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Inhalation April 2023 11 ids concentrations. e solvent continues to diffuse through the solidified crust to the surface of the par- ticle as the remaining solute components continue to precipitate and solidify [7]. e droplet drying stage of atomization impacts the morphology of the final dried particles and is dependent on the selected formulation as well as the thermodynamic condi- tions in the dryer. Different material properties and evaporation rates will lead to different morphologies and surface compositions [8]. Figure 1 and Table 1 depict and explain key stages in the spray-drying process and their associated temperatures. As the liquid feed is atomized, droplets form and the solvent or suspension medium begins to evapo- rate. During the initial stage of droplet drying, sol- vent molecules rapidly evaporate from the droplet surface, due to the heat in the spray-drying cham- ber, and the droplet shrinks in size. During the process, solvent molecules diffuse towards the sur- face of the droplet. As solvent leaves the droplet, the solids components nucleate and precipitate out of solution, typically at the droplet surface, often forming a shell. Precipitation kinetics are driven by supersaturation of the solids components as the sol- vent evaporates, resulting in increased dissolved sol- Stage Temperature at Stage Beginning Temperature at Stage End Key Considerations Droplet formation Liquid feed temperature Wet bulb temperature Droplet size Solid precipitation Wet bulb temperature Wet bulb temperature Kinetics of precipitation Kinetics of crystallization Surface solidification Wet bulb temperature Spray-dryer outlet temperature Surface enrichment Particle surface area Particle finalization Spray-dryer outlet temperature Collection container temperature Particle size Particle density Table 1 Spray-dried particle-engineering stages depicted in Figure 1 Figure 1 Depictions of particle engineering by spray drying Particle Engineering Droplet Formation Solid Precipitation Surface Solidification Particle Finalization Energy Evaporation Spray Dryer Bulk Thermodynamics Droplet Formation and Evaporation Shrink Rate Precipitation and Diffusion