Chinese scientists reveal ‘liquid armour’ secret of Huawei’s foldable smartphone

Much like people seen in TikTok videos running across a pool filled with starch slurry without sinking, the trick is to move quickly, as the slurry hardens directly beneath each step before instantly returning to liquid when the pressure is gone.

Paint and honey can also become non-Newtonian fluids under certain conditions and the phenomenon’s unique property is already used to make military liquid body armour.

Huawei’s researchers said their intention in developing the flexible inner screen was to mitigate the growing risk of shattered screens that has come with the trend for larger and thinner devices.

“Incorporating this ‘strength-on-impact’ material into the screens of foldable phones not only meets the demands of folding mechanisms but also significantly enhances the screens’ resistance to impacts,” the team said.

According to Wei Yanpeng, a professor with the Chinese Academy of Sciences’ Institute of Mechanics who is not associated with Huawei, there are two ways to achieve a non-Newtonian fluid state.

“In terms of composition, [one form of a] non-Newtonian fluid material … is a suspension system, such as starch paste, and the other is made up of a single molecular-level material, which absorbs impact forces through chemical bonds,” he said.

The Huawei team adopted the second option and started work on what would eventually become polysiloxane – a non-Newtonian fluid that is light, foldable and transparent.

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This material’s long molecular chains and perpendicular chemical bonds create a cage-like structure that maintains screen hardness under normal conditions but absorbs impact by breaking the dynamic bonds.

“The flexible inner screen maintains softness during slow bending, aiding the folding process, and instantly hardens upon rapid impact,” the researchers said. The result is akin to a “transparent vest” that protects against accidental drops or sharp impacts.

When it came to producing the material, the researchers said they were able to improve on filtering techniques to achieve a transparency rate of 92 per cent for the finished flexible screen.

Another plasma spray treatment added a hydrophilic layer to the material’s surface, improving adhesion with the optical clear adhesive and easing assembly with other phone parts, they said.

“This technology was first applied in the Mate X3’s composite foldable screen, marking the first use of non-Newtonian fluids in consumer electronics, with the Mate X5 continuing this innovative design,” they said.

According to the research team, the flexible inner screen of the Mate X5 smartphone – which received a five-star impact resistance certificate from SGS Switzerland – is a fourfold improvement on the performance of the earlier Mate X2.

The screen is capable of resisting the impact of lipstick, capped whiteboard pens and other everyday items dropped from a height of one metre (3ft), the team said.