A Hong Kong professor on Friday won the grand prize at this year's Geneva inventions show for a new method of toughening screens for smartphones and other devices to avoid cracks and scratches.

The announcement came after more than 750 exhibitors from 48 countries came together in Switzerland this week at the show, the world's largest event of its kind.

The Grand Prix was awarded to Hong Kong Baptist University professor Cheah Kok-wai, of the Cathay Photonics company, for his process of reinforcing glass screens by applying a thin layer of sapphire.

"This method can be used in many different areas, but especially for smartphone screens which are vulnerable and are often scratched or broken," the organisers of the 44th International Exhibition of Inventions said in a statement.

A "very thin layer" of sapphire, one of the hardest materials in existence, "is enough to guarantee excellent protection," the statement added.

Applying the extra layer, which is done at a high temperature, does not diminish transparency, since optical transmission of the sapphire film is very near to that of glass, it explained.

This method can also be used for glass and quartz screens on watches and televisions.

The inventions fair rewarded 45 other inventions among the 1,000 presented.

The exhibition ends on Sunday.