Chemical Engineering Journal, Vol.147, No.2-3, 373-382, 2009
Liquid marble formation using hydrophobic powders
This work aims to investigate and quantitatively measure "liquid marble" phenomena using hydrophobic powders (granules). The hydrophobic powders based on a copper substrate were prepared by a silver deposition technique of particle sizes 9 mu m, 20 mu m and 320 mu m and of contact angle with water approaching 160 degrees. The hydrophobic powder poly-methylmethacralate (PMMA) particle size 42 mu m and contact angle of 120 degrees was also used to determine the effect of powder density on liquid marble stability. The experimental investigations indicated that for successful formation of liquid marbles a number of variables in addition to hydrophobicity need to be considered, namely: powder density; powder particle size; powder shape: liquid marble formation technique. It was found that liquid marbles were formed using all four powders to varying extents, with a low powder particle size forming more stable liquid marbles. In a series of gravimetric tests, adhered powder mass on liquid marbles was found to be directly proportional to the water droplet surface area. A more complete coverage of the water drops were found with PMMA powder than the hydrophobic granules. Moreover, a further procedure was developed to increase the mechanical strength of the liquid marble, by polymerising methylmethacrylate (MMA) on the surface of a PMMA powder - liquid marble, with the aim of maintaining water within a more robust PMMA liquid marble shell. This technique may prove to be a novel way of encapsulating drug compounds, such as gentamicin sulphate, for PMMA bone cement. (C) 2008 Elsevier B.V. All rights reserved.