In this work the deposition of particles onto the surface of a textile-type fiber was investigated using a novel experimental system in which thin, bare monofilaments are used as light guides. This method was previously developed as a tool for investigating the deposition of oil droplets from an emulsion, the extent of deposition being measured via changes in the attenuation of light transmitted down the fiber. The present system studies the deposition and subsequent evaporation of a droplet of an aqueous suspension containing 1.9 μm tracer particles. The dynamics of the evaporation of such a droplet from a flat surface are known to involve a build up of deposited particles at the drop periphery to form a ring stain, the rate of deposition increasing during the evaporation process due to a diverging flux. In this report the deposition characteristics on a flat surface are confirmed and a systematic sequence of experiments for the evaporation of droplets of suspensions containing tracer particles from a polyester fiber surface is reported. The experiments use both video-microscopy and the change in attenuation along the fiber caused by droplet deposition which is related to the wetted area. An initial loss is followed by a period where only a slow change in attenuation occurs and finally by a rapid and large change as the droplet completes its evaporation and a large number of particles are deposited. The relationship between the initial loss and wetted area and the final loss and total number of particles deposited is discussed.
- contact angle