A highly-wearable single–channel instrument, conceived with off-the-shelf components and dry electrodes, is proposed for detecting human stress in real time by electroencephalography (EEG). The instrument exploits EEG robustness to movement artifacts with respect to other biosignals for stress assessment. The single-channel differential measurement aims at analyzing the frontal asymmetry, a well-claimed EEG feature for stress assessment. The instrument was characterized metrologically on human subjects. As triple metrological references, standardized stress tests, observational questionnaires given by psychologists, and performance measurements were exploited. Four standard machine learning classifiers (SVM, k-NN, Random Forest, and ANN), trained on 50% of the data set, reached more than 90% accuracy in classifying each 2-s epoch of EEG acquired from stressed subjects.

The progressive aging of the population requires reliable, non-invasive, and real-time tools to monitor hydration, prevent dehydration-related complications, and promote active aging in elderly patients. Wearable sensors based on interdigitated electrodes (IDEs) and on Electrochemical Impedance Spectroscopy (EIS) represent a promising tool thanks to their miniaturization, sensitivity to dielectric variations with humidity, and compatibility with flexible substrates. This study reports the design, fabrication, and metrological characterization of inkjet-printed IDEs for skin hydration monitoring, as a building block of a multisensor wearable device. IDEs were fabricated on polyimide substrates using silver nanoparticle-based ink. Their characterization involved the following: (i) morphological evaluation by scanning electron microscopy; (ii) EIS measurements in KCl solutions, leading to developing a regression model to correlate impedance with salt concentration; (iii) in vitro EIS validation on agar gel samples, which demonstrated a robust linear relationship between the impedance phase shift at 199.5 $\mathrm{Hz}$ and water loss, with consistent sensitivity values across sensors. The results confirm the feasibility of IDEs for hydration monitoring, identifying optimal frequency ranges and validating regression models. These findings represent a critical step toward the development of multisensor wearable devices for elderly monitoring, enabling decentralized and continuous health monitoring to improve healthcare sustainability and telemedicine.

Proper polymerization protocol is crucial for the long-term success of full-ceramic crown restorations. This study investigates the margin continuity and degree of conversion (DC) of a universal dual-curing cement under full-ceramic crowns subjected to different polymerization protocols and thermal aging. Intact human upper central incisors and canines were prepared for crowns, digitally designed, and milled from reinforced lithium silicate (Celtra Duo, Dentsply). Crowns were cemented using a universal dual-curing cement (G-Cem One, GC) with two polymerization protocols: (G1) microbrush excess removal, 1 min waiting, and 20 s light curing per side; (G2) 5 s tack curing per side, excess removal with a scaler, and 20 s light curing. Marginal adaptation was assessed using micro-computed tomography, and DC was evaluated with Raman spectroscopy before and after artificial thermal aging (10,000 cycles between 5 °C and 55 °C). Statistical comparisons were performed with significance set at p < 0.05. Results showed significantly poorer marginal adaptation in the tack-curing group, with no post-aging differences between groups. Baseline DC was high in all samples, with no protocol-dependent variations; nevertheless, aging increased DC in G1. These findings highlight the importance of selecting an appropriate polymerization protocol to ensure optimal marginal adaptation and polymerization efficiency.

A customizable Finite Elements Model of human knee is proposed for improving inter-individual reproducibility in NSAIDs transdermal delivery measurement. The model simulates: (i) the measurement system, based on Bio-Impedance Spectroscopy, and (ii) the system under test, namely the knee by five parallel, homogeneous, and concentric layers: bone, muscle, adipose tissue, wet skin, and dry skin. In this paper, first the equations and the architecture of the model are described. Then, the results of the numerical characterization and the preliminary experimental validation are reported. A sensitivity analysis was realized for reducing computational burden during Model customization. Only five parameters out of the 64 used in the Cole-Cole equation were sufficient for fitting experimental data of different subjects.

The concept, the whole system design, along with the hardware and software realization of an on-chip transducer, for real-time noninvasive monitoring of insulin absorption, namely the Insulin Meter, are described in the fifth chapter.

The book presents an innovative technology based on injection of a very weak current to trace the quantity of a drug carried immediately after the administration. The book makes the reader familiar with the technology, from the conception through the design of the instrument, up to the preliminary clinical applications. In the first chapter, the method of transdermal drug delivery and the use of impedance spectroscopy in the dermatological field are presented. The second chapter describes a screening measurement campaign aimed at proving the feasibility of the assessment method and identifying the bandwidth of interest. The prototyping, validation and characterization of an instrument to measure the amount of drug delivered (DUSM: Drug Under Skin Meter) are presented in chapter three. In the fourth chapter three experimental campaigns, based on the electrical analysis of the biological tissue behavior due to the drug delivery, are reported: (i) laboratory emulation on eggplants, (ii) ex-vivo tests on pig ears, and finally (iii) in-vivo tests on human volunteers. In the fifth chapter a behavioral model, based on Finite Elements and Partial Differential Equation, of an impedance-based measurement system for assessing the drug released under the skin, during transdermal delivering, is proposed. The last chapter is dedicated to present a campaign in order to prove the suitability for insulin therapy applications. This book is intended for biomedical engineers, biomedical engineering students, operators working in the field of biomedical instrumentation, biotechnologists, and technicians of transdermal vehiculation.