Electrospray Deposition of Polymeric Materials: Who's in Charge?

In electrospray deposition (ESD), a liquid suspension composed of a solute material in a volatile solvent is atomized into a plume of electrically charged droplets under the influence of a strong electric field. These droplets undergo rapid solvent evaporation, resulting in a spray of solute material that is deposited onto a target surface, forming a thin film. The solute can be deposited in either a dry or partially wet state, each offering unique microstructural properties and functional characteristics. ESD is dominated by the accumulation, transport, and decay of electric charge that is inherent to this process, which significantly influences the growth, evolution, and hierarchical structure of the deposited film. In this presentation, I will discuss the application of ESD for deploying polymeric materials, with a particular focus on the role of electric charge in the deposition process. The charge-driven nature of ESD allows for the precise targeting of fine features and enables the creation of fully conformal coatings. Material deployed by ESD will preferentially deposit onto conductors, providing a means to selectively deliver solute to the conductive portion of a multi-material surface. We have recently explored how the ESD processing conditions and target substrate characteristics govern this preferentiality. Although depositing material onto insulating surfaces poses challenges, these can be overcome by modifying the charge landscape surrounding the target. We are exploring the use of ESD in electronics manufacturing and packaging to reduce costs and enhance reliability. Additionally, our team has employed ESD in an unconventional manner to deliver colloids to a fluid interface to investigate interfacial transport in evaporating sessile droplets. These experiments provide further insight into the important role of charge in the ESD process.