A natural force which causes tiny particles to stick to one another has been reversed by scientists, effectively enabling them to create a type of levitation.

The 'Casimir force', which is sometimes referred to as a 'sticky quantum' force, makes very small, or nano-particles attract one another. It is demonstrated in a gecko's ability to stick to a surface with one toe, the scientists who made the breakthrough said.

The two physicists from the University of St Andrews have discovered a way to reverse the force, meaning that they can make small objects repel, rather than attract, one another in vacuum.

Their findings, which are reported in the August edition of New Journal of Physics, may have applications in "micro-electromechanical systems" – such as those in car airbags – where friction can be a problem.

"The Casimir force is the ultimate cause of friction in the nano-world," Professor Ulf Leonhardt, of the university's School of Physics and Astronomy, said."Tiny mechanical devices which trigger a car airbag to inflate or which power tiny 'lab on chip' devices used for drugs testing or chemical analysis could run smoother and with less or no friction at all if one can manipulate the force."

Professor Leonhardt, who published the research with a colleague, Dr Thomas Philbin, added: "Instead of sticking together, party of micro-machinery would levitate."

The technique would apply only to micro-objects, and for the time being there was no way to levitate human beings, Professor Leonhardt said. "For now human levitation remains the subject of cartoons, fairytales and tales of the paranormal."

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