Durable Arctic Icephobic Materials (AIM)

In the beginning of the project, we tested many commercial coatings to learn the correlations between ice adhesion and other physical parameters. We then moved on to design and fabricate our own durable icephobic coatings using different strategies. The purpose is to compare and select the best strategy. In general, soft material is promising to achieve low ice adhesion strength, however, extremely soft materials are not mechanically robust. We realized that many biological systems have self-healing properties which mean that they are able to repair the damage themselves. By adding self-healing property to the soft materials may extend the service life of icephobic coatings. Based on this hypothesis, we fabricated a series of self-healing icephobic coatings and found one type coating can achieve ultra low ice adhesion strength. We therefore take this coating as a starting point and tested the coating up to 30 icing/de-icing cycles in order to characterize its mechanical durability. It is found that the ice adhesion of this coating slightly increases with the testing cycles, however it still remains at a very low value (around 12.5 kPa) after 30 cycles. In addition to the self-healing strategy, another strategy to fabricate icephobic surfaces by infusing lubricants to polymer has received wide attention. However, such icephobic coatings are either temporarily icephobic or chemically unstable. In the last period, two progresses have been made in this project. Firstly, we tried to solve the lubricant drain problem by developing bioinspired lubricant-regenerable icephobic coatings. The skin-like coatings we developed in the project were able to regenerate surface lubricant constantly by internal residual stress because of phase separation, and survive more than 15 cycles of wiping/regenerating tests, showing a long-term low-ice adhesion strength below 70 kPa. Secondly, we have designed and fabricated a new class of durable icephobic coating. The new coating is based on dry nanoporous polydimethylsiloxane (PDMS with weight ratio 10:1) elastomer which is chemically stable and mechanically robust. Without any surface additives and lubricants as well as sacrificing the crosslinking density of elastomer, the stable ice adhesion strength of the dry nanoporous coating reaches ca. 16.8 ± 5.8 kPa after 50 icing/deicing cycles. In addition, the icephobic coatings show excellent chemical stability and mechanical robustness, and the ice adhesion strengths are all less than 30.0 kPa after acid/base/salt/organic solvent corrosion and 1000 abrasion cycles. The dry nanoporous elastomeric strategy opens up a new avenue for high-performance durable icephobic materials with excellent stability and robustness. In the period of 2018-2019, two new methods have been further developed to synthesize durable anti-icing coatings with high performances. First, we continued to improve the self-healing coating developed in the early stage of the project. For the first time, we combined ultrafast self-healing property with transparency, which is important for the anti-icing application to solar panels, windows and sensors. Our new coating can restore more than 80% of the ultimate tensile strength within 45 min of healing at room temperature after introducing a mechanical cut. This is probably the fastest self-healing icephobic materials reported. The coating showed a stable ice adhesion strength around 50 kPa after 20 icing/de-icing cycles, and similar ice adhesion strength after healing from mechanical damage. This exceptional robustness makes the coating suitable for anti-icing applications where require high mechanical endurance. The coating on glass shows very similar transparency as the bare glass. The coating is also recyclable due to the dissociable crosslinks. In the last period of the project (2019-2020), two highlights are worth of mentioning. In order to overcome the cost and durability problems of the current anti-icing materials, we developed a sustainable and low-cost electrolyte hydrogel, which can both prevent ice/frost formation for an extremely long time and reduce ice adhesion strength to ultralow value (Pa-level) at a tunable temperature window down to ?48 °C. The lowest ice adhesion of our previous anti-icing materials is around 1 kPa, while the ice adhesion strength of the electrolyte hydrogel based new anti-icing material is 3 orders of magnitude lower. In addition, we have developed another elastomer based anti-icing material. There is a well-known trade-off between the elastic modulus and toughness for conventional elastomer materials. The new material we developed breaks down this trade-off and is both strong and tough. We have engaged the technology transfer office (TTO) of NTNU to exploit the potential commercial values of this exciting material.

1) This project made NTNU clearly visible in international anti-icing research front 2) Provide feasible solutions to the durability problem of current anti-icing materials 3) built up a solid foundation for surface phobicity research in Norway.

Icing on offshore structures represents a severe risk for human safety and major limiting factor for Arctic exploration and operation. Any progress in ice management technology will result in huge energy saving across many fields. Nanostructured materials are gaining increasing importance in anti-icing applications due to their ability to control hierarchical roughness levels and to modify the energy of the underlying surface. Despite the pervasiveness of the icing problem and research progress made, the fundamentals of icephobicity have received relatively little attention in the scientific literature and it is not widely understood which attributes must be tuned to systematically design icephobic materials that are resistant to icing. One of the bottlenecks in deploying current anti-icing materials for Arctic applications is their unsatisfactory mechanical durability. The primary objective of the AIM project is to develop and test bio-inspired robust icephobic materials which can survive multiple harsh environmental cycles and impacts. The secondary objectives are to elucidate the icephobic mechanisms by nanotechnology; to develop reliable test methods for Arctic icephobic materials with special focus on mechanical resilience and transferability of laboratory to real Arctic environments; educate one PhD and one post doc in the field of Arctic icephobic materials and lay down a foundation for future industry oriented research activities for establishing material guidelines for Arctic exploration and operation.