Long-term space exploration requires an affordable and continuous provision of food and nutrients that need to be palatable so as not to upset the psycho-physical balance of the crewmembers. Moreover, a proper diet composed of fresh food enriched with key nutrients such as minerals and vitamins can minimize the detrimental effects due to microgravity in terms of bones weakening; in addition, the absence of direct incident light from the sun due to a safety shielding from cosmic rays can cause a significant reduction of vitamin D production in the skin. Smart greenhouses based on aeroponics or hydroponics technologies can represent a valuable solution to genuine food supply. Nevertheless, these structures require an affordable monitoring system able to detect key parameters such as nutrients concentration in the mist, gaseous products/pollutants together with relative humidity and temperature. Flexible, light and low-cost gas sensors based on laser-annealed zinc oxide nanostructures can be implemented for this specific application, using different morphologies within the same material for discriminating the different gases. Unluckily, this active material generally exhibits memory effects and significant drift. In this work, we propose a simple method to dramatically increase the reliability of nanostructured ZnO sensor response to be used at low working temperature (room temperature). The resulting devices exploit the porosity of disordered nanostructures thus monitoring CO, CO2, NOX and other gases present in the greenhouse.

Plants own a complex way to communicate with each other based on the exchange of chemical and electrical signals. Indeed, plants are capable of creating extensive communication networks thus warning each other of the presence of pests. In response, plants trigger natural strategy against the infestation. The main tool used by plants for exchanging information is the emission and detection of specific volatile organic compounds in air. To this end, monitoring these compounds can be crucial to reveal the state of health of a cultivation far before visual symptoms arise. In this work, we present a wireless sensor network where each node is based on highly sensitive zinc oxide nanostructures enabling the detection and the discrimination of several chemical gases such as CO, CO2, NO, NO2, CH4, etc. The response of each sensor is tuned by using excimer laser annealing procedure, a technique that changes the electrical and morphological properties of the sensing material. This wireless sensor network can be an appealing solution to capture signals coming from the plants without the usage of bulky and expensive equipment.

Polymer-based CMUT microfabrication approaches allow low-cost fabrication of flexible transducers. However, they are characterized by processing limitations mainly related to the low glass transition temperature of polymers, reducing the possible choice of materials that can be used for electrodes and in-cavity passivation layers, the latter having a major impact on transducer performance and reliability. In this paper, we experimentally evaluate the electrical properties of these two materials in terms of dielectric dispersion and losses, and high electric field response with respect to state-of-the-art materials.

Silicon-based digital electronics have evolved over decades through an aggressive scaling process following Moore's law with increasingly complex device structures. Simultaneously, large-area electronics have continued to rely on the same field-effect transistor structure with minimal evolution. This limitation has resulted in less than ideal circuit designs, with increased complexity to account for shortcomings in material properties and process control. At present, this situation is holding back the development of novel systems required for printed and flexible electronic applications beyond the Internet of Things. In this work we demonstrate the opportunity offered by the source-gated transistor's unique properties for low-cost, highly functional large-area applications in two extremely compact circuit blocks. Polysilicon common-source amplifiers show 49 dB gain, the highest reported for a two-transistor unipolar circuit. Current mirrors fabricated in polysilicon and InGaZnO have, in addition to excellent current copying performance, the ability to control the temperature dependence (degrees of positive, neutral or negative) of output current solely by choice of relative transistor geometry, giving further flexibility to the design engineer. Application examples are proposed, including local amplification of sensor output for improved signal integrity, as well as temperature-regulated delay stages and timing circuits for homeostatic operation in future wearables. Numerous applications will benefit from these highly competitive compact circuit designs with robust performance, improved energy efficiency and tolerance to geometrical variations: sensor front-ends, temperature sensors, pixel drivers, bias analog blocks and high-gain amplifiers.

