Floating mechanism of a small liquid marble

Abstract

Flotation of small solid objects and liquid droplets on water is critical to natural and industrial activities. This paper reports the floating mechanism of liquid marbles, or liquid droplets coated with hydrophobic microparticles. We used X-ray computed tomography (XCT) to acquire cross-sectional images of the floating liquid marble and interface between the different phases. We then analysed the shape of the liquid marble and the angles at the three-phase contact line (TPCL). We found that the small floating liquid marbles follow the mechanism governing the flotation of solid objects in terms of surface tension forces. However, the contact angles formed and deformation of the liquid marble resemble that of a sessile liquid droplet on a thin, elastic solid. For small liquid marbles, the contact angle varies with volume due to the deformability of the interface.

Measuring the Coefficient of Friction of a Small Floating Liquid Marble

“…The effective marble density can be found by dividing the average mass by the volume. As the floating marble has a small submerged volume and most of its weight is supported by the surface tension of the carrying liquid15, the change in the density of the carrier liquid has a negligible effect on the floating position.…”

“…The meniscus angle can hence be calculated if the contact angle and surface inclination at the TPCL are known. For a floating marble, the apparent contact angle changes due to the deformation of the marble itself15. In this paper, the deformation of the floating marble is negligible due to the small volume used.…”

“…Since this depth is a function of ψ for a known volume, β should be a function of ψ as well. For a small floating liquid marble, the buoyancy force F b is small compared to the surface tension force F C ( y ) 15. Neglecting F b in (10), Equation (11) can be simplified as:…”

“…A liquid marble is a liquid droplet coated with hydrophobic powder, which can roll on a solid surface12345 and float on a liquid surface due to its non-wetting coating678910111213141516. A liquid marble can be driven across a liquid surface using thermocapillarity1718.…”

Non-wetting drops at liquid interfaces: from liquid marbles to Leidenfrost drops

“…Despite the importance of liquid marbles generally, previous analysis of floating liquid marbles has been primarily qualitative [18,11]. Quantitative measurements on the dimensions of such drops have only been reported recently by Ooi et al [30,29]; this data has yet to be explained. In this paper we seek to shed light on the manner in which a non-wetting (or very close to nonwetting) droplet floats at a liquid interface.…”