Towards In-mould Antennas for Geolocation Tags

This paper presents a preliminary study for the construction of an in-mould smart tag as a robust flexible and battery-free label with a radiofrequency energy harvesting sub-system and enhanced geolocation features. The proposed flexible geolocation tag is realized by means of a specific production process applied over printed antennas and hybridized rigid control module. Advanced materials such as highly conductive inks and nanocellulose-based substrates, as well as innovative manufacturing processes covered by the in-mould electronics framework, are investigated. Through simulations and experimental validation, the effect over printed antennas of an over-moulded layer of Thermoplastic Polyurethane (TPU) is explored. Such material due to its dielectric properties and thickness tends to down-shift the resonance frequency of the antenna, favouring miniaturization, but also increases its loss resistance. A 1.25 mm thick TPU was chosen for the final tag to ensure both flexibility and a realized positive gain of +0.7 dBi at 865 MHz. For further development of the tag, materials electrical and dielectric properties must be clearly defined in simulation to correct frequency shifts.