Lun 10 Giu
Seminari e Convegni

Controlling and engineering droplets splitting and transport through multiphysics simulations

Department of Applied Science and Technology (DISAT)

We could achieve the controlled splitting of millimetric water droplets using a supporting surface formed by a z-cut iron-doped lithium niobate (Fe:LiNbO3) crystal coated with a lubricant-infused layer. If the crystal is illuminated with a light spot, dielectrophoretic forces first move a nearby water droplet towards the center of the spot and then split it. One of the two fragments follows a well-defined trajectory. This behavior can be explained by the interplay of pyroelectric, piezoelectric, and photovoltaic effects. I will start introducing the physics required for describing the response of Fe:LiNbO3 to strain, heat and light at the macroscopic scale. Then, I will show how we could easily solve the relative system of differential equations with an in-house finite-difference code. Our simulation reproduces nicely the recorded temperature profiles and permits to disentangle the role of temperature gradient from that of charge accumulation at the slab surfaces due to the photovoltaic effect. Only the combination of the two provides the electric field (so-called evanescent) in proximity of the slab surface which is compatible with the observed behavior of the support dropets.

Paolo Umari graduated in Physics in 1999 at the University of Trieste and received a PhD in Computational Physics from the Swiss Federal Institute of Technology in 2003. Then, he spent two years at MIT, USA at the Department of Materials Science and Engineering. Since 2011 he is at the Department of Physics and Astronomy of the University of Padova as an associate professorfrom 2015.