The authors respond to the comments by Mackay and Lakhtakia.
First of all, we would like to thank Mackay and Lakhtakia1 who have carefully read our paper and for their valuable comments on our manuscript. We agree that the polarizability is a dyadic.
For our aims (analytical models, full-wave simulations, and sensitivity analysis), we have assumed the impinging electromagnetic field as a plane wave having the electric field E parallel to the nanoparticle principal axis (x -axis as depicted in the Fig. 1 of the paper). In this case, Eq. (1) and the following equations refer only to scalar component x ^ x ^ of the dyadic polarizability α − − − − (sufficient to evaluate the nanoparticle response under the aforementioned excitation condition).
We have to point out that for sensing applications the analyzed polarization is crucial in order to obtain the best sensitivity performances.
Skin absorption properties, under diseases conditions, are modified due to the structural variations of chromophores and pigments. The measurement of such different absorptions can be a useful tool for the recognition of different skin diseases. In this study the design of a multi-resonant metamaterial-based sensor operating in the optical frequency range is presented. The sensor has been designed, in order to have multiple specific resonant frequencies, tuned to the skin components spectral characteristics. A change in the frequency amplitude of the sensor response is related to the different absorption rate of skin chromophores and pigments. A new analytical model, describing the multi-resonant sensor behaviour, is developed. Good agreement among analytical and numerical results was achieved. Full-wave simulations have validated the capability of the proposed sensor to identify different skin diseases.
In this contribution optical properties of new metallic nanoparticles for biomedical applications are investigated. These
particles consist of a pair of opposing gold prisms with asymmetric dielectric holes. In this configuration the structure
exhibits multi-resonant behavior in the Visible and Near Infrared Region, useful tool for multi-sensing platform based on
local refractive index measurements. The electromagnetic properties of the structure are evaluated in terms of extinction
cross-section through proper full-wave simulations. The sensitivity performances for the local refractive index variation
are discussed. The obtained results show that the proposed particles could be efficiently applied for sensing applications.
In this paper plasmonic nanoparticles arranged in an array configuration for the detection of glycerol concentration in aqueous solution, are presented. Glycerol concentration measurement is crucial for several application fields, such as biomedical engineering, medicine and biofuels fabrication. The detection of glycerol presence in aqueous solution is not simple, due to the fact that its refractive index shows small changes when different concentrations are considered. For this purpose, an LSPR (Localized Surface Plasmon Resonance) sensor, based on near field interaction of non-spherical dielectric-filled metallic particles (nanoshell) deposited on a silica substrate, is proposed. In this configuration an enhancement of the LSPR phenomenon with high sensitivity performances and a uniform near electric field distribution are obtained. In this way a shift in the position of the sensor response is related to the different concentration of the material under test. Numerical results, performed by full-wave simulations, show that the sensor can be used for the recognition of glycerol and its concentration in a highly accurate and sensitive way.
We present a new analytical study of metallic nanoparticles, working in the infrared and visible frequency range. The structure consists of triaxial ellipsoidal resonating inclusions embedded in a dielectric environment. Our aim is to develop a new analytical model for the ellipsoidal nanoparticles to describe their resonant behaviors and design structures that satisfy specific electromagnetic requirements. The obtained models are compared to the numerical values, performed by full-wave simulations, as well as to the experimental ones reported in literature. A good agreement among these results was obtained. The proposed formula is a useful tool to design such structures for sensing applications.
In this paper, the design of a metamaterial-based sensor, operating in the mid-infrared frequency range, is proposed.
The sensor consists of a planar array of complementary circular inclusions. The resonant frequencies of the sensor are
designed to coincide with the proteins and lipids spectral characteristics, in order to detect the presence of cancer
tissues, by absorption measurements. This sensor can be also used for the recognition of different benign tumours in a
highly accurate and sensitive way. A new analytical circuit model has been developed, useful to describe its resonant
behavior. The sensing device is, then, optimized to obtain high selectivity performances and has been tested through
proper full-wave simulations. The structure can be used as a biological sensor with possible applications in medical
In this paper, an electromagnetic metamaterial resonator operating in the terahertz frequency range is presented. By arranging the resonator in a planar array, it is possible to use the structure as a sensing device for organic and inorganic compounds. The sensor is designed to detect the presence of a biological compound by permittivity or absorption measurements. The presence of the biological matter modifies the effective permittivity and, thus, the resonant frequency significantly varies. In addition, biological compounds typically exhibit absorption characteristics that depend on the corresponding molecular structure. Therefore, it is necessary to illuminate the material selectively. We show that by employing the "selective" properties of the metamaterial resonator proposed, it is possible to enhance the sensing performances. The proposed design is suitable to sense the presence of healthy and malignant tissues, with possible applications in food and medical diagnostics. The operation of the sensing device has been demonstrated through proper full-wave simulations.