Suchergebnisse

In this work, we report on a fabrication protocol to produce fully inkjet-printed temperature sensors on a bendable polyethylene terephthalate (PET) substrate. The sensing layer is made of polymer-based Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) ink that is electrically contacted by an underlying interdigitated electrode (IDE) structure based on a silver nanoparticle (AgNP) ink. Both inks are available commercially, and no further ink processing is needed to print them using a cost-effective consumer printer with standard cartridges. The fabricated sensor modules are tested for different IDE dimensions and post-deposition treatments of the AgNP film for their response to a temperature range of 20 to 70 °C and moisture range of 20 to 90% RH (relative humidity). Attributed to the higher initial resistance, sensor modules with a larger electrode spacing of 200 µm show a higher thermal sensitivity that is increased by a factor of 1.8 to 2.2 when compared to sensor modules with a 150 µm-spacing. In all cases, the sensors exhibit high linearity towards temperature and a response comparable to state of the art. ; This research was funded by the European Union through the fellowship H2020-MSCA-IF-2017 794885-SELFSENS and the TUM Graduate School

Although the number of Internet of Things devices increases every year, efforts to decrease hardware energy demands and to improve efficiencies of the energy-harvesting stages have reached an ultra-low power level. However, no current standard of wireless communication protocol (WCP) can fully address those scenarios. Our focus in this paper is to introduce treNch, a novel WCP implementing the cross-layer principle to use the power input for adapting its operation in a dynamic manner that goes from pure best-effort to nearly real time. Together with the energy-management algorithm, it operates with asynchronous transmissions, synchronous and optional receptions, short frame sizes and a light architecture that gives control to the nodes. These features make treNch an optimal option for wireless sensor networks with ultra-low power demands and severe energy fluctuations. We demonstrate through a comparison with different modes of Bluetooth Low Energy (BLE) a decrease of the power consumption in 1 to 2 orders of magnitude for different scenarios at equal quality of service. Moreover, we propose some security optimizations, such as shorter over-the-air counters, to reduce the packet overhead without decreasing the security level. Finally, we discuss other features aside of the energy needs, such as latency, reliability or topology, brought again against BLE. ; ECSEL Joint Undertaking through CONNECT project 737434 ; Federal Ministry of Education & Research (BMBF) ; European Union's Horizon 2020 research and innovation program ; Spanish Ministry of Education, Culture and Sport (MECD)/FEDER-EU FPU18/01376 ; BBVA Foundation ; University of Granada

This work was supported in part by the European Commission through the fellowship H2020-MSCA-IF-2017-794885-SELFSENS and by the Spanish Government through the predoctoral grant FPU16/01451. ; This case report presents a real example of a study which introduces the use of reconfigurable platforms in the teaching of electronics engineering to establish a bridge between theory and practice. This gap is one of the major concerns of the electronics engineering students. Different strategies, such as simulation tools or breadboard implementations, have been followed so far to make it easier for students to practice what they study in lectures. However, many students still claim to have problems when they face real practical implementations. The use of reconfigurable platforms as a teaching tool is proposed to provide the students the possibility of fast experimentation, reducing both development time and the learning curve. In addition, reconfigurable platforms available on the market make this methodology suitable to be applied throughout the different courses of their curricula. The feasibility of this approach is demonstrated in a course at the M.Eng. level, where the objective is the study, design and development of electronic sensor nodes. We firmly consider, based on the students' results and reflections collected during the course, that this methodology helps students to address the theoretical framework from a practical viewpoint, as well as to acquire some of the fundamental skills for their professional careers, such as the usage of communication protocols and embedded systems programming, in a more intuitive way when compared to traditional teaching methodologies. ; European Commission European Commission Joint Research Centre H2020-MSCA-IF-2017-794885-SELFSENS ; Spanish Government European Commission FPU16/01451

