The Influence of Surface Tension on Radial Wicking in Paper

There is an increasing need to develop portable sensors that can detect the presence of multiple substances from a sample, in a short period of time. For this reason, a large amount of study has been dedicated to the development of paper-based biosensors, working on either free radial wicking of drops, or guided unidirectional diffusion, with the aid of microfluidic channels. As this process relies solely on the capillary action, which is influenced by the material properties of both fluid and substrate, a thorough understanding of the dependencies between these parameters is crucial. In this study, we analysed the radial wicking of different fluids in filter paper. The evolution of stain area in time has been quantified and the possibility of a relation between the spreading mechanism and the fluids' surface tension has been investigated.