Liquid Needle

L'effet lotus (effet de la fleur de lotus) décrit le comportement des surfaces ultrahydrophobes. En raison de la mouillabilité extrêmement faible de ces surfaces, les gouttes liquides, en particulier les gouttes d'eau, forment un angle de contact très élevé, ont une forme virtuelle sphérique et s'écoulent sur la surface une petite inclinaison (angle de réduction progressive). Elles emportent ainsi les particules qui sont présentes sur la surface. Il s'agit du principe de base de l'action autonettoyante des surfaces hydrophobes, tout comme la fleur de lotus qui a donné son nom à cet effet.

Dosing can be carried out much faster (< 0.1 s) with the Liquid Needle compared to a solid needle. Due to standardized dosing conditions, the dynamics and thus the reliability of the method are independent from decisions of the user. Furthermore, dosing drops on very hydrophobic samples is easier because the drop does not have to detach from another media (the needle).

The validity of the Liquid Needle method compared to the classic solid needle was proven in a thorough scientific study in which contact angles were measured on a broad range of samples, giving the same contact angle results for both dosing methods.

Bibliography

Ming Jin, Raymond Sanedrin, Daniel Frese, Carsten Scheithauer, Thomas Willers: Replacing the solid needle by a liquid one when measuring static and advancing contact angles. Colloid and Polymer Science 294(4), 657-665, DOI 10.1007/s00396-015-3823-1 (2016).

A summary of this article is presented in our Application Report AR728