Vibratory micro-dispensing technology of bulk solids and its application in pharmaceuticals and biomaterials

Abstract

Bulk solids technology plays a key part in manufacturing process when handled material is an assembly of solid particles in large quantities. Micro-dispensing technology for bulk solids can improve operation efficiency in dispensing relatively small amount of material. The demand for the technology covers a wide range of areas where materials have diverse flow behaviours and flow problems due to different physical properties.

This Ph.D. project aims to investigate bulk solids flow behaviour and fluidizing mechanism in a hopper under the influence of vibration, and to develop a bulk solids micro-dispensing technique to demonstrate the dispensing process of active pharmaceutical ingredients (API), excipients and biomaterials. Experiment work in this project includes design of vibratory dispenser hopper and dispensing test with vibratory dispensers where mechanical vibration and ultrasonic vibration is utilized as the driving force to fluidize coarse granules and fine powders, respectively. The results suggest that the vibratory dispenser is capable of accurately and fast dispensing “dropwise” bulk solid in a small amount per drop. A doming controlled flow mechanism is identified in the vibratory dispenser. Bulk solids dome formed in the dispenser hopper plays as a “valve” of flow under the influence of vibration.

The dispensing test results show that the design parameters of dispenser hopper, i.e. orifice size, hopper angle and hopper diameter, and vibration signal parameters, i.e. frequency and amplitude, affect the flow rate and dosage conformity in the vibratory bulk solids micro-dispensing technique. Additionally, a triboelectric charging phenomenon is investigated in the ultrasonic vibration dispenser and a solution to the charging issue is proposed with modifying surfaces of dispenser hopper by using platinum plating method. Pt-coated surface reduces the triboelectric charge generated in the dispensing process and improves the flowability of powders. The correlation between discharge rate and design parameters of ultrasonic vibration dispenser is derived. The derived equations are used to predict dosing results in the application of producing solid form oral drugs and biomaterial dry powder libraries for high-throughput screening (HTS) experiment.

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Identifiers

ORCID for Shoufeng Yang: orcid.org/0000-0002-3888-3211

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