This work presents a novel approach for the fabrication of Electrochemical Capacitors (ECs) based on the screen-printing of a commercial carbon-based conductive ink on flexible substrates. This technique enables the fast and cost-effective production of ECs with high flexibility and outstanding performance over bending states and voltage cycling, as demonstrated by means of cyclic voltammetry and galvanometric charge-discharge measurements. Despite the fact that the specific areal capacitances achieved are lower than the ones obtained using other carbon-based materials (~22 μF/cm2), the results show that, as soon as new screen-printable carbon-based pastes become available, this fabrication method will enable the mass production of ECs that can be attached to any surface as a conformal patch, as it is being required by a large number of the emerging technological applications. ; This work has been partially supported by the Spanish Ministry of Education, Culture and Sport (MECD) and the European Union through the pre-doctoral grant FPU16/01451, and its mobility program, the project TEC2017-89955-P and fellowship H2020-MSCA-IF-2017794885-SELFSENS.

We present a versatile sensing platform, intended for ubiquitous and flexible electronics sensing applications based on the controlled reduction of Graphene Oxide by a laser diode. This technique allows the fast and ecological production of reduced Graphene Oxide without the need of expensive lithography masks. We will show results of the conductivity calibration by the photothermal reduction power, as well as the electrical characterization of the bare samples. Finally, a simple demonstrator of the platform based on an ultra-low power System on Chip (SoC) is introduced. ; This work has been supported by the Spanish Ministry of Educaton, Culture and Sport (MECD) through the pre-doctoral grant FPU16/01451, the University of Granada through the scholarship "Initiation to Research", the National Excellence Research Project TEC2017-89955-P and the European Union by the fellowship H2020-MSCA-IF-2017 794885-SELFSENS.

The necessity to place sensors far away from the processing unit in smart clothes or artificial skins for robots may require conductive wirings on stretchable materials at very low-cost. In this work, we present an easy method to produce wires using only commercially available materials. A consumer grade inkjet printer was used to print a wire of silver nanoparticles with a sheet resistance below 1 W/sq. on a non-pre-strained sheet of elastic silicone. This wire was stretched more than 10,000 times and was still conductive afterwards. The viscoelastic behavior of the substrate results in a temporarily increased resistance that decreases to almost the original value. After over-stretching, the wire is conductive within less than a second. We analyze the swelling of the silicone due to the ink's solvent and the nanoparticle film on top by microscope and SEM images. Finally, a 60 mm long stretchable conductor was integrated onto wearables, and showed that it can bear strains of up to 300% and recover to a conductivity that allows the operation of an assembled LED assembled at only 1.8 V. These self-healing wires can serve as wiring and binary strain or pressure sensors in sportswear, compression underwear, and in robotic applications. ; This work has been partially supported the TUM Graduate School (TUM GS), and the European Union through the fellowship H2020-MSCA-IF-2017 794885-SELFSENS. Additionally, this work was supported by the German Research Foundation (DFG) and the Technical University of Munich within the Open Access Publishing Funding Programme.

The irruption of Internet of Things and 5G in our society comes along with several technological challenges to overcome. From an overall perspective, the low-cost and environmental friendliness of these technologies need to be ensured for their universal deployment in different areas, starting with the sensors and finishing with the power sources. To address these challenges, the production and maintenance of a great number of sensor nodes incur costs, which include manufacturing and integration in mass of elements and sub-blocks, changing or recharging of batteries, as well as management of natural resources and waste. In this article, we demonstrate how Radio Frequency Energy Harvesting (RFEH) and printed flexible technology (a growing technology for sensors) can solve these concerns through costeffective mass-production and utilization of energy harvesting for the development of energy-autonomous nodes, as part of a wireless sensor network. We present as illustration a sprayed flexible relative humidity sensor powered with RFEH under the store-and-use principle. ; This work was partially supported by the ECSEL Joint Undertaking through the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No 737434. This Joint Undertaking receives support from the German Federal Ministry of Education and Research and the European Union's Horizon 2020 research and innovation program and Slovakia, Netherlands, Spain, Italy. In addition, the Spanish Ministry of Education, Culture and Sport (MECD) and the European Union supported it through the pre-doctoral grant FPU16/01451 and the fellowship H2020-MSCA-IF-2017794885-SELFSENS.

