Chiara Mariotti

No Battery Required: Perpetual RFID-Enabled Wireless Sensors for Cognitive Intelligence Applications

Over the last decade, radio frequency identification (RFID) systems have been increasingly used for identification and object tracking due to their low-power, low-cost wireless features. In addition, the explosive demand for ubiquitous rugged low-power, compact wireless sensors for Internet-of-Things, ambient intelligence, and biomonitoring/ quality-of-life application has sparked a plethora of research efforts to integrate sensors with an RFID-enabled platform. The rapid evolution of large-area electronics printing technologies (e.g., ink-jet printing and gravure printing) has enhanced the development of low-cost RFID-enabled sensors as well as accelerated their large-scale deployment. This article presents a brief overview of the recent progress in the area of RFID-based sensor systems and especially the state-of-the-art RFID-enabled wireless sensor tags realized through the use of ink-jet printing technology.

Inkjet-printed, vertically-integrated, high-performance inductors and transformers on flexible LCP substrate

Vertically-integrated inkjet-printed inductors and transformers are demonstrated for the first time with high levels of performance and repeatability. The inductive components are fabricated using a well-characterized multi-layer inkjet printing process which is substrate independent and has been optimized for the fabrication of RF components. Printed spiral inductors with values of 10 nH and 25 nH are demonstrated with a maximum Q of over 20 at 1 GHz, which is the highest Q value reported to date for printed components, and a repeatability of within 5% between fabrication runs. Printed inductively coupled transformer-based baluns are also demonstrated which operate at 1.4 GHz with a maximum available gain of -1.7 dB.

Smart Surfaces: Large Area Electronics Systems for Internet of Things Enabled by Energy Harvesting

Energy harvesting is well established as one of the prominent enabling technologies [along with radio-frequency identification (RFID), wireless power transfer, and green electronics] for the pervasive development of Internet of Things (IoT). This paper focuses on a particular, yet broad, class of systems that falls in the IoT category of large area electronics (LAE). This class is represented by “smart surfaces.” The paper, after an introductory overview about how smart surfaces are collocated in the IoT and LAE scenario, first deals with technologies and architectures involved, namely, materials, antennas, RFID systems, and chipless structures; then, some exemplifying solutions are illustrated to show the present development of these concurrent technologies in this area and to stimulate further solutions. Conclusions and future trends are then drawn.

Low-Power Frequency Doubler in Cellulose-Based Materials for Harmonic RFID Applications

This letter presents the design of a Schottky diode frequency doubler suitable for harmonic RFID tags. A microwave frequency doubler is implemented in a cellulose-based (paper) substrate, i.e., an ultra-low cost, recyclable and biodegradable material. The circuit exploits a distributed microstrip structure that is fabricated using a copper adhesive laminate to have low conductor losses. The measurements show a conversion loss of 13.4 dB at the output frequency of 2.08 GHz. This is achieved with an available input power of -10 dBm only. Finally a harmonic RFID experiment proves a reading range of 50 cm, obtained by transmitting 0 dBm and receiving a second harmonic of -60 dBm, i.e., well above the sensitivity of a typical microwave receiver.

Development of Low Cost, Wireless, Inkjet Printed Microfluidic RF Systems and Devices for Sensing or Tunable Electronics

In this paper, a review of recent improvements on inkjet-printed microfluidic-based tunable/sensing RF systems is reported. The devices, such as Radio Frequency IDentification (RFID) passive wireless tags, coplanar patch antennas, bandstop filters, and loop antennas, are all fabricated by combining the inkjet printing technology on photographic paper for metallization and bonding layers, and laser etching for cavities and channels manufacturing. A novelty is also introduced for the loop antennas where the photographic paper is replaced with a polymer based substrate [i.e., (Poly(methyl-methacrylate))], to reduce the substrate losses for the RF part and solve the issue of paper hydrophylia. Along this paper an evolution toward higher working frequencies and higher detecting performance is shown, demonstrating a sensitivity up to 0.5%/εr with at most 6 μL of liquid in the channel.

