Changes of meniscus shapes and capillary rise heights under hypergravity

Abstract

We investigate meniscus shapes and capillary rise heights in glass capillaries with rectangular cross sections (4 × 0.2 mm), which we modified with established coatings to generate a range of surfaces that interact differently with water. Meniscus positions and shapes are imaged while the capillaries are rotated horizontally about their longitudinal axis in order to generate centrifugal forces opposing the capillary driven fluid propagation, i.e. volumetric forces. Changing the rotational speed allows us to balance both forces thereby bringing capillary rise to a stop. In brief, we find very good agreement of the different meniscus shapes we observe over a wide range of centrifugal accelerations (up to 191 g) with two independent simulations of the scenario. In addition, we are able to precisely measure capillary rise heights in differently modified capillaries over a range of centrifugal accelerations and correlate these values. Lastly, we mention how this system will prove useful to investigate wetting phenomena on swellable surfaces, i.e. surfaces whose properties dynamically change upon fluid contact, by providing precise control over the propagation speed of the three phase contact line.