The World in 2030

264 The World in 2030
And yet another astonishing development in plastics, one
that promises to make our environment both more beautiful
and safer, was detailed in The Economist in August 2007
under the heading ‘Opal Fruits’:
A group of researchers from the University of Southampton,
in England, and the German Plastics Institute
in Darmstadt, led by Jeremy Baumberg, have discovered
how to create a plastic with the gemstone’s
iridescent properties. Their invention could be used
to make a sparkling substitute for paint, banknotes
that are hard to counterfeit and chemical sensors that
can act as visible sell-by dates.
Dr. Baumberg has built his opalescent material
from scratch. He and his team grew tiny polystyrene
spheres until they were some 200 nanometres across,
before hardening them with a blast of heat. They
then coated the spheres with a sticky polymer before
heating them again. As the mixture was baked, the
spheres moved naturally into a face-centred cubic
structure.
To use the film to detect food spoilage, Dr. Baumberg
proposes adding a sprinkle of carbon particles
even smaller than the polystyrene spheres. These
would nestle in the spaces between the spheres and
cause the material to scatter light from even more angles,
making it yet more iridescent. This arrangement
could be “tuned” to react to specific toxic chemicals.
Food packaging made from such a material would
thus change colour as the rot set in.