Continuous micro-feeding of fine cohesive powders actuated by pulse inertia force and acoustic radiation force in ultrasonic standing wave field

A continuous micro-feeder for cohesive pharmaceutical materials

Over the past decade, continuous manufacturing has garnered significant attention in the pharmaceutical industry. Still, numerous continuous unit operations need developments, such as powder blending and feeding at low and high throughputs. Especially the continuous and consistent feeding of solid drug substances and excipients at low feed rates remains challenging. This study demonstrates a micro-feeder capable of feeding poorly-flowing pharmaceutical powders at low feed rates. The system performance was investigated using three grades of pharmaceutical powder: croscarmellose sodium (cohesive), magnesium stearate (very cohesive), and an active ingredient, paracetamol (non-flowing). The results show that the micro-feeder can continuously and consistently feed powders at low flow rates (<20 g/h) with low variability (<10 % for non-flowing materials and < 5 % for cohesive materials). Notably, the micro-feeder achieves these results without any feedback control and remains unaffected by refilling, making it a truly versatile and industry-relevant solution. The study's results demonstrate that this micro-feeder system effectively tackles the challenge of consistent and accurate powder feeding at low rates.

Development and implementation of a pneumatic micro-feeder for poorly-flowing solid pharmaceutical materials

Consistent powder micro-feeding (<100 g/h) is a significant challenge in manufacturing solid oral dosage forms. The low dose feeding can well control the content consistency of the dosage forms, which improves drug efficiency and reduces manufacturing waste. Current commercial micro-feeders are limited in their ability to feed < 20 g/h of cohesive (i.e. powders of poor flowability) active pharmaceutical ingredients (API) and excipients (e.g. lubricants) with low fluctuation. To breach this gap, this study presents an advanced micro-feeder design capable of feeding a range of pharmaceutical-grade powders consistently at flow rates as low as 0.7 g/h with <20 % flow rate variation. This was possible due to a novel powder conveying concept utilising particle re-entrainment to minimise flow rate variations. This work details the design of this pneumatic micro-feeder and its excellent micro-feeding performance even for cohesive powders. The experimental studies investigated the influence of the process parameters (air pressure and air flow rate) and equipment configurations (insert size and plug position) on the feeding performance of different pharmaceutical-relevant powders, i.e., microcrystalline cellulose (MCC), croscarmellose sodium (CCS), crospovidone (XPVP) and paracetamol (APAP). It was shown that the system is capable of delivering consistent powder flow rates with good repeatability and stability.

Formation of a 3D Particle Array Actuated by Ultrasonic Traveling Waves in a Regular Polygon Resonator

Acoustic radiation forces have been extensively studied regarding static particles, cell patterning, and dynamic transportation. Compared with standing wave manipulation, traveling wave manipulation can be more easily modulated in real time and has no matching requirement between the size of the resonant cavity and the sound frequency. In this work, we present an efficient, multi-layer microparticle pattern technique in a 3D polygon cavity with a traveling bulk acoustic wave. There are two types of excitation modes: the interval excitation mode (IEM) and the adjacent excitation mode (AEM). We conducted theoretical and simulation analyses, and our results show that both of these modes can form particle arrays in the resonant cavity, which is in accordance with the experimental results. The array spacings in the IEM and AEM were about 0.8 mm and 1.3 mm, respectively, while the acoustic frequency was 1MHz. Double-layer particle patterns were arrayed by a double in the resonant cavity. The spacing between the two layers was set at 3.0 mm. The line spacings were about 0.4 mm in both layers. The line width was 0.2 mm, which was larger than the single layer. The results show that ultrasonic traveling waves are a feasible method to manipulate particles and cells that form 3D patterns in particle-fluid flows.

A solution for low-dose feeding in continuous pharmaceutical processes

Continuous feeding of small quantities of powder is increasingly applied in pharmaceutical manufacturing. With that regard, what is crucial is not only the feasibility, but also the accuracy and stability. To enable stable processing, low amounts of various agents, e.g., lubricants, can be used. Even more important is the exact dosage of highly potent active pharmaceutical ingredients (APIs), which require feed rates within the range of grams per hour. Conventional feeders cannot supply powder at such rates, especially when the material properties are challenging. In this work, a novel micro-feeder was integrated into a continuous manufacturing line and its capability to supply API at feed rates down to one gram per hour was tested. The micro-feeder system is based on the principle of active volumetric displacement: a piston pushes the powder out of the cartridge upwards to the end of a plate, where a scraper places it into the process inlet. In this study, a hot melt extrusion process was used, during which the API was dissolved in a polymer matrix. Samples of the strand were analysed with regard to their content by means of HPLC. The results showed that the novel micro-feeder system can feed powder with good accuracy and reproducibility, indicating its high potential for continuous process implementation.