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Author: search.filters.author.Withayachumnankul, WithawatSubject: search.filters.subject.Metamaterial

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    Metamaterial-based microfluidic sensor for dielectric characterization
    (2013-01-01)
    Withayachumnankul, Withawat
    ;
    Jaruwongrungsee, Kata
    ;
    Tuantranont, Adisorn
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    Fumeaux, Christophe
    ;
    Abbott, Derek
    A microfluidic sensor is implemented from a single split-ring resonator (SRR), a fundamental building block of electromagnetic metamaterials. At resonance, an SRR establishes an intense electric field confined within a deeply subwavelength region. Liquid flowing in a micro-channel laid on this region can alter the local field distribution and hence affect the SRR resonance behavior. Specifically, the resonance frequency and bandwidth are influenced by the complex dielectric permittivity of the liquid sample. The empirical relation between the sensor resonance and the sample permittivity can be established, and from this relation, the complex permittivity of liquid samples can be estimated. The technique is capable of sensing liquid flowing in the channel with a cross-sectional area as small as (0.001λ<inf>0</inf>)<sup>2</sup>, where λ<inf>0</inf> denotes the free-space wavelength of the wave excitation. This work motivates the use of SRR-based microfluidic sensors for identification, classification, and characterization of chemical and biochemical analytes. © 2012 Elsevier B.V.
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    Metamaterial-inspired multichannel thin-film sensor
    (2012-04-24)
    Withayachumnankul, Withawat
    ;
    Jaruwongrungsee, Kata
    ;
    Fumeaux, Christophe
    ;
    Abbott, Derek
    A multichannel thin-film sensor is implemented from a set of microstrip-coupled split-ring resonators (SRRs) with different dimensions. Each SRR exhibits a unique high-Q resonance that is sensitive to the presence of a sample in a particular area. Hence, this SRR-based sensor can function (i) to detect different samples simultaneously to increase the throughput or (ii) to characterise nominally identical samples at multiple frequencies to increase the sensor selectivity. In addition, the sensitivity of this SRR-based sensor is optimized through strategic design of the resonator shape to produce a strong confined electric field at each sensing region. The design principle is validated with simulation and measurement. Owing to the optimized design, sensing a low-permittivity film with a thickness as small as one thousandth of the operating wavelength is achievable. © 2012 IEEE.
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    A review on thin-film sensing with terahertz waves
    (2012-03-01)
    O'Hara, John F.
    ;
    Withayachumnankul, Withawat
    ;
    Al-Naib, Ibraheem
    In the past two decades, the development and steady improvement of terahertz technology has motivated a wide range of scientific studies designed to discover and develop terahertz applications. Terahertz sensing is one such application, and its continued maturation is virtually guaranteed by the unique properties that materials exhibit in the terahertz frequency range. Thinfilm sensing is one branch of this effort that has enjoyed diverse development in the last decade. Deeply subwavelength sample thicknesses impose great difficulties to conventional terahertz spectroscopy, yet sensing those samples is essential for a large number of applications. In this article we review terahertz thin-film sensing, summarizing the motivation, challenges, and state-of-the-art approaches based predominately on terahertz time-domain spectroscopy. © Springer Science+Business Media, LLC 2012.
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    Survey of terahertz metamaterial devices
    (2008-12-01)
    Withayachumnankul, Withawat
    ;
    Abbott, Derek
    Metamaterials have arisen in an attempt to engineer the electromagnetic properties of natural substances. It has been acknowledged that the emergence of metamaterials has implications to nearly all branches of science and engineering exploiting the electromagnetic radiation. This paper reviews seminal work of metamaterials from the vision to the realisation of subwavelength elements that contribute to varieties of electric and magnetic responses. Emphasis is given to the significance and opportunity of this new class of material augmenting terahertz technology. Although now there remain major milestones that scientists and engineers need to conquer, the future of this cutting-edge material technology is very bright. © 2008 SPIE.