Ultra-hard ArmoGlass Protects Screens

Screens of electronic portable devices, such as smartphones and tablets, are prone to scratches, cracks and even breakage. ArmoGlass, invented by Professor Cheah Kok-wai, Associate Head and Chair Professor of the Department of Physics, is an ultra-hard, non-fragile and scratch-resistant material considered to be the best screen protector.


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Prof Cheah Kok-wai


Sapphire is the second hardest material in existence. It is considered a good material for mobile device screens, but even though it is hard enough to prevent scratches, it is too fragile and cracks easily upon impact. The heavy weight and high cost of a sapphire screen renders it an unpopular option, while glass screens are prone to scratches. In view of this, Prof Cheah considered ways to strengthen the screen, but thought that hardened cover glass is not necessarily needed to enhance the hardness of glass. Rather, a hardened surface layer would be sufficient to provide extra protection, while retaining the property of flexibility. Thus, ArmoGlass was invented.


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Second only to diamond in its hardness

ArmoGlass is a thin layer of sapphire coated on tempered glass. The layer is made of pure sapphire crystals, which are split into 1/1000th of its original size, and “plated” on the glass surface. The process is done at a high temperature using thin film technology. The sapphire layer, in a molecular state, is slowly deposited onto the glass surface, forming a thin but ultra-hard cover layer. Prof Cheah said that an 8.5-micron thick layer of coating is enough to guarantee excellent protection, comparable to the protection provided by a block of sapphire, with no downside of high fragility.


According to hardness tests, ArmoGlass exhibits 7 to 8.5 Mohs hardness, which is a level higher than tempered glass. It is also harder than sand and metal, thus it is not easy to scratch. Prof Cheah said, a screen with ArmoGlass is at least 50% to 60% harder than ordinary smartphone screens and can withstand abrasion caused by pencil or steel wool, which usually leaves scratches on tempered glass. The only material that can scratch an ArmoGlass coating is diamond, the hardest material in the world. Since optical transmission of the film is very near to that of glass, i.e., between 89% and 92%, application of the sapphire coating does not increase opacity. “In future, we will not need a plastic screen protector which is not environmentally friendly,” said Prof Cheah.


When it comes to commercialisation and industrialisation of new inventions, fabrication cost is a key factor. Bearing this in mind, Prof Cheah tried every possible means to minimise cost. Though the ArmoGlass coating is made of sapphire, the cost is very low because a small sapphire pellet (weighing around 20 grams) is enough to cover three to four glass screens. When taking into account the entire production cost of the screen, the cost of this layer is insignificant. Also, since the fabrication process is based on standard industrial deposition processes, no additional investment in new equipment is required.


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Prof Cheah introduces ArmoGlass at the 44th International Exhibition of Geneva


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The Hon Leung Chun-ying (seventh from right), then HKSAR Chief Executive, congratulates Prof Cheah for winning the Grand Prix International Invention Award


Highest honour received at Geneva

As a result of the revolutionary product, Prof Cheah received HK$3.24 million from the HKSAR Government via the Innovation and Technology Commission to establish the start-up company Cathay Photonics Limited (CPL). Prof Cheah and CPL participated in the 44th International Exhibition of Inventions of Geneva and won the Grand Prix International Invention Award, the Special Award from the Romanian Association for Nonconventional Technologies and a Gold Medal (with Judge Commendations) in the Industrial Processes category. The judges praised the innovative technology for its wide range of applications, saying “all kinds of glass surfaces can be treated, even rounded ones, such as those on watches or televisions.” Indeed, Prof Cheah and his research team are currently developing sapphire coating for metal surfaces. He added that it can also be applied on plastics.


ArmoGlass has now obtained about 10 patents from around the world. Several international high-tech smartphone, watch, and glasses manufacturers are currently collaborating with CPL to implement the technology in various products. It is foreseeable that the application of ArmoGlass will be extended to an even wider range of goods. In view of this, CPL's market value has already exceeded HK$200 million.