A modeling and design approach is proposed for nanoparticle-based electromagnetic devices. First, the structure properties were analytically studied using Maxwell’s equations. The method provides us a robust link between nanoparticles electromagnetic response (amplitude and phase) and their geometrical characteristics (shape, geometry, and dimensions). Secondly, new designs based on “metamaterial” concept are proposed, demonstrating great performances in terms of wide-angle range functionality and multi/wide behavior, compared to conventional devices working at the same frequencies. The approach offers potential applications to build-up new advanced platforms for sensing and medical diagnostics. Therefore, in the final part of the article, some practical examples are reported such as cancer detection, water content measurements, chemical analysis, glucose concentration measurements and blood diseases monitoring.

In this work, near-zero-index material boundary properties have been exploited to achieve new electromagnetic functionalities. The extraordinary guiding properties of a cylindrical dielectric rod waveguide surrounded by a thin epsilon-mu-near-zero shell is analyzed and discussed. A closed-form solution for the dispersion equation has been developed, able to model and design such properties at will. Analytical and numerical results will confirm that the use of near-zero cover materials leads to extraordinary properties in terms of field configurations, low attenuation, and bandwidth. The dielectric wire acts as an efficient "waveguide" with great potentials for advance nanocircuit and electronics.

In this paper, an analytical and numerical study of a new type of electromagnetic absorber, operating in the infrared and optical regime, is proposed. Absorption is obtained by exploiting Epsilon-Near-Zero materials. The structure electromagnetic properties are analytically described by using a new closed-form formula. In this way, it is possible to correlate the electromagnetic absorption properties of the structure with its geometrical characteristics. Good agreement between analytical and numerical results was achieved. Moreover, an absorption in a wide angle range (0°-80°), for different resonant frequencies (multi-band) with a large frequency bandwidth (wideband) for small structure thicknesses (d = λp/4) is obtained.

In this paper, an analytical and numerical investigation for modified gold nanorod particles, operating in the visible and in the infrared regime is proposed. The modified particles consist in a core/shell structure (dielectric core/metallic shell) embedded in a dielectric environment. Their electromagnetic properties, in terms of extinction cross section (absorption and scattering) for both longitudinal and transverse modes excitation, are evaluated. In particular, new analytical models are developed, describing their resonant behavior. Good agreement among the analytical, numerical, and experimental results was achieved. Exploiting the obtained models, the nanoparticle sensitivity was studied. Analytical and full wave results validate the high sensitivity performances and the potential role of such structures to be used for sensing applications.

Purpose – A novel model of the upper arm under transcutaneous electrical stimulation with multi-pad electrodes is presented and experimentally validated. The model aims at simulating and analysing the effects of surface electrical stimulation on biceps brachii. The paper aims to discuss these issues. Design/methodology/approach – Both the passive properties of tissues surrounding nerve bundles and the active characteristics of the nervous system are included. The output of the proposed model is nerve recruitment and muscle contraction. Findings – Simulations and experimental tests on six healthy young adults have been conducted and results show that the proposed model gives information on electrically elicited muscle contraction in accordance with in-vivo tests and literature on motor unit recruitment order. Tests with different electrodes configurations show that the spatial distribution of active electrodes is a critical factor in electrically elicited muscle contractions, and that multi-pad electrodes can optimise the stimulation effectiveness and patient comfort with sequences of biphasic pulses of 350 μs at 30 pulses/s and threshold values of 2 mA. Originality/value – Results encourage the use of the proposed model of the upper arm as a valid and viable solution for predicting the behaviour of the neuromuscular system when surface electrical stimulation is applied, thus optimising the design of neuroprosthetics.

In this paper we propose a new approach to study the electromagnetic field in Surface Plasmon Resonance (SPR) meta-structures. The geometry is a planar structure infinitely extended with a pulse excitation current embedded in the substrate. The general solution has been applied to a specific geometry that is frequently employed to model practical problems. The minimization of the thickness changes spectral Green's function in a more efficient form, suitable for calculations. Plasmon electric field expression on interface plane is obtained. This kind of meta-structures is suitable in various fields of application (e.g. optoelectronics and electromagnetic sensors).

