Nanoparticle surfactants and structured liquids

Abstract

Materials are usually classified as solids or liquids, based on their structural stability, dynamic response, and rheological properties. Structured liquid, a new state of matter, has attracted much attention in recent years. Different with either solid or liquid, structured liquid combines the desirable characteristics of fluids with the structural stability of a solid, showing a myriad of potential applications in encapsulation, biphasic reactors, and programmable liquid constructs. Here, a brief review is given, by introducing a new strategy to structure liquids based on the formation, assembly, and jamming of nanoparticle surfactants (NPSs) at liquid-liquid interfaces. The interfacial packing of the NPSs can be effectively manipulated using external triggers, endowing the structured liquids with adaptiveness and responsiveness to changes in their external environment.

Layer‐by‐Layer Engineered All‐Liquid Microfluidic Chips for Enzyme Immobilization

“…The thermodynamic driving force to reduce interfacial area jams the NPSs, generating an elastic layer that locks in the shape of the microchannel in a highly nonequilibrium state. [ 24,25 ] In comparison to solid microfluidic chips, the flexible nature of the microchannel, as well as the surrounding liquid environment, are more like an in vivo environment, affording an ideal platform to mimic biomimetic systems. [ 26,27 ]…”

Responsive Interfacial Assemblies Based on Charge‐Transfer Interactions

“…With surfactants assembled at the interface, one liquid can be dispersed in another immiscible liquid to form emulsion droplets, which typically take spherical shapes to decrease the interfacial area and, therefore, to reduce the interfacial energy [5–8] . Recently, by using the electrostatic interactions or host–guest interactions between nanoparticles (NPs) dispersed in aqueous phase and polymeric/oligomeric ligands dissolved in oil phase to form nanoparticle surfactants (NPSs) at the oil–water interface, an alternate strategy is put forward to stabilize the oil–water interface [9–12] . Due to the self‐regulated number of ligands anchored to the NPs, the binding energy of the NPs can be significantly enhanced to withstand the compressive force exerted on the particles when the interfacial area decreases, allowing the stabilization of liquids in nonequilibrium shapes, i.e., structuring liquids [13–15] .…”

Gated Molecular Diffusion at Liquid–Liquid Interfaces

“…Nanoparticle surfactants (NPSs) provide an alternative strategy to construct interfacial NP assemblies by dispersing NPs in one liquid and dissolving functionalized polymer ligands in a second liquid immiscible with the first [21, 22] . Unlike polymer‐capped NPs where NPs are fully covered with polymer ligands, [23] “Janus‐like” NPSs form in situ at the interface by the electrostatic interactions between NPs and polymer ligands, assemble into a monolayer and, when jammed, generate a robust assembly with exceptional mechanical properties [24–26] .…”

“…[14][15][16][17][18][19][20] Nanoparticle surfactants (NPSs) provide an alternative strategy to construct interfacial NP assemblies by dispersing NPs in one liquid and dissolving functionalized polymer ligands in a second liquid immiscible with the first. [21,22] Unlike polymer-capped NPs where NPs are fully covered with polymer ligands, [23] "Janus-like" NPSs form in situ at the interface by the electrostatic interactions between NPs and polymer ligands, assemble into a monolayer and, when jammed, generate a robust assembly with exceptional mechanical properties. [24][25][26] By taking advantage of the interfacial jamming of NPSs, liquids can be sculpted into complex shapes using all-liquid moulding and 3D printing, [27,28] showing tremendous potentials for all-liquid microfluidics, biphasic micro-reactors and chemical separation systems.…”