In this work, the application in Radiofrequency Identification (RFID) of different additive manufacturing (AM) 3D-printing technologies is discussed. In particular, the well-known Fused Deposition Modeling (FDM) technology is compared with the promising Digital Light Processing (DLP), which is based on the photopolymerization of liquid resins. Based on the research activity of the authors on this topic, a brief introduction to the fundamentals of 3D-printing in electromagnetics as well as to the different applications of both FDM and DLP in realizing Radio Frequency (RF) devices, is firstly given. Then, a comparison of the two technologies is deeply faced. Finally, after evaluated the rugosity of substrates produced with both techniques to verify the potential impact on the design of electromagnetic structures, the two techniques are both exploited for the realization of the dielectric parts of a tunable RFID tag with unconventional shape. It consists of two elements interlinked one each other. The movement between them enables tuning of the resonance frequency as well as the impedance of the antenna. Despite the differences in terms of losses, rugosity, resolution, and dielectric constant, both techniques guaranteed satisfactory values of tag sensitivity, maximum reading range, and tunability. Nevertheless, the careful analysis of the results proposed at the end of the paper suggests how the selection of one technique over the other must be taken considering the specific application constraints.

3D-Printing in antenna design is a recent research branch which is attracting academic and industrial interest. Nevertheless, despite the advantages in terms of antenna customizability, common filaments exhibit limitations in some contexts where platform tolerability, flexibility, and compactness are simultaneously required. Indeed, other than a rather low permittivity of commercial 3D-printable materials, when flexibility is required, also significant loss tangent values must be accounted. To address this problem, a method to realize conformable flexible low-loss substrates with increased and customizable permittivity is proposed in this work. It is based on the synthesis of ceramic-doped silicone structures shaped through 3D-printed molds by using Alumina and Barium Titanate as ceramic filler. Different substrates were firstly realized and characterized in terms of permittivity and loss tangent at different doping percentages. Then, a first validation on 2.4 GHz conformal patch antennas exploiting both third dimension and increased permittivity is presented. Finally, a wearable and compact bracelet-shaped UHF RFID PIFA-inspired flexible antenna is designed, tested when applied on the human body, and compared with a previously realized version 3D-printed in Polylactic Acid. In spite of comparable performance, the novel device exhibits considerable size reduction and improved wearability, thus confirming the effectiveness of the proposed approach.

This paper presents a compact AMC structure used as a shielding element for a generic wearable RFID tag at UHF frequencies for on-body applications, with an overall footprint limited to an area of only 0.03 λ ₀ ² (41.4 mm × 82.8 mm). Thanks to the isolation provided by the AMC planar structure, the tag antenna gain and reading range are increased of about one order of magnitude in comparison with the case of a conventional tag attached to the human body. The designed antenna is platform tolerant, with a very good robustness and isolation with respect to the human body, exhibiting a high reliability. The AMC structure is implemented on a thin, flexible and biocompatible high permittivity silicon-doped dielectric substrate, with apertures both in the substrate and in the ground plane to allow skin transpiration. Therefore, the presented device can be effectively used also as an epidermal antenna, allowing the “on-skin” sampling of the most typical health parameters. The presented configuration has been designed using CST Studio Suite. A prototype has been fabricated and fully characterized, and measured results are in very good agreement with simulations.

One of the most promising and exciting research fields of the last decade is that of 3D-printed antennas, as proven by the increasing number of related scientific papers. More specifically, the most common and cost-effective 3D printing technologies, which have become more and more widespread in recent years, are particularly suitable for the development of dielectric resonator antennas (DRAs), which are very interesting types of antennas exhibiting good gain, excellent efficiency, and potentially very small size. After a brief survey on how additive manufacturing (AM) can be used in 3D printing of antennas and how much the manufacturing process of DRAs can benefit from those technologies, a specific example, consisting of a wideband antenna operating at 2.4 GHz and 3.8 GHz, was deeply analyzed, realized, and tested. The obtained prototype exhibited compact size (60 × 60 × 16 mm³, considering the whole antenna) and a good agreement between measured and simulated S₁₁, with a fractional bandwidth of 46%. Simulated gain and efficiency were also quite good, with values of 5.45 dBi and 6.38 dBi for the gain and 91% and 90% for the efficiency, respectively, at 2.45 GHz and 3.6 GHz.

In this work, three promising Additive Manufacturing (AM)/3D-printing technologies, able to realize conductive elements, are adopted in the realization of antennas. The selected techniques are Fused Filament Fabrication (FFF), Aerosol Jet Printing (AJP), and Laser-Induced Graphene (LIG), which have been compared by measuring the performance of an ultrahigh (UHF) radiofrequency identification (RFID) tag, specifically designed, and realized for the scope. Results have also been analyzed against to data obtained by a reference sample realized in Aluminum. The FFF tag has been manufactured by extruding the Electrifi conductive filament over an ABS printed substrate, used also for the AJP-made antenna. Conversely, the LIG tag has been produced by laser-burning a Kapton polyimide sheet. All the tested technologies, each one with its pros and cons, allowed to realize working prototypes, even if, as expected, with performance lower than the comparison sample. An electroplating process has been also adopted to increase conductivity, with improvements in the FFF prototype. The obtained results are quite satisfactory. Those related to LIG technology do not yet guarantee performance comparable to the other techniques. Nevertheless, the prospect of creating “green” and cost-effective antennas pushes towards further studies, already underway, which include the study of antenna shapes more suitable for the specific technique as well as process optimizations to increase conductivity.