Purpose – The purpose of this paper is to contribute an analytical and numerical study of a new type of nanoshell particles operating in the visible regime. Design/methodology/approach – The structure consists of a core/shell particle, arranged in a planar array configuration, with a polymethyl methacrylate (PMMA)-graphene core and gold thin shell. Findings – By exploiting the proposed analytical model the design of a metamaterial-based sensor, operating in the optical frequency range, for the detection of tissue diseases is shown. Originality/value – Full-wave simulations confirm the capability of the proposed sensor to identify different compounds by refractive index measurement.

In this work electromagnetic properties of a new type of graphene nanoparticles are investigated.The particles consist of graphene circular and square rings, embedded in a dielectric environment.The electromagnetic behavior in terms of resonant frequency position, magnitude and amplitude width for the absorption cross-section and the near electric field distribution are evaluated.Moreover, the influence of the geometrical parameters is also evaluated.The electromagnetic analysis is derived through proper full-wave numerical simulations.Numerical results show that the nanoparticles can be successfully used for the development of future graphene-based antennas operating in the TeraHertz Band.

In this contribution the stimulus complications in DBS (Deep Brain Stimulation) are evaluated and discussed. In particular we present a new method to predict the network response when a DBS stimulus is applied. A neural network similarly to ipsi-contralateral nerve topology is presented. The network consists of 175 neurons arranged in three layers. To validate the DBS stimulus propagation extensive numerical analyses have been conducted through Neuron software simulations. Results confirm the possibility to predict the correct stimulation parameters.

In this contribution a nanodevice based on Localized Surface Plasmon Resonance (LSPR) phenomenon for biological characterization operating in the Visible and Near Infrared frequency Regime is proposed. The device consists of coupled biconical nanoparticles deposited on a silica substrate. By using a very small inter-particle distance it is possible to obtain a strong near electric field enhancement at the resonant wavelength suitable for ultra-sensitive biosensing applications. Full-wave simulations confirm the possibility to use the device as an optical sensor to detect in a ultra-sensitive way different cholesterol concentrations of the lipid membrane.

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.

Purpose – Metamaterial unit cells composed of deep subwavelength resonators brought up new aspects to the antenna miniaturization problem. The paper experimentally demonstrates a metamaterial-inspired miniaturization method for circular patch antennas. In the proposed layouts, the space between the patch and the ground plane is filled with a proper metamaterial composed of either multiple split-ring or spiral resonators (SRs). The authors have manufactured two different patch antennas, achieving an electrical size of λ/3.69 and λ/8.26, respectively. The paper aims to discuss these issues. Design/methodology/approach – The operation of such a radiative component has been predicted by using a simple theoretical formulation based on the cavity model. The experimental characterization of the antenna has been performed by using a HP8510C vector network analyzer, standard horn antennas, automated rotary stages, coaxial cables with 50 Ω characteristic impedance and absorbers. Before the characterization measurements we performed a full two-port calibration. Findings – Electrically small circular patch antennas loaded with single layer metamaterials experimentally demonstrated to acceptable figures of merit for applications. The proposed miniaturization technique is potentially promising for antenna applications and the results presented in the paper constitute a relevant proof for the usefulness of the metamaterial concepts in antenna miniaturization problems. Originality/value – Rigorous experimental characterization of several meta material loaded antennas and proof of principle results were provided.

In this contribution we will present our research activities recently developed at Roma Tre University in the field of plasmonic nanoparticles for biosensing applications. We show several innovative sensing platforms, operating in the visible and near-infrared frequency regime. The contribution of our group regards to the electromagnetic modeling of such nanoparticles and their applications for the analysis and recognition of organic compounds. Numerical results, performed by full-wave simulations, show as the sensors can be used for the recognition of different organic compounds and their concentrations in a highly accurate and sensitive way.

In this contribution, we present the design of efficient electrically small apertures loaded with metamaterial-inspired sub-wavelength resonators. The employment of omega and modified protractor resonators enables efficient radiation and automatic impedance matching, without increasing the physical dimensions of the aperture. This phenomenon is applied to the design of several microwave components, some of which are presented in the paper: a. linearly-polarized open-ended waveguides and horn antennas and b. linear-to-circular polarization transformers. The results are supported by proper numerical simulations and measurements.

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.