At New York University, a group of researchers led by professors Jun Zhang and Leif Ristrof has developed a technology called “liquid gears.” This is a hydrodynamic mechanism in which traditional gears do not come into direct contact with each other — the space between them is filled with a mixture of water and glycerin. When one gear rotates in this viscous substance, vortices are created that set the second gear in motion. 

If the distance between the gears is small, microscopic vortices are created that cause the gears to rotate in opposite directions. As the distance increases, the rotation becomes uniformly directed. By varying the distance between the gears and the composition of the liquid, engineers can regulate the rotation of the components and thus change the transmission ratio of the system.

In a liquid environment, the problem of contamination and debris disappears—the liquid simply flows around obstacles. The lack of direct contact between the gears reduces their wear and tear, and such a system is protected from jamming. Moreover, it does not require lubrication; you only need to select the appropriate liquid composition to ensure smooth rotation.

Such developments raise the question of designing gearboxes from scratch. They are also very useful for creating “soft robots”; with their help, it is possible to create a common fluid circuit and transmit rotation without using reducers at each joint. In such a system, there are extremely few stress zones and pinch points in the mechanisms compared to classic gear transmissions. And it is easier to adjust the volume and composition of the fluid than to replace individual broken gears.

Source: techcult.ru