Screen-printed Organic Electrochemical Transistors for the detection of ascorbic acid in food

[EN] Methods traditionally used for ascorbic acid (AA) detection in food are often expensive and complex, making them unsuitable for day-to-day determinations. In this work, we report on the use of all- PEDOT:PSS Organic Electrochemical Transistors (OECTs) for fast, simple and low-cost determination of AA in food. The performance of these OECTs was tested first with in lab-prepared solutions of AA with different concentrations. The effect of the geometry on the transistors performance for AA sensing was also investigated by comparing the response of two OECTs with different channel and gate areas ratio (g), in terms of current modulation, sensitivity, background signal and limit of detection (LOD). OECTs with smaller gate electrode than the channel (large g) show the best performance for AA sensing: these devices display smaller background signal, higher sensitivity, larger modulation and better LOD value (80.10^-6 M). Since the AA content in food rich in Vitamin C is in the mM range, these transistors can be considered sensitive enough for quantitatively monitoring AA in food. In order to demonstrate the reliability of the proposed sensors in real food samples, the response of these transistors was additionally measured in a commercial orange juice. The amount of AA obtained with the OECTs is in good agreement with that determined by HPLC and with values reported in the literature for orange juices. Furthermore, these OECTs can be considered promising candidates for the selective detection of AA in the presence of other interfering antioxidants.This work was supported by Spanish Government/FEDER funds (grant number MAT2015-64139-C4-3-R (MINECO/FEDER)) and Generalitat Valenciana funds (grant number AICO/2015/103).Contat-Rodrigo, L.; Pérez Fuster, C.; Lidon-Roger, JV.; Bonfiglio, A.; Garcia-Breijo, E. (2017). Screen-printed Organic Electrochemical Transistors for the detection of ascorbic acid in food. Organic Electronics. 45:89-96. https://doi.org/10.1016/j.orgel.2017.02.03789964

A Rapid Electrochemical Impedance Spectroscopy and Sensor-Based Method for Monitoring Freeze-Damage in Tangerines

[EN] This study focuses on the analysis and early detection of freeze-damage in tangerines using a specific double-needle sensor and Electrochemical Impedance Spectroscopy (EIS). Freeze damage may appear in citrus fruits both in the field and in postharvest processes resulting in quality loss and a difficult commercialization of the fruit. EIS has been used to test a set of homogeneous tangerine samples both fresh and later frozen to analyze electrochemical and biological differences. A double-needle electrode associated to a specifically designed electronic device and software has been designed and used to send an AC electric sinusoidal signal 1 V in amplitude and frequency range [100Hz to 1MHz] to the analyzed samples and then receive the electrochemical impedance response. EIS measurements lead to distinct values of both impedance module and phase of fresh and frozen samples over a wide frequency range. Statistical treatment of the received data set by Principal Components Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA) shows a clear classification of the samples depending on the experienced freeze phenomenon, with high sensitivity (1.00), specificity (>= 0.95) and confidence level (95%). Later Artificial Neural Networks (ANN) analysis based on 20-3-1 architecture has allowed to create a mathematical prediction model able to correctly classify 100% of the analyzed samples (CCR =100% for training, validation and test phases, and overall classification), being fast, easy, robust and reliable, and an interesting alternative method to the traditional laboratory analyses.This work was supported by the Spanish Government/FEDER funds [Ministerio de Economia y Empresa (MINECO)/Fondo Europeo de Desarrollo Regional (FEDER)] under Grant RTI2018-100910-B-C43 and in part by the Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana under Grant GV/2018/090.Albelda Aparisi, P.; Fortes Sánchez, E.; Contat-Rodrigo, L.; Masot Peris, R.; Laguarda-Miro, N. (2021). A Rapid Electrochemical Impedance Spectroscopy and Sensor-Based Method for Monitoring Freeze-Damage in Tangerines. IEEE Sensors Journal. 21(10):12009-12018. https://doi.org/10.1109/JSEN.2021.3065846S1200912018211

Low-Temperature Soldering of Surface Mount Devices on Screen-Printed Silver Tracks on Fabrics for Flexible Textile Hybrid Electronics

