Authors: A. Egatz-Gomez, S. Melle, A.A. García, S. Lindsay, M.A. Rubio, P. Domínguez, T. Picraux, J. Taraci, T. Clement, M. Hayes and D. Gust
Affilation: Arizona State University, United States
Pages: 501 - 504
Keywords: microfluidics, droplet, magnetic field, superhydrophobic surfaces
We present a novel method to control water drop movement on superhydrophobic surfaces through magnetic fields. Water drops with paramagnetic particles can be moved on fractal Si-nanowire superhydrophobic surfaces at high speeds by displacing a magnet. A drop pinned to a surface defect can be combined with another drop containing paramagnetic particles thus allowing moving the newly formed drop. A drop can also be split using two magnetic fields. Under a magnetic field, paramagnetic particles form chain-like clusters. The movement generating force appears as a consequence of chains pushing against the drop skin at the drop bottom, with chains acting as a lever and drop surface tension as a fulcrum.<br>Little is known about aqueous drops moving on non-patterned superhydrophobic surfaces by mechanisms different from gravity. Several technologies may benefit from advances in this field. Digital microfluidics has been demonstrated using electrowetting arrays for droplet transportation. Our findings demonstrate the feasibility of using magnetic fields to move, combine and split aqueous drops on non-patterned superhydrophobic surfaces with the only driving force of magnetic fields, which appears as a promising way to manipulate small discrete amounts of water. By analogy with electrowetting digital microfluidics, we name this phenomena digital magnetofluidics.