Researchers have modified muscle cells to move in response to light, which could eventually result in "bio-bots" useful for health or environmental applications. The breakthrough was made possible by the rapidly expand field of optogenetics, in which algae genes are spliced with muscle tissue from mice to make it sensitive to blue light. The team from the University of Illinois started with a 3D-printed hyrogel skeleton, then looped a ring of the modified tissue around. By firing a flash intermittently, they were able to make the muscle move, and even "exercise" it to become stronger.

The researchers previously stimulated bio-bots with electrical signals, but those can adversely affect a biological setting and don't allow for selective control. "Light is a noninvasive way to control these machines," says the school's bioengineering head Rashid Bashir. "It gives us flexibility in the design and motion." By strategically positioning the rubber-band like rings of muscle on the backbone, the team was able to make bio-bots that perform a variety of functions. "We can have multiple legs and multiple rings. With the light, we can control which direction things move," says Bashir.

Previous bots used thicker pieces of muscle, but the thin tissue can more easily absorb light and nutrients. The researchers also exercised the muscle daily using light, making it stronger and able to move farther when contracted. The next step will be to design different types of 3D-printed skeleton designs and use them as "building blocks" for larger bots.