Briefs: Edible optics to prevent food poisoning
Edible nanosensors made from silk could alert consumers regarding potential contamination of food thanks to a hologram-type indicator embedded in the pack. Researchers at Tufts University in the US are working on the development of bioactive silk sensors (in the form of lenses, microlens arrays and holograms) that will indicate the presence of Escherichia coli, salmonella and other potentially dangerous microorganisms in bags of fresh produce. To form the devices, the team boiled cocoons of the Bombyx mori silkworm in a water solution and extracted the glue-like sericin proteins. The purified silk protein solution was poured onto negative moulds of ruled and holographic diffraction gratings with spacing as fine as 3600 grooves/mm. The cast silk solution was dried to create solid fibroin silk films. A similar process was followed to create lenses, microlens arrays and holograms. The films with thicknesses ranging from 10 to 100 µm were characterized for transparency and optical quality.