The NASA/ASI imaging x-ray polarimetry explorer, which will be launched in 2021, will be the first instrument to perform spatially resolved x-ray polarimetry on several astronomical sources in the 2-to 8-keV energy band. These measurements are made possible owing to the use of a gas pixel detector (GPD) at the focus of three x-ray telescopes. The GPD allows simultaneous measurements of the interaction point, energy, arrival time, and polarization angle of detected x-ray photons. The increase in sensitivity, achieved 40 years ago, for imaging and spectroscopy with the Einstein satellite will thus be extended to x-ray polarimetry for the first time. The characteristics of gas multiplication detectors are subject to changes over time. Because the GPD is a novel instrument, it is particularly important to verify its performance and stability during its mission lifetime. For this purpose, the spacecraft hosts a filter and calibration set (FCS), which includes both polarized and unpolarized calibration sources for performing in-flight calibration of the instruments. We present the design of the flight models of the FCS and the first measurements obtained using silicon drift detectors and charge-coupled device cameras, as well as those obtained in thermal vacuum with the flight units of the GPD. We show that the calibration sources successfully assess and verify the functionality of the GPD and validate its scientific results in orbit; this improves our knowledge of the behavior of these detectors in x-ray polarimetry. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE)

The large-scale implementation of solar hydrogen production requires an optimal combination of photovoltaic systems with suitably-designed electrochemical cells, possibly avoiding power electronics for DC-DC conversion, to decrease costs. Here, a stable, solar-driven water splitting system is presented, obtained through the direct connection of a state-of-the-art proton exchange membrane (PEM) electrolyzer to a bifacial silicon heterojunction (SHJ) solar module of three cells in series with total area of 730 cm. The bifaciality of the solar module has been optimized through modeling in terms of the number of cells, module height and inclination. During outdoor operation in the standard monofacial configuration, the system is able to produce 3.7 gr of H hm with an irradiation of 1000 W m and a solar-to-hydrogen efficiency (STH) of 11.55%. The same system operating in bifacial mode gives rise to a higher H flux and STH efficiency, reaching values of 4.2 gr of H hm and STH of 13.5%. Such a noticeable difference is achieved through the collection of albedo radiation from the ground by the bifacial PV system. The system has been tested outdoors for more than 55 h, exhibiting very good endurance, with no appreciable change in production and efficiency.

To effectively control gaseous pollutants in air it is mandatory to fabricate reliable and non-expensive monitoring systems that can be easily deployed in urban areas. Sensing devices based on metal oxide nanostructures offer many advantages respect bulk material in detecting multiple hazardous gases such as, high stability, easy surface functionalization and potentially low operating temperature. Among diverse nanostructures, ZnO nanorods can be obtained with low cost and simple process at a low manufacturing temperature opening the possibility to integrate the material with flexible substrates. Additionally, laser annealing procedure can be exploited to improve or tune the morphology and the electrical properties of these materials. In this work, we present a comparison between the performance of as deposited and laser-annealed devices in the detection of NO and NO2. Different sensors characteristics at increasing gas concentrations and dynamic behaviors are shown and discussed evaluating the mechanisms involved in the diverse pollutant detection. As result, the laser-annealed sensor exhibits a sensitivity one-order higher respect to as-grown sample in detecting NO (3.9x10(-3) vs 2.7x10(-4) [1/ppm]) while for NO2 sensitivity is more than four times higher (3.8x10(-3) vs 8.4x10(-4) [1/ppm]).

In this paper we demonstrate the implementation of a micro-scaled integrated system with the aim to sort, estimate and monitor the biomass of living cancer cells suspended in a culture medium. For this purpose, a 3D microfluidic network is designed to route small volumes of biological samples to the testing sites and dielectric spectroscopy is chosen as investigation method. Comparative electrical analyses are guaranteed by the separation of sole medium and medium-cells mixture in two different areas of the chip. A polyimide-based micro-sieve, placed between two microfluidic channels, is used to perform cell filtering and sorting. Two couples of thin-film metal electrodes ensure the comparative dielectric measurements of the separated materials. Preliminary experiments were carried out in order to test the microfluidics and demonstrate its particle-separating capabilities. The first results prove the robustness of the chosen materials, the effectiveness of the micro-sieving device in terms of particle separation from a liquid solution and its successful integration in the microfluidics. The proposed system represents a promising step for the development of novel valid solutions in the field of micro-scaled integrated cell sorting, cell monitoring and cell counting for a wide range of applications, such as tissue engineering, tumor cells research and biological monitoring in space environment.

Two-transistor zero-VGS amplifiers made with polysilicon source-gated transistors achieve voltage gain approaching 300 (49dB). TCAD simulations reveal the effect of load and driver transistor geometry on gain and operating frequency. The SGT circuits have simultaneously superior gain and reduced layout area (two-transistor, channel length L = 3 mu m and width W = 10 and 30 mu m), relative to conventional TFT implementations. These results recommend low-complexity, compact SGT designs for flexible and printed amplifiers, such as bio- and chemical sensors.