A novel inkjet-printed microfluidic tunable coplanar patch antenna

In this paper, a novel inkjet-printed microfluidic tunable coplanar patch antenna combining microfluidic-based sensing technology and inkjet printing technique is proposed. The antenna is fabricated using a rapid, low-cost, and environmental friendly inkjet printing process on paper substrate. Based on the fluid pumped in the sensor, the resonant frequency of the antenna is tuned due to variation in the fluid permittivity. 13% frequency shift can be easily achieved, which verifies that the sensitivity of this antenna is good and allows for an easy tunability of the operating frequency from 3.8 GHz, for an empty microfluidic channel, to 3.3 GHz, for a water-filled channel. The antenna features a return loss better than 30 dB in the tunable frequency range of 3.5 to 3.8 GHz. This antenna can be used in multiple applications such as liquid monitoring and identification, bio-liquids sensing as well as low-cost reconfigurable antennas with the advantage of requiring the use of less than 25 uL of liquid.

24 GHz Single-Balanced Diode Mixer Exploiting Cellulose-Based Materials

A 24 GHz single-balanced diode mixer in paper substrate is presented. The microstrip 180 degrees hybrid junction (rat-race) is fabricated exploiting a copper adhesive tape that is shaped by a photo-lithographic process and transferred to the hosting (paper) substrate using a sacrificial layer. Only three discrete devices are necessary for the mixer operation, namely: two low-barrier, Schottky diodes and a 0 Ω resistor, used as a jumper. The measurements show a conversion loss of about 10 dB at 24 GHz with a 50 MHz IF signal. At the same frequency the isolation between LO and RF ports is better than 35 dB. The record performance achieved demonstrates, for the first time, the feasibility of K-band mixers exploiting cellulose-based materials.

Review of the present technologies concurrently contributing to the implementation of the Internet of Things (IoT) paradigm: RFID, Green Electronics, WPT and Energy Harvesting

This paper summarizes the most important technologies, concurrently participating to build the technological platform needed for a realistic implementation of the Internet of Things (IoT) paradigm. At the present state of the evolution of IoT, these technologies are mostly: Radio Frequency IDentification (RFID), Green Electronics (GE), Wireless Power Transfer (WPT) and Energy Harvesting (EH). This contribution briefly explains the reason for that, and shows a collection of scientific contributions which can be seen as examples. The deep description of the proposed systems can be found in the relative referenced papers.

A 1.2 V, 0.9 mW UHF VCO Based on Hairpin Resonator in Paper Substrate and Cu Adhesive Tape

A 1.2 V, 0.9 mW, 998 MHz voltage controlled oscillator (VCO) adopting a distributed hairpin resonator in paper substrate is described. The microstrip resonator exploits a copper adhesive tape that is shaped by a photo-lithographic process and transferred to the hosting substrate using a sacrificial layer. To minimize the number of components, a cross-coupled differential VCO circuit is adopted. As a consequence only 3 external devices are necessary: a single-package BJT pair, a resistor and a by-pass capacitor. The measurements show a phase noise of -99 dBc/Hz at 100 KHz offset from the carrier. At 1.2 V the output power is -22 dBm, whereas the tuning sensitivity is about - 100 MHz/V. The proposed design shows the feasibility of low-power oscillators for autonomous wireless sensors based on green materials.

State-of-the-Art Inkjet-Printed Metal-Insulator-Metal (MIM) Capacitors on Silicon Substrate

Vertically-integrated metal-insulator-metal (MIM) capacitors on silicon are demonstrated for the first time utilizing an entirely additive RF-specific inkjet-printing process. The inkjet-printed MIM capacitors demonstrate a high capacitance per unit area of up to 33 pF/mm2 by utilizing novel dielectric inks, while achieving quality factors (Q) up to 25 and self-resonant frequencies (SRFs) above 1 GHz. Measurements of dielectric permittivity, leakage current, voltage breakdown, and fabrication repeatability are presented confirming the high-performance operation of the printed MIM capacitors.