Using a glycerol-water solution, scientists from New York University (NYU) demonstrated how fluid can both avoid the limitations of mechanical gearing (i.e. Like most geared devices, one of the gears was powered, while the secondary gear remained passive, and the team added bubbles to the mixture to track fluid movement. What they found is that the flows created by the active mechanism could be manipulated to subtly influence the secondary gear in a variety of ways. For example, if the gears were close together, the flows functioned like typical teeth, causing the secondary gear to spin in the opposite direction. “Fluid gears are free of all these problems, and the speed and even direction can be changed in ways not possible with mechanical gears.”When the ancient world first put toothed gears to work, it revolutionized engineering.