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This article describes sensors and radio frequency (RF) components manufactured by applying selective-metallization processes (metal foil tape, liquid metal filling, electro and electroless plating, and surface embossing) to 3-D-printed and flexible dielectric substrates. All these technologies can be implemented at room temperature, thus enabling the adoption of unconventional materials and biopolymers with low glass transition temperatures. In this article, we also describe how the above technologies are used to manufacture wireless transponders for tracking and sensing applications. Several examples of RF components are reported, including antennas, beamforming networks, Doppler radars, and wireless passive transponders based on backscatter radio. Innovative circuit design approaches (such as the via-less approach) are presented and their impact on circuit manufacturing and recyclability is discussed.

This article presents a wireless passive vibration sensor based on harmonic backscattering. The adopted vibration transducer is a commercial piezoelectric cantilever. The cantilever is connected to the gate of an NMOS transistor, which controls the self-bias point of the Schottky diode responsible for the second-harmonic generation. This way, vibrations induce the amplitude modulation of the backscattered second harmonic. A technique is presented to retrieve the vibration information (both acceleration and frequency) from the acquired spectrum. The vibration frequency is computed as the average frequency difference between the carrier and the first sidebands, while the vibration acceleration is encoded in the duty cycle of the amplitude modulation of the backscattered harmonic. In this contribution, we demonstrate for the first time that this information can be retrieved from the magnitude ratio of the first and second sidebands of the acquired spectrum regardless of the tag-to-reader distance. A complete wireless prototype, working at $f_{0}=1.5$ GHz, is manufactured and tested in a laboratory environment for tag-to-reader distances up to 1.3 m. Despite some sensor limitations, i.e., the nonlinear relationship between the duty cycle and the vibration acceleration and the dependence of the sensor sensitivity on the vibration frequency, excellent results are obtained for vibration frequencies around the natural oscillation frequency of the cantilever (i.e., 130 Hz), and for variable accelerations and distances, which testifies the high sensitivity and the robustness of the proposed solution.

Electronics is adapting to the implementation of smart objects to be used in daily life, fostering the evolution of information and communication technology toward the Internet of Things (IoT). With the development of increasingly efficient wireless sensor networks (WSNs) with a reduced form factor, everyday objects are able to acquire information, exchange data, and even make decisions, thus bringing benefits to all aspects of daily life [1]. This trend is now expanding to sectors such as health care, safety at work, production process control, and many others where high reliability and new manufacturing techniques are required for the relevant electronics [2], [3].

The IEEE Wireless Power Technology Conference and Expo is a prestigious event, gathering experts from both the IEEE Microwave Theory and Technology Society (MTT-S) and the IEEE Power Electronics Society community, working on wireless power technology solutions for a variety of applications, ranging from electric vehicles to Internet of Things and medical devices. Since its first edition in Perugia, Italy (my home region), in 2013, it has grown tremendously, attracting ever more people from industry and academia interested in the latest advances in the field.

Providing energy to Internet of Things (IoT) apparatuses is ever more challenging. Humans are increasingly invested in the revolutionary new scenario that experts call Industry 4.0, where billions of electronic devices are interconnected with one another. The operations of battery charging or battery replacement for these devices will soon become infeasible. As a consequence, radiative wireless power transfer (WPT) will soon become a leading technology as it is the only method available to support this technological revolution, and several information communication ­technology companies have already begun to actualize their interest in it.