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Details of Grant 

EPSRC Reference: EP/Y018079/1
Title: Microplastic sensors based on terahertz metasurface
Principal Investigator: Park, Dr S
Other Investigators:
Researcher Co-Investigators:
Project Partners:
National Physical Laboratory NPL University of Leeds Water Research Centre WRc
Department: Sch of Electronic Eng & Computer Science
Organisation: Queen Mary University of London
Scheme: New Investigator Award
Starts: 01 April 2024 Ends: 31 March 2027 Value (£): 449,855
EPSRC Research Topic Classifications:
Materials Characterisation Materials Synthesis & Growth
EPSRC Industrial Sector Classifications:
Environment R&D
Related Grants:
Panel History:
Panel DatePanel NameOutcome
25 Oct 2023 EPSRC Physical Sciences Prioritisation Panel B- October 2023 Announced
Summary on Grant Application Form
Plastic particles with a size between 1 micron and 5 mm, so-called microplastics, have become an enormous global issue for the aquatic ecosystem and may affect human well-being through the food chain. Various hygiene products such as body wash, shampoo, and toothpaste use microbeads made of either polystyrene, polypropylene, or polyethylene and these microbeads are found to be accumulated in various ecosystems including rivers, lakes, and oceans. A study reported that microbeads found in bottled water have typical sizes between 1 micron and 5 microns. To monitor microplastics quantitatively and qualitatively in the aquatic ecosystem, Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy have been used to examine the microplastic specimens. However, liquid specimens containing microplastics often need to go through a density separation step as a pre-treatment before the examination. During the density separation process, microplastics are extracted from the liquid sample by letting microplastics float in the solution with a higher density than microplastics. This process often takes 5 hrs to up to 1 day and makes the detection of microplastics using FTIR, and Raman spectroscopy a labour-intensive and time-consuming job. Limitations on examination time and particle size in existing microplastic detection methods make developing novel in situ and fast monitoring methods for microplastics in aquatic ecosystems imperative.

On the other hand, THz biosensing applications operating in the frequency range of 0.1 - 10 THz have been intensively investigated in the last couple of decades to develop novel biosensors owing to unique properties such as non-contact, non-destructive, and label-free detection. However, it has been reported that the low scattering cross-section between the samples and the THz waves can lead to low responsivity in the THz spectrum particularly when the sample size is relatively small compared to the wavelength of the THz waves. This low responsivity in the THz spectrum can be overcome and enhanced by introducing the THz metasurface. THz metasurface has an inductive-capacitive resonance at a specific frequency as it has a capacitive gap and an inductive ring in its geometry. The resonant frequency is highly sensitive to the dielectric environment change near the capacitive gap and hence it has been receiving great attention as a promising sensor platform. THz metasurface also offers an ideal platform to detect micron scale target particles (e.g. microbeads) as the THz metasurface with a few microns gap width provides optimised sensitivity. It is noteworthy that the geometrical parameters of the THz metasurface such as gap width and the length of the side arm can be easily controlled to optimise the sensitivity depending on the size of the target particles.

The vision of this proposal is to realise novel microplastic sensors based on THz metasurface that can monitor microplastic particles in aquatic ecosystems using free-space/on-chip THz spectroscopy. This will lead to the design of optimised THz metasurface and meta-atoms, through fundamental experiments and simulation work, and ultimately the development of on-site, fast, sensitive, and selective microplastic sensors working in aqueous environments. Also, the development of on-chip THz microplastic sensors will greatly push the sensitivity for monitoring microplastics in aquatic environments beyond the current state-of-the-art technology by achieving in-situ single microplastic particle detection.

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