EPJ E Highlight - The hidden threat posed by inconspicuous stripes

Stripy patterns observed during the processing of medicinal powder. © N. Nirmal Thyagu

Physicists investigate the cause of striped patterns formed by fine particles deposited on surfaces

Patterns fascinate. Particularly stripes. Found in nature in zebras, they are also found in the most unlikely places, such as powdered drugs’ mixing vessel walls. In an article just published in EPJ E, Nirmal Thyagu and his colleagues from Rutgers University, New Jersey, USA, propose a traffic model to predict the formation of different patterns, ranging from stripes to spots.

Thanks to simulations, Thyagu and colleagues showed the underlying stripe formation mechanism, which they propose stems from traffic-like jams, whereby particles move more slowly when surrounded by other particles. This numerical model revealed three distinct patterns of how “sticking” can occur. These include stripe formation, clearing of surfaces between stripes, sharpening lead edges of the stripes, and stripe-to-spot transitions. These results were subsequently confirmed through experiments.

What is more, the authors found, striped patterns invariably form, provided that the relative humidity is in a range between 40 and 60%, and the tumbler surface is sufficiently rough enough to give hold to an initial layer.

Striped patterns formed by particles limit micro-patterned circuit size in electronics, inhaled medicines’ effectiveness and polymer manufacturing efficiency. These patterns also adversely affect pharmaceutical manufacturing, as stripes appear on the walls of mixing vessels used for the production of powdered drugs.

More specifically, the authors also showed that active pharmaceutical ingredients can preferentially stick to mixing vessels’ walls, and can carry as much as twice the concentration of active ingredients. As a result, the bulk powder used for tablets is less concentrated than it should be, or can be too concentrated if the highly concentrated material falls back into the bulk. Research focusing on how the effect carries over when scaling up to pilot- and full-scale manufacturing is currently underway.

Stuck in traffic: patterns of powder adhesion. N. N. Thyagu, A. Vasilenko, A. Voyiadjis, B. J. Glasser, T. Shinbrot (2012), European Physical Journal E 35:105, DOI: 10.1140/epje/i2012-12105-y

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

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