Luigi La Spada

Metamaterial-Based Sensor Design Working in Infrared Frequency Range

In this paper, we propose the design of high sensitivity and selectivity metamaterial-based biosensors operating in the THz regime. The proposed sensors consist of planar array of resonant metallic structures, whose frequency response is modifled through the variation of the surrounding dielectric environment. We consider difierent resonator geometries, such as the squared, circular, asymmetrical, and omega ones, and the analysis of the biosensors is conducted through proper equivalent quasi-static analytical circuit models. The metallic particles are assumed deposited on a glass substrate through proper titanium adhesion layers. Exploiting the proposed analytical model, which is verifled through the comparison to full-wave numerical simulations, we study the biosensor resonance frequencies as a function of the geometric parameters of the individual inclusions. Finally, we optimize the structure in order to obtain high sensitivity and selectivity performances. The numerical results show that the proposed structures can be successfully applied as biosensors working in the THz region.

Electromagnetic modeling of ellipsoidal nanoparticles for sensing applications

Abstract. 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.

Metamaterial resonator arrays for organic and inorganic compound sensing

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.

Nanoplasmonic sensor for chemical measurements

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.

Multi resonant platform based on modified metallic nanoparticles for biological tissue characterization

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.

Sensor design for cancer tissue diagnostics

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 diagnostics.

Response to “Comment on the paper ‘Electromagnetic modeling of ellipsoidal nanoparticles for sensing applications’”

Abstract. The authors respond to the comments by Mackay and Lakhtakia.