We experimentally demonstrate that electromagnetically thin polyimide substrates can mitigate substrate-induced detrimental effects to the performance of metallic metasurfaces. A planar quarter-wave plate for the microwave K-band is fabricated on a polyimide substrate of deep subwavelength thickness by means of standard photolithography. By properly selecting the combination of the polyimide thickness and the aluminum layer thickness of the metasurface, conversion from linear to circular polarization is achieved at the design frequency. The proposed approach is generic, and it can be applied to the fabrication of mechanically robust, flexible metallic metasurfaces, which are primarily designed to work in a free-standing configuration. ? 2019 Author(s).

IXPE scientific payload comprises of three telescopes, each composed of a mirror and a photoelectric polarimeter based on the Gas Pixel Detector design. The three focal plane detectors, together with the unit which interfaces them to the spacecraft, are named IXPE Instrument and they will be built and calibrated in Italy; in this proceeding, we will present how IXPE Instrument will be calibrated, both on-ground and in-flight. The Instrument Calibration Equipment is being finalized at INAF-IAPS in Rome (Italy) to produce both polarized and unpolarized radiation, with a precise knowledge of direction, position, energy and polarization state of the incident beam. In flight, a set of four calibration sources based on radioactive material and mounted on a filter and calibration wheel will allow for the periodic calibration of all of the three IXPE focal plane detectors independently. A highly polarized source and an unpolarized one will be used to monitor the response to polarization; the remaining two will be used to calibrate the gain through the entire lifetime of the mission.

The understanding of brain processing requires monitoring and exogenous modulation of neuronal ensembles. To this end, it is critical to implement equipment that ideally provides highly accurate, low latency recording and stimulation capabilities, that is functional for different experimental preparations and that is highly compact and mobile. To address these requirements, we designed a small ultra-flexible multielectrode array and combined it with an ultra-compact electronic system. The device consists of a polyimide microelectrode array (8 µm thick and with electrodes measuring as low as 10 µm in diameter) connected to a miniaturized electronic board capable of amplifying, filtering and digitalizing neural signals and, in addition, of stimulating brain tissue. To evaluate the system, we recorded slow oscillations generated in the cerebral cortex network both from in vitro slices and from in vivo anesthetized animals, and we modulated the oscillatory pattern by means of electrical and visual stimulation. Finally, we established a preliminary closed-loop algorithm in vitro that exploits the low latency of the electronics (<0.5 ms), thus allowing monitoring and modulating emergent cortical activity in real time to a desired target oscillatory frequency.

In this paper we propose the use of spontaneous galvanic displacement as a promising solution to produce nickel foam electrodes functionalized with interconnected platinum nanoparticles. Scanning Electron Microscopy analyses, coupled with X-ray Energy Dispersive Spectroscopy show that, under proper conditions, we can overcome the limits of other deposition techniques, achieving a uniform Pt coverage throughout the 3D structure of the Ni foam. We show that such a condition, not deeply investigated in previous literature, turns out to be crucial for the long term stability of the electrodes under constant current stress. The amount of Pt on the Ni foam has been experimentally evaluated, obtaining optimal results with 0.015 mg cm of noble metal in a 0.16 cm thick electrode. Such a low amount corresponds to a Ni foam cost increase of less than 0.1%.

Organic material deposition by gravure printing is a promising pathway for the realization of large area flexible electronic devices. Nevertheless, in order to achieve high performance it is required to improve the electronic ink printability, operating on the fluid dynamic mechanisms involved during the process. In this work, this issue has been faced working on ink characteristics for a conductive and a dielectric material. The suitable ink features have been defined studying the influence on the printability of the different forces that act in the fluid during the printing process, using an experimental approach. Properly defined ink formulations have been printed, considering different shapes and dimensions of the cells on the gravure cliche to fit the ink features. The printing outcomes have been compared and analysed through the evaluation of several significant fluid dynamic parameters and the rheological characterization of the materials. Finally, exploiting the results of this study, high performance fully printed organic thin film transistors have been realized.

