New light-powered molecular motors designed by researchers in Japan repeatedly bend and unbend. Scientists say the development moves them one step closer to their goal of developing molecular robots capable of executing complex tasks.

The motors are made of azobenzene and oleic acid crystals. Azobenzene is an organic compound used in dye manufacturing, and oleic acid is a common ingredient in cooking oil. Azobenzene arranges itself in two different molecular forms. When exposed to blue light, it switches back and forth between the two arrangements -- known as cis and trans.

Researchers designed crystals with uneven amounts of cis and trans azobenzene molecules to test whether repeated conversion would influence the crystal structure.

When the thin crystal layers were suspended in a solution and exposed to blue light, researchers observed a constant bending-unbending oscillation. The frequency of the motion went up and down with the frequency of the light. In some instances, the oscillation recalled a swimming-like motion, propelling the crystal through the solution.

Previous light-powered nano-motors have mostly relied on deformation, but the new crystals don't compromise structural integrity. Both the bent and unbent formations -- inspired by the cis and trans configeruations of azobenzene -- are stable and predictable.

"The ability to self-organize rhythmic motions, such as the repetitive flipping motion we observed, is one of the fundamental characteristics of living organisms," Yoshiyuki Kageyama, a chemical engineer at Hokkaido University, explained in a news release. "This mechanism can be used in the future to develop bio-inspired molecular motors and robots that will find applications in wide areas, including medicine."

Scientists shared their latest invention in a new paper, published this week in the journal Angewandte Chemie.