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Tin-doped indium oxide (ITO) nanoparticle (NP) films were fabricated as a cost-effective and highly transparent electrode for high-performance thin film heaters (TFHs), using a solution coating process on glass substrate. The electrical and optical properties of the ITO NP films depended on the number of spin coatings and post-annealing with various conditions (temperature, time, and ambient gas). The optimized three layer ITO NP films annealed at 600 °C under ambient N2 showed a low sheet resistance of 14 Ω/sq and a high optical transmittance of 88% in the visible wavelength region of (400–800) nm. Cross-sectional TEM images showed the ITO nanoparticles to be evenly dispersed in the thin film with good crystallinity and well-defined elliptical shape in the range of 10 to 25 nm. X-ray diffraction analysis confirmed that heat treatment increased the size of the ITO NPs. The KPFM result exhibited that as the heat treatment duration increased, the surface roughness of the ITO NP films reduced. X-ray photoelectron spectroscopy surface analysis showed a relatively higher area ratio of oxygen vacancies and a more stable Sn state in the chemical states of the O 1s and Sn 3d5/2 spectra than those of typical ITO films deposited by a magnetron sputtering after heat treatment. Due to the thermal stability and uniformity of the ITO NP film, ITO NP-based TFHs showed a stable time–temperature profile and uniform IR imagery. Therefore, solution-processed ITO NPs films can be applied to a promising low-cost transparent electrode in the next-generation smart window for buildings and automobiles.

Latte is a mixture of coffee and milk and a model of complex fluids containing biomolecules, usually leaving complex deposit patterns after droplet evaporation. Despite the universality and applicability of biofluids, their evaporation and deposition dynamics are not fully understood and controllable because of the complexity of their components. Here we investigate latte droplet evaporation and deposition dynamics, primarily the crack development and inhibition in droplet deposit patterns. With regard to a mixture of milk and coffee, we find that the surfactant-like nature of milk and intermolecular interactions between coffee particles and milk bioparticles are responsible for achieving uniform crack-free deposits. This finding improves our understanding of pattern formation from evaporating droplets with complex biofluids, offering a clue to applications of bioinks with both printability and biocompatibility.