Paint it black

A new paint will soon warn us of damage to buildings and cars

Published: Thursday 31 December 1998

VEHICLES and buildings could soon inform us if they are feeling up to the mark or not. Scientists in Japan have developed a paint that can 'sense' vibrations that warn of impending structural damage.

Shigenori Egusa at the Japanese Atomic Research Institute and his colleagues from Kansai Paint Company made the paint by mixing epoxy in resin with powdered lead zirconate fitanate, a piezoelectric ceramic (piezoelectric substances emit electrical pulses when com- pressed). The surface is painted with the sticky resin mix and left to dry.

If a surface coated with the mixture starts vibrating, the resin layer flexes, 'squeezing' the lead zirconate titanate particles. Each particle then generates a tiny electrical signal that can be picked up by metal electrodes placed on either side of the resin layer. Areas that vibrate the most send out the largest electrical signals.

In their experiments, Egusa and his team found that squares of paint five centimetres across on an aluminium beam can successfully map the beam's vibrations between frequencies of 0 and 250 hertz (Journal of Smart Materials and Structures, Vol 7, p438).

Egusa believes that similar patches on vehicles, building supports and plane wings could give an early warning of structural failure. "Potentially, the paint can be applied to all kinds of metals, ceramics and concrete," says Egusa. "Smart paints that respond to their environment are part of the future," says Geoffrey Forrilinson, a mechanical engineer at the University of Sheffield, UK. "Assumirig that they are robust and that the signal output can be optimised, piezopaints offer an interesting and promising alternative to existing sensors."

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