Control of heteropolymeric to oligomeric character in electrospray deposited melanin films

Abstract

The physicochemical\ud properties of eumelanin thin films realized by spray and electrospray deposition methods were investigated. We find a consistent improvement above the film quality reached from liquid solution, minimizing the detrimental effect of the solvent in the final morphology of the films. Furthermore a clear trend towards specific aggregation modalities made us able to significantly unveil some of the cumbersome physical mechanisms at the basis of the various properties that are often invoked for this important functional biomaterial. In particular, temperature dependent electrical resistance evidenced a semiconductor-like character, with peculiar features of melanin organization explicated through crosslinked secondary structure as emerged from many observations obtained by different spectroscopic and microscopic techniques. © 2016 Society of Chemical Industr

Obtaining Thickness-Limited Electrospray Deposition for 3D Coating

“…Namely, there exist a large set of conditions that would mitigate SLS effects by favoring either charged melt or electrowetting spray. Many sprays are either (1) of conductive materials, ,,,,, (2) conducted in a wet regime, ,, (3) conducted at low flow rate or solids loading, ,,,,,, (4) conducted above the softening temperature of the sprayed material, ,,, or (5) performed in a regime of slow cross-linking/solidification. ,, Returning to the result of Altmann et al, spray of hydrophilic polymers from mixtures of isopropyl alcohol and water, even at very low solid loadings, would be expected to occur as an electrowetting or charged melt spray, especially at early times. This is, in fact, the result we obtained when we attempted to repeat one of the demonstrations reported in their publication, although evidence of self-limiting at longer times was obtained similar to PS sprayed at 70 °C, but at a thickness >1 μm (Figure S4).…”