Towards Design of Super-Low Ice Adhesion Surfaces

In this project, we have identified a novel mechanism called MACI to effectively lower the ice adhesion. Based on the mechanism, we designed and fabricated PDMS coating with ice adhesion 5.7 kPa. In the last period, we continue the development of the novel MACI concept for super-low ice adhesion surfaces by pushing the ice adhesion to the lowest possible value! In particular, we created PDMS sponge structures combined the advantages of both reduced apparent elastic modulus and most importantly, the macroscopic crack initiators at ice-solid interface, resulting in dramatic reduction of ice adhesion strength. Our design of sandwich-like sponges achieved an unprecedentedly low ice adhesion strength as low as 0.9 kPa for pure PDMS materials without any additives. Interestingly, the super-low ice adhesion strength remains constant after 25 icing and deicing cycles. In the last period, we also studied the effect of ice type on the ice adhesion strength. In the literature, bulk water ice was widely used for ice adhesion testing. In collaboration with Anti-icing Materials international lab (AMIL) Canada, we discovered that ice adhesion strength surprisingly correlate inversely to the ice density for the same material surface - the porous ice from nature will display much higher (sometimes 3 times) ice adhesion than the laboratory ice. This finding has strong implications to the future ice adhesion testing method development. In the period from 2018-2019, significant progress has been made in designing and synthesizing super-low ice adhesion surfaces. Most of the current icephobic surfaces reported in the literature are of static nature. These surfaces lose their ability to keep low ice adhesion at extremely low temperature. We for the first time proposed dynamic anti-icing surfaces, which can melt ice or change the ice?substrate interfaces from the solid to liquid phase after the formation of ice. The key was to create a polymer system that slowly releases ethanol to create a non-freezing lubricating layer at ice?material interfaces. Our dynamic anti-icing surfaces can last for 593 days at extremely low temperature without having to replenish the ethanol. The ice adhesion strength decreased in an unprecedented manner, from 709?761 kPa to 22?25 kPa at a low temperature of ?60 °C. The results were published at the high impact journal Material Horizons and were specially reported by the Chemistry World News on the 7th of July 2019. Another highlight was that the project team organized an International Symposium on Materials for Anti-icing. More than 40 scientists from 5 countries, both from academia and industrial sectors attended the symposium. our anti-icing research received wide attention. One of the challenges in anti-icing research is that there are no ice adhesion testing standards available. Since the super-low ice adhesion surfaces developed in the SLICE project are tested by our own testing method, it is of great interest to calibrate our home-made vertical shear testing method against the other recognized testing methods. To this purpose, in the period from 2019-2020, we have carried out an interlaboratory testing program with our Canadian project partner. For identical coatings and under same testing conditions, we found that the NTNU ice adhesion testing method results in higher ice adhesion value compared with the centrifugal testing method used by our Canadian partner. This interlaboratory testing program implies that if the super-low ice adhesion surfaces developed in the SLICE project will be tested by the Canadian testing method, in fact a lower ice adhesion would have been reported. There were two PhD dissertations planned in the project. One PhD dissertation on atomistic simulation of ice adhesion was delivered in March 2020, another PhD dissertation on dynamic anti-icing surfaces will be defended in October 2020.

1) surfaces with world's lowest ice adhesion without surface additives and oil. 2) unique method to design super-low ice adhesion surfaces 3) NTNU on the map of world anti-icing research

Preventing the formation and accretion of ice on exposed surfaces is of great importance for renewable energy, electrical transmission cables in air, shipping and many other applications. Active de-icing involving chemical, thermal and mechanical methods are currently used to remove the ice that has already accumulated. These techniques, however, require periodic applications and high energy consumption, and have major detrimental effects on both the structures and the environment. A more appealing solution would be to design passive icephobic surfaces. Icephobicity is a relatively new term and was often related to surface superhydrophobicity. However, it is now under debate as whether there is an essential correlation between superhydrophobicity and icephobicity. Compared with the increasing maturity in superhydrophobicity, the research on icephobicity has just started. A realistic scenario is perhaps to live with ice, but, with lowest possible ice adhesion such that the formed ice can fall off automatically by its own weigh or natural wind. In this project, multiscale models will be developed to maximize the effects of crack initiators at three different length scales, and optimal surface and sub-surface structures will be identified such that ice-solid interfaces can be fatally weakened. The primary objective of this project is to establish and demonstrate design principles towards super-low ice adhesion surfaces. The research consists of three main aspects: 1) to advance the fundamental understanding of ice-solid adhesion, 2) to explore novel methods which can fatally weaken the ice-solid interfaces and 3) to develop and demonstrate surfaces with super-low ice adhesion.