Study of the evaporation of colloidal suspension droplets with the quartz crystal microbalance.

In this Article, we report the application of the quartz crystal microbalance (QCM) to study the evaporation of colloidal suspension droplets. Droplets of alumina particle suspensions with varying particle size and solid concentration have been investigated. Characteristic responses of the resonance frequency of the QCM associated with the different evaporation stages have been established. Quantitative analysis of the experimental results has been performed by the proposed QCM models. An interesting finding is that frequency increase after complete drying has been observed in some cases. Interpretation of the frequency increase has been developed in terms of the contact stiffness. The possible physical mechanisms are also discussed and quantified in terms of various interparticle forces.