Edible electronics will facilitate point-of-care testing through safe devices digested/degraded in the body/environment after performing a specific function. This technology, to thrive, requires a library of materials that are the basic building blocks for eatable platforms. Edible electrical conductors fabricated with green methods and 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 (≥mg kg −1 body weight per day) are proposed. Conductive oleogel 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 using 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.

Molecular doping of conjugated polymers is extremely desirable to control charge density gradients and shape the electric field across polymer electronic devices, including highly efficient organic solar cells. It is also a fundamental requirement for organic thermoelectrics and a powerful strategy to boost charge injection and transport properties in transistors. Yet, currently available doping approaches are far from offering a suitable level of control, particularly in the case of n-type doping. We here reveal that part of this limitation lies in the lack of understanding of dominant factors in doping efficiency. In particular, we highlight the key role played by very small amounts of a specific decomposition product formed during processing of the widely used molecular dopant 4-(2,3-dihydro-1,3dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (DMBI-H) in influencing the n-type conductivity in polymer blends. We show that such an overlooked decomposition product acts as a nucleating agent for a new crystalline phase of DMBI-H, with the overall effect of boosting the electrical conductivity of the final doped polymer films. Such results, confirmed by control experiments performed with a different nucleating agent, focus on the crucial role played by the solid-state microstructure in molecular doped semiconductors and offer ground for a significant change in design guidelines for molecular doping strategies.