Modeling, Fabrication and Integration of Wearable Smart Sensors in a Monitoring Platform for Diabetic Patients

Abstract

The monitoring of some parameters, such as pressure loads, temperature, and glucose level in sweat on the plantar surface, is one of the most promising approaches for evaluating the health state of the diabetic foot and for preventing the onset of inflammatory events later degenerating in ulcerative lesions. This work presents the results of sensors microfabrication, experimental characterization and FEA-based thermal analysis of a 3D foot-insole model, aimed to advance in the development of a fully custom smart multisensory hardware–software monitoring platform for the diabetic foot. In this system, the simultaneous detection of temperature-, pressure- and sweat-based glucose level by means of full custom microfabricated sensors distributed on eight reading points of a smart insole will be possible, and the unit for data acquisition and wireless transmission will be fully integrated into the platform. Finite element analysis simulations, based on an accurate bioheat transfer model of the metabolic response of the foot tissue, demonstrated that subcutaneous inflamed lesions located up to the muscle layer, and ischemic damage located not below the reticular/fat layer, can be successfully detected. The microfabrication processes and preliminary results of functional characterization of flexible piezoelectric pressure sensors and glucose sensors are presented. Full custom pressure sensors generate an electric charge in the range 0–20 pC, proportional to the applied load in the range 0–4 N, with a figure of merit of 4.7 ± 1 GPa. The disposable glucose sensors exhibit a 0–6 mM (0–108 mg/dL) glucose concentration optimized linear response (for sweat-sensing), with a LOD of 3.27 µM (0.058 mg/dL) and a sensitivity of 21 µA/mM cm2 in the PBS solution. The technical prerequisites and experimental sensing performances were assessed, as preliminary step before future integration into a second prototype, based on a full custom smart insole with enhanced sensing functionalities.

Artificial Intelligence Methodologies Applied to Technologies for Screening, Diagnosis and Care of the Diabetic Foot: A Narrative Review

“…It is worth noting that some studies already moved in the direction of integrating different sensors for diabetic foot monitoring. Specifically, some recent studies the proposed integration of temperature and pressure sensing, plus, possibly, glucose levels in sweat [ 90 , 91 ]. However, as stated above, skin resistance and humidity sensors should be integrated; we suggest that there should be at least two resistance sensors for each foot, one possibly placed between the second and third metatarsal head regions, and one between the lateral and medial heel regions, whereas at least one humidity sensor per foot should be used, possibly placed between the lateral and medial midfoot regions.…”

Screen-Printed Textile-Based Electrochemical Biosensor for Noninvasive Monitoring of Glucose in Sweat

“…Several reports show a consistent correlation between sweat and blood glucose levels [17][18][19]. In addition, sweat glucose sensors offer an easy and noninvasive method [20]. Hence, sweat can be used as an alternative body fluid for noninvasive glucose detection.…”

Estimation of loads for off-grid solar photovoltaic systems

“…The renewable power inverter's input capacity must always be more than the hardware's total energy a nominal voltage of the solar power inverter and the battery must be the same [16]. The solar power inverter for stand-alone systems must be capable of handling the whole quantity of Watts you will be using at any given moment [17].…”