Electrospray deposition as an efficient alternative to coat medical devices

Electrospray deposition (ESD) is a common thin film coating technique that can produced charged droplets at the micro- and nano-scale capable of being used in medicine, such as for drug delivery purposes and medical implants. In ESD, an electrostatic force is applied to a solution, which then disperses charged droplets loaded with the materials to be deposited. Our lab has categorized various modes of ESD, including self-limiting electrospray deposition (SLED). In SLED, the material arrives onto a target as a dried spray, carrying a charge that eventually begins to repel itself over time. The charged spray is redirected to regions that are uncoated such that manipulation of the electrostatic repulsion, hydrodynamic forces, and evaporation kinetics can be employed to conformally cover 3D architectures with micro-coatings. The generated coatings are hierarchical, possessing either nano-shell, nanoparticle, or nanowire microstructure, which can be smoothed through further post processing. We envision SLED as being a replacement for dip or conventional-spray coating, where its greatest advantage would be the potential for much higher materials utilization. While many studies have presumed high efficiency in ESD, this is rarely quantified. Here, I will show how architecting the local charge landscape can lead to SLED coatings approaching 100% deposition efficiency on microneedle arrays and other complex substrates of relevant therapeutics and model materials, including biocompatible polymers, DNA vaccines, and bioactive small molecules.