1 Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, Sonneggstrasse 3, CH-8092 Zurich.
2 Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, Sonneggstrasse 3, CH-8092 Zurich;, Email: andreas.guentner@ptl.mavt.ethz.ch.