Interfacial Assembly and Jamming of Polyelectrolyte Surfactants: A Simple Route To Print Liquids in Low-Viscosity Solution.

Nanoparticle surfactants (NPSs) assembled at the oil-water interface can significantly lower the interfacial tension and be used to structure liquids. However, to realize the three-dimensional printing of one liquid in another, high-viscosity liquids, for example, silicone oil, have been generally used. Here, we present a simple, low-cost approach to print water in low-viscosity toluene by using a new type of polyelectrolyte surfactant, sodium carboxymethyl cellulose surfactant (CMCS), that forms and assembles at the oil-water interface. The interfacial activity of CMCSs can be enhanced by tuning parameters, such as pH and concentration, and the incorporation of a rigid ligand affords excellent mechanical strength to the resultant assemblies. With CMCS jammed at the interface, liquids can be easily printed or molded to the desired shapes, with biocompatible walls that can be used to encapsulate and adsorb active materials. This study opens a new pathway to generate complex, all-liquid devices with a myriad of potential applications in biology, catalysis, and chemical separation.