Abstract
The next future strategies for improved occupational safety and health management could largely benefit from wearable and Internet of Things technologies, enabling the real-time monitoring of health-related and environmental information to the wearer, to emergency responders, and to inspectors. The aim of this study is the development of a wearable gas sensor for the detection of NH3 at room temperature based on the organic semiconductor poly(3,4-ethylenedioxythiophene) (PEDOT), electrochemically deposited iridium oxide particles, and a hydrogel film. The hydrogel composition was finely optimised to obtain self-healing properties, as well as the desired porosity, adhesion to the substrate, and stability in humidity variations. Its chemical structure and morphology were characterised by infrared spectroscopy and scanning electron microscopy, respectively, and were found to play a key role in the transduction process and in the achievement of a reversible and selective response. The sensing properties rely on a potentiometric-like mechanism that significantly differs from most of the state-of-the-art NH3 gas sensors and provides superior robustness to the final device. Thanks to the reliability of the analytical response, the simple two-terminal configuration and the low power consumption, the PEDOT:PSS/IrOx Ps/hydrogel sensor was realised on a flexible plastic foil and successfully tested in a wearable configuration with wireless connectivity to a smartphone. The wearable sensor showed stability to mechanical deformations and good analytical performances, with a sensitivity of 60 ± 8 μA decade−1 in a wide concentration range (17–7899 ppm), which includes the safety limits set by law for NH3 exposure.
Highlights
Among hazardous gaseous compounds causing severe health issues, ammonia has good warning properties thanks to its pungent smell and to the low odour threshold of our olfactory system [1]
The aim of this study is the development of a wearable gas sensor for the detection of NH3 at room temperature based on the organic semiconductor poly(3,4-ethylenedioxythiophene) (PEDOT), electrochemically deposited iridium oxide particles, and a hydrogel film
Relevant examples include wearable sensors realised using PANi-coated ZnO nanosheets [13] and PANI-functionalized multiwalled carbon nanotubes (MWCNTs) [14,15] on fabric substrates and plastic fibers, graphene oxide/PANi nanospheres [16] and PANi-CeO2 nanocomposite [17] on plastic foils, and bacterial cellulose functionalised with co-doped PANi nanorods [18]
Summary
Among hazardous gaseous compounds causing severe health issues, ammonia has good warning properties thanks to its pungent smell and to the low odour threshold of our olfactory system [1]. Adaptation or olfactory fatigue upon routine exposure makes NH3 inhalation a bio-threat for operators working in many industrial contexts, including agriculture, the fertilizer and automotive industries, animal breeding, and industrial refrigeration [2]. In this regard, the fast-evolving field of wearable electronics may be a great resource for future occupational safety and health management strategies, wirelessly providing health-related and environmental information in real time to the wearer, emergency responders, and inspectors. Thanks to inherent CP advantages, including lightweight, low cost, room temperature stability, flexibility, and easy processing from solutions and dispersions with respect to other bulk semiconductors, some examples of NH3 chemiresistive sensors have been designed in a wearable form-factor in recent years. CP-based NH3 gas sensors have been obtained using nanostructures and composites of poly(3,4-ethylenedioxythiophene) (PEDOT) [19,20,21], as well as Polypyrrole (PPy) [22,23]
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