[EN] The combination of flexible-printed substrates and conventional electronics leads to flexible hybrid electronics. When fabrics are used as flexible substrates, two kinds of problems arise. The first type is related to the printing of the tracks of the corresponding circuit. The second one concerns the incorporation of conventional electronic devices, such as integrated circuits, on the textile substrate. Regarding the printing of tracks, this work studies the optimal design parameters of screen-printed silver tracks on textiles focused on printing an electronic circuit on a textile substrate. Several patterns of different widths and gaps between tracks were tested in order to find the best design parameters for some footprint configurations. With respect to the incorporation of devices on textile substrates, the paper analyzes the soldering of surface mount devices on fabric substrates. Due to the substrate's nature, low soldering temperatures must be used to avoid deformations or damage to the substrate caused by the higher temperatures used in conventional soldering. Several solder pastes used for low-temperature soldering are analyzed in terms of joint resistance and shear force application. The results obtained are satisfactory, demonstrating the viability of using flexible hybrid electronics with fabrics. As a practical result, a simple single-layer circuit was implemented to check the results of the research.This work was supported by the Spanish Government FEDER funds (RTI2018-100910B-C43) (MINECO/FEDER). The work presented is also funded by the Conselleria d'Economia Sostenible, Sectors Productius i Treball, through IVACE (Instituto Valenciano de Competitividad Empresarial) and cofunded by ERDF funding from the EU Stretch Project, application No.: IMAMCA/2022/6.Silvestre, R.; Llinares Llopis, R.; Contat-Rodrigo, L.; Serrano Martínez, V.; Ferri, J.; Garcia-Breijo, E. (2022). Low-Temperature Soldering of Surface Mount Devices on Screen-Printed Silver Tracks on Fabrics for Flexible Textile Hybrid Electronics. Sensors. 22(15):1-23. https://doi.org/10.3390/s22155766123221

Influence of potential pulses amplitude sequence in a voltammetric electronic tongue (VET) applied to assess antioxidant capacity in aliso

[EN] Four signals configurations were studied, two of them built by small increases of potential and two with bigger increments. The highest current values were obtained when pulses with bigger change of potential were used although the best results were shown by the pulse sequence which included an intermediate pulse before the relevant pulse. A mathematical model based on trolox pattern was developed to predict antioxidant capacity of aliso, employing information obtained from all the electrodes, although model validation could be done only employing the information from gold electrode.Fuentes-Pérez, EM.; Alcañiz Fillol, M.; Contat-Rodrigo, L.; Baldeon-Chamorro, E.; Barat Baviera, JM.; Grau Meló, R. (2017). Influence of potential pulses amplitude sequence in a voltammetric electronic tongue (VET) applied to assess antioxidant capacity in aliso. Food Chemistry. 224:233-241. doi:10.1016/j.foodchem.2016.12.076S23324122

Inexpensive Measuring System for the Characterization of Organic Transistors

[EN] A measuring module has been specifically designed for the electrical characterization of organic semiconductor devices such as organic field effect transistors (OFETs) and organic electrochemical transistors (OECTs) according to the IEEE 1620-2008 standard. This device has been tested with OFETs based on 6,13-bis(triisopropylsilylethinyl) pentacene (TIPS-pentacene). The measuring system has been constructed using a NI-PXIe-1073 chassis with integrated controller and two NI-PXI-4132 programmable high-precision source measure units (SMUs) that offer a four-quadrant +/- 100V output, with resolution down to 10 pA. LabVIEW (TM) has been used to develop the appropriate program. Most of the main OFET parameters included in the IEEE 1620 standard can be measured by means of this device. Although nowadays expensive devices for the characterization of Si-based transistors are available, devices for the characterization of organic transistors are not yet widespread in the market. Fabrication of a specific and flexible module that can be used to characterize this type of transistors would provide a powerful tool to researchers.All financial support from the Spanish Government and FEDER funds (MAT2015-64139-C4-3-R (MINECO/FEDER)) and the Generalitat Valenciana (GVA funds) (AICO/2015/103) is gratefully acknowledged.Pérez Fuster, C.; Lidon-Roger, JV.; Contat-Rodrigo, L.; Garcia-Breijo, E. (2018). Inexpensive Measuring System for the Characterization of Organic Transistors. Journal of Sensors. 2018:1-9. https://doi.org/10.1155/2018/4286894S19201

Organic Electrochemical Transistors as an Emerging Platform for Bio-Sensing Applications: A Review

