Abstract
Transport of dry solid particles to a liquid is relevant to a number of emerging applications, including ‘liquid marbles’. We report experiments where the transport of dry particles to a pendent water droplet is driven by an external electric field. Both hydrophilic and hydrophobic materials (silica, PMMA) were studied. For silica particles (hydrophilic, poorly conductive), a critical applied voltage initiated transfer, in the form of a rapid ‘avalanche’ of a large number of particles. The particle-loaded drop then detached, producing a metastable spherical agglomerate. Pure PMMA particles did not display this ‘avalanche’ behaviour, and when added to silica particles, appeared to cause aggregation and change the nature of the transfer mechanism. This paper is largely devoted to the avalanche process, in which deformation of the drop and radial compaction of the particle bed due to the electric field are thought to have played a central role. Since no direct contact is required between the bed and the drop, we hope to produce liquid marble-type aggregates with layered structures incorporating hydrophilic particles, which has not previously been possible.
Highlights
The second source of interest was the resemblance of the resulting metastable agglomerate to the ‘liquid marbles’ – liquid drops encased in a shell of non-wetting particles – first observed over a decade ago [2], which have remarkable properties and a variety of current and potential applications [3,4]
Unlike these ‘traditional’ liquid marbles, our agglomerates consisted of a water droplet entirely filled with hydrophilic particles – a configuration which cannot be achieved using the conventional marble formation method of rolling the drop on a particle bed
Our electrostatic process raises the prospect of a new class of liquid marble complexes with layered structures, for a variety of new applications
Summary
The second source of interest was the resemblance of the resulting metastable agglomerate to the ‘liquid marbles’ – liquid drops encased in a shell of non-wetting particles – first observed over a decade ago [2], which have remarkable properties and a variety of current and potential applications [3,4]. Unlike these ‘traditional’ liquid marbles, our agglomerates consisted of a water droplet entirely filled with hydrophilic particles – a configuration which cannot be achieved using the conventional marble formation method of rolling the drop on a particle bed (as the drop soaks in).
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