Spray drying represents an important and versatile production method for microspheres, particularly for ceramic and polymer microspheres, as well as for certain metal oxide and composite particles. This process involves atomizing a precursor slurry or solution into fine droplets, followed by rapid solvent evaporation that solidifies the droplets into spherical particles . Spray drying is widely used for large-scale microsphere production and is particularly suitable for process scale-up .

The spray drying process begins with the preparation of a precursor slurry or solution containing the desired material, along with additives such as binders and plasticizers that promote polymer coalescence, film formation, and the formation of spherical and smooth-surfaced microspheres . The slurry is then atomized into fine droplets using a spray nozzle or rotary atomizer, and the droplets are dried rapidly in a heated chamber. The solvent evaporates, leaving behind solid spherical particles with controlled size and morphology.

Recent research has demonstrated the importance of precursor rheology in determining microsphere quality. A 2025 study published in Chemical Engineering Research and Design investigated the viscosity-controlled formation of spherical hydroxyapatite microspheres via spray drying. The results identified precursor viscosity as a key parameter influencing microsphere morphology. Low-viscosity suspensions produced collapsed or irregular particles due to insufficient resistance to droplet deformation during solvent evaporation, whereas excessively high viscosities hindered atomization and resulted in non-uniform particle formation. An optimal viscosity window of approximately 800–900 mPa·s provided the best balance between atomization efficiency and droplet stabilization, producing highly spherical microspheres with an average particle diameter of approximately 40 μm .

The spray drying segment is benefiting from ongoing innovations in process control and formulation technology. The Ohnesorge number, which describes the balance among viscous, inertial, and capillary forces during droplet formation and drying, provides a quantitative framework for optimizing spray drying conditions. Increasing the Ohnesorge number enhanced droplet stability and improved microsphere sphericity, indicating that microsphere formation is governed not simply by viscosity itself but by the underlying force balance during atomization .

Spray drying is particularly valuable for producing microspheres from materials that cannot be easily processed by spheroidization or other high-temperature methods. The process is widely used for ceramic microspheres, polymer microspheres, and composite particles, enabling the production of spherical particles with tailored properties for diverse applications. For more information on spray drying microspheres, visit Metallic Microsphere Market Report.

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