Forces Acting on a Single Particle in an Evaporating Sessile Droplet on a Hydrophilic Surface

摘要

The evaporating sessile droplet of a mono/didispersencolloid on a plate is a very useful and handy technique innmicroano/bioapplications to separate, pattern, andncontrol the particles. Although the fundamental nature ofnthe evaporation phenomena and its applications havenbeen extensively proposed, the crucial forces affecting ansingle particle motion in an evaporating droplet are notnreported yet. To elucidate the impact of various forcesnincluding the drag, electrostatic, van der Waals, andnsurface tension forces on the particle motion in suspension,nthe magnitudes of them are compared using thenscale analysis. In the early stage of the evaporation, innwhich the contact line is fixed, the motion of a singlenparticle suspended in liquid are mostly affected by dragnforce. Later, with the incidence of the contact line recession,nthe surface tension force takes over the control ofnthe single particle motion.