Ionogel Thin Films as Compatibilizing Pretreatments for Electrospray Deposition

Electrospray deposition (ESD) is a targeted coating method that is growing in relevance for applications that require micro-/nano-scaled coatings. For ESD, a surface conductive substrate is required. It has previously been reported that hydrophilic surfaces in ambient humidity satisfy this requirement. In this work, it is observed that the application of hydrophilic coatings onto hydrophobic, insulating substrates allows for sufficient dissipation of charge deposited by electrospray in the self-limiting electrospray deposition (SLED) regime, but requires around a micron of coating. This work further explores abilities of coating insulating substrates with ionogel thin films. It is shown that insulating substrates coated with ionogel film layers of >100 nm are able to produce ESD coatings of similar thickness to those produced on conductive surfaces, independent of humidity. At greater film thicknesses of around 700 nm, significantly thicker SLED coatings are observed, indicating ionogel mobility and a possibility for coating accumulation with SLED materials. With facile removal processes, including ethanol dip-treatment or 75 °C heat-treatment, ionogel thin films appear to be a sufficient pretreatment for the application of conformal sprayed coatings using SLED.