Droplet-Assisted Deposition Aerosol and Inkjet

Conventional spray coating, where a sol-gel solution is atomized in relatively small droplets before being impacted on the substrate surface, is considered the 

The generation of droplets of controlled size is technologically easy today and uses either thermal or piezoelectric ejection process for conventional inks. The development of inkjet printing for the controlled deposition of functional materials is very interesting because it allows a cheap and infinitely modulable top-down synthetic method for designing the siuface of substrates or for building midtilayer 2D and 3D materials [73,74]. Its development for sol-gel inks is fairly recent, as it was reported at the end of the 1990s [75]. This first work, aimed at 

1) Similarly to usual inks, sol-gel inks must follow strict physicochemical properties of surface tensions and viscosities whose limits are fixed by different nozzle dimensions and fluid velocity. The example given for a DOD nozzle of diameter r = 60pm in Ref. [76] shows that for a controlled ejection of solution droplets (considered Newtonian liquids), the ratio RelWe must have a value between 1 and 10 (Re and We being, respectively, Reynolds and Weber numbers)  

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