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Nowadays, there is a high demand for sensitive and selective real-time analytical methods suitable for a wide range of applications, from personalized telemedicine, drug discovery, food safety, and quality control, to defense, security, as well as environmental monitoring. Biosensors are analytical devices able to detect bio-chemical analytes (e.g., neurotransmitters, cancer biomarkers, bio-molecules, and ions), through the combination of a bio-recognition element and a bio-transduction device. The use of customized bio-recognition elements such as enzymes, antibodies, aptamers, and ion-selective membranes facilitates achieving high selectivity. Among the different bio-transduction devices currently available, electrolyte-gated field-effect transistors, in which the dielectric is represented by an ionic liquid buffer solution containing the targeted analyte, are gaining increasing attention. Indeed, these bio-transduction devices are characterized by superior electronic properties and intrinsic signal amplification that allow the detection of a wide range of bio-molecules with high sensitivity (down to pM concentration). A promising semiconducting material for bio-transduction devices is represented by carbon nanotubes, due to their unique electrical properties, nanosize, bio-compatibility, and their simple low-cost processability. This work provides a comprehensive and critical review of electrolyte-gated carbon nanotube field-effect transistor-based biosensors. First, an introduction to these bio-sensing devices is given. Next, the device configurations and operating principles are presented, and the most used materials and processes are reviewed with a particular focus on carbon nanotubes as the active material. Subsequently, different functionalization strategies reported in the literature, based on enzymes, antibodies, aptamers, and ion-selective membranes, are analyzed critically. Finally, present issues and challenges faced in the area are investigated, the conclusions are drawn, and a perspective outlook over the field of bio-sensing technologies, in general, is provided., Applied Physics Reviews, 8 (4), ISSN:1931-9401

In this work, Schottky diodes based on amorphous indium-gallium-zinc-oxide (IGZO) were fabricated on cellulose microfiber paper substrate. Silver lines used as the Schottky barrier were printed, in parallel to thermally evaporated Cr/Au ohmic contact, using a dispense printer. The morphological and electrical characteristics of the devices are presented. The fabricated diodes exhibited rectification ratios ranging from 3.4 to 34.9 at ±1V with ON voltages that range from 1.1V to 1.4 V, for device lengths (Ag to Au distance) from 145 µm to 894 µm. The diodes were characterized in a temperature range between 25°C and 80°C. They showed a decrease of the ON current when increasing temperature, which is mainly attributed to the change of the cellulose microstructure. Indeed, an opposite of the ON current behavior was registered when the diode was realized on a polyimide substrate. The realized flexible paper-based diodes offer a potential promising choice for printed environmental-friendly electronics.

Energy harvesters for smart wearables are gaining increasing attention world-wide. Among the various type of options availabel, triboelectric nanogenerators harvesting mechanical energy from human body movements are especially attractive. In this work, a flexible sandwich-type triboelectric nanogenerator (FS-TENG) based on ridged and biocompatible silicone elastomers and thermoplastic polyurethane is proposed. The proposed FS- TENG exhibits the open-circuit voltages and maximum power density of ~80 volts and 0.35 mW/cm2, respectively. This preliminary performance already makes the device extremely promising to power low energy smart wearable devices, as well as monitor pressure in bespoke biomedical applications.

In this work, we realized a flexible electrolyte-gated field-effect transistor (EG-FET) based on a spray-coated semi-conducting single-walled carbon nanotube (SWCNTs) network. The device was functionalized with anti-spermidine antibodies for a specific detection of polyamine spermidine - a well-known chemical indicator of food quality. The spray-coated SWCNTs films were modified with a bifunctional molecule, which binds to the nanotubes via non-covalent π−π interactions and leaves a free NHS-ester group for amide coupling of the antibodies, ensuring controlled immobilization. Transfer and output curves were recorded for device characterization, showing a typical p-type behavior with an on–off ratio of 190 A/A and a threshold voltage around 0 V. The calibration curve of the fabricated EG-FET immunosensor shows a linear detection range for spermidine from 0.001 to 100 nM, with 99.83% coefficient of determination.

In this work, we demonstrate the advantages and the potentials of dispense printing (V-One, Voltera) for the realization of conductive contacts of flexible electronics. Printing parameters were optimized for Ag inks on different substrates (PCB, Si/SiO 2 and polyimide), leading to straight homogeneous printed lines with minimum feature size of $159\pm 22\mu \mathrm{m}$ . Hybrid-manufactured Ag/InGaZnO Schottky diodes, with an average rectification ratio of 80 and an ON voltage of 0.63 V, were successfully demonstrated on flexible foils.

Since its first discovery in 2014, laser-induced graphene (LIG) has gained increasingly attention as a simple and low-cost alternative to printing techniques, which instead require additional materials such as functional ink or adhesive layers. While there are several works on LIG supercapacitors, gas sensors, and triboelectric generators, this method is still very unexplored for antennas, especially if realized on eco-friendly paper substrates. In this paper, we realized a microstrip patch antenna using LIG on a food-derived cellulose-based paper. The antenna was first designed and simulated using a High-Frequency Structure Simulator (HFSS) software, using different values of relative permittivity ϵ r (from 2 to 3.6), to understand the impact of laser-induced graphitization of the substrate on the resonance frequency. The subsequently fabricated antenna showed a strong resonance peak of −25dB at 2.4 GHz, corresponding to an ϵ r of 2.2, in agreement with experimental results.

The last years have seen a surge in the interest for “smart objects” obtained with the integration of electronics and custom designed structures. One of the possible approaches for the fabrication of such devices is 3D printing supporting elements and attach to them discrete electronic components. Opposed to this approach, we demonstrate the facile integration of conformal organic electronics devices in 3D printed structures, where the device is directly fabricated on or in the printed object. To obtain cost-effective and easy-to-scale devices, the substrates are fabricated via a Fused Deposition Modeling (FDM) procedure which leads to inherently rough layers. In order to enable the fabrication of functional layers few hundreds of nm thick, we develop a process, based on spray-deposition, for the planarization of the structure and the in situ deposition a functional layer. The realization of conductive and semi-transparent CNTs, AgNW and PEDOT:PSS thin films on a 3D-printed substrate is demonstrated and the films are characterized in terms of transmittance and sheet resistance. The technique is finally applied for the realization of a semi-transparent heating chamber with an arbitrary shape with potential applications in the field of bioelectronics and consumer applications.

We present a portable impedance analyzer based on the AD5933 integrated circuit for fruit quality monitoring. The system, custom designed, allows a flexible tuning of parameters (i.e. excitation voltage, feedback resistor, settling time) in order to allow a precise system calibration over a frequency range from 10 Hz to 100 kHz. The employment of Low-Energy Bluetooth and USB communication, together with a micro SD data storage and a rechargeable battery, increases the system portability and its connectivity especially for precision and smart agriculture applications. The system (7.5×2×4cm in volume), runs MicroPython on an STM32 microcontroller and provides 300 mAh Li-Po battery storage with USB recharge. The developed system is validated by comparing it with a bench-top impedance analyzer, using two-terminal measurement, for the specific analysis of tomatoes and bananas, showing an average Root Mean Square Error (RMSE) as low as 0.6% and 4.1%, for impedance magnitude and phase, respectively.