Shear adhesion of a sessile drop under a centrifugal field. Fakes or fails in interfaces/surfaces

Fecha: 7 de Junio de 2023.
Hora: 12:30h a 13:30h.
Lugar: Aula G11 de la Facultad de Ciencias.
Ponente: Prof. Miguel Ángel Rodríguez Valverde (Universidad de Granada).

Resumen:
1) Shear adhesion of a sessile drop under a centrifugal field Non-wetting surfaces with high contact angle hysteresis are challenging because the conventional goniometry methods are unable to resolve the very low receding contact angles of static sessile drops. Recently, dynamic methods based on moving drops are promising for probing extreme wettabilities. The energy input transferred with theses force-based methods is enough to overcome the multiple metastable drop configurations. A sessile drop placed on a rotating surface reveals a behaviour similar to tilted drops although the driving force is not constant. Unlike gravity, centrifugal force depends on the rotation speed and the distance of the drop center to the rotating axis. The titled and rotating drops are elongated while the drop center remains static (in terms of noticeable drop displacement). We postulate that the lateral length of a rotating sessile drop at the most-stable configuration remains constant even at increasing speeds. However, the lateral length is maximized, for a few milliseconds, when the rotating drop is at the motion onset. Both values of lateral drop length allow to identify the critical rotation speed related to the inertial force that matches the shear drop adhesion, accordingly.

2) Fakes or fails in interfaces/surfaces?
We are all aware of how complicated it is to work with interfaces/surfaces because of the control of their purity. The existence of adventitious elements on solid surfaces can alter the desired behavior. In this brief review, some examples of impact publications based on unexpected artifacts are presented.

Organiza el Grupo de Física de Fluidos y Biocoloides de la UGR.