Preparation of pH-responsive Clear Liquid Marble

Liquid marble (LM) can be prepared by the adsorption of hydrophobic powder on the gas–liquid interface of a water droplet. Generally, LM is prepared using hydrophobic powder with a size of >100 nm. LM is opaque and the inside of LMs cannot be observed because the surface powder adsorbs and scatters the visible light. In this study, a pH-responsive clear LM (CLM) is prepared using tertiary amino groups containing hydrophobic silica particles with a diameter of ∼20 nm. The shape of CLM changed under acidic conditions, because the tertiary amino groups on the silica particles became hydrophilic under these conditions. pH-responsive clear liquid marble (CLM) was prepared using tertiary amino groups containing hydrophobic silica particles with a diameter of ∼20 nm. The shape of CLM changed under acidic conditions, because the tertiary amino groups on the silica particles became hydrophilic under acidic conditions.