In electrospray printing, large electric fields are used to generate a spray of electrically charged microdroplets of a precursor suspension. Material dispersed in the suspension will be contained inside the emitted droplets. Owing to their small size, the droplets evaporate in-flight until the solvent is completely removed, leaving behind the dry solute. This dry material is delivered to a target surface where a uniform film with thicknesses of several microns is formed. Electrospray printing is low-cost, materials versatile, and does not require high/low temperatures or pressures for operation. This technology provides electric field guided deposition, in which the trajectories of the emitted particles are guided by electric field lines from the spray origin to the target surface. The field lines can wrap around complex geometries to provide conformal coatings on 3D surfaces that would otherwise be difficult or impossible to achieve with other printing technologies. Here, we report on the electrospray printing of polyimide, an important material in electronics manufacturing, medical devices, and environmental applications. The films were printed onto a variety of surfaces, including silicon chips and small diameter (~20 ��m) copper wires bonded to metallic pads. Passive electrostatic focusing is used to improve the print efficiency and produce films with thicknesses up to 20 ��m. Owing to the accumulation of charge in the growing film, the thickness is self-limiting (i.e. asymptotic). The electrospray-printed polyimide films exhibit high dielectric strength, with breakdown fields of up to 150 V/��m. The films are hydrophobic with an average contact angle of 110°, which decreases moisture penetration and improves the corrosion resistance for metallic surfaces. Using a salt immersion assay, we showed that a bonded copper wire with an electrospray-printed polyimide coated can provide 25 times better corrosion resistance compared to an uncoated wire.

Electrospray printing of polymeric films

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.