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Particle Shape Analysis with Dynamic Imaging

Particle analysis is concerned with measuring the same material of different sizes or the constituent parts of a sample. This requires different components to be measured and identified for characterisation; a process which is impossible with standard particle size analysers or particle counters. There are numerous measurement methodologies that fall under the overarching field of particle analysis. Concentration, particle size distribution, and particle shape are just a few of the challenging measurements that must be carried out to roundly characterise the various components of samples.

Fluid Imaging FlowCam 8100, Image Analyser

Simply counting the number of particles in a sample can be complicated by aggregating phenomena which cause dispersed particles to agglomerate and form non-uniform clusters. This can significantly complicate both particle shape and size analysis. In many applications with sensitive samples, these clumped particles can be separated through dispersion. Samples can then be subjected to testing using one of a number of different technologies.

Particles are often characterised by size, which provides a measurement of volume (mass or particle concentration (number) against size. This method is particularly applicable in the formulation of suspensions and dispersions. The issue of particle shape complicates this technique however as the size of acicular, disc, rod, or angular particle shapes cannot be readily characterised as a single figure. Particle size analysis overcomes this issue by presenting the size of irregularly shaped particles as the diameter of a volumetrically-equivalent sphere. Calculating the equivalent spherical diameter (ESD) allows various particle shapes to be quantified and expressed as a single number. This has limited real-world applications as materials are typically heterogeneous, containing particles of widely varying shapes.

Static imaging particle shape analysis was envisaged as the solution to standard volumetric particle characterisation techniques. However, this is a time-consuming process. The onset of dynamic imaging particle analysis (DIPA) has since eclipsed the capacities of static techniques, providing a new standard of particle shape analysis.

Outlining Dynamic Imaging Particle Analysis (DIPA)

DIPA is a novel technique that can reliably count and size particles while capturing real-time in situ imagery of particles up to several millimeters. This technology encompasses a range of optical acquisition techniques which are optimised for different sample types and varying resolutions.

The basic principle of dynamic imaging analysis involves a fluidic sample flow across the optical axis of a digital camera. This flow is illuminated with a light source that flashes in tandem with the mechanical shutter of the camera. Images of particles in the flow cell are captured against this backlight and processed by the intuitive electronics of the imaging system. Each of these images is subjected to a range of measurements pertaining to particle shape, size, and morphology. Measurements such as sphericity, aspect ratio, transparency, perimeter, etc can help to identify different types of particles such as protein aggregates from silicon oil droplets in therapeutic protein solutions or different species of algae in water samples.

The FlowCAM range of dynamic imaging analysers can perform over 30 different measurements per frame, providing detailed information pertaining to particle length, width, circularity, ESD, and more. This capacity is enhanced by its VirtualSpreadsheet software which allows analysts to interactively filter data by particle shape or size. It is a uniquely broad product range capable of characterizing any type of particle across a broad measuring range.

Dynamic Imaging Analysis with Meritics

Meritics is the UK’s leading supplier of particle analysers for research applications. We hold a range of FlowCAM analysers for particle shape and size analysis, including:

• FlowCAM Nano;
• FlowCAM Macro.

If you would like any more information about performing particle shape analysis with Meritics, please do not hesitate to contact us.