  Edible electronics will facilitate point-of-care testing through safe and
cheap devices that are digested or degraded in the body or environment after
performing a specific function. Its thrive depends on creating a library of
materials that are the basic building blocks for eatable technologies. Edible
electrical conductors fabricated with green methods that allow production at a
large scale and composed of food derivatives, ingestible in large amounts
without risk for human health are needed. Here, conductive pastes made with
materials with a high tolerable upper intake limit (major of mg/kg body weight
/day) are proposed. Conductive oleogel paste composites, made with
biodegradable and food-grade materials like natural waxes, oils, and activated
carbon conductive fillers, are presented. The proposed pastes are compatible
with manufacturing processes such as direct ink writing and thus are suitable
for an industrial scale-up. These conductors are built without the use of
solvents, and with tunable electromechanical features and adhesion depending on
the composition. They have antibacterial and hydrophobic properties, so that
they can be used in contact with food preventing contamination and preserving
its organoleptic properties. As a proof-of-principle application, the edible
conductive pastes are demonstrated to be effective edible contacts for food
impedance analysis, to be integrated for example in smart fruit labels for
ripening monitoring.
