A sticky situation

Friction, the force that makes objects stick or slide, is essential in technologies like semiconductor device manufacturing, where silicon wafers must be held and moved with extreme precision. However, friction is currently determined by a choice of materials and cannot be actively controlled.

A new project led by Bart Weber at UvA-IoP and ARCNL, funded by an NWO Vidi grant, will explore a new approach: using electrical charge trapped in thin insulating layers to tune how strongly surfaces attract or repel each other. By controlling this charge, friction can be increased or reduced on demand. This could enable more accurate, faster chip production and open the door to smart surfaces with adjustable grip and motion.

Long-range, reversible, and tunable

When two insulating solid materials touch, the mechanical contacts between them generate and trap electrical charge. These trapped charges can cause parts of the interface to be more “sticky” than others, because of how opposite charges attract. Because stickiness, or adhesion, governs friction, trapped charge can directly modify forces at the interface. Being able to control where such charge-trapping occurs could therefore allow friction to be tuned.

Unlike chemical modifications, electrostatic interactions are long-range, reversible, and electrically tunable. “While charge trapping is well established in memory devices, its role in load-bearing sliding contacts remains largely unexplored,” says Weber. “If we can stabilize charge under these conditions, adhesion – and thus friction – becomes programmable.”

Applications and impact

In modern semiconductor equipment, friction is not a design parameter that engineers can tune, but a side effect of the materials and surfaces involved. “Improved control over friction in these systems would directly enhance positioning accuracy, stability, and throughput,” says Weber. “This not only translates into economic growth, but also reduces energy consumption, as computer chips with finer features consume less power.”

Beyond semiconductor manufacturing, the ability to actively control friction opens up new possibilities for adaptive mechanical systems. “Surfaces could switch between low-friction and high-friction states depending on the task,” explains Weber, “enabling efficient motion when needed, and strong grip when required.” Such functionality is relevant for robotic manipulation, precision engineering, and high-performance mechanical systems.

Support for emerging leaders in science

This project will be funded through an NWO Vidi grant in the domain Applied and Technical Sciences. The Vidi grant is an individual research grant aimed at researchers who are in the process of transitioning to leadership roles. More information about the Vidi grant and awarded projects can be found on the NWO website.