Manufacturing of Super-Repellent Surfaces with High Mechanical Resilience

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Surfaces that mimic lotus leaves and have super-repellent properties have numerous applications, including drag reduction, anti-icing, heat transfer, and anti-biofouling. However, most presently-manufacturable surfaces are repellent to an insufficiently-broad range of fluids and lack mechanical durability. To enhance their liquid repellency, nanoscale overhangs in the surface structures can be incorporated. However, overhangs resemble an inverted pyramid shape that is mechanically weak, making these surfaces even more prone to damage from everyday mechanical stresses, such as being touched by human fingers. This project aims to address this fundamental conflict and pave the way for a new type of super-repellent surface that combines universal liquid repellency and mechanical resilience, which have so far been believed to be mutually exclusive due to their contrasting geometric requirements. The research will focus on developing a novel design and manufacturing method to enhance the mechanical robustness of repellent surfaces, making them resilient to various mechanical loads, such as folding and hammering. The outcomes of this research could have significant implications for a wide range of real-world applications that were previously hindered by mechanical fragility. This interdisciplinary project encompasses nanomanufacturing, material science, microfluidics, and interfacial science. It also includes initiatives to engage undergraduate and high school students in collaborative research tasks to foster inclusivity and provide hands-on STEM training, including for groups that have traditionally been underrepresented in the field. Unlike existing solutions that primarily rely on sacrificing a fraction of the top surface structures to delay the loss of repellency, this manufacturing method will use a combination of soft and rigid materials to create hybrid surface structures. This innovation prevents the surface structures from being damaged, because when subjected to mechanical loads, the hybrid surface structures deform into the soft substrate and subsequently recover their original shapes once the load is removed. Consequently, the super repellency on these hybrid surface structures can be maintained. This project aims to study the mechanical durability of hybrid surface structures and analyze the impact of material variations and detailed geometries on their design. It will thus yield fundamental insights and engineering guidelines for manufacturing super-repellent surfaces with high mechanical resilience. By reconciling the inherent conflict between the shape requirements for strong liquid repellency and mechanical robustness, this study is expected to overcome a scientific barrier to the practical utilization of super-repellent surfaces. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.