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|Title:||ALS-CXRO Seminar Series | Frieder Mugele|
|When:||10/30/2013 3:00 PM - 4:00 PM|
|Description:||ALS/CXRO Seminar Series|
Wed, Oct 30, 2013
15-253 Conf Rm
Prof. Frieder Mugele
Physics of Complex Fluids; Univ. Twente; PO Box 217; 7500 AE Enschede (The Netherlands)
Shaken not stirred: how dynamic electrowetting allows for dynamics drop control on solid surfaces
Surface tension forces dominate the behavior of sessile drop with sizes of order millimeter or smaller. Gaining efficient control on wetting is therefore a key paradigm in microfluidics. While patterning of surfaces enables spectacular behavior such as superhydrophobicity, dynamic drop control requires external actuation. Electrowetting (EW) is the arguably most flexible tool to so, routinely achieving contact angle variations of more than 90° within milliseconds with millions of actuation cycles without degradation.
Starting from the basic physical principles governing the contact angle reduction in EW, I will focus in this lecture on two aspects, (i) EW drop on structured surface, and (ii) dynamic aspects of drop control. Using the example of the Cassie and the Wenzel state on superhydrophobic surfaces, I will show EW allows for tuning the energy landscapes experienced by the fluid on structured surfaces to enable reversible transitions competing fluid morphologies. In the second part, I will show how dynamic excitation and the use of inertia allow us to overcome energy barriers and to generate internal flow patterns within drops, leading amongst others to efficient mixing and to the suppression of coffee stains in evaporating drops.