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Abstract To increase the connectivity of the molecular structure but not to prevent softening, small amounts of tetraethoxysilane (TEOS) were added to phenyl‐substituted melting gels. The limit of the additions was determined when the melting gel lost its ability to soften. A comparison was made between TEOS diluted with ethanol, TEOS diluted with methanol, and tetramethoxysilane (TMOS) diluted with methanol. The additions had slight effects on the glass transition behavior, the gelling time and the indentation hardness. The role of the TEOS was both a form of dilution and a cross‐linking promoter. 

Electrospray deposition (ESD) uses strong electric fields to produce generations of monodisperse droplets from solutions and dispersions that are driven toward grounded substrates. When soft materials are delivered, the behavior of the growing film depends on the film’s ability to dissipate charge, which is strongly tied to its mobility for dielectric materials. Accordingly, there exist three regimes of electrospray: electrowetting, charged melt, and self-limiting. In the self-limiting regime, it has been recently shown that the targeted nature of these sprays allows for corona-free 3D coating. While ESD patterning on the micron-scale has been studied for decades, most typically through the use of insulating masks, there has been no comparative study of this phenomenon across spray regimes. Here, we used test-patterns composed of gratings that range in both feature size (30–240 μm) and spacing (⅓x–9x) to compare materials across regimes. The sprayed patterns were scanned using a profilometer, and the density, average height, and specificity were extracted. From these results, it was demonstrated that material deposited in the self-limiting regime showed the highest uniformity and specificity on small features as compared to electrowetting and charged melt sprays. Self-limiting electrospray deposition is, therefore, the best suited for modification of prefabricated electrode patterns. 

Melting gels are a class of hybrid organic-inorganic silica based gels prepared via the sol-gel process that are solid below their glass transition temperatures, near room temperature, but show thermoplastic behavior when heated. While this phase change can be repeated multiple times, heating the gel past its consolidation temperatures, typically above 130 oC initiates an irreversible reaction that produces highly crosslinked glassy organic-inorganic materials via hydrolysis and poly-condensation. This ability makes melting gels uniquely compatible with processing techniques inaccessible to other sol-gels. By properly tuning their properties, it should be possible to create protective coatings for electronics and anti-corrosive coatings for metals that are highly hydrophobic and insulating. However, melting gel consolidation reactions are highly dependent on charge interactions, raising the question of how these materials will respond to a processing technique, like electrospray deposition (ESD), which is dependent on charge delivery. In this study, we focus on the role that substrate temperature and charge polarity play on film morphology, consolidation chemistry, and surface properties. Optical images, film thickness measurements, nanoindentation, and FTIR were used to characterize the sprayed melting gel with the goal of developing a robust processing space for producing highly cross linked, hydrophobic, dielectric coatings.