TECHNOLOGY n 21 www.drivesncontrols.com February 2026 US RESEARCHERS HAVE CREATED a gear mechanism that uses fluids, rather than mechanical teeth, to produce rotation. They believe their invention could lead to a new generation of devices that offer greater flexibility and durability than existing gears. “We have invented new types of gears that engage by spinning up fluid rather than interlocking teeth, and we have discovered new capabilities for controlling the rotation speed, and even direction,” says Jun Zhang, a professor of mathematics and physics at New York University (NYU), where the research was performed. Gears are among the oldest machine parts, dating back to 3,000 BC in China, where they were used in chariots. But, their teeth – whether wood, metal or plastic – are inflexible and vulnerable to breaking, and must interlock perfectly to work. “Regular gears have to be carefully designed so their teeth mesh just right, and any defect, incorrect spacing, or bit of grit causes them to jam,” explains Leif Ristroph, an associate professor of mathematics at NYU, who was a member of the team. “Fluid gears are free of all these problems, and the speed and even direction can be changed in ways not possible with mechanical gears.” The researchers, from NYU’s Courant Institute School of Mathematics, Computing, and Data Science, wanted to know if it was possible to make devices that work like gears, but don’t need teeth to be in contact with each other to function. Recognising that air and water flows are used to rotate structures such as turbines, the team, led by Zhang, hypothesized that fluids could also serve as gears’“teeth”, if their flows could be directed accurately. They conducted an series of experiments that included immersing cylinders or rotors in a glycerolwater solution whose properties, such as viscosity and density, they could manipulate. One cylinder was powered actively to rotate, while a second was unpowered or passive. The researchers hypothesised that the active cylinder could generate fluid flows that would cause the passive one to rotate. To monitor this, they added tiny bubbles to the mixture, allowing them to track the movement of the flows and to see how the fluids functioned as gears. They ran experiments with the cylinders at various separations, and with the active cylinder rotating at different speeds. They found that the active cylinders, combined with fluid flows, could cause the passive cylinders to move in ways that were sometimes similar to gears, and sometimes more like pulleys connected by a belt. When the cylinders were close, the flows functioned in a similar way to teeth that engage on the facing sides of two gears, causing them to rotate. The swirling flows effectively gripped the passive rotor and made it spin in the opposite direction to the active one. However, when the cylinders were further apart, and the active one was spun faster, the flows looped around the outside of the passive one, like a belt around a pulley that then rotates in the same direction as the active one. Fluid-based ‘gears’ could outperform mechanical devices Leuze’s AI system uses sample data to learn how brightness and surface texture affect a distance sensor’s measurements. This makes it much easier to correct the measured values. Tests have shown that the AI-based calibration technique can reduce the dependence of measurement results on surface and distance by more than half. It results in more robust and accurate measurements, even with difficult surfaces. The benefits include: n fewer measurement errors, resulting in much more precise results; n the flexibility to operate with different types of sensor and surfaces; n improved learning from real data, even with strongly oscillating 3D curve characteristics; and n future-proof operation, thanks to its use of AI. Leuze expects typical applications to include: n navigation and collision avoidance on robots and mobile platforms n materials handling – checking positions and distances on conveyor belts n quality assurance – measuring distances to workpieces with difficult surfaces n AGVs – providing precise distance control when parking and manoeuvring; and n safety – detecting proximity to machines and systems. Two spinners inside a circular container surrounded by liquid. The left spinner is driven by a motor (not shown) to rotate, while the one on the right rotates passively due to the flows. Bubbles help to visualise the flows. Image: NYU's Applied Mathematics Laboratory
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