High resistance to impalement of highly hydrophobic polycarbonate surfaces with nanosilica-coated rectangular pyramid arrays

Since the surface structure of natural biology was discovered, highly hydrophobic surfaces, deriving from cuticles of animals and plants with extremely high or low water droplet adhesion, have attracted a great attention due to their significance in basic research. The present work proposes flexible template replication methods for bio-inspired polycarbonate (PC) surfaces with highly structured square micropillars and rectangular pyramids arrays. Further, silica nanoparticles (SNPs) or the 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) coated on templates were transferred to the PC melt during the process of hot compression molding and firmly adhered to the skin of the PC replicas, forming hierarchical microstructure. The low-surface-energy matter SNPs or FDTS can increase the heights of microstructure in the open-ended templates and miniaturize the dimensions of microstructure in the conically ended templates. The results indicate that the SNPs can enhance the physical topology of PC replica surfaces, and the FDTS can diversify the chemical ingredients of PC replica surfaces. The consequent surface frame containing air-pockets that house highly water-resistant and mechanically rigid submicron structure formed by accumulation of SNPs. Apparently, with the ability to work under a water pressure of up to 1100 Pa, the microstructured PC surface exhibits a high-efficiency self-cleaning performance by a combination of droplet bouncing and rolling behaviors with a maximum height of bounced droplets up to ∼3.98 mm (i.e., 1.6 times the diameter of the droplet) after impacting. Graphical abstract