Assessing polymer sorption kinetics using micromachined resonators

This paper introduces a new approach to investigate polymer sorption kinetics by weighing the polymer films using micromachined in-plane resonators. A custom gas-testing setup enables fast analyte concentration changes, which are necessary to study analyte diffusion into thin polymer coatings deposited on top of the microresonators. Short-term frequency stabilities of the microresonators in the 10^-8 range in air yield sub-picogram mass resolution and enable real-time measurement of analyte uptake into μm-thick films with time constants ranging from seconds to minutes. As an example, the diffusion of alcohols and aromatic hydro-carbons into poly(epichlorohydrin) and poly(isobuty-lene) films, which are of interest for chemical sensing applications, has been investigated.