Liquid materials with shape reconfigurability can open a pathway for fabricating smart all-liquid constructs with tremendous potential applications. Creating such materials usually relies on controllable jamming/assembly of nanoparticle surfactants at liquid/liquid interfaces. Here we show that lignin nanoparticles (LNPs), one kind of well-established green Pickering emulsifier, can act as a simplified alternative to nanoparticle surfactants for regulating liquid morphologies. Owing to their good dispersibility in water and inherent high binding energy and strong associations at the soybean oil/water interface, the LNPs can generate jammed, highly elastic interfacial films that enable them to lock both the oil and water droplets into largely distorted, nonequilibrium geometries at pH >4. They will undergo agglomeration and lose their liquid structuring capacity with their interfacial binding energy and mechanical strength strongly decreased at lower pH values, thus allowing reversibly reconfiguring liquid shapes via adjusting the pH of the aqueous phase.
Tian et al. (Tue,) studied this question.