There are already a number of vacuum devices, suction cups, which allow people or robots to climb walls and other vertical surfaces, but all these devices have one significant drawback – they all work efficiently and reliably only on smooth surfaces. However, Chinese researchers were able to develop a system that can be held on rough surfaces, using the high-speed rotation of water.

This technology, called ZPD (zero-pressure difference), was developed by a team from Zhejiang University, led by Xin Li and Kaige Shi. In it, in this technology, special rubber cups are used, in each of which a ring of water is created, rotating at high speed at the boundary between the plane of the cup and the surface. The resulting inertial forces generate a steep pressure drop, due to which a sufficiently deep vacuum arises in the center of the cup, and at the pressure of the cup, atmospheric pressure remains. The main advantage of this approach is that the vacuum in the central region of the cup will never be lost due to the loose fit of the cup to a rough surface.

And another added bonus is that, compared to traditional systems, the ZPD system requires much less energy to create a vacuum with a certain depth inside the suction cup. In addition, the device itself is smaller and less massive than conventional devices based on traditional vacuum suction cups.

Currently, scientists have manufactured and tested ZPD-cups of three different sizes. One of the types of such cups was mounted on an automated manipulator arm and, thanks to this, the manipulator could capture objects of any shape and with a surface of any type. The second type of cups was used to create a device that allows a person to climb walls like a Spider-Man, and the third type cups, the smallest ones, were used in the construction of a robot that gained the ability to move along walls like an insect.

Realization of technology ZPD

“Compared to other robots that can climb walls, our robot using ZPD technology demonstrates greater efficiency and productivity”, says Xin Li. “Our next step is to reduce water consumption, which will allow the robot to function for a long time using water from our own tank and not being tied to a large tank by the hose, as it is now”.