanical systems), but they have met with limited success due to the damage caused by extracting the muscle.
At the University of California at Los Angles, bioengineer Carlo Montemagno and his colleagues have pioneered a new approach: growing muscle directly onto a silicon machine. First, the researchers coat the machine, which resembles a bent paperclip, with a polymer that prevents cell attachment. Then they remove the polymer from selected areas and add a fine metal film. When the team incubates the machine in a solution containing heart cells, the cells attach to the exposed metal, and further coaxing causes these cells to develop into true muscles. In the finished device, described in the online 16 January Nature Materials, the heart muscles contract rhythmically to drive the machine, drawing energy from the glucose in the solution around them. Montemagno believes that such microrobots could soon function as electrical generators that could power tiny, bodily implants.
"It's cool, it's interesting, and I think there's a real future in it," says bioengineer Robert Dennis, of the University of North Carolina. "It's using cells to do something that cells do very well, which is regulate and control motor proteins".