Wearable electrical sensors based on zeolite can be used for breath monitoring. The high silicon content of clinoptilolite makes this type of zeolite as very adequate for fabricating sensitive water sensors. In addition to sensitivity also response fastness represents a sensor characteristic of fundamental importance for breath monitoring. Here, the response fastness of a clinoptilolite-based water sensor has been evaluated by measuring the current intensity behavior upon exposition to a constant humidity atmosphere (75% moisture). In particular, the clinoptilolite surface has been biased with a sinusoidal signal (20 Vpp, 5 kHz) and the true-RMS current intensity value has been recorded during exposition to a constant humidity atmosphere. Since current intensity is proportional to the adsorbed water concentration (only hydrated cations are charge carriers) a kinetic analysis has been possible. The clinoptilolite dehydration kinetics in a dry atmosphere has been evaluated too. According to this kinetic analysis water adsorption is described by a Lagergren pseudo-first-order model with a rate constant of (58.6 ± 0.9)·10-4 min-1, while desorption in dry air follows a first-order kinetic model with a specific rate of 202.7 ± 0.3)·10-4min-1 at 25°C.
Zeolite-Based Fast-Responding Sensors for Respiratory Rate Monitoring
2019
Abstract
Wearable electrical sensors based on zeolite can be used for breath monitoring. The high silicon content of clinoptilolite makes this type of zeolite as very adequate for fabricating sensitive water sensors. In addition to sensitivity also response fastness represents a sensor characteristic of fundamental importance for breath monitoring. Here, the response fastness of a clinoptilolite-based water sensor has been evaluated by measuring the current intensity behavior upon exposition to a constant humidity atmosphere (75% moisture). In particular, the clinoptilolite surface has been biased with a sinusoidal signal (20 Vpp, 5 kHz) and the true-RMS current intensity value has been recorded during exposition to a constant humidity atmosphere. Since current intensity is proportional to the adsorbed water concentration (only hydrated cations are charge carriers) a kinetic analysis has been possible. The clinoptilolite dehydration kinetics in a dry atmosphere has been evaluated too. According to this kinetic analysis water adsorption is described by a Lagergren pseudo-first-order model with a rate constant of (58.6 ± 0.9)·10-4 min-1, while desorption in dry air follows a first-order kinetic model with a specific rate of 202.7 ± 0.3)·10-4min-1 at 25°C.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
