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What is High-Shear Processing?

Written by Maja Hunter, Ph.D.
 
The beginnings of high-pressure homogenization date back to 1899. The first high-pressure homogenizer was used for milk emulsification, which was followed by the invention of the French Pressure Cell Press used for cell disruption a few decades later. In the 1980s, the field of microfluidics revolutionized high-pressure homogenization with the introduction of microchannels, a core feature of high-shear processors.
 
Nowadays, high-shear processing is indispensable in Pharma, Biotech, Chemical, Food, Cannabis and Cosmetic industries to create nanoemulsions, nanoencapsulations, liposomes, nanodispersions, nanosuspensions and for deagglomeration, cell disruption and size reduction of polysaccharide molecular weight. These can all be achieved using the ShearJet® processor with different set ups.
 
How does it work?
In short, the preprocessed sample is poured into the inlet reservoir and the multiplier high pressure pump drives the sample to reach high velocities before being forced through the microchannels of the Reaction Chamber® module. The processed sample passes through a heat exchanger to quickly cool down the acquired temperature of the sample, due to the supplied energy in the homogenization process. The sample exiting the system can be led via the tube into a beaker, or recycled into the inlet reservoir for another pass through the system, depending on the application´s requirements.
 

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Figure 1. The product-contact parts of high-shear processor are shown.

 

High pressure pump

The high-pressure pump provides sufficient energy to force the liquid sample through microchannels in the Reaction Chamber® module, creating consistent shear rates. The operational pressures on ShearJet® processors can be set from 5,000 to 30,000 psi.

 

Reaction Chamber® modules

The liquid sample is forced through the microchannels of the Reaction Chamber® module, reaching high velocities, up to 500 m/s. The stream accelerates and the particles collide with the walls of the microchannels and themselves, generating shear and impact forces. These forces disrupt cells and create fine nanoemulsions that can be easily sterile-filtered. There are two configurations of Reaction Chamber® modules. Type T is used for liquid-to-liquid dispersions, such as nanoemulsions, lipid nanoparticles, liposomes, encapsulations, vaccine adjuvants and polymer particles. Whereas, type L is used for suspension of the solid into the liquid, for example for cell disruption, deagglomeration, polysaccharide molecular weight and particle size reduction in general. On the laboratory processor, the Reaction Chamber® module contains one microchannel and on the production processor, the Reaction Chamber® module used would have multiple microchannels in parallel, which is key to a linear scale up. 

 

Efficient cooling

As the temperature rise in the high-shear homogenization process is 1.7 °C per every 1,000 psi (69 bar), efficient cooling is vital for preservation of activity of temperature-sensitive proteins. Efficient cooling also prevents coalescence of nanoemulsion droplets and affects their viscosity as well as stability. Dyhydromatics ShearJet® processors have a heat-exchanger installed directly after the Reaction Chamber® module. A heat-exchanger connected to the chiller ensures efficient temperature control of the sample after high-shear processing and therefore reproducible results. 

 

Processing conditions are formulation-dependent

Each formulation has unique properties and sample processing conditions, such as operational pressure, number of passes through the microchannels, required inlet and outlet temperatures, which need to be determined individually. 

 

What is difference between high-pressure homogenizer vs. high-shear processor?

High pressure homogenizers have a narrow orifice with adjustable size, whereas high-shear processors feature fixed geometry Reaction Chamber® modules, containing microchannels instead. The Reaction Chamber® module contains no moving parts that need to be regularly maintained or exchanged. On the contrary, diamond coating ensures their longevity. Longer residence time within these microchannels under near-constant pressure allows every mL of processed sample to experience identical processing conditions. Because of this, often the desired results are achieved in fewer passes with high shear processing, and have narrower particle size distribution regardless of the particle size. 

 

Why Dyhydromatics?

Our number one priority is building solid business relationships with our customers and suppliers and our strength is a responsive and friendly customer service team. As a small company, we have room for innovation inspired by customers´ requirements. Dyhydromatics specializes in manufacturing, selling and maintaining high-shear processors that can process aforementioned formulations to reach reduced particle sizes. Additionally, we supply quality spare parts and perform proof-of-concept testing, so your purchase is risk-free. Our Dyhydromatics ShearJet® processors are available in lab and pilot scale. 

Posted December 7, 2023

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