Structural Control at Fluidic Interfaces with Nanoparticle Surfactant Assemblies

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

This project will use synthesis, experiments, and numerical simulations to examine the dynamics of immiscible liquid drops that are encased by nanoparticles (NPs) at the interface between the drop and surrounding liquid. Encasing the drop with NPs prevents the drops from coalescing with each other, which makes this special kind of emulsion of great interest. A mixture of NPs that preferentially interact with each other will be synthesized so that they undergo a phase separation at the interface, producing drops that have patchy areas of different NPs on their interfaces. Tailoring the structure of the interface in this way will enable control over the spatial arrangement that a large collection of drops assumes when they are forced to pack closely together. This technique can be used to produce objects with distinct interconnection points and channels between adjacent drops. Such constructs would provide access to transduction pathways for the transport of charges, particulates, or chemicals from one compartment to another and would form the basis for materials with controlled optical, magnetic and transport properties. The research team will develop outreach activities for junior high and high school students in critically important areas of STEM training with hands-on participation in laboratory research. This reinforcement of foundational principles in STEM at early educational stages will help address opportunity inequities of students from underrepresented groups and will contribute to an educational pipeline for the benefit of all participants. The goal of this project is to design functionalized nanoparticles that phase separate on the interface of liquid drops in ways that promote controlled 3D arrangements of drops and, ultimately, the formation of macroscopic structures with unique properties. NPs dispersed in one liquid that are coated with ligands dissolved in a second immiscible liquid are nanoparticle surfactants with high binding energy to the interface. The project will explore using heterogeneous interfacial assemblies of functionalized NP mixtures that undergo 2D phase separation to form droplets with interfaces having distinct NP domains from which hierarchical assemblies of drops will be generated. Furthermore, NP reorganization at the liquid-liquid interface can generate inter-droplet channels as an interconnected, compartmentalized system having transduction pathways, dictated by the interactions between the ligands and the 2D phase separated morphologies, for transport, separations, and flow-through media. The project will focus on the fundamental underpinnings of functionalized nanoparticle surfactant assemblies (NSAs). Experiments will probe the synthesis of ligand-functionalized NPs for generating NSAs and the in situ characterization of the structure and dynamics of NSAs on liquid droplets. They will be accompanied by simulations that predict the phase behavior of mixed NSAs and investigation of macroscopic 3D arrays of mixed NSAs. Results from the project will open new opportunities in technologically important areas, including additive manufacturing, while providing opportunities for the professional development of researchers at the intersection of nanoscale engineering. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.