An illustration of microscopic gold flakes on surface
An illustration of microscopic gold flakes on surface.
Photo: Falko Schmidt

Casimir vs Casimir - using opposing forces to improve nanotechnology


A well-known problem in micro- and nanotechnology is stiction. Friction between tiny parts and surfaces cause issues in utilizing new technologies - but recent results presented in Nature Physics can help clear this hurdle and move the field forward.

As technological advancements are made on the micro- and nanoscale, things tend to get tricky. Nanoscopic devices are built using metals, like gold, due to their favorable properties like high stability, biocompatibility, ease of processing. However, since they are operating on such a tiny scale, the parts end up stuck together because of Casimir-Lifshitz forces.

These forces, due to electrodynamical quantum and thermal fluctuations, end up pushing the parts of micro-devices together, causing friction and stiction. Friction and stiction stop the devices from working as intended.

“In this project we demonstrate that we can use another type of

Giovanni Volpe
Giovanni Volpe
Photo: Johan Wingborg

fluctuation-induced force, namely critical Casimir forces, to counteract the friction caused by quantum-electrodynamical Casimir-Lifshitz forces. This is achieved by using a liquid mixture which makes the interaction between the surfaces of the device repulsive, hence pushing the small metal parts away from it”, says Giovanni Volpe, professor in physics at the University of Gothenburg.

Tuning with temperature

By altering the functionalization of the surface, an environment is created where the Casimir forces at play influence the tiny gold flake by counteracting each other. The effect helps the flake move freely and not get stuck. It is even possible to control the movement of the flake by altering the temperature of the liquid mixture.

“Since critical Casimir forces can be controlled by temperature, we can easily switch them on and off. This has the potential of becoming an extra handle with which to control nanodevices – one that hasn’t been explored until now,” says Giovanni Volpe.

“As a theoretical physicist collaborating with experimentalists, it is always impressive to see how challenging the interpretation of experimental data can be and how fundamental concepts and ideas of statistical physics eventually provide the key to understanding the world at such small scales,” says Andrea Gambassi, professor of theoretical physics at SISSA, Italy.

An illustrated model of a nano device with gold flakes in different states.
An illustrated model of a nano device with gold flakes in different states.
Photo: Falko Schmidt

Tiny parts in smartphone cameras

The effects demonstrated by the researchers were theoretically expected but had yet to be observed and measured experimentally before now. The demonstration in itself is a proof-of-concept, not meant to be applied as is in any actual device. However, the breakthrough could lead to untold advancements in the fields of micro- and nanotechnology.

“Removing friction from nanodevices would make them more long-lasting, smaller, and more versatile. Electromechanical devices are already used in plenty of appliances we use in daily life. For example, the tiny components like lenses, coils and magnets used in smartphone cameras. Current micro- and nanoelectromechanical devices could benefit from exploring the kind of enhancement in the technology we demonstrate in our work. But that would be way down the line, in the future,” says Giovanni Volpe.

The results are published by the prestigious scientific periodical Nature Physics.

Read the full article here

Project details

The research project is a collaboration between Gothenburg University, Chalmers, University of Düsseldorf, Friedrich Schiller Universität and SISSA (Trieste, Italy).

First author is Falko Schmidt, former PhD-student at Gothenburg University, currently Post-doc at Friedrich Schiller Universität (FSU).