Porous liquid marble shell offers possibilities for gas detection and gas reactions

The hydrophobic shell of a liquid marble prevents direct contact of the liquid core of the marble with any condensed phases (i.e. solid or liquid) outside the marble, but allows gas and vapour to diffuse across the shell. This property of a liquid marble naturally enables it to discriminately absorb or emit gaseous and vaporous compounds across its shell while denying contact or transport of liquids. Liquid marbles can, therefore, be used to form micro-gas reactors for gas detection application when loaded with an indicator solution. Liquid marble can also be used as a gas emitter; the relatively thin liquid marble shell enables the gas dissolved in the liquid marble core to be emitted to the supporting surface from a very close range, making it possible to carry out chemical sensing using the emitted gas as an indicator. In this study we show the potential of liquid marbles as gas sensors in different arrangements, i.e. with dissolved indicator in the liquid core to sense gases diffusing into the liquid marble from outside, or with soluble gas in the liquid core that is emitted out of the liquid marble where it is sensed (or used to indicate chemical species outside of the liquid marble). An important implication of this study is that other types of superhydrophobic surfaces may also be used to design sensors for sensing gases and vapours, or to use emitted gases and vapours as indicators for chemical sensing.