Micro-dosing of fine cohesive powders is the key technology in additive manufacturing\nand especially in high-potency active pharmaceutical ingredients (HPAPI). However, high accuracy\nmicro-dosing (<5 mg) of fine cohesive powder is less trivial and still remains a challenge because it is\ndifficult to eliminate the aggregation phenomena caused by the strong interparticle cohesive forces\n(in small capillaries). This paper presents a novel micro-dose method of fine cohesive powders via a\npulse inertia force system. A piezoelectric actuator is used to provide a high enough pulse inertia\nforce for a tapered glass nozzle and drive powder particles in the nozzle to be discharged from the\nnozzle orifice with the help of particle self-gravity. The nozzles with outlet diameters in the range\nof 100ââ?¬â??2000 Ã?¼m were fabricated via a glass heating process. The Ã?±-lactose monohydrate powder is\nused as the micro-dosing powder. The influences of the tapered nozzle outlet diameter, amplitude\nof the applied pulse voltage, and angle of the nozzle axis on micro-dosing mass are researched.\nThe minimum mean dose mass is 0.6 mg for a single pulse inertia force. The coefficient of variation of\ndose mass, which represents the micro-dosing stability, can be controlled below 5% when the dose\nmass is relatively small.
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