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Courtesy of the Samueli School of Engineering and Applied Science Bionanotechnology researchers Jianzhong Xi (left) and Carlo Montemagno teamed up to build a biomachine.

Blurring the line between organism and machine

Muscle cells on metal make microbots move

Imagine a future where an amputee can grow his own muscle cells over artificial bones to create a new leg or rebuild severed fingers.

Nanotechnology researchers at the Henry Samueli School of Engineering and Applied Science have opened the door to just such a future by creating the first self-assembled microrobot powered by living heart muscle.

These hybrid devices — part machine, part organism — were grown on silicon chips using the same principles and technology now used to make integrated circuits. The research was undertaken as part of the Institute for Cell Mimetic Space Exploration.

Viewed under a powerful microscope, each tiny bot is composed of a sheath of cardiac muscle grown from rat cells connected to an arch of gold. Immersed in a sugar and protein mixture that emulates the body’s natural environment, the bot shuffles forward each time the muscle, which has an intrinsic beat, contracts and relaxes.

“I was surprised when I first saw the bots walk and realized that it had worked,” recalled Jianzhong Xi, a member of the research team. “Honestly, I had this picture in my head that they would somehow swim. And then I thought, ‘Wow! Swimming or walking — they’re moving.’ It was a great moment.”

In the past, researchers have managed to incorporate living muscle tissue into machines, but “transferring muscles from an organism to a micro-device manually isn’t really practical,” Xi said.“The living tissue is often damaged because you’re working on such a tiny scale to attach muscle to a minuscule device and make it stay there.”

To accomplish the recent breakthrough, UCLA scientists used a specific kind of polymer. Incorporating chip-industry methods — normally harmful to living cells — a silicon chip was first etched with “supporting beams” before being coated with a biocompatible polymer and then an arched layer of gold.

Using a method developed at UCLA, scientists inject the liquid culture with heart muscle cells once the polymer devices are in place.Deposited muscle cells begin to grow on the gold, while the polymer inhibits random cell growth and acts as a kind of mold.

Because the cells attach and grow only on the exposed metal, the bots are, in a sense, “self-assembling” units. Finally, the polymer is dissolved and the beams securing the device in place on the chip are snapped away. It’s at that point that the microbot begins to move, drawing energy from the glucose in the surrounding solution.

“We can make hundreds of thousands as easily as we can create just one,” said Carlo Montemagno, chair of the Bioengineering Department, who oversees the project.

Muscle-powered microelectromechanical systems, or MEMS, are an attractive option for researchers for many reasons. By feeding on glucose in the blood, these devices could “potentially be used for micro-surgery, maybe clearing plaque build-up in arteries,” Xi explained.

Montemagno believes that microbots “could eventually function as electrical generators that could power tiny, bodily implants, or even to drive mini-electrical generators to power computer chips, among many other possible uses.” NASA, which provided funding for the project, has its own ideas: One day these bots may be used to repair the outside of space shuttles while in orbit.

For these microbots, the sky may indeed no longer be the ultimate limit.