© 2021 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] Organic electrochemical transistors (OECTs) have been recognized as a major emerging technology in the area of flexible electronics in the last decade. Although they have yet to be incorporated in common electronic fabrication technologies, they have considerably advanced as an emerging platform for biosensing applications. The paper provides a comprehensive and critical review of the most important advances in the field of OECT-based biosensors. A brief description of the device physics is given with the most important equations and a comparison has been made with the conventional MOSFET devices and characteristic equations. The use of OECTs as an emerging biosensing platform has been explored and their application as biomolecule, enzyme, bacteria, viruses, cells, nucleotide detectors as well as electrophysiological and wearable sensors has been reported. Furthermore, trends have been extracted and described in the paper in terms of fabrication technologies, electrode materials and most importantly, the semiconducting polymer. Additionally, future perspectives on the development and fabrication technologies of these devices have been further explored.This work was supported in part by the University of Cyprus Internal Funds, Advanced Researchers Article 102, the Research and Innovation Foundation of Cyprus, under Grant POST-DOC/0718/0163 and in part by the Spanish Government/FEDER for Funds (MINECO/FEDER) under Grant RTI2018-100910-BC43.Sophocleous, M.; Contat-Rodrigo, L.; Garcia-Breijo, E.; Georgiou, J. (2021). Organic Electrochemical Transistors as an Emerging Platform for Bio-Sensing Applications: A Review. IEEE Sensors Journal. 21(4):3977-4006. https://doi.org/10.1109/JSEN.2020.30332833977400621

Multicomponent Pyrolysis Model for Thermogravimetric Analysis of Phenolic Ablators and Lignocellulosic Biomass

[EN] A multicomponent kinetic mechanism has been developed for the pyrolysis at low heating rate of carbon/ phenolic thermal protection material and a wood species. An experimental campaign has been carried out using thermogravimetric analysis to study the mass loss under different conditions of crucible (with or without a lid) and heating rate for both materials. Using a pierced lid to cover the crucible during pyrolysis promotes char production compared with the case of open crucible. Kinetic parameters were then extracted from the experiments by an optimization approach using an in-house-developed kinetic identification code. The parameters recovered for the two applications allow to reproduce accurately the mass loss evolution.The research of F. T.-H., V. L., and T. E. M. is sponsored by the European Research Council Proof of Concept Grant #713726. The samples of the ablator studied in this project were provided through the European Space Agency (ESA) Research Program ABLARADABLA project #ESA ITTAO/1-7987/14/NL/RA. Niaouli samples were provided through the European Research Council Proof ofConcept Grant #713726. We would like to thank Gregory Pinaud (ArianeGroup) for his suggestions on the fitting algorithm. Gertjan Glabeke von Karman Institute (VKI) is acknowledged for his support during the experimental campaign. Christian Zuber and Thomas Reimer (German Aerospace Center [DLR] Stuttgart) are acknowledged for providing characterization support and information regarding the production of ZURAM (R).Torres-Herrador, F.; Leroy, V.; Helber, B.; Contat-Rodrigo, L.; Lachaud, J.; Magin, T. (2020). Multicomponent Pyrolysis Model for Thermogravimetric Analysis of Phenolic Ablators and Lignocellulosic Biomass. AIAA Journal. 58(9):4081-4089. https://doi.org/10.2514/1.J0594234081408958

Monitoring Freeze-Damage in Grapefruit by Electric Bioimpedance Spectroscopy and Electric Equivalent Models

[EN] Grapefruit is a cold-sensitive citrus fruit, and freezing can spoil the harvest when the fruit is still on the tree and even later during manufacturing and transport due to inappropriate postharvest management. This study performed a specific Electric Impedance Spectroscopy (EIS) analysis and statistical data treatment to obtain an EIS and Artificial Neural Networks (ANN)-based model for early freeze-damage detection in grapefruit showing a Correct Correlation Rate of 100%. Additionally, Cryo-Field Emission Scanning Electron Microscopy observations were conducted on both fresh and frozen/thawed samples, analyzing the different impedance responses in order to understand the biological changes in the tissue. Finally, a modified Hayden electric equivalent model was parameterized to simulate the impedance response electrically and link the electric behavior of biological tissue to the change in its properties due to freezing. The developed technique is introduced as an alternative to the traditional ones, as it is fast, economic, and easy to carry out.This research was funded by the Spanish Government/FEDER funds, Ministerio de Economia y Empresa (MINECO)/Fondo Europeo de Desarrollo Regional (FEDER), (Grant No. RTI2018-100910-B-C43).Romero Fogué, D.; Masot Peris, R.; Ibáñez Civera, FJ.; Contat-Rodrigo, L.; Laguarda-Miro, N. (2022). Monitoring Freeze-Damage in Grapefruit by Electric Bioimpedance Spectroscopy and Electric Equivalent Models. Horticulturae. 8(3):1-15. https://doi.org/10.3390/horticulturae80302181158