University of Limerick
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Novel corrugated long period grating surface balloon-shaped heterocore-structured plastic optical fibre sensor for microalgal bioethanol production

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journal contribution
posted on 2023-07-05, 10:38 authored by Sanober Farheen MemonSanober Farheen Memon, Ruoning Wang, Bob Strunz, Bhawani Shankar Chowdhry, TONY PEMBROKETONY PEMBROKE, Elfed LewisElfed Lewis

A novel long period grating (LPG) inscribed balloon-shaped heterocore-structured plastic optical fibre (POF) sensor is described and experimentally demonstrated for real-time measurement of the ultra-low concentrations of ethanol in microalgal bioethanol production applications. The heterocore structure is established by coupling a 250 µm core diameter POF between two 1000 µm diameter POFs, thus representing a large core—small core—large core configuration. Before coupling as a heterocore structure, the sensing region or small core fibre (SCF; i.e., 250 µm POF) is modified by polishing, LPG inscription, and macro bending into a balloon shape to enhance the sensitivity of the sensor. The sensor was characterized for ethanol–water solutions in the ethanol concentration ranges of 20 to 80 %v/v, 1 to 10 %v/v, 0.1 to 1 %v/v, and 0.00633 to 0.0633 %v/v demonstrating a maximum sensitivity of 3 × 106 %/RIU, a resolution of 7.9 × 10−6 RIU, and a limit of detection (LOD) of 9.7 × 10−6 RIU. The experimental results are included for the intended application of bioethanol production using microalgae. The characterization was performed in the ultra-low-level ethanol concentration range, i.e., 0.00633 to 0.03165 %v/v, that is present in real culturing and production conditions, e.g., ethanol-producing blue-green microalgae mixtures. The sensor demonstrated a maximum sensitivity of 210,632.8 %T/%v/v (or 5 × 106 %/RIU as referenced from the RI values of ethanol–water solutions), resolution of 2 × 10−4 %v/v (or 9.4 × 10−6 RIU), and LOD of 4.9 × 10−4 %v/v (or 2.3 × 10−5 RIU). Additionally, the response and recovery times of the sensor were investigated in the case of measurement in the air and the ethanol-microalgae mixtures. The experimentally verified, extremely high sensitivity and resolution and very low LOD corresponding to the initial rate of bioethanol production using microalgae of this sensor design, combined with ease of fabrication, low cost, and wide measurement range, makes it a promising candidate to be incorporated into the bioethanol production industry as a real-time sensing solution as well as in other ethanol sensing and/or RI sensing applications. 


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Sensors 23(3), 1644



Other Funding information

European Union Erasmus Mundus INTACT Program; the Postgraduate Research Residential Scholarship by the Plassey Campus Centre, University of Limerick, Ireland; the Department of Electronic and Computer Engineering, University of Limerick, Ireland University of Limerick’s programme for COVID-19-Related Research Costed Extensions, which was supported by the Higher Education Authority and the Government of Ireland’s Department of Further and Higher Education, Research, Innovation, and Science.

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  • Bernal Institute

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  • Chemical Sciences
  • Electronic & Computer Engineering

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