Chitosan and Citric Acid Thin Films as Renewable Compatibilizing Pretreatments for Self-Limiting Electrospray Deposition

Electrospray deposition (ESD) requires that the deposited charge be dissipated at a similar rate to its deposition. Here, we explore whether thin films of acetic/citric acid-doped chitosan deposited on insulating fused quartz substrates can stand in for a traditionally conductive surface. It is shown that, in humid environments, a layer of chitosan of 2 µm is sufficient to dissipate the charge deposited by electrospray in the self-limiting electrospray deposition regime, where charge is allowed to build up to form asymptotic thickness coatings. Sprays conducted in these conditions produce coatings of similar self-limiting thickness to those produced on a conductive surface. The same technique demonstrated potential for applicability to complex surfaces, such as those produced by AM or non-woven polypropylene fabric, and can be integrated into roll-to-roll continuous manufacturing. In this way, it is shown that dip coating of objects in chitosan is a surface-agnostic pretreatment for the application of conformal sprayed coatings to complex, insulating surfaces.