Electrocorticography (ECoG) is receiving growing attention for both clinical and research applications thanks to its reduced invasiveness and ability of addressing large cortical areas. These benefits come with a main drawback, i.e. a limited frequency bandwidth. However, recent studies have shown that spiking activity from cortical neurons can be recorded when the ECoG grids present the following combined properties: (I) conformable substrate, (II) small neuron-sized electrodes with (III) low-impedance interfaces. We introduce here an ad-hoc designed ECoG device for investigating how electrode size, interface material composition and electrochemical properties affect the capability to record evoked and spontaneous neural signals from the rat somatosensory cortex and influence the ability to record high frequency neural signal components. Contact diameter reduction down to 8 µm was possible thanks to a specific coating of a (3,4- ethylenedioxytiophene)-poly(styrenesulfonate)-poly-(ethyleneglycol) (PEDOT-PSS-PEG) composite that drastically reduces impedance and increases electrical and ionic conductivities. In addition, the extreme thinness of the polyimide substrate (6 - 8 µm) and the presence of multiple perforations through the device ensure an effective contact with the brain surface and the free flow of cerebrospinal fluid. In-vivo validation was performed on rat somatosensory cortex.

Automotive sensors market has valued 19.7 USD billion in 2014 with an expectation of growth up to 30.0 billion in 2020 [1]. Among the different types of sensors for automotive, devices for safety applications result particularly important and appealing. In this scenario, elastomeric polymers represent a low cost, easy-to-use choice that results to be suitable for large-scale application. In this work, we propose a new sensing system based on the use of a smart steering wheel for the increase of driver's safeness. The wheel is able to detect the presence of the hands of the driver and reports the absence of contact thanks to high sensitive resistive pressure sensors based on elastomeric polymers distributed uniformly on the steering wheel and a specifically designed electronic control unit (ECU) connected to the CAN bus. All the components of the system are described and the performances of the whole prototype are reported, demonstrating high reliability.

Pilots and astronauts can generally experiment high stress during their working activity since they have to manage in a short time a large number of tasks usually in extreme conditions. Moreover, in case of fighter pilots, the management of the stress is even more crucial and it can represent the first cause of accident or death. In this scenario, the real time monitoring of different parameters such as heart rate, ventilation rate, oxygen saturation, and muscle reactivity represents a unique method to collect the information that can activate safe procedures and reduce the danger or train to manage these situations. At the same time, it is fundamental to provide sensing systems that have to minimize the discomfort of the pilot. The usage of bulky devices in fact can hinder the normal activity of the pilot or even can result dangerous for his safeness. For this reason, the implementation of fully wearable sensing systems are mandatory in order to create a smart invisible network that does not affect the pilot movements. In this work, we present a wireless, fully wearable wristband equipped with ultra-thin flexible PVDF-TrFE pressure sensor and highly stretchable strain gauge sensors. The devices are deployed inside or above the wristband avoiding any sense of discomfort or stiffness of the arm. The wearable system can detect the cardiac activity of the pilot without the need of a tight contact with the skin and the fine movements of the hand can be collected to determine the reactivity of the pilot during the flight.

An analog circuit on a flexible substrate is demonstrated for integration with charge sensitive chemical and biochemical sensors. A preamplifier circuit based on low temperature poly-Si thin film transistors (LTPS TFT) for integration with an extended gate ion sensitive field effect transistor (EG-ISFET) has been realized on a flexible polyimide substrate. This circuit, where sensors and preamplifiers are integrated on the same die, is intended for bio-sensing and wearable applications where the flexibility has an advantage.

A novel fully wearable system based on a smart wristband equipped with stretchable strain gauge sensors and readout electronics have been assembled and tested to detect a set of movements of a hand crucial in rehabilitation procedures. The high sensitivity of the active devices embedded on the wristband do not need a direct contact with the skin, thus maximizing the comfort on the arm of the tester. The gestures done with the device have been auto-labeled by comparing the signals detected in real-Time by the sensors with a commercial infrared device (Leap motion). Finally, the system has been evaluated with two machine-learning algorithms Linear Discriminant Analysis (LDA) and Support Vector Machine (SVM), reaching a reproducibility of 98% and 94%, respectively.

In this work, we present a comparison among four different piezoelectric materials (PVDF-TrFE, Piezopaint, AlN and ZnO), all deposited at low temperature (from RT up to 160 degrees C) on flexible substrate such as thin Polyimide, in order to investigate their possible implementation as flexible tactile sensors. Flexible capacitive sensors were tested by using a mini-shaker, investigating the sensors behavior in force and frequency with the intent of mimicking the human sense of touch. We optimized the piezoelectric properties of the materials by using specific texturing buffer layers or maximizing the poling procedure to increase the dipole alignment. Finally, by using a multi-foil approach, the different sensors have been integrated with polysilicon thin film transistor fabricated on flexible substrates and the specific device sensitivity was evaluated.