Critical Meniscus Height of Liquids at the Circular Edge of Cylindrical Rods and Disks

In this study, we examined the maximum meniscus height of liquids at the top edge of vertically oriented rods and disks. Poly(tetrafluoroethylene) (PTFE) and polycarbonate (PC) rods (and disks) were placed in clear containers, and then water or ethylene glycol was slowly added. Liquid rose along the sides of the rods before forming a meniscus around the top edge. The maximum meniscus height was measured at the critical juncture just before liquid engulfed the top of the rod. In each case, the critical meniscus height increased with the rod diameter. With greater surface tension and lesser density, water showed larger menisci for a given material and rod diameter than ethylene glycol. The wettability of the rods strongly influenced the meniscus height. The more lyophobic PTFE rods showed taller menisci than the PC rods for both liquids. A simple analytical expression allowed accurate estimation of the meniscus height from the rod diameter and the inherent material properties of the liquid and solid.