idw – Informationsdienst Wissenschaft

Nachrichten, Termine, Experten

Grafik: idw-Logo
Grafik: idw-Logo

idw - Informationsdienst
Wissenschaft

Science Video Project
idw-Abo

idw-News App:

AppStore

Google Play Store



Instanz:
Teilen: 
08.06.2022 10:41

More than a coffee ring

Blandina Mangelkramer Presse und Kommunikation
Friedrich-Alexander-Universität Erlangen-Nürnberg

    What do coffee, red wine and ink have in common? The stubborn stains they leave behind. Anyone who has ever knocked over a cup of coffee will know that coffee dries in an unusual pattern, the stain is lighter at the center but it gets darker around the perimeter, an effect known as the coffee ring. Prof. Dr. Nicolas Vogel and his team of researchers from the Department of Chemical and Biological Engineering at Friedrich Alexander Universität Erlangen Nürnberg (FAU) and their colleagues in Edinburgh are investigating a strategy to tackle the coffee ring effect and produce a consistent drying pattern. Their findings have been published in the reputable journal Nature Communications.

    Image of two typical stains.A liquid containing particles shows the characteristic drying pattern of a coffee ring (left). If the surface of the particles is modified with surface-active polymers, the dispersion dries in a homogeneous film (right). (Image: Marcel Rey)

    When a droplet of coffee dries, the liquid evaporates faster at the edges than in the center Small, solid particles are present in the coffee when it is brewed. They are drawn to the edge of the droplet by different drying speeds and separate there, forming the characteristic pattern of a coffee ring. This is a universal phenomenon which occurs when liquids containing particles dry, so-called dispersions, for example ink, paint or red wine. Ring patterns are just as undesirable in technical processes as when we spill our coffee. They lead to irregular print images, defects and performance degradation in various coating methods and printing processes.

    Researchers have discovered that the trick to achieving consistent drying patterns is modifying the surfaces of the particles with polymer chains so that they efficiently repel each other while being strongly attracted to the surface of the droplet. Spatial repulsion prevents particle accumulation at the edge of the droplet, while particle attachment to the droplet surface results in a homogeneous particle film. When they are combined both effects prevent the formation of a coffee ring.

    Importantly, this method not only allows coffee droplets to dry evenly: it can be used with a wide range of commercially available pigment particles and different liquids. As the method is easy to implement and versatile, the new method paves the way to reliable coating processes and inkjet-printed electronic devices in a wide range of advanced technologies, for example, solar cells, transistors or biosensors.


    Wissenschaftliche Ansprechpartner:

    Prof. Dr. Nicolas Vogel
    Phone: +49 9131 85 20357
    nicolas.vogel@fau.de
    www.vogellab.de


    Bilder

    Merkmale dieser Pressemitteilung:
    Journalisten
    Chemie
    überregional
    Forschungsergebnisse
    Englisch


     

    Hilfe

    Die Suche / Erweiterte Suche im idw-Archiv
    Verknüpfungen

    Sie können Suchbegriffe mit und, oder und / oder nicht verknüpfen, z. B. Philo nicht logie.

    Klammern

    Verknüpfungen können Sie mit Klammern voneinander trennen, z. B. (Philo nicht logie) oder (Psycho und logie).

    Wortgruppen

    Zusammenhängende Worte werden als Wortgruppe gesucht, wenn Sie sie in Anführungsstriche setzen, z. B. „Bundesrepublik Deutschland“.

    Auswahlkriterien

    Die Erweiterte Suche können Sie auch nutzen, ohne Suchbegriffe einzugeben. Sie orientiert sich dann an den Kriterien, die Sie ausgewählt haben (z. B. nach dem Land oder dem Sachgebiet).

    Haben Sie in einer Kategorie kein Kriterium ausgewählt, wird die gesamte Kategorie durchsucht (z.B. alle Sachgebiete oder alle Länder).