Bioactive Self-Limiting Electrospray for Efficient Additive Manufacturing

Electrospray deposition is a spray coating process that utilizes a high voltage to atomize a flowing solution into charged microdroplets. These self-repulsive droplets evaporate as they travel to a target grounded substrate, depositing the solution solids. In self-limiting electrospray deposition (SLED), specific manipulation of the electrostatic repulsion, hydrodynamic forces, and evaporation kinetics can be employed to conformally cover 3D architectures or targeted microscale electrodes with microcoatings. The generated coatings are hierarchical, possessing either nanoshell or nanowire microstructure. For these reasons, SLED is a spray method that is highly compatible with 3D printing due to its ability to coat re-entrant and shadowed features and also with microelectronic pattering, since it removes masking requirements and the associated processing steps. Here we demonstrate that SLED can also be a highly efficient tool for the additive manufacturing of bioactive coatings for passive medical devices or tissue models, including SLED inks that incorporate proteins, biocompatible polymers, bioactive small molecules and DNA vaccines. While many studies have presumed high efficiency in electrospray deposition, this is rarely quantified. By architecting the local charge landscape can lead to SLED coatings approaching 100% deposition efficiency can be achieved, delivering designer payloads to complex surfaces. We further explore the direct integration of SLED into 3D printing to create a combined spray-print paradigm that allows for the coating functionality to be embedded directly into formed components. Both the post-processing and spray-print approaches of SLED separates the nanostructured and functional aspects from the print material. This allows for the print ink to be optimized for the structural demands of a given application, while the functional requirements can instead be programmed into the SLED ink. This shifts the formulation burden away from the 3D print material and allows for a relaxed optimization requirement.