From Water Trampolining to ice jumping: Physics and Nanoengineering of Materials with Intrinsic Extreme Icephobicity

Wednesday, April 26, 2017

2:30pm - 3:45pm


115 Goodwin Hall

Professor Dimos Poulikakos
Institute of Energy Technology
Director, Laboratory of Thermodynamics in Emerging Technologies

Abstract:

Spontaneous removal of discrete condensed matter from solids is of extreme importance in nature and in a broad range of technologies, e.g. self-cleaning, anti-icing, and condensation. Despite progress, the understanding of phenomena leading to such behaviour, combined with rational surface design promoting their manifestation, remain a challenge. In this lecture I will  show how water droplets resting on superhydrophobic surfaces in a low-pressure environment can self-remove through sudden spontaneous levitation and subsequent trampoline-like bouncing behaviour, i.e. sequential droplet-substrate collisions with restitution coefficients greater than unity, despite complete surface rigidity, seemingly violating the second law of thermodynamics. I will show  that trampoline bouncing results from the combined effect of droplet vaporisation, vapour flow in the surface texture, and substrate adhesion leading to a forced, underdamped, mass-spring-damper system behaviour. Due to the high-vaporisation rates experienced by droplets, and the inherently associated significant cooling, recalescent freezing can occur. We show how increasing vaporisation —triggered suddenly by recalescent freezing— has a strong boosting effect and can spontaneously remove surface icing (by levitating or even launching away generated icy drops) the moment they freeze. I will also briefly discuss a new mechanism showing droplets self dislodging and creeping out of nano-engineered surface textures employing inherent physics of freezing. Finally I will demonstrate how surface flexibility can work collaboratively with droplet dynamics to enhance hydro- and icephobicity. I will conclude with a new method for the accurate determination of surface forces during vaporisation or freezing of drops from compliant surfaces based on monocrystalline arrays of nanoprinted quantum dot discs, enabling reference free traction force microscopy.

Biography:

Professor Dimos Poulikakos holds the Chair of Thermodynamics at ETH Zurich, where in 1996 he founded the Laboratory of Thermodynamics in Emerging Technologies in the Institute of Energy Technology. He was a Member of the Research Commission of ETH (2001-2005). He served as the Vice President of Research of ETH Zurich in the period 2005-2007. Professor Poulikakos was the ETH director of the IBM-ETH Binnig-Rohrer Nanotechnology center, a unique private-public partnership in nanotechnology at the interface of basic research and future oriented applications (2008-2011). He served as the Head of the Mechanical and Process Engineering Department at ETH Zurich (2011-2014).

His research is in the area of interfacial transport phenomena, thermodynamics and related materials with a broad range of emerging technologies and applications. The focus is on understanding the related physics, in particular at the micro- and nanoscales and employing this knowledge to the development of novel technologies. Specific current examples of application areas are the direct 2D and 3D printing of complex liquids and colloids down to nanoscale feature size and resolution, the science-based design of supericephobic and omniphobic surfaces, the chip/transistor-level bio-inspired 3D integrated powering and cooling of electronics, the development of facile methods for the fabrication of plasmonic sunlight absorbers and the development of surface textures for biological applications under realistic fluidic environments (accelerated and guided cell adhesion, re-endothelialization, antifibrotic surface textures and materials). 

Professor Poulikakos has supervised to completion over 65 Doctoral dissertations to date. He has published over 400 research articles in top peer reviewed journals in areas such as materials, thermofluidics, energy, nanotechnology, chemistry and chemical engineering, applied physics, and bioengineering/biophysics, as well as numerous articles in proceedings of professional conferences and a graduate level textbook on Conduction Heat Transfer (Prentice Hall, 1994).  He has also edited and co-authored a special volume of Advances in Heat Transfer (1996), dedicated to transport phenomena in materials processing. In Thomson Reuters WOS he has over 11’500 citations and an h-factor of 52. In Google Scholar he has over 17’800 citations and an h-factor of 70.

Among the awards and recognitions he has received for his contributions are the White House/NSF Presidential Young Investigator Award in 1985, the Pi Tau Sigma Gold Medal in 1986, the Society of Automotive Engineers Ralph R. Teetor Award in 1986, the University of Illinois Scholar Award in 1986 and the Reviewer of the Year Award for the ASME Journal of Heat Transfer in 1995. He is the recipient of the 2000 James Harry Potter Gold Medal of the American Society of Mechanical Engineers. He was a Russell S. Springer Professor of the Mechanical Engineering Department of the University of California at Berkeley (2003) and the Hawkins Memorial Lecturer of Purdue University in 2004. He received the Heat Transfer Memorial Award for Science in 2003 from ASME. In 2008 he was a visiting Fellow at Oxford University and a distinguished visitor at the University of Tokyo.  He is the recipient of the 2009 Nusselt-Reynolds Prize of the World Assembly of Heat Transfer and Thermodynamics conferences (awarded every four years), for his scientific contributions. He is the 2012 recipient of the Max Jacob Award, for eminent scholarly achievement and distinguished leadership in the field of fluidics and heat transfer. Awarded annually to a scholar jointly by (ASME) and (AIChE), the Max Jacob Award is the highest honor in the field of thermofluidics these professional organizations bestow. He was presented with the Outstanding Engineering Alumnus Award of the University of Colorado in Boulder in 2012. He received the Dr.h.c. of the National Technical University of Athens in 2006. In 2008 he was elected to the Swiss National Academy of Engineering (SATW), where from 2012 to 2015 he also served as president of its science board.

Professor Poulikakos has been a frequent plenary speaker in many conferences worldwide. He is the Editor or member of the board of many international journals and conferences. He is a Fellow of the American Society of Mechanical Engineering (ASME).