Passive QCM sensor system for monitoring of water absorption and drying in Nafion® polymer membranes

This work deals with the development of a Passive Quartz Crystal Microbalance (QCM) Sensor system for liquid environment to follow the water uptake and drying characteristics of Nafion® polymer membranes. An automated system for the electro-acoustic characterization of a quartz crystal resonator using an impedance analyzer was designed and implemented. The developed system allows carrying out in situ and real time measurements of the equivalent circuit and resonance frequency of the resonator in highly damping media where QCM oscillator sensors (active way sensors) present operation problems with low resonator quality factors. The sensor was used to observe the hydrate and drying properties of Nafion® polymer membranes. Also, a study of noise and resolution of the sensor was carried out. 9MHz commercial quartz crystals provided by Maxtek were used, with a deposition area of 0.2 cm². A resolution of 25 ng / cm² was obtained.