Anti-Icing Properties of Vertically Aligned TiO₂ Nanopillars

Inspired by the superhydrophobic and anti-icing properties of Berberis thunbergii leaves for the first time, a surface with vertically aligned TiO₂ nanopillars (VATiO₂NPIs) has been developed, which shows excellent anti-icing properties even at -25 °C. The height and diameter of TiO₂NPIs arrays were 200 and 70 nm, respectively, and were fabricated using TiO₂ atomic-layer deposition in an aqueous solution on an anodized aluminum oxide substrate and modified with stearic acid. The water contact angle measurements for VATiO₂NPI-based aluminum surfaces indicated high contact angle (170.2°), low contact angle hysteresis (5°), excellent delay time (385 s), appropriate robustness (>20 cycles of freeze-melt), and low adhesion strength (<95 kPa). The VATiO₂NPI surface analyses were done using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and Fourier transform infrared spectroscopy (FT-IR) methods, and they showed that the stearic acid stably absorbed on VATiO₂NPIs. Our results indicated that the long delay time of the heterogeneous nucleation and freezing process could be obtained by the desired structural match between the VATiO₂NPI apices and water molecules in the initiation of the heterogeneous nucleation. In this study, smooth apices of the VATiO₂NPIs with highly potent morphology presented significant anti-icing properties because of the strong phonon scattering between nanopillars that can interrupt the heat transfer process. Such results are not achievable by conventional anti-icing methods and give new insight into the mechanism of the anti-icing process.