Exploring interfacial physics to inspire disrupting technologies

Institute of Microengineering - Distinguished Lecture

Campus Lausanne BM 5202 (live)
Campus Microcity MC B0 302 (video)
Zoom Live Stream: https://epfl.zoom.us/j/440644837

Abstract: Interfaces separating different kinds of matter, or different phases of the same matter, abandon in nature and technology. What is more, they invariably play a critical role in all systems where they occur, from regulating transport of energy and species, to dictating system shape and form. Interfaces differ in their structure and properties from the bulk matter they surround. I note here the famous quote of Wolfgang Pauli that “God made bulk (materials) but surfaces are the work of the devil”. Interfaces are of course of critical importance in small scale systems and even more so as we move toward nanoscales, where their proportion in a given system increases dramatically and their effect dominates system behaviour.

In this lecture I will primarily focus on liquid/gas and liquid/solid interfaces as they manifest themselves in simple systems, such as small droplets and nanoparticles, in particular when they are at a metastable thermodynamic state or under the regulated influence of an external field (gravitational, acoustic, electric or electromagnetic), showing in parallel novel applications deriving from understanding their physics.  

First, I will address the spontaneous removal of discrete condensed matter from surfaces, of importance in nature and in a broad range of technologies, e.g. self-cleaning, anti-icing, and condensation. The understanding of phenomena leading to such behavior, combined with rational micro/nano surface texture design promoting their manifestation, remain a challenge. 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 behavior, i.e. sequential droplet-substrate collisions with restitution coefficients greater than unity, despite complete surface rigidity, seemingly violating the second law of thermodynamics. Due to the high-vaporization rates experienced by droplets, and the inherently associated significant cooling, freezing from a metastable state can occur. I will show how increasing vaporization —triggered suddenly by metastable state freezing— has a strong boosting effect and can spontaneously remove surface icing (by levitating or even launching away generated icy drops/particles) the moment they freeze. This work exemplifies how surface texturing aware of such interfacial phenomena alone, can prohibit water droplet retention on surfaces, also when they freeze.

Next, a remarkably simple process for the maskless direct printing of nanoparticles of all kinds, through electrohydrodynamic “NanoDrip” printing of colloidal nanodroplets will be presented and the related interfacial physics and transport phenomena leading to the tunable formation of in- and out-of-plane functional nanostructures as single entities or large arrays will be explained.  A host of applications enabled by NanoDrip printing will be discussed, ranging from plasmonics, driven by single photon emitters (quantum dots, or even precisely printed single organic molecules) to the printing of transparent conductive grids and to tracking force microscopy (TFM) methods for cells with unprecedented facility and resolution.

Finally, I will discuss the controllable manipulation of biological and synthetic nanoscopic species in liquids at the ultimate single object resolution (biological quantum level), important to many fields such as biology, medicine, physics, chemistry and nanoengineering. I will present the concept of electrokinetic nanovalving, with which we confine and guide single biological nano-objects in a liquid, solely based on spatiotemporal tailoring of the free energy landscape guiding the motion. The electric field generating this energy landscape is readily modulated collaboratively by wall nanotopography and by addressable embedded nanoelectrodes in a nanochannel. I will demonstrate guiding, confining, releasing and sorting of biological nano-objects, ranging from macromolecules to adenoviruses, but also a broad palette of other nano-objects such as lipid vesicles, dielectric and metallic particles, of various sizes and inherent charges, suspended in electrolytes with to biological buffer solution levels. Such systems can enable individual handling of multiple entities as well as simultaneously obtaining accurate information of the properties of their such as electrical conductivity and permittivity, in applications ranging from chemical or biochemical synthesis to precise drug delivery, in a continuous lab-on-chip environment with biological quantum level resolution.


Bio: 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 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). He is currently the Chairperson of the Energy Science Center of ETH Zurich and a member of CORE, the advisory board of the Swiss government on issues related to energy. As of January 2020, he is also the president of Division IV the of the Swiss National Science Foundation (SNF) and member of the presiding board of SNF.

His research is in the area of interfacial transport phenomena, thermodynamics and related materials nanoengineering, with a host of related 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 with nanoscale feature size and resolution, the science-based design of supericephobic and omniphobic surfaces, the chip/transistor-level, bio-inspired 3D integrated cooling of supercomputer electronics, the development of facile methods based on plasmonics for sunlight management and the development of nanofluidic technologies and surface textures for biological applications under realistic fluidic environments (accelerated and guided cell adhesion, re-endothelialization, antifibrotic surface textures and materials, single virus trapping and transport).

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.


Note: The Seminar Series is eligible for ECTS credits in the EDMI doctoral program

Note: After the lecture, there will be time for discussion and interaction with the distinguished speaker, sandwich lunch and refreshments sponsored by the Institute of Microengineering will be provided for attendees in front of the lecture hall (BM 5104, ca. 13h15)