Sunday, August 29, 2010

Soft armour that hardens upon impact

Aug 28, 2010

S'pore invention inspired by corn starch's 'shear thickening' property
By Lester Kok

SINGAPORE scientists have invented a 'smart' padding which hardens upon impact, but remains soft under normal conditions.

Being malleable, it can be adjusted to conform to many shapes, suitable for sports padding and bulletproof body armour.

Potential uses for this technology include protective gear and clothing for sports and military applications, an area that is estimated to grow to US$4.5 billion (S$6.1 billion) by the year 2012.

Other important sectors such as automobile and health care can also benefit from this new technology, as there is a need for protection against impact.

The idea first came about from a corn starch experiment, which is normally used to demonstrate the versatility of materials to the public.

Corn starch, when mixed with water, is soft and malleable, but turns stiff upon hard impact - a property known as shear thickening.

Dr Davy Cheong, a senior research engineer with the Institute of Materials Research and Engineering at the Agency for Science, Technology and Research (A*Star), said that during science outreach demonstrations to the public, many people asked him if corn starch could be used for bulletproof vests.

'So I actually put some corn starch into a latex glove and brought it around for discussion. But the real epiphany came when my team had a discussion and we discovered how we can utilise this to make a composite. From there, we improved its performance,' he said.

Dr Cheong said he and his partners, Mr Phyo Khant and Assistant Professor Vincent Tan from the National University of Singapore (NUS), spent two years on this project, eventually finding other materials to replace corn starch, which would sour over time. Also assisting them was NUS Department of Mechanical Engineering PhD candidate Shang Jia Shun.

A key difference between their patented material and other shear-thickening technologies is that it does not require external wrapping such as foam and can be used as a standalone.

In ballistic tests which applied the same impact as a large pistol bullet, the padding reduces blunt force up to 60 per cent better than bulletproof fabrics.

On top of being on a par in performance with the ceramic and steel plates normally used in bulletproof vests, it is only one-third the weight of a steel plate of the same size and can float on water.

When compared with conventional impact foam used in sports gear, the new padding does not crack under repeated impact and spreads out high impact more effectively.

Since the padding is still under development, there is no direct equivalent in the market for a cost comparison, but it is understood that the raw materials used to make the composite are relatively inexpensive.

The team uploaded videos showing tests on the new composite material at, and several parties from the United States and Canada have expressed interest in collaborations.

The videos show the team smashing a watermelon with a hammer, cushioning the blow with normal impact foam and with the new padding material.

One popular video clip shows a researcher wearing the pad on his forearm and hitting it with a hammer, a metal spike, and against iron surfaces.

At the end of the clip, he removes the pad and shows his arm, which bears no bruises despite all the abuse.

The videos were also used by the team for a presentation in the United States to demonstrate visually how the technology works.

'We are also trying to improve the current system so that, maybe in the future, we can have an entire 'super suit' made of the material that is flexible and yet takes bullet shots, without the need for Kevlar layers in front,' Dr Cheong said.

[For civilian use, perhaps it can be used for bicycle and motor cycle helmets?]

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