Manufacturing softpellets using triboelectric agglomeration of fine powders on a vibrated inclined plane: Method and application to dry powder inhalion

Fine powders are required in many industrial applications, but their poor flow properties make handling and processing challenging. In Dry Powder Inhalation (DPI), for instance, inhaled particles must have an aerodynamic diameter between 1 and 5 μm to ensure therapeutic efficiency. However, these fine powders are difficult to manipulate, particularly during capsule or reservoir filling. To address this issue, we propose a set-up to form brittle agglomerates, referred to as softpellets, which exhibit enhanced flowability while maintaining the ability to break up when needed. Our method is based on a vibrating stainless steel inclined plane on which fine particles flow under controlled vibration, leading to agglomeration. The powder is dispensed after being sieved, and the process parameters have been optimized. For that, two powders were used: a fine lactose (Inhalac® 500) and a homemade engineered spray-dried powder. Experimental results suggest that triboelectric charging plays a key role in particle cohesion, driving agglomeration. The resulting softpellets are spherical, approximately 800 μm in diameter, and exhibit significantly improved flowability compared to the initial powder. Their mechanical robustness was assessed using a texture analyzer and laser diffraction under varying pressures. Finally, low-inspiratory flow impactor analyses confirm that the agglomerates are effectively released from the capsule device and dissociate upon inhalation, achieving a fine particle fraction of nearly 60 %. This study demonstrates a promising strategy for enhancing the flowability of micronized powders without the addition of binders or other excipients. While this proof-of-concept was developed for DPI formulations, the approach could be extended to other pharmaceutical or industrial powder applications.