Influence of the relative humidity on the morphology of inkjet printed spots of IgG on a non-porous substrate.

Mujawar, L.H.; Kuerten, J.G.M.; Siregar, D.P.; Amerongen, A. van; Norde, W.


During the drying of inkjet printed droplets, the solute particles (IgG-Alexa-635 molecules) in the drop may distribute unevenly on the substrate, resulting in a “coffee-stain” spot morphology. In our study, we investigated the influence of the relative humidity on the distribution of inkjet printed fluorophore labeled IgG molecules on a polystyrene substrate. A theoretical model for an evaporating droplet was developed in order to predict the changes in the spot diameter, height and volume of a drying droplet. An experiment was performed where a sessile droplet was monitored using a CCD camera installed on a goniometer and good agreement was found between the experimental results and simulation data. We also compared the predicted morphology for an inkjet-printed microarray spot with the experimental results where IgG molecules were printed for various relative humidities. The spot morphology of the dried spots was analyzed by a confocal laser microscopy. At a lower relative humidity (i.e.,