Oxygen Gas Sensing Using a Hydrogel-Based Organic Electrochemical Transistor for Work Safety Applications

open8noOxygen depletion in confined spaces represents one of the most serious and underestimated dangers for workers. Despite the existence of several commercially available and widely used gas oxygen sensors, injuries and deaths from reduced oxygen levels are still more common than for other hazardous gases. Here, we present hydrogel-based organic electrochemical transistors (OECTs) made with the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) as wearable and real-time oxygen gas sensors. After comparing OECT performances using liquid and hydrogel electrolytes, we identified the best PEDOT:PSS active layer and hydrogel coating (30 µm) combination for sensing oxygen in the concentration range of 13–21% (v/v), critical for work safety applications. The fast O2 solubilization in the hydrogel allowed for gaseous oxygen transduction in an electrical signal thanks to the electrocatalytic activity of PEDOT:PSS, while OECT architecture amplified the response (gain ̴ 104). OECTs proved to have comparable sensitivities if fabricated on glass and thin plastic substrates, (−12.2 ± 0.6) and (−15.4 ± 0.4) µA/dec, respectively, with low power consumption (<40 µW). Sample bending does not influence the device response, demonstrating that our real-time conformable and lightweight sensor could be implemented as a wearable, noninvasive safety tool for operators working in potentially hazardous confined spaces.The work was supported by the European Union FESR FSE, PON Research and Innovation 2014-2020 and FSC, project number ARS01-00996 "TEXT-STYLENuovi tessuti intelligenti e sostenibilimultisettoriali per il design creative e stileMade-in-Italy" and by the Italian Ministry of Economic Development 2020-Project "AlmaMater patents-Monitoraggio in continuo di pH e idratazione-MIRAGE".openFrancesco Decataldo, Filippo Bonafè, Federica Mariani, Martina Serafini, Marta Tessarolo, Isacco Gualandi, Erika Scavetta, Beatrice FraboniFrancesco Decataldo, Filippo Bonafè, Federica Mariani, Martina Serafini, Marta Tessarolo, Isacco Gualandi, Erika Scavetta, Beatrice Frabon

Smart Bandaid Integrated with Fully Textile OECT for Uric Acid Real-Time Monitoring in Wound Exudate

: Hard-to-heal wounds (i.e., severe and/or chronic) are typically associated with particular pathologies or afflictions such as diabetes, immunodeficiencies, compression traumas in bedridden people, skin grafts, or third-degree burns. In this situation, it is critical to constantly monitor the healing stages and the overall wound conditions to allow for better-targeted therapies and faster patient recovery. At the moment, this operation is performed by removing the bandages and visually inspecting the wound, putting the patient at risk of infection and disturbing the healing stages. Recently, new devices have been developed to address these issues by monitoring important biomarkers related to the wound health status, such as pH, moisture, etc. In this contribution, we present a novel textile chemical sensor exploiting an organic electrochemical transistor (OECT) configuration based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) for uric acid (UA)-selective monitoring in wound exudate. The combination of special medical-grade textile materials provides a passive sampling system that enables the real-time and non-invasive analysis of wound fluid: UA was detected as a benchmark analyte to monitor the health status of wounds since it represents a relevant biomarker associated with infections or necrotization processes in human tissues. The sensors proved to reliably and reversibly detect UA concentration in synthetic wound exudate in the biologically relevant range of 220-750 μM, operating in flow conditions for better mimicking the real wound bed. This forerunner device paves the way for smart bandages integrated with real-time monitoring OECT-based sensors for wound-healing evaluation

An all-PEDOT:PSS electrochemical transistor as a platform for biosensing

Organic electrochemical transistors (OECTs) are devices which find growing interest in the field of biological and chemical sensing. Although the OECT transduction is based on electrochemical reactions, the transistor architecture offers several advantages respect to amperometric sensors such as signal amplification, use of an easy and cheap readout electronics, low supply voltage (usually < 1 V), low power operation (< 100 \u3bcW), bio-compatibility. Moreover, they can be easily miniaturized and adapted to non-flat, flexible and even textile devices [1]. This contribution reports on the potentiality of such devices by describing an OECT based only on PEDOT:PSS as conductive material, which can be exploited to obtain low cost sensors [2, 3] with very high performance. The sensor was optimized by studying its response to different redox compounds of biological interest such as ascorbic acid, dopamine, adrenaline and uric acid. The bio-molecules react with PEDOT:PSS by extracting charge carriers from the transistor channel, and, consequently, when the analyte concentration increases the absolute value of the drain current decreases. Typically, the main drawback of such devices is the lack of selectivity which hinders their wide use in real applications. To overcome this problem we have developed a potentiodynamic approach that exploits the variation of the operating gate bias voltage in order to obtain a trans-conductance curve wherein the waves due to different redox compounds are separated. The intensity of the signal linearly depends on the analyte concentration. The sensitivities and limit of detection obtained with the OECT have been compared with those obtained by potential step amperometric techniques employing a PEDOT:PSS working electrode. The OECT performance is comparable or even better than those obtained by DPV. References: [1] I. Gualandi, M. Marzocchi, A. Achilli, D. Cavedale, A. Bonfiglio, B. Fraboni, Scientific Reports 6 (2016) 33637. [2] I. Gualandi, M. Marzocchi, E. Scavetta, M. Calienni, A. Bonfiglio, B. Fraboni, J. Mater. Chem. B 3 (2015) 6753-6762. [3] I. Gualandi, D. Tonelli, F. Mariani, E. Scavetta, M. Marzocchi, B. Fraboni, Scientific Reports 6 (2016) 35419

Textile Chemical Sensors Based on Conductive Polymers for the Analysis of Sweat

Wearable textile chemical sensors are promising devices due to the potential applications in medicine, sports activities and occupational safety and health. Reaching the maturity required for commercialization is a technology challenge that mainly involves material science because these sensors should be adapted to flexible and light-weight substrates to preserve the comfort of the wearer. Conductive polymers (CPs) are a fascinating solution to meet this demand, as they exhibit the mechanical properties of polymers, with an electrical conductivity typical of semiconductors. Moreover, their biocompatibility makes them promising candidates for effectively interfacing the human body. In particular, sweat analysis is very attractive to wearable technologies as perspiration is a naturally occurring process and sweat can be sampled non-invasively and continuously over time. This review discusses the role of CPs in the development of textile electrochemical sensors specifically designed for real-time sweat monitoring and the main challenges related to this topic

Nanoparticle gated semiconducting polymer for a new generation of electrochemical sensors

The development of portable and wearable sensors is of high importance in several fields such as point-of-care medical applications and environmental monitoring. Here we design, synthesize and exploit a new composite material based on Ag/AgCl nanoparticles and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate)) to fabricate a novel kind of sensor inspired by the organic electrochemical transistor (OECT). We are able to integrate an Ag/AgCl gate electrode into the semiconducting polymer in the form of NPs. As a consequence, our sensor combines an intrinsically amplified response with a simple two terminal electrical connection. Electrostatic Force Microscopy and Electrochemical Impedance Spectroscopy demonstrate the electronic coupling between the electrochemically active nanoparticles and the ionic charge gated semiconducting polymer, allowing to explain the sensor amplified transduction. The analytical signal is the current that flows in the composite polymer and its variation is directly proportional to the logarithm of Cl 12concentration in the range 10 124to 1 M, with a limit of detection of 0.5 10 124M. Moreover, the device exhibits a shorter response time than the one of a conventional OECT endowed with an Ag/AgCl gate electrode. The sensor was used for in-situ detection of salinity in water and a textile device was obtained by depositing the composite material directly onto a cotton yarn for real-time sweat monitoring