Deformation of a floating liquid marble

Abstract

A rigid spherical particle floating on a liquid is a known problem with well-defined solutions. Under the combined effect of gravity and surface tension, the rigid particle deforms the liquid surface. However, in the case of a floating soft particle such as a liquid marble, not only the liquid surface but also the particle itself deforms. In this paper, we investigate the deformation of a floating liquid marble and characterise its height as well as aspect ratio. The experimental results show that theoretical models for a rigid spherical particle suit well for small liquid marbles. Larger marbles require an oblate liquid spheroid model. We will discuss the limitations of the two models and characterise the deformation of these marbles.

Measuring the Coefficient of Friction of a Small Floating Liquid Marble

“…where h ( r, ψ ) is the height of the meniscus, measured vertically from the TPCL to the free liquid surface sufficiently far away from the marble; h is a function of r and ψ , and can be solved using methods described in our previous work12.…”

“…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.…”

“…The measurement of these two parameters for a solid spherical particle is relatively straightforward. However, a floating liquid marble deforms, and its meniscus angle does not necessarily depend on the apparent contact angle12. Furthermore, the radius of the TPCL varies with the marble volume.…”

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

“…For relatively non-wetting droplets, some analytical progress is possible when the droplet may be approximated as two spherical caps [33]. In other circumstances, particularly for larger drops, numerical techniques are again used [17] though some understanding may be obtained by modelling the drop as two halves of an oblate spheroid [30]. Mahadevan et al [21] also presented a detailed study of the (low gravity) behaviour of a compound drop sitting on a rigid substrate: here four phases frequently meet at a single point.…”

“…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.…”