Nonlocal Effective Medium (NLEM) for Quantitative Modelling of Nanoroughness in Spectroscopic Reflectance

Spectroscopic reflectance is a versatile optical methodology for the characterization of transparent and semi-transparent thin films in terms of thickness and refractive index. The Fresnel equations are used to interpret the measurements, but their accuracy is limited when surface roughness is present. Nanoroughness can be modelled through a discretized multi-slice and effective medium approach, but to date, this offered mostly qualitative and not quantitative accuracy. Here we introduce an adaptive and nonlocal effective medium approach, which considers the relative size and environment of each discretized slice. We develop our model using finite-difference time-domain simulation results and demonstrate its ability to predict nanoroughness size and shape with relative errors < 3% in a variety of test systems. The accuracy of the model is directly compared to the prediction capabilities of the Bruggeman and Maxwell–Garnett models, highlighting its superiority. Our model is fully parametrized and ready to use for exploring the effects of roughness on reflectance without the need for costly 3D simulations and to be integrated into the Fresnel simulator of spectroscopic reflectance tools

Development and Bioanalytical Applications of a White Light Reflectance Spectroscopy Label-Free Sensing Platform

The development of a sensing platform based on white light reflectance spectroscopy (WLRS) is presented. The evolution of the system, from polymer film characterization and sensing of volatile organic compounds to biosensor for the label-free determination of either high (e.g., proteins) or low molecular weight analytes (e.g., pesticides), is described. At the same time, the passage from single to multi-analyte determinations, and from a laboratory prototype set-up to a compact device appropriate for on-site determination, is outlined. The improvements made on both the sensor and the optical set-up, and the concomitant advances in the analytical characteristics and the robustness of the assays performed with the different layouts, are also presented. Finally, the future perspectives of the system, aiming for the creation of a standalone instrument to be used by non-experts, will be discussed

Non-Destructive Characterization of Selected Types of Films and Other Layers via White Light Reflectance Spectroscopy (WLRS)

In this work, we consider White Light Reflectance Spectroscopy (WLRS) as an optical methodology for the accurate, fast and non-destructive measurement of film thickness in the 1 nm to the 1 mm range and for applications that include microelectronics, photonics, bioanalysis and packaging. Films to which WLRS is applicable can be either homogeneous or layered-composite ones, while thickness and composition might be fixed or varying with time; in the latter case, real-time monitoring of the kinetics of processes such as certain transitions, film dissolution and bioreactions is possible. We present the basic principles of WLRS and a selection of characteristic application examples of current interest, and we also briefly compare WLRS with alternative methods for film measurement

Wireless measurement system for capacitive pressure sensors using strain compensated SiGeB

A prototype of miniaturized, low power, bidirectional wireless communication system was designed for in vivo pressure monitoring. The capacitive pressure sensors have been developed particularly for the medical field, where packaging size and minimization of the power requirements of the sensors are the major drivers. The pressure sensors have been fabricated using a 2.4 μm thick strain compensated heavily boron doped SiGeB. In order to integrate the sensors with the wireless module, the sensor dice was wire bonded onto TO package using chip on board (COB) technology. The telemetric link and its capabilities to send information have been examined on a test bench. A full pressure range from 0 to 10kPa was generated using either air or water pressure pumped through connected tubes to simulate the environment similar to the one inside the gastro Intestinal (GI) tract

Ultrafast Multiplexed-Allergen Detection through Advanced Fluidic Design and Monolithic Interferometric Silicon Chips

A silicon-based miniaturized sensor chip combined with an advanced microfluidic module for the simultaneous, label-free immunochemical determination of four allergens, bovine milk protein, peanut protein, soy protein, and gliadin, is presented. The sensor chip consists of an array of 10 broad-band Mach-Zehnder interferometers (BB-MZIs) monolithically integrated on silicon, along with their respective broad-band light sources. The BB-MZIs were biofunctionalized with the targeted allergens and their responses during immunoreaction were monitored by multiplexing their transmission spectra through an external miniaturized spectrometer. The assay is performed by running mixtures of calibrators or samples with the antibodies against the four allergens followed by an antispecies specific antibodies solution. Employing a fluidic module of nearly one-dimensional geometry, that provided for uniform delivery of the reagents, CV values <6% were achieved for the responses of the 10 BB-MZIs, allowing for reliable multianalyte determinations. The analysis is completed in 6.5 min, and the detection limits were 0.04 μg/mL for bovine k-casein, 1.0 μg/mL for peanut protein, 0.80 μg/mL for soy protein, and 0.10 μg/mL for gliadin. The assays were accurate (recoveries 88-118%) and repeatable (intra- and interassay CVs <7% for all four allergens). Finally, the sensor was evaluated by analyzing samples from a cleaning in place system (CIP) of a dairy industry and the results obtained were in good agreement with those received by the respective ELISAs. The analytical characteristics of the sensor combined with the short analysis time and the small chip size make the proposed system an ideal tool for on-site multianalyte determinations

Development of wireless pressure measurement system for short range medical applications

A prototype of miniaturized, low power, bi-directional wireless communication system was designed for in vivo pressure monitoring. The capacitive pressure sensors have been developed particularly for the medical field, where packaging size and minimization of the power requirements of the sensors are the major drivers. The pressure sensors have been fabricated using a 2.4 pm thick strain compensated heavily boron doped SiGeB. In order to integrate the sensors with the wireless module, the sensor dice was wire bonded onto TO package using chip on board (COB) technology. The telemetric link and its capabilities to send information have been examined on a test bench. A full pressure range from 0 to ]OkPa was generated using either air or water pressure pumped through connected tubes to simulate the environment similar to the one inside the gastrointestinal (GI) tract