Spontaneous self-coating of a water drop by flaky copper powders: Critical role of the particle shape

Cheng Chung Chang, Cyuan Jhang Wu, Yu Jane Sheng, Heng Kwong Tsao

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The self-coating process of solid particles over a liquid drop is important for the formation of a liquid marble. Generally, some external forces such as rolling or flipping are used to cover a drop by small particles. In this work, it is observed that flaky copper powders can spontaneously spread over the planar water surface and form a dense flat cluster with a fractal dimension of 2. Moreover, flaky copper powders can cover the water pendant and sessile drops spontaneously and rapidly. This powder-coated drop can roll on an inclined plane at a relatively high speed. However, spontaneous self-coating disappears for spheroidal copper powders. To explain our observations, the shape factors of particles are introduced into the spreading coefficient S for powders on the liquid surface. The flaky powders have the lowest shape factors and therefore spontaneous self-coating formation, with S > 0.

Original languageEnglish
Pages (from-to)4469-4475
Number of pages7
JournalSoft Matter
Volume11
Issue number22
DOIs
StatePublished - 14 Jun 2015

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