Collaborative Research: Self-Limiting Electrospray Deposition of Nanowire-Particle Composites for Advanced Coatings

One-dimensional nanostructures, such as nanorods, nanowires, and their assemblies, have numerous applications in surface modification for advanced mechanical, optical, or bioactive functions. However, established techniques for manufacturing these nanomaterials and their deposition as coatings are limited to small scales and often flat surfaces due to cost, throughput, or complexity.

This grant supports fundamental research to provide needed knowledge for manufacturing multifunctional nanomaterial and composite conformal coatings at scale. The development of new manufacturing processes based on electrostatically-induced sprays of waterborne gelling polymers enables the mass production of nanowire coatings on versatile surfaces with complex shapes and three-dimensional features, which can be widely used in energy storage, tissue engineering, smart textiles, and water/air filtration.

Simultaneously, the gained understanding can be translated into additional materials systems and new applications, which benefit the U.S. economy and prosperity. The broader impacts activities contribute to the research education pipeline and workforce development to secure U.S. global leadership in materials manufacturing by training students and research fellows at various levels and engaging with the broader scientific community and the general public through outreach.

Electrospray deposition has shown great promise for manufacturing polymeric nanostructures. Typical morphologies of electrospray deposits are hierarchical assemblies of nanoparticles and overlaid in-plane nanofiber mats if droplet breakup is suppressed (i.e., electrospinning). The goal of this project is to enable electrospray deposition of aqueous methylcellulose solutions to produce polymer and polymer-nanoparticle composite nanowires with well-controlled dimensions on a drop-by-drop basis.

This research fills the knowledge gap on the interplay between self-assembly and morphology development in multiphase droplets generated in the sprays. The research team integrates advanced experimental techniques, including X-ray characterization, microscopy, and laser strobe imaging, with mesoscale multiphysical modeling to determine the physical mechanisms of dropwise nanowire formation and deposition.

New dissipative particle dynamics simulations elucidate the self-assembly dynamics of methylcellulose in nonequilibrium conditions and predict the electrohydrodynamic deformation of composite droplets. The effects of particle-polymer interaction, particle entropy, and spatial confinement are explored for controlling filler distribution and functional properties of the composite wires.

The team extends the study to other materials to demonstrate the generality of nanowire formation in electrospray by rapid, homogeneous viscosity transition in the droplets. Through collaborative experimental and modeling efforts, this research advances the understanding of the electrospray of complex fluids and provides a foundation for scalable manufacturing of nanowire composites and their superstructures.

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.