Characteristics of Liquid Marbles Formed with Plasma-Treated Hydrophobic Cellulose Powder

Liquid marbles, non-stick droplets encapsulated by fine particles, were prepared with cellulose powders (CPs). Since CPs were very hydrophilic, they were treated with O2 plasma, followed by the adsorption of tetramethylcyclotetrasiloxane (TMCTS) before liquid-marble formation. Plasma treatment of CPs was carried out in a flask-rotation type reactor, which required 45 min to adsorb adequate amounts of TMCTS. In TMCTS adsorption, a successive reaction with ammonia was utilized for a secure chemisorption of TMCTS. After the adsorption, CPs became very hydrophobic. The prepared liquid marbles, water drops surrounded by TMCTS-adsorbed CP, were so robust that their compressibility exceeded 90%. A liquid marble containing 0.1-M CoCl2 aq solution was applied for an ammonia gas sensor. In the presence of a highly diluted ammonia solution (0.6%) in a desiccator, the color of the liquid marble turned from pink to blue within a few minutes.