This research was partially supported by the fellowship H2020-MSCA-IF-2017-794885-SELFSENS and by the Spanish Ministry of Education, Culture and Sport under Grant FPU18/01376 and funded by Spanish ministry of Science and Innovation grant number PGC2018-102052-B-C21. ; In this letter, we present the extension of a previous work on a cost-effective method for fabricating highly sensitive humidity sensors on flexible substrates with a reversible response, allowing precise monitoring of the humidity threshold. In that work we demonstrated the use of three-dimensional metal-organic framework (MOF) film deposition based on the perylene-3,4,9,10-tetracarboxylate linker, potassium as metallic center and the interspacing of silver interdigitated electrodes (IDEs) as humidity sensors. In this work, we study one of the most important issues in efficient and reproducible mass production, which is to optimize the most important processes' parameters in their fabrication, such as controlling the thickness of the sensor's layers. We demonstrate this method not only allows for the creation of humidity sensors, but it also is possible to change the humidity value that changes the actuator state. ; Spanish Ministry of Education, Culture and Sport H2020-MSCA-IF-2017-794885-SELFSENS ; Spanish Government FPU18/01376 ; PGC2018-102052-B-C21

This work presents a detailed study of the photothermal ablation of KaptonR polyimide by a laser diode targeting its electrical conductivity enhancement. Laser-treated samples were structurally characterized using Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), as well as Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. The results show that the laser-assisted ablation constitutes a simple one-step and environmental friendly method to induce graphene-derived structures on the surface of polyimide films. The laser-modified surface was also electrically characterized through the Transmission Line Method (TLM) aiming at the improvement of the conductivity of the samples by tuning the laser power and the extraction of the contact resistance of the electrodes. Once the laser-ablation process is optimized, the samples increase their conductivity up to six orders of magnitude, being comparable to that of graphene obtained by chemical vapor deposition or by the reduction of graphene-oxide. Additionally, we show that the contact resistance can be decreased down to promising values of ~2 W when using silver-based electrodes. ; This work has been partially supported by the Spanish Ministry of Education, Culture and Sport (MECD), the European Union and the University of Granada through the project TEC2017-89955-P, the pre-doctoral grant FPU16/01451, the fellowship H2020-MSCA-IF-2017 794885-SELFSENS and the grant "Initiation to Research". Additionally, this work was supported by the German Research Foundation (DFG) and the Technical University of Munich within the Open Access Publishing Funding Programme.

Herein, we present, for the first time, a 2D-MOF based on copper and 4-hydroxypyrimidine-5-carbonitrile as the linker. Each MOF layer is perfectly flat and neutral, as is the case for graphene. High pressure X-ray diffraction measurements reveal that this layered structure can be modulated between 3.01 to 2.78 Å interlayer separation, with an evident piezochromism and varying conductive properties. An analysis of the band structure indicates that this material is conductive along different directions depending on the application of pressure or H doping. These results pave the way for the development of novel layered materials with tunable and efficient properties for pressure-based sensors. ; European Union (EU) 604391 ; Swiss National Science Foundation (SNSF) 200020_162861 ; Spanish Government CEX2018-000805-M CTQ2015-69163-CO2R1 PGC2018-102052-B-C21 PGC2018-102052-A-C22 PGC2018102047-B-I00 FIS2016-80434-P PID2019-109539GB-C43 ; Junta de Andalucia FQM-394 ; Comunidad Autonoma de Madrid through the Nanomag COST-CM Program S2018/NMT-4321 ; University of Seville ; National Council for Scientific and Technological Development (CNPq) 405107/2017-0